CA2005734A1 - Technique for dynamically changing an isdn connection during a host session - Google Patents

Abstract

Abstract of the Disclosure A technique is disclosed for use in conjunction with an ISDN communications system for permitting a host is connected through the system, to dynamically change an ISDN access path, that connects the user to the host computer and carries the host session therebetween, between a packet switched connection and a circuit switched connection during the occurrence of the session in order to provide the particular connection that is most suited to the communication requirements of a task currently being executed during the session by the host computer. Any such dynamic change of the ISDN access path is invoked by the host computer, does not disrupt the host session and is substantially transparent to the user.

Description

XO~S~34 BA~; ~UND 0~ q!Hl~ ~NV~
S
1 Fi-ld o~ th- Inv-ntlon Th lnv-ntion r-lat-- to ~ t-c~nigu- ror u~- in an I8DN cs~unlc~tlon~ y-t~a th~t provld-- ~n SQDN ~cc-~ p~th lo ror conn-cting a ho-t co put-r to a u- r t-r~lnal Sn partlcular, thl- t-chnlgu- p rnlt- th- ho-t co-put-r to dyna lcally chang th- SSDN acc--- path b tw n a ~ackct wltch d conn-ctlon ~nd a clrcult wltch`d~conn ction during ~n ongolng ho-t ---lon wlth th u -r in ord r to provld p~rtlcular S~DN connoctlon th t 1- ao-t ult d to th co~ounlcatlon r-gulr - nt- Or a curr nt ta-k b ing Y cut d by th- ho-t conput-r durlng th ---lon .~

2 D -crlptlon o~ t~- Prlor Art Th- Snt grat d 8-rv1c-~ Dlgltal N twork (~S8DN~) 1- curr ntly - n a- a rra. wor~ rOr provldlng n-w r~cl-nt volc- ~nd data t-l-phonlc -rvlc - ln th- n~r ~utur A~
~uch, S8DN N ltch-- ar b lng now k-lng anutactur d by varioua v ndor and lnt gr t d lnto th t-l- p on n-twork by local t-l- p on- op ratln~ co F~nl .-Wlthln th S8DN, an S8D~ acc--- lln conn ct- ach call-r ~n~ an ~8DN wltch lo~ t-4 at a c ntral orrlc- Sn on~ conrlguratlon, 1.- ba-lc cc -, an I8~N acc--- p~th ¢on l-t~ o~ two S8DN ~B~ dlglt~l ch-nn~ nd on S~DN ~D~ -dlgltal cb~nn l. ~ach ~B~ c~ nn l h~ ¢~iaolty o~ 6~
kblt-/- con~ ~hll-, th- ~D~ c~ nn l Aa~ ~ cap~city o~ 16 kblt-/- cond. Th- ~D~ chann l can only c~rry paaX-t-~ whll-3~ ach or t~ ~B~ chann-l- can ¢-rry'-ith r pa¢k-t~ or ,, : , " . , ~ , ,, ".

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,, , , , ': ' , ,: ,, ;~OC~ 734 - contlnuou~ (clrcult ~wltch-d) 8i~nal- ~o ln~tlat- an r8DN call, a callor's t-r~lnal gulp~-nt plac~ ign~lllng in~ormation contaln-d withln a pack t onto th- ~D~ ch~nn l in ord-r to, int-r alla, sp-clry to th- ISD~ ~wltch what 5 8p~cl~1c conn-ctlon should b- provld-d ~ron th- swltch to th- caller and what p-cl~lc ch~nn-l should b- us d to provid- thl- conn-ction, p-clrlcally wh-th-r a pacX-t swltchod nD~ chann-l conn ctlon, or 1~ a ~B~ ch~nn-l 1~ to b- u--d, whlch ~p-el~la ~B~ ch~nn-l hould b- u d ~nd wh-th-r a pack t or clrcult ~wltch d conn-ctlon 1- to b-e~tabli-h-d on that chann-l - Wlth thl~ arrang ~ nt, ~n ISDN ~wltch can provld-lth-r a clrcult wltch d conn-ctlon or a pack-t wltchod conn-ctlon to a call-r A clrcult ~wltch d conn-ctlon, whlch can only occur on th- ~B~ chann-l, provld-- a ~ultlpl-x-d corounlcatlon path, ln g pac- and/or ti~-dlvl~lon nultlpl x~d ra hlon, b tw n th- c~lllng and c~ll d partl-- that la-t~ throughout th- ntlr duration o~ th c~ll A~ uch, only on- c ll 1~ abl- to u-- any glv n ~wltch d conn-ctlon through th n-tYork at any on- tl~ . ~n contra~t, a pack t wltch-~ conn-¢tlon ~ r-ly r~ on - gu-ulng pack-t- o~ dat~ at an ~DN ~wltch ~or tran nl~lon b-tw on a call-r, ~r qu ntly a u~-r, and a call-d party, 2S typically a hoJt co put-r, and th n ~-gu-ntlally tran-nlttlng tho~- paok~t~, rro~ point to polnt withln th-p~ck t n twork that Sor~ p rt ot th~ I8DN a- tr~n-~l--lon ca~clty b coa~- avallabl- th ~b tw -n. ~n~- udA a- ch u~or oS ~ ~a¢kot N ltch d conn-ctlon r ly r-qulr~ a ~-parat addr ln a ~ nory oP a local ~wltch, g a ~ ory locatlon, to whlch ~ack t~ can b tr~nJ-itt d and troa whlch ~ack t- c~n b r-c-lv-d and h-nc- conJu --r-lativ-ly r-v n-two~k r ~ourc-- throughout th durat~on oS
th call, ~ny dlr~-r-nt pack t ~vltch-d call~ c~n sh~r all ;~0~ 3~

th- r~lning n-twork racllltl-~, lncludlng ld-ntlcal com~unlcatlon path-Du- to th- substantl~l dirr-r~nco- b tw~n th- two s dl~r~nt typ-~ Or lSDN conn-ctlon-, circult ~w~tch-d and pack-t swltch-d conn-ctlon~ acb provld-~ dl~r-r-nt advantag-- and drawbackJ Plr~t, a clrcuit Jwltchod conn~ction provld-~ a contlnuou- tran-~lJ~lon path rrO~ th-call-r to th- call-d p~rty throughout th- duratlon o~ a c~ll Such a connoctlon l-part- r-latlv ly littl-, 1~ any, tran-nl--lon d-lay to any coi unlcatlon carrl d ov-r th-p~th Th-r-~or , clrcult wltch d conn-¢tlon- ar- uJad ln tho-- co~nunlcatlon appllcatlon-, uch a~ ~llu~tratlv ly conv-r~tlon~l volc- tra~lc or hlghly lnt ractlv- data tra~ric, wh-r ~ny appr cl~bl- trun al~-lon d-lay can not tol-rat d 8-cond, clrcult wltch d conn-ctlon~ provld-hlgh-r throughput th~n do ~ny pacX~t wltch d n-twork~, Juch ~ ~p-¢l~lcally X 25 typo pac~ t wltch d n-t~ork- A~
uch, co~aunlc~tlon~ ~ppllc tlono that r-qplr a hlgh throughput and low d-lay tranJal--lon p~th, uch ~
lllu tratlvaly r ~l-tl-~ tr~nJr-r o~ l~rg- rll-- or tr~nJ~-r Or hlgh d-n-lty dlqltlz d ~Jaq--, ar ld-~l ~or tran~port ov-r clrcult wltch d conn ctlon- Un~ortunat-ly, lnc~
only on- call, at l-a-t ~roa th t~ndpolnt o~ a loc l 2S ~wltch ~nd apart rro~ any u~-r nNltl~l-xlng, can b- carrl-d ov-r a glv n clrcult vltch d conn ctlon through ~h n~twor~
~ro~ a call~r to ~ call-d party, u-- o~ a clrcuit wltch d conn ctlon t-ndJ to b qult- xpon~lv partlcularly 1~ th-conn c~lon 1~ to b xalnt~ln-d ov r a prolong d p-rlod o~
tl~.

ot~r con unloatlon a~pllc~tlon~, whloh ar~
typl~l~d by r-latl~ ly lon~ lat ncy p rlod- b tw n ucc-~lv- $ran~rl~10n~ ~ron ~n- party to th~ oth-r, ~r~
3S bur~ty ln natu~ and ~--~ntlally unar~-ct-d by appr-cl~bl--, ;~0~'734 trans~lsslon delay Bur-ty co~unlcatlon~ ar ld al ~or carrlag- ov-r a pacX-t n-twork Co~ounlcatlon ot thl~ ~ort illu-tratlv-ly includ- tran-port ot u~-r co~andc tro~ a us-r'~ t-r~lnal to a ho-t co~put-r to inltiat- ~x-cution o~
a progra~ that requlr-- a r-latlv-ly long proc-~lnq tl~
and r~latlv ly llttl- u--r ntry ot ln~or~atlon thor a~t-r o~ten, wh~n-v-r a u~-r und-rtak~- lln- orl-nt d int-ractiv op-ratlon~ with a ho~t conput-r, th- u~-r xp-ct~ to ~ncount-r ~o~- d-lay art-r h or h- nt-r~ ach lln- ot ln~or~ation typlcally a co~ and tollow d by a lln-d-li~it-r whlch 1- ~r-gu-ntly a c rrlag- r-turn, and b ror-control i- r-turn d to th- u--r Durlnq th- d-lay lnt-rval th ho-t co~put-r proco---- th- nt-r d ll~-Untortunat-ly wh-n a pack t vltch d n-twork p cl~$cally ~n X 2S n-twork, c~rrl-- a ho~t ~ lon th- n-twork ott-n in~-ct~ a notic-abl- anount ot tran-port d-lay lnto th-~ lon in addltlon to th d-lay lnh-r nt in th proc--~lng tl~ r-qulrod by ~ ho-t appllcatlon. Th tl~- r-qulr~d by th- ho~t co~put-r to proc--- ach ¢baract-r ln th- lln- ot intor~tion 1- ott n ub-tantlally bort-r than th-tran~port d-lay ot th pack t n-t~ork Nov, lt th- ho~t co~put-r w~ r-qulr d to cho acb cbaract-r that th- us-r nt-r- back to th- t-r~ln~l tor local dl~play, th n th-tran~port d-lay lnh-r nt ln tb pack t n-twork would torc-th- u--r to walt untll ~o~- tiu~ att-r ach charact-r wa~
nt-rod ln ord-r to ~ tb ln~or~tlon whlcb tbat lln-contaln d ~b d lay p rc lv-d by th- u--r and ~--oclat d wlth ho~t ba- d c~olng 1- tr qu ntly r t-rr d to a~
~ chopl-x.~ ~n - ucb a- n-twork d l~y, whl~h 1- th pr 40nln~nt cau-- ot chopl-x pr v-ntJ th- u--r ~ro~
obtalnlng ~ - dlat- t- dback ot th- con~ nt- ot th- curr-nt lln- and xp dltlou ly ¢orr-ct~ng any l-t~X th-r-on, ~4ny u--r tlnd chopl-x to b hlgbly unJatl~tactory and gult-~nnoylng ~n an ttort to ll~ln t- chopl-x that aay ~
3S xp-rl nc-d vlth a p~ck-t wltah-4 n-t~ork, th- ~rt t-~cb--;~O~ 3'~
_ -5-th~t ~ local p~ck-t a~-ibly/dl~aJ-o~bly (~PAD~) runctlon should b- lncorporat-d into a u~-r t-rmln~l In thl~
r~gard, ~-- "Pack-t A~ bly/Dl~a~-mbly Paclllty (PAD) ln a Publlc D~t~ N-twork~, ~ , 198~, ccIIr S document AP VTII-57-~, p~g-- 22-~4 In partlcul~r, th- PAD
runction ochoo~ loc~lly nt-r~d char~ct-r~ rOr dl~play and as--~bl-- ~n outgolng p~cX t o~ nt-r d ch~r~ct-r~ up to a pr--d~rin~d ~axl~ua ch~ract-r linlt and th-n tran~lta tho pack-t upon r-c-lpt Or ~ uit~bl- d-li~it-r, typlcally a c~rrlag- r-turn rro~ th- u~-r, ov-r tho n-twork In additlon, th- PAD runctlon al~o dl~-a-~-obl-- ~ch lncoming pack t auppll d through th- n-twork rro~ th- ho-t co-put-r and locally dl~play- th charact-r- contalh d ln that pack t on th- t-r-inal 8y provldlng local cholng, th PAD
1~ runctlon advant~g-ou ly ll~in~t-- chopl-x and, rr u~-r'- tandpolnt, app ~r~ to hlrt all th- d-lay, 1 -n-twork tran~port ~nd hoat proc---lng, to th- nd Or ach nt-r d lln-, 1 - a~t-r that lln wac dl~play d to a u~-r, wh-r that d-lay 1- r~r 1--- ob~ ctlon~bl- to th u--r H nc-, b-cau-- Or th- -- ntlally d-lay-in~ naltlv n~tur-Or bur~ty coumunlcatlon~, thl- typ Or comnunlcatlon, p~relcul~rly ln~olving a u~ r t-r~in~l th~t provld-~ th- PAD
~unctlon, c~n b tr~nJport-d rar r cono d c~lly through pack~t Jwltch-d conn-ctlon tb~n throug~ a clrcult wltch-d 2S conn-ctlon.

Thu~, by vlrtu- o~ th pot-ntlal h~rlng lnh-r nt in ~ck-t vltch d conn ctlon- und th- d dlcatlon ot 8 wltch d ~th ln a clrcult ~ltch-d conn-ctlon, p~ck-t wltch-~ conn ctlon provld a hlqbly cono~i¢~l though --d-lay pron polnt-to-polnt tran port ~ dla~ wAll-, by contra-t, clrcult vltch d conn-ctlon- provld a r l~tl~ ly xp n-lv but n arly ln tant~n ou~ tran-port ~ dl~ vlth a r latlv ly ~ throughput .
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20()S73~

ort-ntlm~, a ho-t ---ion will contaln p-riod~ ot highly int-ractiv- co~unlcatlon~ charact-rlz-d ~y trlng n~
maximu~ d-lay r-guir ~ont~ b-tw n th- ho-t co~put-r and th-user, during whlch th- loc~l ~cho ~nd lin- butr-rlng PAD
S ~unction~ are disabl-d by th- hoat, and lat-nt p-riod~ that ar- punctuat~d by bur-ty tran~nl~iona For x~pl-, a sub~tantial amount o~ thla lnt-ractivlty, on a k-y~trok--by-k-y-trok- b~ , o~t n occur~ dur$ng u~- or an int-ractiv- ~cr- n d$tor ln partlcular, ~n lnt-r~ctlv-cr--n oditor o~t n utlllz-- th- a~ charact-r k y to provld- ~-v-ral dltt r nt tunctlon-, wlth ach runctlon s-l-ct-d by d-pr--~lng k yboard -qu nc- containing a glv-n charact-r X y, o g a ~ k y, along~vlth varlou~
control, ~unctlon or acap- X y- A~ ~uch, to provld th-approprlat- lndlcatlon on th u--r t-r ln~l, g ~ov$ng ~
cur~or down on- lln- wh n ~ k-y la d-pr--a d whll- tho u~-r 1- ln th- control od Or a ~UNIX~ ~vl~ w r ~n dltor (VNIX 1~ a r gl-t-r d trad--ark o~ th A~ rlc~n T l-phon-~nd T-l graph Co~pany)~ in ll-u o~ alw~y- dl-playlng th-charact-r ~ a--oclat-d wlth th d-pr ~a d X y lt--l~, th-ho-t ~ppllcatlon (- g. th ~UNIX~ ~vl~ dltor) di-~bl-- th PAD ~unctlon on th- ua-r t-ru$nal and provld-- approprlat-cb~ract-r cholng or oth r $ndlcatlon back to th u--r t-r lnal ~n th$- r gard, ~Proc dur ~ ~or th- ~xchang ot Control ~n~or -tlon and U -r D~t~ b tw -n a Pac~ t A--o~bly~Dl-~--~bly Paclllty IPAD) and ~ Pack t ~od- D5~ or Anoth r PAD~, cc~sr R~con~Mng~ X 22~ CCIT~ dscun nt AP V5~ 9-~, 198~, pag - 55-~ To a--ur~ th~t th- u~-r i~
provld d wlth a Ju~lcl ntly ia-t r -pon~- ti~- to ~upport a hlgh d gr ot k-y-trok- lnt-ractlvlty wlthout ob~-ctlon~bl-chopl-x, th- cou unlcatlon u dl~, uch a- a n-t~orX
conn ctlon, that conn ct- th ho-t co put-r to th- u~-r i~ -con train d to i~part 1--- th n a pr -d tln-d ~xi~u~ u~ount ot tran port d-lay to any tranJ l~-ion carri d th-r-ovor ;~005';'34 _~_ Fro~ tlm- to tl~J, th- uJ-r ~ay t-~ away ~ron ter~inal or turn to an ~ntlr-ly dltt-r-nt ~at~-r r ~ulting ln a te~porary c-~atlon ot ho-t actlvlty wlth th- u--r Such a c~ tlon, d-p-ndlng upon what th- us-r 1~ dolng, Jay S last sQv-ral hour- Durlng Juch a c---atlon, th- ho~t s-~lon lt~olt ~tlll r-QAln- actlv-, although th- ho~t co~put-r 1- only ln~tructlng th t-r~lnal to dl~play a cur~or to pro~pt th- u~-r tor ube-qu-nt lnput ~hl~
~unctlon 1~ typlc~lly h~ndl~d by ~ lo~ l-v-l co~unlcatlon~
proc-~ that x-cut-- ln th- ho-t conput-r or ln a tront nd co~unlcatlon- proc--~or a--oclat d th-r-wlth It th- u~-r t-r~lnal 1~ con~lgur~d to provld- local proc-~lng, uch a-th~t whlch could occur vlth lllu-tratlv ly~ p r-onal co~put-r or work-tatlon, th n l-llar ho-t lnactlvlty could occur onc- th- work~tatlon r c-lv-- ~ r-gu--t-d ~ ro~
th- ho~t conput-r and proc--d- to proc-e- th- ~11- loc~lly a- ln-truct d by th u--r Ihough, ln thl- in t~nc-, th ho-t ~---lon 1~ typlcally ~ lntalnod ln an actlv ~tat-whll- local proc---lng occur , co~uunlcatlon wlth th ho~t couput-r, oth-r th n ~ ~lnlJ l ~ ount n c-o-ary to k--p th-ho-t --~lon ~ctlv-, g n-rally only occur~ ~h n-v-r ln~or~tlon 1- to b tr~nJ~ rr d to or ~rov th- ho~t co~put-r to th work~tatlon H r- too, d p ndlng upon th-a~ount o~ proc lng th~t 1- to b locally acconpll~h d, th 2S ho-t co~put-r ~ay ~ etlv ly -- a c--~at~on o~ w tlvity ~ro~ th w r ov r a p rlod o~ tin- that ~y la~t ~-v-r~l hour-I~ r oognltlon tb4t data co~aunl¢atlon- c~n contain both hlghly lnt-ractlv d-lay---n ltlv-tr~nJ~ lon vbl¢h ar b -t trano ltt~d ov r ~ clrcuit ~wltch d conn ctlon ~nd bur~ty tr~nJal--lonJ whlch ar ~-~t tranJ~ltt d ov r a paok t n-twor~ 1- --n ln lllu tratlv ly Unlt d ~tat~ pat nt ~,539,676 [l--u d to ~ A. ~u¢a- on S-pt-ab-r 3, 1985 an~ h r lnaft-r r-t-rr~d to ~- ~h '676 ....

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' 200~j~34 pat~nt) Sp-cltlc~llY, th- '676 p~t-nt dl~clo~ n int-grat-d volc-/d~ta, though non-ISDN, wltch th~t contaln~
a s-parat- clrcult switch and a -p~r~t- p~ck-t wltch E~ch u~or t~r~lnal provld-- lncoDlnq ~ntor~tlon to th-volc~/data swltch $n th- tor~ ot a p~lr ot lght bit byt Each p~ir or byt~J contain~ a control byt- that ha~ a routlng blt and a d~ta byt- Th- t-r~in~ t- th- routlng blt to an corr~ponding valu- that ~p-¢i~ wh4th-r th-acco~panylng d~ta byt- i- to b- rout d wi~hln th- voic-/data - 10 ~wltch to ~lth-r th- clrcult wltch or to th- p~ck-t swltch tor tran-ui~-lon to a c~ll d d--tlnatlon through a r-~p-ctlv- clrcult ~wltch d n-twork or pack-t ~wltch d n-twork A- uch, ucc---lv- dat~ byt-- can b- rout d ~la lth r ~- clrcult wltch-d or ~ p~ck-t wltch~d conn-ctlon b~- d upon th- valu- ot th- corr -pondlng routlng blt- To provld- thl~ routlng wlth nlnl al d-lay, th voic-/d~t~
~wltch and th- n-twork- ~r dl-advantag-ou-ly r-qulr~d to lnt~ln both th clrcuit ~wltch d conn ctlon ~nd th pack-t ~wltch d conn-ctlon ln ~n actlv- t~t- throughout th- ~ntlr-dur~tlon ot th- call. Con~-qu ntly, th n thodoloqy t~ught by th- '676 pat-nt t-nd to b- qult- ln-ttlcl-nt tor th-t-l-phon- n-tworX ~nd xp n-lv tor ~ u--r Now, lt an 18DN acc--- path 1- u- d to conn-ct a ho-t to a u--r, th n, a- 1- taught ln th- ~rt, th-partlcular conn ctlon ~clrcult vltch d or pack-t ~wltch~d) th~t 1- -tabll h d ~t th lnc-pt~on ot th- lSDN c~ll to provld~ thl- pnth i~ that whlch occur througAout ~h-r-~lnd r o~ th~ I8DN call, 1 - th ho-t ~---lon S~ or x~-pl-, Unlt d 8t~t-- p~t nt~ 4,731,782 ~l~-u d to T
8hl-l~u ot 1 on ~brch 15, 1988) ~nd ~,S69,0~1 ~i--u-d to T
Tak-uchl ot ~1 on r bru ry ~ U). althoug~ thl- ~ppro~ch ln th- ~rt h~- ~-v r~l dr~vb ck~ dl-cu-o-d b lov, p rtlcul~rly wh n co~ unlc~tlon ne-d~ ch~ng- dur~ng ~ ho~t 3S ~ lon, ~ u~-r 1~ ahch aor- ~pt to r-~dlly ~ccopt th-~-Z00573~
g_ drawback~ rath-r than to ~ubDlt to th- burd-n~ a~ocl~t-d wlth changlng ~n ISDN conn-ctlon durlng th- ho-t ---lon In partlcular, c-rt~ln application~ wh-r- local S proc~sslng can not b- u~-d, ~uch u-- ot ho~t ba~-~ k-y~trok int-ractiv- scr- n edltor-, r-ly on th- ho-t to cho ach charact-r that th- u~-r nt-r~ lnto a t-r~inal, through a point-to-point co~unic~tlon circult th~t i- ~-ua d to hav-low d-lay, b~ck to th- t-r~inal tor approprlat- local dl~play Un~ortunat-ly, th- d opl x th~t r-~ult~ wh-n ho~t ba--d choing 1- carrl d ov r a pack-t wltch d n-twork rr-qu-ntly ~ru-trat-- and annoy- u--r Con--qu-ntly, 1~ a u--r ha- lnitlat d ~ ho-t ---$on throuqh à pack t wltch d oonn-ctlon ~nd nt-r- what h- or h- b ll-v-- to b- a p-rio~ --lS Or h-avy k-y-trok- int-ractivlty with th ho-t and which typically r-gulr-- ~tring nt naxl~un d-lay r-gulr-~ nt- ~nd ho-t applicatlon di-abllng ot ny PAD tunctlon~llty at th-t-r~ln l, th n, to clrcu v nt th- ~ru tratlon a--ool~t d wlth ohopl-x th~t would oth-rwl-- oc¢ur durlng thl- p rlod, th u--r aay b- con traln d to tollov on- ot two ~It-rn~tiv proo dur-- Plr-t, th- u--r could t-~r down th- curr-nt ho-t ---lon ~nd lnltl~t- a ub--qu nt ho-t ---lon ov-r a ; clrcult vlt¢h d ¢onn ctlon to und rtak thl- lnt-ractlvlty - T arlng down and th-n r -inltlatlng a ho-t ---lon typl¢ally r-qulr - t-r-lnatlng varlou- ho-t pro¢ ~--- th-n x cutlng, ~vlng tll--, loggln~ ot~ th ho-t, dl--connc¢tlng th-p~ck t wlt¢h d IQDN llnk,. r----tabll-h$ng ~n n-w ISDN llnk on a olrcult ~ltch d c~ nn-l, r-- x-cutlng a ~logln~
pro¢ dur lnoludlnq vhat ~- ott-n a I-ngthy -curlty ch ck proc dur , ~cc ~-lng th ~l- that ha- ~u-t b- n ~vod, and r --tartlng th~ ho~t pro¢----- that w r- pr vlou-ly t-r ln~t~d A on- can r adlly appr ¢lat-, thl- pro¢-dur- ~-lnvolv d wlth -tabll~hlng a n Y ~o-t ~--lon 1- both tl~
con uulng aruL both-r on- 8-¢ond nd alt-~n4tlv-ly, 1~ th- -ho-t op ratlng y-t--'p r-it- DUltipl- ho~t ~o--lon~, a- 1~

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200~i734 th- ca-- wlth lllu~tr~tlvsly th- ~UN~X~ opor~tlnq ~y~t-~, th- u~-r could allocat- th- curr-nt ho~t s---lon ~taSll~h 4 through a p~cX~t swltch d conn-ctlon to on- wlndo~, and op n - a s~cond window cont~inlng ~ ~-cond ho~t s-~lon ~taSll~hod through a circult wltch-d conn-ction With thl~
arr~ng-~-nt, th- u~-r could wltch b-tw ~n th- J--~ion to utiliz- a circuit witch d conn-ctlon ~or tho~- highly int-r~ctiv- d-l~y---n-itiv- ho~t t~kJ th~t di-abl- th- PAD
ln th- loc~l t-r~lnal ~nd a p~ck t witch-d conn-ctlon ~or oth-r ho~t t~k~ Un~ortun~t-ly, with thl~ ~lt-rn~tiv-proc-dur-, th- u~-r 1~ tlll r guir d to bulld ~ -cond s-~ion ~nd r---x-cut- ~ l ngthy ~lo~in~ proc dur which i~
both both-r-o~- ~nd tin- con-u~ing to th b--r Th-r-ror , to ~vold ~ollowing oith r o~ th--- proc-dur--, a u~-r g n-r~lly ~t~bll-h-~ ~ clrcult ~wltch d ISDN conn-ctlon to th- ho~t conput-r prlor to th- lnc-ptlon o~ ~ ho-t ~ lon r~th r th~n ~ p~ck-t wltch d conn-ction ~nd th n r t~in th~t circuit witch d conn ctlon throughout th- ntir ho~t ~ lon r-g~rdl-~ o~ th p cl~lc ho-t ~ppllc~tlon(~) th4t 1- x cut d during th t ---lon Untortunat-ly, th- pr - nc- o~ bur-ty con~unlc~tion- ln a typlo~l ho-t --~ion po--- ~-v-r~l dr~wb~ck~ to both tho u -r co aunlty ~nd th~ loc~l tol-~hon-2S conp~nl-~ w -r 1~ p d tt-d to Jt~bll-~ ~ clrcult ~wltch-d I8DN conn ctlon to a ho-t co~put-r and th-n r tain th~t conn ctlon tbrouqhout a l ngthy ~o-t ~-~-ion Por a u--~, clrcult vltch d conn ction- ar 2ar nor- xp n lv-th~n pac~ t vltch-d conn-ctlon ~h-r-ror , durlng any p rlod o~ r latlv inactlvlty p~rtlcularly durlng ~
prolong-~ lnt rv~l Or tia-, a u-~r 1- paylng a lgnlrlcant pr alur rOr u lng a clrcult ~wltch d conn-ctlon wh-n, in ract~ llttl-, i~ any, co ~unlcatlon 1- b~lng tr~n~r-rr~d th-r-ov-r. ~n addltion, th w$tch-- in tall d in th-c-ntral orrlc-- Or th local t-l-phon- conp~nl-- rr-qu ntly do not hav- ~u~lcl-nt cap~clty to h~ndl- a ~lgnl~lcant numb-r o~ ultan-ou-ly occurring clrcult witch d connQctlon~ ~ach havlng a long holdlng tl~-, uch a- ~-v r~l hour- ~n p~rtlcul~r, local t-l-phon- wltch-- ~r-genorally deslgn-d to pro~ld- a c~paclty or 3-4 CC8 (on-hundr-d call -cond~) p-r acc-~- lln-, 1 - a loc~l wltch d~-lgn-d to handl- 30,000 di~-r~nt acc--- lln-- wlth a c~p~city or 3 CCS can l~ultan-ou-ly acco~odat- a call lasting S alnut-- on ~ch dirr-r nt lln-. H nc-, th-occurr~nc- Or ~ ~ub-t~ntlal nu b r o~ ultan-ou-ly occurrlng circult wltch d ISDN call~ wlth r latlv ly long holdlng tl~ - c~n s-v-r-ly traln th- c~p~clty ot ~ loc~l swltch Unrortun~t-ly, local t-l-phon- co~pan$-~ ~r ~i~ply unabl- to ~dd urrlcl nt clrcult wltch d c~paclty to ~ndl-th ~- c~ whll- tlll provldlng clrcult wltch d conn-ctlon- ln a r-l~tlv-ly co-t--rr-ctl~- m~nn-r ~ h-r-ror-, a n--d Yl~t~ ln th art tor a t-chnlqu ror u-- in con~unctlon wlt~ an I8DN ~wltch rOr dynunlcally ch~nging ~n I~DN acc--- p~tb, that conn-ct- a uJ-r to th- ~wltch And th-r-through to a ho-t co~put-r, b-tw n a clrcult wltch-d conn ctlon and a pack-t wltch d conn-ctlon durlng a ho~t ~ lon accordlng to th-co~munlcatlon d-aand- o~ th ho t comput-r that occur durlng th- ~ lon By changlng th- acc--- path ln thl~ ra-hlon, a us-r would h abl- to uch or frlcl-ntly ~nd ¢onoulc~lly utlllz- th- ~DN t~an ha b- n po--lbl- ln th ~rt Purtb-r or , to ad~nt g ou l~ ln~t ~ny burd n on th-u~-r, any uch dyn~alc ch~nq hould b- ~ad- ~n a a~nn r th~t l~ invo~ d by th ho~t co~put-r, do-- not dl-rupt ~h-ho~t ~ lon ~nd 1- ~ub-tantl~lly, if not tot~lly, trunsp r nt to th- u r Hor ov r, ~y dynaaically ~tchlng th- I8DN acc -- p~th to th- band~idt~ r qplr---nt- o~ th curr nt t~ b inq x cut d on th- ho-t, th- t~ci-ncy Or th- ~8DN ~dv~nt~g-ou~ly inor ~ do-~ th ~blllty Or th-~00~734 local t-l-phon- co~p~ny to pro~ld- ISDN 9-rvlc-~ ~u~lcl-nt to ~-t th- xp-ct~d d~and o~ all lt- u~-r-SUM~ARY OF TH~ INvENrIoN
Thos- and oth-r lnil~r d-~lcl-ncl-- a~ociat~d wlth ~SDN co~unlc~tion ~y~t--J Xnown in th- art ar adv~nt~g-ou~ly ll~lnat-d ln accordanc- with th pr-~-nt lnv-ntlon by dyna lc~lly cbanglnq th- I8DN ~cc-~- path that 1~ ~t~bll~h-d through ~n I~DN co~nunlcatlon y~t-~, g an ~SDN ~wltch, b-tw--n ~ u~-r t-r~lnal ~nd a ho~t co~put-r fron a rlr-t conn-ctlon, uoh a~ ~ B chann-l clrcult - ~wltch d conn-ctlon, to a -con~ conn-ctlo~, uch a- a D
ch~nn-l pack~t wltch d ¢onn-ctlon or ~lc- v-r~a durlng an ongolng ho-t ~ lon carrl d ov-r that ~cc-~- path ln ord-r to provld- th- partlcular conn ctlon, lth-r B chann~l clrcult wltch d or D chann-l pac~ t wltch~d, that 1~ ~o~t ult d to th- curr-nt conounlcatlon n--d- o~ th- ~---lon A~ uch, th- I~DN Gonn-¢tlon provld d ov-r th- ~cc--- p~th, rat~-r than b-lng tatlc ~- 1- taught ln th- ~rt, dynu~lcally chang-~ ln r--pon~ to co~ndJ ~-ult~bl-control ~ ag -) that ~r l--u d by th- ho-t co~put-r th-r by rr-ctlv ly atchln~ un avallabl- co~nunlcatlon chann l to th- curr nt ho~t taak b-lng x-cut~d durlng th-s---lon. ~hl- dyna lc J t~hlng Or n twork r--ourc-~ to ho~t r-qulr a-nt~ advant~g-ou d y ln~ lz-- w~-t-d tran~Jl~lon bandwldth and ¢on--rv-- n tvork r-~ourc-~

ln p~rtlcular, th- aFp~ratu- that ~bodl-~ our lnv ntlv t cbnlgu- h~ n an~, tor ¢onn ctlon to on- nd ot th w ¢ -- p th and to ~ ho-t co~put-r, tor ln tru¢tlng co~aunl¢atlon y-t-~, g th- ~N n-two~k, that provld-~th ~cc--- path to c~ ng- ~ conn ¢tlon provld-d ov r that path b tw ~n ~ B ¢hann-l conn-otlon ~n~ ~ ~ chann-l 3S conn-¢tlon ln r -po~ - to ~ c9- and rqc-lv d trc~ th- ho-t ' '~ , .

comput-r during axecution ot th- ho-t ~ lon, wh-r ln th-- instructlng m-an- haJ m-an~ rOr ~tabll~hlng ~n lnt-r~ac- to th~ ho~t comput-r to b-gin th- ho-t ---lon and ~or m~intalning th- int-rrac- sub~tantlally throughout th-remaindQr ot th- ho~t ~ lon and ~-an~, r--pon-l~ to th-~nt-r~c- ~nd rOr conn-ctlon to tho on- nd ot th- acc-~
path, ~or rQc-ivlng a co~ nd ov-r th- int-r~ac- tro~ th-host comput-r r~gu--tlng a chang- ln th- conn-ctlon provld-d ov-r th- acc-~- p~th b-tw--n D ~nd B ch~nn-l conn-ctlon- and rOr supplylng th- co~ and ov-r th- ~cc-~ path ~n a p~--d-tln-d tor~ a- ~n ln-tructlon to th- co~unlc~tlon y-t-~ to rr-ctuat- th- r-gu--t d chanq-rn accordanc- wlth a p-cltlc abodl~-nt ot th lS in~-ntlon, ~ co~unlcatlon~ proc-~or call d a ~brok-r~ 1-conn-ct-d b-tw- n th- ho-t co~put-r and th I8DN n-twork Th- brok r pa---~ connunlcatlon b tw n th- bo-t co~put-r and tb r~DN n-twork nd, ln r -pon-- to tb con- nd~
g-n-r~t d by th- ho-t conput-r to chang- th- r8DN
conn-ctlon, l--u-- corr--pondlng ln-tructlon-, to tb-n-twork ln ord r to tt-ctuat- ach ucb chang ~h--- ho~t co~and~, uch a- ~ran ltlon to D Cb nn-l~ nd ~Tr~n-ltlon to B C~-nn-l~ ar d-t-rnln d by tb- co-~unlcatlon r-gulr n nt- ot th- curr nt ta-k, 1 -. ho-t appllcatlon progran, x cutlng durlng tb ---lo~ -A u r t-r~lnal, whlch 1~ conn-ct-d to an n~ Or th 18DN acc path that ~- oppo-lt- to that conn ctcd to th- brok r, bl-dlr ctlon lly con unlcat-- wlth th- ho-t o~-r th- acc -- path To tabll~h a ho~t ---lon, a u--r ~ltu~t-~ ~t th- u--r t-r~inal nt-r- n approprl~t- ~-s-ag-- ld ntltylng th- ho-t co put-r lnto th- u--r t-r~ln~l Ih-u--r t-rnln~l th n provld-- a control x--~8g to th ~8DN
n-tvork that-ln-truct~ th n-t~ork to -tabll~h a D chann~l ~8DN conn-ctlon to th~ t-rolnal ani xt-nd thi- conn-ctlon - . ,:- .,,, , , , - ~;, . ~ , , ,, .
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2005'734 to th- brok-r A~t~r th- n-tworX 1~ abl- to succo~-~ully extend th- ISDN D chann-l conn-ctlon to th- brok r, th-brok-r e-tabll-h-- a conn~ctlon, uch a- ov-r a local ar ~
n-twork (~AN), to th- d--lr-d ho-t co~put-r and th-r-a~t-r provld-~ appropriat- protocol conv-r~lon, such a~ X 25 to Eth-rn-t protocola, to nabl- th- u~-r to co~unlcat-through th- ISDN n-tworX to th- hoat co~put-r At thi~
polnt, th- u~-r t-r~inal, th- brok-r and th- ho-t co~put-r all ~ointly rQald- ln a D Chann-l St~ady Stat- condltlon lo Th- u--r th-n r-c-lv-a a ~logln~ -qu nc- ~ro~ th- ho~t whlch, lr ~ ucc---rul logln occur~, p-r~lt~ th- u~-r to sub~-gu ntly ox-cut- ho-t appllcatlon prograa Th- D
chann-l ~tat- contlnu-- throughout th- dur~tlon o~ th- ho-t ~ lon rn th- v-nt t~- u--r x-cut-- a ho-t appllcatlon that ha- trlng nt d~l~y r-gulr-~ nt- and, a~ ~uch, can g-n-rat- ob~-ctlonabl- chopl-x 1~ carrl d ov r ~ D chann-l pack-t conn-ctlon, th- ho-t conput-r g n-rat-~ a co~and to th- brok r to lnltlat- a tran ltlon Or th- ~8DN
conYunlcation chann-l tro~ D to B Th- brok-r, ln r-~pon~-to uch a co~ 4nd, g n-rat-- an ~pproprlat- in~tructlon, such a~ a corr -pondlng Q 931 control ~ ag-, to th-n-twork Th- n-twork th-n -tabll-h-- a B chann-l clrcult wltch d conn-ctlon to th- brok r and al-o xt-nd- thl-conn-ctlon to th- w r t-ra~nal I~ thl- conn ctlon 1-2~ ucc~-~rully -tabll h~d by th n-twork b-tw n th u~-r t-rnlnal and th brok r, th w r t-r~lnal, th- brok r and th- ho-t co put-r all ~olntly r--ld- ln a B Chann-l St~ady 8tata condltlon. AJ ~uch, whll- $n thl~ tat-, data i-ub--qu ntly carrl-d ov-r th B chann-l conn-ct$on Although th- D chann l conn-ctlon r-~aln- actl~-, lt only carrl-~ I8DN control n---ag -, l - ln th- X 25 and Q 931 protocol- whll- th 8 chann-l conn ctlon i~ ln u-~ Onc-th n--d rOr a clrcult wltch-d ~DN conn-¢tlon dl-app-ar~, ~uch a- ~or xa~pl- by th u--r lnst~uctlng th ho-t to 3~ x-cut- a dl~-r nt appllcatlon progru~, th- ho-t co~put-r , ,, , : , . -... . .

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- -lS-gen-rat-~ an approprlat- eo~nd to th- brok-r to lnltlat- a tran-lt$on bacX to th- aetlv- D ehann-l eonn-ctlon ~nd t-~r down th- 8 ch~nn-l eonn-etlon Proa th$- polnt, d~ta co~un$c~t$on $~ c~rrl~d a~ X 25 p~ck-t tra~rlc ov-r th-ISDN access path b~tw~-n th- u~-r t-r~$n~1 and ho~t co~put-r A ~ub--gu-nt B ch4nn-1 eonn!ctlon wlll b-~uee---iv-ly ~t~bl$-h d w$th th- u~-r t-r~$n~1 w$th data co~un$c~tlon b-$ng e~rr$ d th-r-ov-r ~nd th n torn down wlth data co~aun$c~tlon b lng ~b$St~d to th- D ch~nn-l a-co~un$c~tlon n-~d- o~ th- ho-t eo~put-r dyn~u$c~11y chanq~
durlng th- ho-t s-~-$on sR~E~DEscRIprIo~ OF ~InL~LUiLiGY

lS Th- t-achlng- o~ th- pr-- nt lnv-ntlon ~y b-r-~d$1y und-r-tood by Gon ld-rlng th- rollow$ng d-ta$1 d d--er$pt$on $n eon~unetlon vlth th- ~oeo p~nylng dr~w$ng-, ln whlch~
. .
FI¢ 1 d-plct- a block dl~gru o~ ~ p-cl~le e~bod$a nt o~ our ln~ ntl~ y-~ or dyna leally changlng ~n I8DN ~ee--- p~th, that eonn-ct- ~ u--r to ~n I8DN ~iteh and th-r-through to ~ ho-t eouput-r, b tw -n a clrcult - svlteh d eonn~etlon and ~ p~c~ t wlteh-d eonn-etlon during 2S a ho-t ~---ion aeeordlng to th~ ¢onounleation d--~nd- o~ th-ho-t eo~put-r th4t oecur dur~ng th~ lon~
a. ~ hov~ th- prop r allgnJ~nt Or th- drawlng ~h--t- ror r~a-. 2A and 2B~
P~G-. 2A and 2B coll~tlv-ly d-plct a tat-dl~gra- o~ th- ottw4r that 1- i-pl--~nt-d wlthin U -r PC
10 that tor~ p~rt or y-t-~ 5 sh~wn ln P~G 1 and u~ d in con~unctlo~ wlth dyna lcally ~glng ~ olngl- ~8DN acc~--3S patb ~pp aring th r ~nt ': ' ' ' . ' ' . " ,, " ,~. . . .
'" :-""' .

Z005~34 F~G 3 8how- th- prop-r allgn~-nt ot th- drawing ~h~ or FIGJ 3A and 3B~
:
FIGs 3A and 38 coll-ctiv-ly d-pict a stat-diagra~ o~ tho ~o~twar- that 1~ i~pl-~-nt~d wlth~n 8rokor PC
So that rOrDJ part Or ~y-t-n 5 hown in PI~ 1 and u~d in con~unction wlth dyn~lc~lly ~anaging a ~lngl- I8DN acco~-path ~pp-~ring th-r lns PIC ~ d-plct- a co~ unlc~tion -gu n¢- th~t occur- a~ong th- ~a~or ~ nt- o~ ~y-t-~ 5, qp-cl~ic~lly th- U--r PC, th- I8DN ~vltch, th- Bro~ r * and a ho~t , conput-r, ~or ~t~bll~hlng a ho~t ~ lon b-tw--n t~- ho~t co~put-r ~nd th- U--r PC~

PIC 5 d-plct- a co~nunic~tion ~-qu-nc- that occur~ u~ong th- ~a~or l-n nt- o~ ~y~t-n 5 ~or ~oving a ho-t ~---lon rrO~ a B chann l clrcuit wltch d conn-ction to a D ch~nn l pack t wltch-d conn-ctlonJ

P~C 6 d-plct- a co- unlcatlon ~-qu-nc- that occur~ a ong th ra~or I-nont- ot ~y~t-~ 5 ~or ~ovlng a ho~t ~ lon rrO~ a D chann-l pac~ t wltch d conn ctlon to ~ B chann l clrcult awltch d conn ctiont P~a. 7 d plct~ a coa unlcatlon -~u-nc- th~t occur~ ~rong th 4~or o nt~ o~ yat-~ 5 ~or invoklng a ~ lo~ lnltl~t-d di-conn ct ln or~ r to t-r~ln~t- ~ ho~t ~ lon~

~ra. 8 d-plct- ~ q n r ll~ d Qnbodln~nt (sultl-broX~r ~rchlt ctur ) o~ our lnv ntlv y t-~ ln wblch ~ plur~llty q~, g. two, brokon~ ~r lnt-r-conn-¢t d 3S through ~n ~DN to c~ry ~ lon th r-b-t~ -n and wh-r~

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;~00~734 eith-r brok-r can dyn~lcally chanq- an ~SDN a¢c ~ path that conn-ct~ th- co~unicatlng brok-r- b-tw n a clrcult ~wltch-d conn-ctlon ~nd a pack t wltch~d conn-¢tlon accord~ng to th- co~unlc~tlon d-n~ndJ that occur durlng th 5 ~os-ion~ and FIG 9 ~how- th- prop r allqn~-nt oS th- dra~lng sh--t- ~or FIG- 9A ~nd 9Bt lo F~G- 9A ~nd 9B coll-ctl~ ly d-plct ~ t~t-; dlagr~ o~ th- ~o~twar- that 1- l-pl-s nt-d wlthln any brok-r that ~or~ ~ultl-brok r y-t-~ 800 hown $n PI¢. 8 and u--d ln con~unct$on wlt~ dyna ically hnag$ng a ~$ngl-I~DN a¢c--- path ~pp ~ring th-r-~n.
1~
~ o racllltat- und-r-tandlng, ld ntlc l r r~r nc nu~ ral- ha~ b n u- d, wh r po--lbl-, to d not- $d nt$cal l-~ nt- that ar- coa on to ~ar$ou- rlgur--.
~

A~t-r r -dlng th ~ollovlng d-tall d d--crlptlon, tho-- ~Xlll-~ ln th- art vlll cl-arly r 11~- th t th - t-~chlng o~ th- pr - nt $nv ntlon c~n b- r-adlly appll~d to 2S ~nd lncorpor t-d ~lthln ub-t n~$ally ~ny tr~n~nl-~lon n twork th t can eonn et a ho-t eonput r to ~ u r through two or r -~rat eo- unlc tlon eonn ¢tlon- tb~t h~v dl~ rlng ~ttrlbut- , ueh ~ lllu tr-tlv ly tbroughput, tr n port d l~y or co-t Or u -. Por xa pl-, on- ueh conn etlon ~y b optl iz d to e rry hlgb d n~lty low-d-l~y tr~rrle~ ~hll- th~ otb r eonn tlon ~y b o~tl~ d to e~rry r latlv ly low d n lty tr~rr~ that 1- r lat~v-ly d-l-y in -n ltlv-. A~ ueh, th n tvork eould b a prlvst-n-tworX vlt~ ~ 21 ~eXbon ln wblcb ~ portlon or th-3S ~v~ bl- n tvork b~n~vldth 1- ~lloGat d to n X ~5 typ --,. ..
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' ' ' : ' ' ' ' pack-t n~tworX wlth th- r-~lnd~r ot th- b~ndwldth ~llocat-d to tra~lc th~t 18 to b- rout-d through a r-latlv ly ta~t swltchlng d-vic-, such a- an l-ctronlc clrcult ~witch Alt~rn~tiv-ly, th~ n-twork could b- a bro~dband ~SDN n-twork in whlch a continuou~ dlgltlz d vld-o lgn~l could b-rout-d through a clrcult wltch d conn-ctlon -tabll-h-d ov-r ~ny on- ot ~-v-r~l broadband chann-l-) volc- ~nd oth-r d-lay -n-ltlv- tr~t~lc could b- rout d ov r clrcult Qwltch-d conn-~tlon- ~-tabll h d through any on- o~ ~ nu~b r o~ r latl~ ly narrowband c~nn-l-, ~nd oth-r tr~tlc could b- rout-d on ~ pacX-t ba~l~ through p~ck-t wltch d conn-ctlon~ otabll h d through chann 1~ d--lgn-~ to b-lnt-rt~c-d to r-op-ctlv- local and/or ~ tropollt~n ~r ~
n-tworX~ Non-th-l--o, tor purpo--- or lllu-tr~tlon and to ~5 ol~pllty th- tollowlng dl~cu olon, th l~v ntlon wlll b-dl-cuo--d ln th- cont-xt Or u-- vlth narrowband ~sDN ~B~ and ~D~ ch~nn-l-, 1 - ba-la ~8DN a -~ lln-- that ach h4- two 6~ kblto/--cond ~B~ ch nn-l- Ithat ~ch provld-o lth-r clrcult owltch-d or p~ck t wltch d conn-ctlon~) ~nd on- 16 Xblto/o-cond ~D~ chann l (that only provld-~ p~ck t wltch d conn-ctlon-) Wlth thl~ ln nlnd, PIC 1 d plct~ a block dl~gra~
ot th hardwar- that lspl---nt- inv ntlv sy~t-~ 5 tor dyn~ lcally ~h~nglng n ~8DN w c--- path, that conn-ct~ a u~-r t-r lnal to an I8DN wltch and th-r-through to a ho-t cooput r, b tv n a clrcult wltch~d conn-ctlon and a pacX-t owltch d conn~ctlon durlng ~ ho-t ~ lon ~ccordlng to th co~ unlcatlon d n~nd~ o~ th ho-t co~put-r that occur durlng th - ~lon. In thl~ r ga~d, hlghly lnt-r~ctlv-d-lay-~-n~ltl~ ho-t ta k~ th4t dl~blo a p~ck t 4 --nbly/dl~ bly (~PAD~) ~unctlon in th- loc~l t-rDin~l ~r carri-d ov r a circult witch-d TSDN conn-ction, whll- a pacX-t ~wltcp d TSDN conn ction i- w d to c~rry trar~$c rOr oth-r ~o-t t~-X

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' X00~734 --lg--A~ shOWn, 8y8t~ S ~tabllsh-~ ~n I8DN conn-ction b~tw--n us-r ~lt- 20 and ho~t slt~ 80 ~or carrylng a ho~t s~lon th-r~b-tw -n on lth-r a B chann-l clrcuit ~wltch d S and/or D channol pacX-t swltch-d ba~l~ Th- I8D~ B chann-l pack~t capablllty i~ not us-d by our inv-ntiv- ~y~tQ~ ~nd, a- ~uch, will not b- dl-cu~- d h-r-lna~t-r U~-r t-ruinal lo i~ ~ituat-d at u~-r ~it- 20 ~nd con~i~t~ o~ p-r~onal co~put-r ~2, 8UC~ ~- illu-trativ-ly an ~IaM~ ~od-l PC or ~PC/XT~ p-r-on~l co~put-r (PC) ~IB~ i~ a r-gi~t-r d trad-~ark o~ th- Int-rnational Bu ln-~- Machln-- Corporatlon o~ Ar~onk, ~-w York whlch al~o own~ tho trad~ark PC/XT~ or th- llk , and in-~lot t-r~lnal adapt-r 1~ ~hlch 1~ ~ount d withln th- PC Th~ t-r~lnal adapt-r 1- illu-trativ-ly an lS "ISDN ~nt qrat d T-rulnal Adapt-r~ nu b r T-l-o~ B~OOPC
aurr ntly ~anu~actur-d by T-l-o- Conounlcatlon~ Corporatlon locat d ln Patontown, N w J-r~-y wlth lt- acco panylng control ~o~twar- a1JO avallabl- ~ro~ ~ o~ Con unicatlon~
Corporatlon~ ~nd x-cutlng withln th- PC Th u~-r t-r~ln~l lnclud-a ~ u~-r k-yboard and a u~-r dl~play ~cr--n Thi~
t-r~lnal could includ- oth-r p-riph-ral d-vlc-~ (w ll known and not ~hown), uch a~, ~or xa pl-, rloppy and/or hard dl-~ drlv -, ~ cann-r and/or a prlnt-r, whlch can b u~d ~or purpo~-- o~ u~-r lnput and output To i~pll~y th-~ollo~lng di-cu-~ion, u--r lnput wlll orlglnat- ~ro~ th-k-yboard and u~-~ output wlll b- writt-n to th ~l~play ~cr n Por th aX- o~ con~ ni nc-, th- ntir- u~-r t-rain~l w111 b h r ina~t-r r-~-rr d to a- th- U--r PC
Tho t-rnlnal adapt-r coupl-- th- U-ar PC to a phy~lcal I8DN
2~ D~ conn ctlon app aring on lln ~5 and ~upport~
~ott~ar that x-cut-- ln th U -r PC t~t i~ultan-ou ly u~ D~ ch-nn l p~cX-t ~wltchlng ~nd ~B~ chann-l circult ~wltchlng conn otion- In additlon, th t-r lnal adapt-r al-o provid-! t~- PAD ~unction a~ d-~ln-d ~y CCITT
R cona-ndatlon X 3 ~or d-tail~d $nrorn~tlon r~gardlng thlJ

.

;~OO~j 734 tunctlon, ~h- r-~d~r 1~ r-torr-d to ~P~ck-t As~ombly/D~ bly Paclllty ~PAD) ln a Publlc D~t~
Network~, CCI~r R~C~UUU-L;Lll XL~ 198~, CCIIr docuDent AP VI~I~5?-~, pag-- 22-~ Th- U~-r PC 1~ conn ct~d, vla line 15, to n-twork t-r~ln~t$on 18 ~ltuat-d at th- us-r sit- Th- n~twork t-r~ln~tlon, typlc~lly a uodol ~ISDN/NT~
n~twork ter~ination ~nutactured by Sl-~-nJ Corporation, t-r~$n~t-~ th- I8DN acc--~ lln-j whlch ~y b- i~pl-~ont~d ov-r ~ ~ultlpl-x d dlgit~l loop c~rri-r (D~C) llnk, runnlng o ~ron ISDN ~wltch 3S loc~t d ~t lSDN c-ntr~l ortlc- 30 to th-u~-r ~lt- D p-ndlng upon th- n--d- ot th- u~-r, th-n-twork t-r~ln~tlon c~n u-r-ly provld- ~ two or ~our wlr-loop ~roa ~ D~C llnk or c~n b- pr$v~t- b~nch xch~ng-(PBX) whlch provld-- loc~l ~ultlpl-xlng, ~wltchlng, protocol handling ~nd conc-ntr~tlon ~unc~lon- So l~pllry th-dl~cu--lon, ~11 th- n-twork S-rnln~tion~ vill b ~--un d to r ly coupl- ~ b~-lc I8DN ~cc--- lin-, 1 -. 2~B~D~
link, o~ r ~ DLC link tro~ th I8DN witch lnto ~ two w$r loop, g lln- 15, tor conn ction to ~-oci~t-d t-rnin~l ad~pt-r~ ISDN w itch 35 i~ lllu-tr~tiv-ly ~ od-l EW8D/PH
ISDN witch curr ntly ~ nut~ctur d by ~ n~ Corpor~tlon ~nd i- itu~t-d ~t ~ c-ntr~l ottic- op rat d by ~ loc~
t-l-phon conp ny Con unic tion 1- c~rrl~d ov-r th- D
ch~nn l on ~n nd-to--nd b~ u~lng th- CCl~T X 25 protocol ~h-r-ln~t-r r-t-rr~ to ~ th X 25 protocol), whll-co~uunic~tion 1- c~rrl d ov r th ~ ch nn-l on n nd-to--nd b~ uJlng th- CCITT V 120 linX lay r protocol ~hor lna~t-r r-t-rr d to ~ th- Y 120 protocol) tor r-li bl- dat~
c~rrl~g . ~or d-t~ll d intor-~tlon r g~rdln~ th V 120 pro~ol, -- cc~ R~9~ t~ V. 12Q, IXth Pl-n~ry a~--obly~ ~ lbourn , lssa, p~g-J 111-1~5. Although a ~lngl~
~DN wltch 1- hown ~t on c ntr~l o~tl~ , thl~ wltch would ln ~ctu~llty llX ly ~- r plac d by ~n ~SDN n-twork th~t cont~ uultlpl- ISDN wltch-J int-r-conn ct d by 3S approprl~t nd-to--d~ trun~port ~nd toll wlt¢hlng . , . . .. : , , .: ~ , , ' ' , ' , .:, , .

. .
.
' ' ,,' ' , ' ~acilltl-~ ~on~th~ or lapli~lcation, th- dr~wlng and tho n~uing dlgcu~slon will di~cus~ th- I8DN n-twork in th- cont-xt o~ cont~lning ~witch 35 ltuat-d at c-ntral r~$c- 30 S
Switch 3S al~o provld-~ ~ ba~lc 2~B~+~D~ T8DN
conn-ctlon, vl~ acc-~ lln- 3S, to ho~t ~lt- 80 Wlthln th-ho~t $t-, inco~ing co~uunlc~tlon ~ro~ th u~-r t-r~in~l to ho~t sy-t-~ 70 1- c~rrl d rro~ acc--- lln- 35 -qu-ntl~lly through n-twork t-r~lnatlon 40 and PC 50 through local ar~
n-twork (L~N) 60 onward to th- ho-t y-t-a and ln th-r~v-r-- diroction ~or outgolng tra~io ~ro~ th- ho-t y-t--to th- U--r PC ~o-t sy-t-~ 70 lllu-trati~ ly contain~
ind-p-nd-nt hoat co~put-r- 701 and 72~ aoh o~ which i~
lS illu-tratiY ly a ~DEC~ ~VAX~ oo~put-r curr~ntly ~anuractur-d by th- Dlgltal Equlpuont ~orporation o~
Haynard, Ma--aohu--tt- (w~loh al-o own~ th- trad-narka D~C
and ~VAX) x-cutlng th- ~UNIX~ op ratlng ~y t-a (UNIX 1- a r g$~t-r d trad- ark o~ A~-rloan ~ l-phon- and ~ l graph Or N w York, N-w York) A u~-r o~n conduct a hoat -J-lon wlth lth-r ho-t co~put-r, d-p nding upon wh-r- ~ d--ir-d ho-t applioation progr~n r-~ld-~ Ina- uch a~ th- ~ollowing di-cu--ion appli-- gually to both hoot conput-r-, th n, to 8i pli~y thl~ dl~cu-~ion, th d-alr-d bo-t applicatlon will 2S b ~-aun d to r ~ld- ln ho~t co~put-r 701 wlth whlch, unl--~oth-rwi~- p cl~icolly not d b low, th- u--r will conduct a ho-t ~ lon.

P~ SO, h r-lnart-r r ~-rr d to ~ th- ~roX-r PC~, ~unctlon~ a~ ~ coo unlcatlon~ proc-~or ~o provid- an ISDN
int r~c- to th- ho-t y-t-o 70 and al~o to in~truct ISDN
~wltch 3S to dyn~ lc~lly c~ang t~ ISDN conn-ctlon provid d durlng ~ ho-t -~lon ov both ~cc-~ p~th~ 2S ~nd 3S
b tw n ~ B ch~nn-l clrcult ~wltch-d conn-ctlon ~nd a D
3S ch~nn l p~c~ t ~witc~ d conn ctlon ~ccording to th X00~7~

co~unlc~tion d~and- 9~ th- ta-X pr---ntly x cuting on host comput-r 701 a- p~rt o~ a curr nt ho-t ~ ion Th ~roX-r PC 1~ lllu-tr~tlv ly an IBM ~od-l ~PC/A~ p r~onal computer curr-ntly aanur~ctur d by th- IBM Corporatlon (whlch aiso own~ th- r gi-t-r d trad-aark PC/A2) or th-llk- A~ dl~cu~ d ln d-tall ~ low, th- ho-t co~put-r sultably ln~truct~ th- BroX r PC to chang th- co~unlc~tlon chann-l during an on-golng ho~t~ lon rrO~ clrcult awltch-d to pacX-t ~wltch~d a- th- con~unlcatlon n--d~ Or lo t~- ho-t co~put-r that occur durlng th- ho~t ---lon chang Thl- ch~ng occur~ ln a ra hion th~t do-- not dl~rupt th-ho~t ~ lon ~nd 1~ ub-t~ntlally, lr not totally, tran-par nt to th u~-r By dyna ically ~l-ctlng th-~p clrlc I9DN conn ctlon avallabl- ov-r ~8DN acc-~ p th- 25 ~nd 35 to ~t¢h th- bandwldth r qulr ~ nt~ Or th- curr nt ta~k b lng x cut d on th ho-t ¢o~put-r, th rricl-ncy 0~
th- ~8~N n-twork advant~g ou ly incr a--- a- do-~ th-ablllty oS th- loc~l t-l-phon co pany to provld- S8DN
-rvlc-~ urrlcl-nt to n -t th xp ct d d- ~nd Or ~11 lt~
~9DN u~-r-9p ciSl¢ally, at th- ho-t ~it , n-twork t-r~lnatlon 40 coupl b ~lo 18DN 2~+~D~ ~cc-~ lln- 3~ to th- Brok r PC vi~ lln 45. Ih~ Bro~ r PC 1- lt~ coupl~d to ho~t y t-o 70 through w ll-kno~n IAN lnt rrac- 55 ~hich, ln turn, iJ conn ct d to lo~ r a n-twork 60, ~hl¢h 1 lllu tratl~ ly an ~th rn t LAN th~t w - ICP~P protocol ~tranJol--lon control pro~oçnl/lnt-rn t protocol) Yor d-tall-d ln~or--tlon r gardln~ th TCP/SP protocol, - D~
~ , D ~ n~ Coa unlc tlon Ag ncy, D c- b r 19~5, pag ~ 2-99 to 2-1~9 ~or tb- ~P protocol and p go- 2-179 to 2-269 ~or th TCP protocol Tb- ~N lnt-r~ac- 1~ lllu tratl~ ly ~n ln--lot ~od~l ~XOB 205T ~nt-lllg nt ~th rn-t Con~roll-r 3S curr ntly ~nu~actur~d by EXC~L~N ~ncorporat d o~ San ~o~-, ... . . .
... .
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' ' , ' ''. '' ;.; ' ' ;;''''- : .

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;~00~ 34 Call~orn~a and whlch utlllz--, aJ co~unlcatlon ~ottwar ex-cutlng wlthln th- Brok r ~C, ~Th- ~AN WorXplac- ~or PC
Do8 80cX~t Llbrary~ progr~ that 1- curr-ntly ~llabl- ~ro~
EXC~AN Incorporat-d LAN lnt-rtac~ 5S and ho~t coJput-r~
701 ~nd 72 ach po~ dl~t-r-nt n-tworX addr ~ on LAN
Co Th- ~AN carrl-~ Eth-rn-t ~AN pack t~ Th-~- pacXot contaln $th-r pacX-t trartlc ~-~oclat d wlth th- ~D~
ch~nn-l th~t torac p~rt Or ba~lc S8DN acc-c~ lln- 35 or clrcult ~wltch-d tratrlc a~oclat~d wlth a corr-~pondlng on-ot th- ~B~ ch~nn-l- th~t ~l-o tor~ part ot thl~ ba~lc ~SDN
~cc-~ lln- Tb- ~rok-r PC contaln~ ln--lot t-r~ln~l adapt-r 53 whlch 1- ~ub~tantlally ld ntlc~l to t-r~in~l adapt-r 14 Aiapt-r 53 coupl-~ th- Brok-r~PC to a phy~lc~l two wlr- ISDN 2~B~+~D~ conn-ctlon ~pp-~rlng on lln- 45, upport~ ~ottwar- that x-cut-- ln thl- PC tor ~$~ultan-ou-ly u-lng ~D~ chann-l p~c~ t wltchlng ~nd ~B~
chann-l clrcult ~wltching conn-ctlon- and al~o lncorporat--th PAD tunctlon d-tln-d by th- CCS~T X 3 ~nd X 29 R co D nd~tlon- wlthln th- BroX-r PC.
Th- dl-cu--lon wlll nov addr-~- th- ~ottwar that 1- u~ d wlthln lnv-ntlv- y~t-~ 5. Thl- ~ottwar- con~l~t~
ot thr - ~ ctlon s that whlch x cut-- wlthin U~-r PC ~0, that whlch x cut-- wlthln BroX~r PC 50 and la~tly that whlch x cut-- wlthln th- ho-t conput-r Th- ottwar ln x-cut$ng in th U -r and Brok r PC 1- o~ nt asld g n rally lnt rrupt drl~ n and trlgg r d prinarlly through r-gu ~t-orlgln tlng wlth th ho~t conput-r to chang th- I~D~ -co- unlcatlon path Wlth thl- ln nlnd, th- ~ottwar x cuting ln th- U~-r PC and th Brokor PC wlll b- pr-~-nt-d ln t-r Or ~tat- dlagran~ rath r than ~lowchart- ln~uch a- th-~- dlagra d-plct th- v nt drlv n op ratlon o~ th~
~ottwar ~or ¢l- rly and r xpllcltly than do tlowchart- Th ~ottwar x~cutlng ln th- ho~t conput-r 1~
not d-plct d du- to ~t ~ pllclty but wlll b- xplaln d ln " ,; ~ ,, ,, .. , . , . :
,, ", - ,, ",, , ..,; . ,., ..", ., ~r ' ' ;~00S;734 , , n-e~ ry d-tall b-low Glv-n th- v~rlouJ ~t~t-~ ~n4 th-~v-nt~ th~t trlgg-r a tr~nJltlon b-tw -n th~ tat-J, a-~hown and dl~eu---d ln d-tall ~-low, ~nyon- klll d ln th art c~n r~dlly eo~po~- ap~roprl~t- co~put-r progr~ that implement thl~ so~tw~r-. .
Syst-~ 5 e~n aeeo~od~t- a ~ultltud- o~ u--r~ to dyna~leally ch~ng- th- I8DN eh~nn-l (b tw--n elreult and p~ck t ~witch-d) u--d by ~eh u--r in ~ccordanc- wlth co~unlcatlon r-qulr-~-nt- o~ aeh corr-~pondlng ho-t ~-J~lon th-r by dyn~lc~lly ~atchlng th- avall~blo eo~unlcatlon bandwldth to th- ho-t t~-k pr-- ntly b-lng x-cut-d ~or that u--r To ~eeo~od~t- ~or th~n on- u--r, th- U~-r PC ~nd th- ~roX-r PC ~eh ~lloc~t a ~-t o~
lS ~-p~r~t- t~t-~ to aeh dl~-r-nt I5DN acc-~- p~th that xlJt~ ~or aoh u--r eo~ounl¢atlng th-r-through and ~or aeh dl~t-r nt ho-t ---lon ln th- v nt ~ny u--r h~ -t~bll-h-d nor th~n on ho-t ---lon lnvolvlng on or ~or- ho~t eo put-r~ Typle~lly, ~ U -r PC wlll ~upport only on- u~-r at ~ tl~ ~ whll- ~ Brok r PC wlll upport up to lllu tr~tl~ ly lgbt l ult~n-ou~ ho-t ~ lon~
cor~un$e~tlng through lght dl~-r-nt I8DN ~ee--- p~th~ to lght eorr -pondlng U--r PC Th- tat-- alloeat-d by th-U~-r PC and lnvolvlng an I8DN ~cc--- path ar hown ln FIG~
2A and 2Bs whll- tho-- tat - allocat d by th- Brok r PC ~or th- u I8DN ACC ~- path ~r ~hown ln PIG- 3A and 3B
In~ uch ~- y-t-a ~ op rat-- ln an ld ntlcal ~hlon ~or ~c~ dl~ ~ nt 18DN a ~- ~ath -tabll~h d b tw -n lth-r a dl~ r nt u~ r and~or ~ dl~-r nt ho-t ~-~-lon an~ ~ ho-t co put r, th-n, to l-pll~y th dr~wlng~ ~nd th- ~ollowlng dl~cu -lon, acb u~-r wlll b a~-u-~d to hav -t bll-h-d only on- ho~t ~-J~lon ~nd th drawlnq- an~ n u~ng dl-cu~lon wlll c nt-r on th- ~n~g-~ nt o~ on I~DN acc--~p~th xl-t~ng b tv n th- U~-r PC ~nd th- ho~t c~put-r ' ' , , ',' : , , ,,, ,,,, , . , ,,,, , i "
, , ;~OOS7~4 AJ such, a tat- dlagra~ o~ th- o~twar that l-i~ple~-nt-d wlthln U~-r PC 10 and u~-d ln con~unctlon wlth dyna~lcally managlng a ~lngl- I8DN acc-~- path ap~ arlng in syst~ 5 i~ coll~ctlv ly d-pict-d ln PIG~ 2A and 2B~ th-proper aiign~-nt o~ th- dr~wlng h-et~ tor th~-a ~lgur~
~hown ln FIG 2 Sp-cl~$cally, 1~ ~n I8DN call ha- not b--n ~ad-~ro~ th- U--r PC to th- ho-t co~put-r, th n th U--r PC
r--ld-- ln t-r lnal ldl- tat- 210 In thl- tat-, th U~-r PC r-saln~ ln an ldl- condltlon wlth a w ll known t-r~lnal ~ulatlon progra x-cutlng and walting rOr input rron a u--r onc- a u~-r b gin- nt-rlng lnror~aèlon lnto th-t-r~inal ln an att-~pt to inltlat- an ~DN call to a r- ot-ho-t, th n th- vJ-r PC att-upt~ to tran ltlon to ~ n~w tat-d-p ndlng upon wh-th-r th- call wa- ucc---tully plac-d In partlcular, lna-nuch a~ th- c ll 1- to b- rlr-t -tabll-h d ov-r a D ch~nn-l p~ck t vltch d conn ctlon, th- U--r PC
through th t-r~lnal -ulatlon progran -nd~ an X 2S C~ll R-qu -t pack-t vhlch p cltl-~ th- Brok r PC a~ lt~
d--tlnatlo~ through th I8DN vltch. In th- v nt th- I8DN
wltch cannot rout- th ~8DN D chann l call ~ron tho U -r PC
onward to th ~rok r PC, uch a~ ~or xu pl- 1~ a ~alluro occur~ ln th vltch, th~n th- vltch nd~ an X.2t Clo~r pack t back to th U r PC. ~n r -pon~- to th- r c-ipt o~
thl- pack~t, t~o U -r PC ~bort th- call and th n lt~ ~t~t- -tran ltlon~ back to t-r in l ldl- ~tat- 210, ~- lndlcat d by lln 213. Alt-rn~tlv ly, in th v nt th w itcb ucc-~tully tabll h ~ a D chann l conn-ctlon ~roa th-V--r PC to th Bro~or PC, 1 - by allo~atlng a ult~bl-vlrtu~l X.~5 conn ctlon th-r b tw n, thon th I8DN ~wltch wlll tr nJ lt an X 25 call Conn ct pack t back to th~ U -r PC ln ll-u o~ an X 2~ Cl- pack t ~n ro-yon-- to t~-r-c lpt o~ th- X 25 Call Conn ¢* pack t, th- ~tat o~ th-U~-r PC tr~nJltlona lnto th- D Cb~nn-l ~t-~dy 8t~t tat-, ;~OO~j~3~
. .

220 Whll- ln thl- tat~, th- U--r PC 1~ abl- to r-c lv - lnput data ~ro~ th- us-r k-yboard that ~or part o~ th U~-r PC, proc~-- th$- dat~ accordlng to th- X 3 and X 29 P~D
R~com~ ndatlon- and th-n tran- it thl- data ~- X 25 pack-t-through th- ~SDN ~witch ov r th- n-wly -tabll~h-d D chann l conn-ctlon to th- Brok-r PC In th- v nt any X 25 pack t~
ar- r-c-lv-d at th- U -r PC ~ro~ th- ~SDN vltch whll- th-U--r PC r~ain~ ln tat- 220, th-n th- U -r PC ~111 dl~play any X 2S data pr-~ nt in th-~- pack-t- onto th- u~-r Jcr-~n lo that ~or part o~ th- U -r PC and app~oprlat-ly proc--~ any PAD co~and- that ar- pr-~-nt ln th--- pack-t~ accordlng to th- X 3 and X 29 PAD R co -ndatlon Now, w~$1- th- U~-r PC r -id-- ln tat- 220, th U~-r PC c~n r-c-lv- a ~ ag , p cl~lcally a ~Call 8-tup~
~-~-ag- ln th- CCITT Q 931 protocol (h-r-lna~t-r r ~-rr~ to a- th- Q 931 protocol), ov-r th D ch nn l ~ron th- I8DN
~wltch All Q 931 ~-~aq-- ar carrl d a- ~ultabl- pacX t-ov-r th- D chann-l ¢onn-ctlon ~or d-tall-d ln~or atlon r gardlng th Q 931 protocol, ~ - ~Dlgltal Acc--- 81gnalllng 8y-t-o~, CCS ~ , VSSSth Pl-nary A ~ Qbly, Malaga-Torr Jollno-, 8-19 Ootob-r 1984, pag -57-193 ~h Q.931 protocol p ol~ th proc-dur - ~or -tabll~hlng, ~alntalnlng and cl-arlng o~ n tworX
conn ctlon- at n I8DN w r-n twork lnt ~ac- In any vont, r ¢-lpt o~ th Q 931 8-tup ~ --ag , lS lt orlglnat-a wlth th Brok r PC, lndlcat-- that th ~ro~ r PC und th-r~tbroNgh tho S8DN ~wltc~ ha~ b~on lnJtruct~d by t~
ho-t co put-r to chang th I8DN conn ctlon b t~--n th U--r PC and th Brok r PC rron D ch nn-l pack t ~wltch-d ~o B
ch nnol clrcult ~wltch d and th~t th U -r PC hould approprlat-ly Jvltch lt- I~DN conn ctlon to th- wltch Sp clrlcally, onc- th- Q 93~ Call ~-tup n---ag ha~ k--n r-c-l~ d by ~h U -r PC, th U ~r PC vlll ~-ri~y wh-th-r thl- n---ag orlglnar d wlth th Brok r PC, 1 -. ~rok-r PC

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. : ,: . , ,, . : , ,, : , ', ' :,' ~ , , ,, , . ' , , '", '' :' ' " ,' :, , , ~005~
--2'7--- 50 shown ln PIC. 1, by xa~lnlng th- cont-nt~ ot ~ Calllnq Party rdentlrlcatlon Sl-ld that Sors~ p~rt o~ thl~ g Ir thl~ sag- did not orlgln~t- wlth th- Brok-r Pc, th n, as ~hown by lln- 223 ln PIC- 2A ~nd 2B, an rror condltlon s has occurr-d ina~uch a~ th- U--r PC h~ r-c-lv-d a Q 931 m---ag- Sro~ a 8rok-r PC that 1- not pr ~-ntly a~oclat~d wlth th- u--r PC A~ uch, th- U~ r PC wlll tran~lt a Q 931 Call DlJconn-ct ~---~g- ov r th- D ch~nn-l to th- rSDN
~wltch to ln-truct th- wltch to t-ar down th- B Chann-l lo clrcult wltch-d conn-ctlon that lt h~- ~u~t rron-ou~ly e-tabll~h d to th- U~-r PC Onc- thl~ Dl~conn ct ~ ag- 1 tr~n-~ltt-d, t~- ~tat- Or th U~-r PC tran~ltlon- b~cX lnto D Ch~nn-l St-~dy St~t- ~ lndlc~t~d by lin~ 223 rr, hov v r, th- orlglnator Or th- Q 931 Call s-tup ~ -ag- w~-th- prop-r 8rok-r Pc, 1 - BroX r PC 50 hown ln ~rc 1, th n, a- hown ln PIC~ 2A ~nd 2B, th U--r PC wlll tran~ltlon ~long lln ~27 to B Chann-l ~t~bll~h~ nt t~t-230 to ~ult~bly chang lt~ I~DN conn-ctlo~ to th- vltch ~ Ch~nn-l ~- W bll~hn nt ~tat- 230 1~ a tran~ltory stat- Th- U--r Pc wlll xl~t vlthln thl- ~tat- rOr a v-ry hort p rlod oS tlD Whll- ln thl~ ~tat-, th- U--r Pc vlll not tran~nlt ~ny data n ~ag ~ to th- ~8DN ~ltch How v-r, tho U~-r PC wlll ~cc-pt ~ny k yboard lnput Sror th- u~-r and locally buSr-r thl~ dat~ Sor ub-oqu nt tr~n- l--lon IS
- any X 25 p-ck-t- ~r r c lY d Sro~ th I8DN JWltch ov r th-D ch~nn-l conn ctlon th-r to, th n th- U -r PC w111 loc~lly dl pl~y ~b- data Gontaln d wlthln th -- Fack~t- and wlll ~pproprl~t ly proc-~ any PAD co~n~nd- cont~ln-d wlthln th ~- pacXat- accordlng to th- X 3 and X 29 PAD
R-cclouund tlon~ Al~o, ln th v nt ~ny B ch~nn-l d~t~ 1-r-c-lv d, th- U~-r PC wlll approprlat-ly butt r ~hl- d~ta tor ~ub~-~u nt dl~play Nov, ba-od upon wh-th-r a ucc-~tul B-ehann-l conn-ctlon can ~ ~tabll-h~d b tw -n tho U ~r PC ~nd th- ~8DN wlt~h, th- U -r PC wlll tran ltlon ,~

~00~'~3~

to on- o~ thr-- ~tat--s D Chann-l 8t-ady 8tat- 220, ~or~lnal Idl- stat- 210 or B Chann-l St-ady Stat- 2~0 .
In particular, ln th- v-nt that, whll- th- U~-r PC re-ide- in tat- 230, th- ~wltch n xt -nd- a Q 931 Call Dl~conn-ct ~-ssag- to th- U--r PC ov-r th- D chann-l instructlng th- U~-r PC to t-ar down th- B chann-l conn-¢tlon to th- wltch, th n th- tat- o~ th- U~-r PC
tran-ltlon- along lln- 23~ back to D Chann-l 8t-ady 8tat-220 Th- U--r PC wlll al-o r-turn to tat- 220 ln th- Qv-nt it ~-ndJ a Q 931 Conn-ct ~ ag- ov-r th- D chann-l rollow~d by a ~ailur- ot th- V 120 protocol that 1- u~ d ~or B
chann-l co~un$catlon to prop-rly lnltlallt- Sp-cl~lcally, a Q 931 Conn-¢t ~---ag- wlll b- nt by th r-clpl-nt Or a Q 931 Ca11 8-tup ~---ag-, h r th- U -r PC, in r--pon-- to thl- Call s-tup ~---ag 1~ th- r-clpl nt ucc---~ully -tabll-h-~ a B chann-l conn-ctlon to th- -nd-r Or th Call 8-tup n --ag-, h-r th ~8DN vltch Th r ~or-, 1~ th- U -r PC ucc---rully -t~bll-h-~ a B Ch~nn-l conn-ctlon to th I~DN ~wltch ln r-~pon-- to th Q 931 CA11 8-tup u---ag- lt r c-l~d ~ron th wltch, th n th Ua-r PC wlll tran~lt a Q 931 Conn-ct back to th vlto~. Onc- thl~ occur-, th-U~-r PC wlll th n lnvok th- V 120 protoool to handl-ub--qu nt B chann-l con~unlcatlon. 1~ thl- protocol rall-2~ to prop-rly lnltlallz~ b tv n both th U -r PC and th-BroX-r PC, th-n t r~lnal adapt-r 1~, a~ hown ln r~G 1, wlll approprlat-ly lqnal th U~-~ PC. IN r~pon~-, th- -U~-r PC, a- ahonn ln ~5G~ 2A and 2B, wlll nd a Q 931 Dl~conn ct n a~aq b ck to th l~DN ~wltch to ln truct th-wltch to t- r down thl~ B ch nn-l conn-ctlon Th-r~art-r~
th- t-t- ot th U -r PC wlll alao tran~ltlon along lln- 23 back to D Ch nn-l 8t ady 8tat- ~tat- 220. A~ uch, no B
ch4nn-1 wlll b ~t~bll~h d through th- I~DN vltch b tw n th U~-r PC and th Brok-r PC.

", - ,., ~ ':
,:

' .

;~00S~34 Th- U~-r PC, whll- exi-tlng ln B Ch nn-l E~tabllsh~-nt stat- 230, eould ~1JO r-e-lv- ~n X 25 Cl-ar p~eXot tro~ th- ho-t eo~put~r, th-r by lndlcatlng that th- D
chann~l p~cX-t eonn-etlon ~hould b- torn down Thl- could oceur wh-n th- ho-t co~put-r t-r~lnat-~ th- eurr~nt ho~t ~-s-ion wlth th~ u~-r A D eh~nn-l conn~ctlon, whlch m-r~ly involv~ a vlrtu~l X 2S conn-etlon that eon~un-~ n$ni~al ~wlteh and n-twork r-~oure-~ alw~y~ n~int~n d during a ho~t ~ lon, wlth a B eh~nn l eonn-ctlon, whlch eon-u~-- a r-latlv-ly larg-r ~h~r- o~ n-twork r -oure-~, b-lng -t~bll-h d or torn down ~- eo D unlcatlon r-gylr-~ nt~ ot th- ho-t eonput-r ehang durlng th- ~ lon AJ ueh, a~
long ~- a ho-t -~-lon 1~ ln progr--- a D chann-l eonn-etlon wlll xl~ts how v-r, one- ~ ho-t ~---lon 1- t-r ln~t d, th-n th- D ehann-l eonn-etlon wlll b t-ralnat-d ~- w ll ~h-r-ror-, lr th- U -r PC r e-lv-~ an X 25 Cl-ar paek-t whll- lt r--ld-- ln 8 Chann-l ~tabll~hn nt ~tat- 230, th n th- U--r PC wlll r-lln~ul-h th D ehann-l eonn-etlon ~nd tr~n-alt ~ Q 931 Dl-conn ct ~ ~-~j- to th- I8DN wlteh ov-r th- D ehann l ln~tructlng th- wlteh to t-ar do~n th- B
ehann-l Gonn ctlon, 1~ lt pr - ntly xl-t-, to th- U -r PC
Th U~-r PC wlll th-n r-llnqul-h th- B ehann l eonn-ctlon, ~hould lt xl~t, ~nd tr~n~ltlon back to T~r lnal ~dl- ~tat-210, ao lndlc t-d by lln 232.

No~, alt-rnatlv ly, ln th- vont that th- 8 ehann l eonnoctlon haa b- n ucc--~ully o-t~bll~h d b tw -n th- ~ r YC and th- Brok~r PC aa lndlo~t~d ~y th-tr n~ lon o~ a Q 93~ Connoct ~ g- ~y th- U~-r PC
~olloY ~ ~y ucc ~rul lnltlstlon o~ th V 120 protocol ~t tho ~ -r PC, th n th- ~roXor PC vlll tran~-lt a ~-Allng~
a-~g ov r th- X 2S D ch~nn l conn-otlon to th~ U~-r PC
~uch a ~ q 1- ua-d to ~--al~ O~r th- X 25 conn-ctlon ~ron carryl*g ~urth r co~aunlc~tlon wh$1- th~ B ch~nn l 1-3S in ua- Th n-ad ~or uch a ~--aag arl~ A that onc- th-;~005734 - B ch nn~l clrcuit ~wltch-d conn-ction ~ tabl~-h~d b-tw n th- U--r PC and th- Brok-r PC, two parall~ DN conn ct~onJ
~xl-t b-tw -n th--- PC-s ~ B chann-l c$rcult wltch d conn-ct~on ~n~ ~ D ch~nn-l pacX t wltch-d conn-ctlon. AJ
S dl~cu--~d abov , th- B chann-l conn-ctlon ha- a ~uch hort r tran~port l~g ~ocl~t-d wlth lt th~n do-- th- D ch~nn-l conn-ctlon How-v-r, hortly prlor to th- lnc-ptlon o~ th-B chann-l conn-ctlon, an X 25`d~t~ p ck t could b-tran~nltt d ov r th D chann-l conn-ctlon to th- U~-r PC and du- to tr~n-port lag- a--ocl~t-d wlth th I8DN p~ck t n-twork not arrlv- at th- U -r PC untll a~t r th- 9 chann-l conn-ctlon ha- b--n t~bll h d. In uch a ltuatlon, th-U -r PC alght rron-ou-ly lnt-rpr-t or lgn~r- thl~ pacX t o~
dat~ To a--ur- th-t t~- U r PC h~- r-c-lv d th- l~-t X 25 dat~ p~ck-t ov r th- D ch nn-l, th BroX-r PC tran-~lt- a pr--d-rln-d data n----g-, 1 - a o-c ll d ~--allng~
--ag , ~- ~n X ~5 pacX-t ov r th D chann l Thl- ~ allng ~ --ag , wh n r-c-lv-d at th- V -r PC, p cl~l-- that, now - -whll- th- B chann-l conn ctlon Yl-t-, th- V--r PC wlll t-~porarlly r-colv no or- data ov-r th D chann-l A-~uch, thl- ~ --ag- al-o ln-truct- th- V--r PC to r c lv all data ov r th- 8 chann-l and to ub--~u ntly lgnor X 25 data that 1- r c l~ d ov-r th D ch nn-l. Non-th-l-~-, t~- U~-r PC 1- tlll abl- to r-c lv and proc--- X 25 co~-~n~
pacX-t-, uch ac an X.2S Cl ar p cX t, 4nd Q.931 ~ -~ag that app ar ov-r th- D ch nn l. R nc-, wh-n th- U- r PC
r c-lv a -~llng n ~-ag ~roa th Brok r PC, th U--r PC
d-t r in-a th t th-r- 1~ no *urth-r X 25 pacX t data to - di-play to th u--r A~ uch, th U~-r PC wlll th-n rout-any and ~11 bu~-r d B chann l data to th- u--r ~cr -n rOr dl-play. onc- thlc ha- occurr d, th U -r PC wlll tran ition lnto B Ch~nn-l ~t-ady ~tat- tat- 2~0 a-lndlcat d by lln- 236 ' ' ' ' -''' ' ',, .

. .
.
, ;~00~34 Whll- ln B Chann-l St-~dy 8tat- ~tat- 2~0, th-Us-r PC acc-pt- any data whlch th- u--r nt-r- vi~ th- UJ-r keybo~rd, proc~ thl- d~ta accordlng to th- X 3 and X 29 PAD r-co~-nd~tlon- ~nd th-n tr~n--lt- th- r--ultlng ¢lrcuit swltchQd data ov-r th~ B chann-l conn-ctlon through th-switch to th- Brok-r PC Corr--pondlngly, ln th- ~v-nt that th- Us-r PC r~c~lv-- any X 3 and X 29 PAD co~nd- and data and ov~r th- B chann-l clrcult witch~d conn-ctlon, th- U--r PC approprlat-ly proc----- th- paD cos~nd- ~nd s-nd~ th-r--ultlng data to th- u--r cr -n for loc~l dl~pl~y Por purpo--- o~ pllrylng th- actual inpl-n ntatlon o~
lnv-ntlv- sy-t-o 5, w hav- cho--n not to ~llow th- U--r PC
to dl-abl- th- PAD ~unctlon- r ly colncld-nt wlth th-~t~bll~h~-nt Or ~ clrcult witch-d conn-ctlon b tw -n th-U--r ~nd ~rok r PC Sp cl~lcally, to ~i~pllfy th-oftwar-, th- v~rlou- routln - th~t provld- th- PAD
funct~on, fron a oftwar- ~rchlt-ctur~l t~ndpolnt, ln t~-U--r PC x cut- ~t a hlgh r l-v l th n do th- X 25 routln--whlch control th t-r~lnal adapt-r in th~ U--r PC T~ough th- PAD functlon~ provld r latlv ly llttl- b n-~lt wlth a clrcuit ~witch d conn-ctlon owlng to th- Dlnl al tr~nsport lag lnh r nt ln uch a conn ctlon, th-r app ar- to b no di~dvantag- to l-tt~ng th--- ~unctlon- op rat- ln th- U--r PC wi~h th -- conn ctlon~, unl--- th- ho-t p cl~lcally dl~abl th -- ~unctlona. In p rtl¢ular, a~ not d and dl~cu~-~d b lo~ ln d tall, th ho-t con~utor chang-- th-I~DN ~ J- ~ath b tw n D and B ch nn-l conn-otlon-wh nov r tho ho-t co~p~t-r d-t r ln-- th~t loc~l bufr ring at th U -r PC 1- not conp~tibl- vlth th~ co~unicatlon r qulr ~nt- o~ th~ ho-t ~ppllc~tlon curr-ntly x-cutlng wlthln ~h ho-t -~-lon nd ~l~o turn~ O~r thl- buS~rlng ln th- U -r PC vhlch oth-rvl-- would ~ provld-d by th- PAD
Sun¢tlon- In u¢h 4 ltuatlon, th ho-t co~put-r approprl~t ly lnJtruct- th- U~-r P~ to ~pproprla~oly dl~cbl-;~()05~34 th- PAD runctlonalltY wh-n~v-r ~uch a ho-t ~pplicatlon, Juch as a cr--n editor, i~ x-cuting Onc- th- t~t- o~ th- U -r PC tr~n~$tlon~ lnto B
chann-l St-ady Stat- tat- 240, th- U--r PC r-~ain~ ln thl~
~tat~ until it r c-~v-- ith-r ~ Q 931 Dl-conn~ct ~ ~ag- or an X 2S Cl-ar pack-t Sp cl~lc~lly, lt th- U~-r PC r-c-lv a Q 931 Dl~conn-ct ~ ---q-, thl- lndlcat-- that th- uJ-r PC
l~ to t-~r down th- B cbann-l clrcult wltch d conn-ction ~nd wltch to D chann-l pacX-t co~ unlcatlon A uch, th-Us-r PC will th n r-llnqul-h th- B chann-l conn-ctlon, should it xl-t, and tr~n-ltlon back to D Ch~nn-l St~dy gtat- ~tat- 220, a- lndlc t d by lln- 243;`to ub--qu-ntly co~ounlc~t- ov r th- xl-tlng D chann-l conn-ction lS Alt-rnatlv-ly, 1~ tb- U-or PC r-c-lv - an X 25 Cl ar pack t ov-r th- D chann l conn-ctlon, th n, a- di-cu J-d abov , th - UJ-r PC wlll r-llnqul h th- D cb nn-l conn-ctlon and tr n-~lt Q 931 DlJconn ct n --~g to th r~DN wltch ov-r th- D chann-l ln-tructlng th- wltch to t-Ar down tb- B
chann-l conn-ctlon to th- U -r PC. ~h U -r PC wlll tb-n r-llnqui h th- B ch~nn l conn ctlon ~nd tr~n itlon back to T-r~lnal rdl- t~t- 2~0, a- lndlcat~d by lln- 247 to ~walt th lnltl~tlon o~ tb- n xt bo-t ---lon A tat- ~iagra~ o~ th o~tvar i~pl-- nt d wlthin Brok r PC 50 t~at ~or pa~t o~ y-t-a 5 hown ln YIG. 1 and u~ d ln con~unctlon wlth dynu lc lly ~anaqlng th- IQDN
acc -- p~t~ ~ tw -n th- U--r PC and th ~rok r PC i~
- coll-ctl~ ly d ~lct~d ln ~IG- 3A and 3BJ th- prop r ~llgnn nt ot th dr~vlng h--t- ~or th--- rlqur-- 1J shown ln ~IC. 3 Inltlally, 1~ a ho-t -~-lon ha- not b--n -t~bll-h ~ b tw n th- U-~r PC and th ho-t co put r ~-rv d by th- BroX-r PC, ~ r Brok r P~ S0 hc~n ln ~C 1, t~-n '.
, ~005734 th- Brok-r PC r-~aln- ln Port ~dl- tat- 310 ~hown ln FIGJ 3A and 3B In thi- tat-, th- bro~-r ~ r-ly ~t- ~or an int-rrupt to b- g-n-rat-d by lth-r ~AN int-r~ac- 55, sho~n ln FIC 1, slgni~ylng that th- hoJt co put-r ha- ~nt s a ~CP/IP pack~t ov-~ th- L~N to th- Brok-r PC or by t-r~inal adaptor 53 slgnl~ylng that th- U--r PC 1- att-~pting to conn-ct through th- ISDN witeh to th- Brok-r PC In partlcular, upon r-c-ipt o~ an X 25 Call S-tup ~ckot th-Brok-r PC will d-t-r~in- ~h-th-r lt h~- an ISDN port avallabl- to -rv- th- calllng p~rty, h-r- th- U--r PC, and that th- calllng party ha- both a valld CCI5r ~ 164 addr ~
ror clrcult swlteh d trarrle and a valid corro~pondlng CCITT
X 121 ~ddr -- ~or paek t witch d trat~ie ~ It ~uch an ~8DN
port 1- not availabl- or lr lth-r CCS5S addr--- 1- lnvalid, th-n th- BroX-r PC r-turn- an X 25 Cl-ar paek-t to th- ~8DN
~witeh and it- tat- tran-ltlon-, a- hown ln ~lC- 3A and 38, bacX to Port Idl- tat- 310, a- indleat d by lin- 313 Alt-rnativ ly, 1~ a port 1~ avallabl- and th- U -r PC haJ
valld addr-~---, th-r by indlcatlng that th- U~-r PC ha-succ---~ully dlal-d into th- Brok-r PC through th- ISDN
Jwiteh, th- BroX-r PC th n tr~n alt- an X 25 Call Aec~pt pack-t back to th I~DN wlteh to aeknowl dg- that it ha--tabli-h-d ~n X 2S paek t conn-etion to th- witch Th-r~a~t-r, a- ahown by lln 317, th- ~tat- o~ th BroX~r PC
2S tran-ltlon- to U--r 8---lon ~-tabll-hn nt t t- 320 Thi~
~tat- i- l-ply a tran ltory tat during wbleh no op ratlon~ occur. T~ BroXor PC wlll xlt tron thl~ tat-and tran-ltlon lth-r t~c~ to Port Idl- ~tat- 310 or onw~xd to D Ch~nn l 8t-~dy gt t- ~tat- 330 d-p~ndlng upon ~h-th-r th- Brok-r PC c~n ucc---tully -tabll~h a conn ctlon ov-r th I~N to th ho-t conput-r In partl¢ul-r lt th- BroX-r PC 1- not ~bl- to conn ct to th- ho-t covput-r, b c~u--, tor x~npl-, th ho-t co~put-r and/or th- ~UN 1- not op ratlng, th n th- B~oXor PC tr n-nlt- an X 2S data pac~ t cont~lnlng 3S th- n---aq ~Ho-t Un~vall~bl-~ back through tho vltch to ;~00~i734 th- User PC ~or local di-play to th- u~-r ltuat-d th-r~at - onc- thi- p~ck-t i- tr~n~ltt-d, th- BroX r PC th n tr~n~it~ an X 2S Cl-~r pack-t to th~ ISDN ~wltch to lnstruct lt to t-~r ~own th- D ch~nn-l conn-ctlon Ther~a~ter, th~ Brok-r PC r turn- to Port ~dl- tat- 310, a~
indicat-d by lin- 323 Alt-rnativ-ly, i~ a conn-ctlon wa~
succQs~ully e-t~bli~h-d ov-r th LAN b-tw- n th- 8roXer PC
and th- ho-t coaput-r, a- part o~ which th- brok-r ha~
e~t~bliJh-d ~ corr -pond-nc- b-tw -n ~n ~v~ bl- port addr-s- on ~N 60 ~nd th- ho-t corpu~-r, th n, a- indicat~d by lin- 32?, th- t~t- Or th- Brok-r PC tr~n-ition~ into D
Ch~nn-l St-ady St~t- tat- 330 ~n D Chann-l St-~dy ~t~t- t~t- 330, th- ~rok r PC
acc-pt~ X 2S pacX-t- ~ro~ th- U -r PC through t~- Jvltch, conv-rt- th--- p~ck t- into Eth-rn-t ~AN p~ck t- ~nd th-r a~t r tran-rit- th--- ~AN pack-t- ov r th- -t~bll~h-d ~aN conn-etlon to th- ho-t conput-r ~or proc---ing Lik-wl--, th- Brok r PC al-o ~cc-pt- X 25 p~ck-t- ov-r th-L~N conn-ction rrO~ th- ho-t, conv rt- th ~- pack-t~ into X 25 pack-t- and th-r ~t-r tran- lt~ th-~--X 2S p~cX-t~
through th- wltch to th U -r PC Th- BroX-r PC do-- not utlll~- th- PAD ~unction- to proc--c th d~t~ lt r c lv ~ron th- ho~t co put-r but r~th-r p~---- th- d~t~ it r-c-lv-~ t-r ult~bl- protocol conY r lon, ~ tw n th-ho-t conput r ~nd th- U -r PC ov ~ th- ~8DN ~CCA p~th Th- ~rok r PC r ll- on th- ho-t to proYld- th- n c-~-~ry PAD functlonJ. 5n- BroX-r PC w~ v ~tat- 330 und r v~riou~ condltlon s ~n X 2~ Cl-Ar ~ --~g- i- r-c-lv d ~ro~
th wltch to dl-conn-ct th- D cb~nn l conn-ctlon, th- LAN
conn ctlon to th ho~t 1- to b dl-¢onn~ot-d, or a B ch~nn-l conn ctlon 1- to b -t~bli-h d 8p cl~lc~lly, lr an X 2S
Cl-~r ~ g 1- r c-lv-d ~ro~ th- SSDN wltch, th-n th Brokor PC t-~aln~t-~ th ~ lo~. In thl~ c~J-, th- Brokor 3~ PC ln truct- LAN lnt~r~c- 60 (-o- ~sa. s) to dl-conn ct th-... ..

., 200573~1 ~CP/~P ~AN conn-ction to th- ho-t co~ut-r an~, onc~ thl~
ha~ occurr-d, th- ~tat- ot th- Brok-r PC tran~ltlon b~ck into Port Idl- ~tat- 310, a- lndlc~t-d by lln- 336 ~hown ~n FIG~. 3A and 3B. Alt-rnatlv ly, ln th- v-nt th- ho-t computer di~conn-ct- th- ~AN conn-ctlon by ~-ndlng an appropriat~ ~CP/TP ~ ag- to th- brok-r, th-n th- ~tat- Or th- Brok-r PC tran-ition- to 8---ion Tnltl~t~d Di~conn-ct - ~t~t- 360, a- lndic~t-d by lln- 33~ Stat- 360 i~ ~-r-ly a - tran-itory tat- which, wh n nt-r d by th- BroX-r PC, i~
i~n di~t-ly ~ollow d by tran~i--ion ot an X 2S Cl-ar pack t by tb- Brok-r PC to th- ISDN vitch ln ord-r to di~conn-ct th- D Ch~nn-l conn-ctlon to th- wltch ~nd, ln turn vl~ th-swltch ~- dl-cu---d abov-, th-r-through to~th- U--r PC
onc- thl~ p~ck-t 1~ tr n~ltt-d, th- t~t- ot th Brok-r PC
lS tr~n-ltlon- b~ck to Port Tdl- ~tat- 310, ~- lndlcat-d by lln- 365 Now, alt-rn~tlv ly, lt th- BroX r PC rec-lv-~ a ~Tr~n~ltlon to B Ch~nn-l~ control ~ --ag- ov-r th- LAN
conn-ctlon froa th- ho-t co~put-r, th-n th- Brok r PC 1~
b-lng ln-truct d by th- ho-t conput-r to ch~ng- th- T5DN
conn-ctlon tro~ ~ D to ~ B chann-l conn ctlon AJ uch, th-Brok-r PC tlr-t v rltl-- th~t an ldl- 8 chann-l 1- avallabl-~t t-r~ln~l ~d~pt-r ~3, ~- hown ln PIG 1, rOr ub--qu-nt u-- ~h-r-~t-r, lt uch ~n ldl- ch nn-l ~ ~v~ bl-, th-n, ~ ho~n ln ~TG-. 3A an~ 3B, th- Brok-r PC r---rv--th~t cbann-l ~nd ub--qu ntly tranJ~lt- ~ Q 931 ~-tup g- to tb ~8DN vltch Onc th~ tup ~ ~g- b~-b--n tran~-ltt d, th- tat- ot th Bro~r PC th n tran ltlon along lln- 332 troa D Chann-l St-~dy 5S~t- tat-330 to B Chann l E-t bll~ha-nt t t- 340 Tb- B C~nn-l E~t bll~h~ nt t~ al-o ~
tran~l nt tat-~ how v-r, th- Brok r PC r-aaln- ln thl-~tat- tor what-~ r lnt-rval Or tl- 1- n~c--~ary ~o ith-r ucc---tu~ly -t up a B chann 1 conn ctlon wlth th- ~wltch 3S or d-t-raln- th~t ~ch a B chann I conn-¢tlon c n not - .

. .
, . . . . . . . . . . . .
' ~ ,, ' . . .

;~OO~j7;~4 e~tabllshed Whll- th- Brok-r PC r-~aln- in Jtat- 340, thi~
PC Gontinu~- to bi-dir-ctionally pa-- X 2S pacX-t~ b-tw~-n th- Us-r PC, through th- I8DN ~witch, and, vla th- ~AN
conn-ctlon, th~ ho-t co~put-r, a- occur~ ln D Chann-l 8t-ady stat- ~tat- 330 Now, lr 8rok r PC d-t-r~ln~- th~t an idl-B chann~ not av~ bl- or, lr uch ~ B chann-l 1-avail~bl- but a B ch~nn-l conn-ctlon can not b ~t~bli~h-d through th- ~witoh ov-r thlJ chann-l, b c~uJ- ~or xa~pl-th- Y 120 protocol wlll not prop rly initializ-, th n th-Brok-r PC tr~n~nit- a ~Non-~cknowl-dg-~-nt~ (NAX) ~ ag-back to th- host co~put-r to indlcato that ~ B ch~nn-l conn-ction can not b- e~tabll-h d ~t thi~ tl~- Th- stat-Or th- Brok-r PC th n tr~n-ition- along li~- 3~3 b~ck into D
Chann-l St-~dy 8tat- t~t- 330 Alt-rn~tiv-ly, lr th-lS ~rok r PC r-c-iv-~ a Q 931 Conn ct ~---ag- rro th- ~witch ~nd an indication (~uch a~ th- V l~0 protocol h~o proF-rly initlall2 d) rrO~ t-rnln~l ~d~pt r S3, hown ln PIC 1, indlc~tlng th~t th- B ch~nn-l conn-ctlon ha~ ~u-t b--n ~ucc-~ully ~t~bll~h d wlth th- -vltch, th n, a~ ~hown ln FIC~ 3A and 3B, th- Brok r PC tr~n~nlt- an ~Acknowl dg~-nt~ (ACX) ~ --~g back to th- ho-t to conrlr~
th- xl~t nc- Or pr---ntly op r~tlon~l B ch~nn-l conn-ction through th- witch onc- thl~ occur~, th- Brok-r ~C
tran~nit~ llng~ n-~-~g , a- dl-cu~-d ~bov-, wlthin an 2~ X 2~ pack t ov r tb- D ch nn l throug~ th- wltch ~nd to th-U--r PC. Onc- thl- ~J-~g i- tranJnltt d, th n th ~t~t-Or th- BroX-r PC tran~lt~ona along lln- 347 into B Chann-l gt-~dy 8t~t- t~t- 3~0 Whll- ln B Ch~nn-l 8t-Ady 8tat- t~t- 3SO, th-Bro~ r PC acc-pt- d~ta in V 120 ~or~ ov-r th- B ch~nn-l circult wltch d conn ctlon tron th witch and origin~ting wlth th- U~-r PC and con~ rt~ thlo data lnto ~CP/~P p~ck t~
that lt th-n tr~n~lt~ ov-r th- ~N conn-¢tlon to th- ho~t 3S co put-r Lik-~l~ h- Brok r PC ~cc-pt~ TCP/~P pack-t-., .
, . . . . .. . . .
, ' , . ', ~ ~ , :

.. . . . .
,, , ~ , , , ' " ' ;~005734 app-Arlng on th- LAN conn-ction and orlginat$ng with th ho~t co~putsr, conv-rt~ thi- data into V 120 tor~ ~nd th n tr~n~mit~ thi- V 120 d~ta through th- B chann-l conn-ction throuqh;th- ~witch ~or ~ub~-gu-nt tran-~i--ion to th- U~-r PC A~ not-d abov-, th Brok r PC ~-r-ly pa~ data att-r appropri~t- protocol conv-r~ion ~-~w--n th- U~-r PC and th-hoot co~put-r wlthout ~lt-rlng th- cont-nt ot th- data in any way ~h- 8rok-r P~ r-~ln~-ln ~tat- 350 untll th- ho~t co~put-r disconn-ct~ th- ~N conn ctlon, th- wltch di~conn-ct- th- B chann-l conn-ction or th- ho~t co~put-r ln-truct~ th- BroX-r PC to chanq- rrO~ th- curr-nt ISDN
acc-~ path ~ro~ a 8 to a D cbann-l conn-ction In particular, lt th- 8rok-r PC whll- r-~ldl~ ln tat- 350 r-c-lv-- a ~AN Dl-conn-ct --ag- tron th- ho~t ¢o~put-r indicating that th- ho-t ha~ t-r-inat d th- ho~t ~ lon and that th- LAN conn-ctlon b-tv -n th BroX r PC and th- ho~t conput-r hould b- torn down, tb-n th- Brok-r ~C tran- lt~ _ Q 931 Dl-conn-ct ~ --ag- to tb- I8DN ~wltcb to t-ar down th-curr-nt B chann-l conn ctlon through th wltch and b-tw -n th- BroXor PC and th U~-r PCs. Onc thl~ occur~, th- ~tat-o~ th- BroX-r PC tran~ltlon~ ~long lln- 352 lnto 8-~lon Inltlat-d Dl~conn-ct t~t- 360, ~- dl-cu-~ d abov-, ln ord-r to dl~conn ct th- curr nt D ch nn l conn ctlon through th ~witch and b tw -n t~- 8roX r and U~-r PCr Now, rathor th_n di~conn-ctlng th I8QN acc-~ th ln r-~pon~- to th-t-rnlnatlon ot ~ ho-t ~-J-lon, th- ~roX-r PC could alt-rn~tlv ly, thougb not hown, provld- a ~ ~ag- to th-U~-r PC r gu tlng that th- u~-r nt-r a na-o Or a dl~-r-nt ho~t, .g. ho~t coJput-r 72 ~hown ln ~IG l, lnto th U~-r PC ~o ~ to -t bll~h a LAN conn-ction th r-to ~nd a ho~t ~-~-lon thor vlth ~n th- v nt th~t th u--r d cld-~ not to ~tabli h a ~-~-ion wlth dl~tor nt ho-t con~ut-r and nt-r~ an approprlat- ln t N ctlon lnto th- ~ -r PC, th-n th-~rok-r PC~ upon r-c-lpt o~ thl~ ln-tructlon, cou~d th-n .
,, : , , , , , "
: , - , - . , " ~ , , :
:, , . :
.

;~00573~

approprlat-ly disconn-ct th- I8DN acc-~ path to th- U--r PC.

Now, 1~ th- BroX-r PC, whll- r-~idlng ln Jtat-- 5 3so, r~c-lv-- a Q 931 Dl-conn-ct ~ ag- ~ro~ th- ~wltch, th~r by lndicatlv- o~ lth-r th- ~wltch or th- u~-r d~sconn~ctlng th- B chann-l conn-ction and, by 80 dolng, ter~lnatlng th- ho~t ~ lon, th-n th- Brok-r PC dlsconn-ctg th- us-r ~ro~ th- ho-t and ~r--- ~11 r~m~lnlng ~SDN
r-~ourc-- th~t ar- b lng con-u~ d by th- u--r Sp-ci~lc~lly, th- Brok-r PC ~ nd~ both an X 25 Cl-~r ~ ag-to th- ~witch to t-ar down th- D chann-l p~ck t conn-ction ~nd ~n TCP/IP dl~conn-ct ~ ---g- to th- ho t to t ar down th- ~AN conn~ction th-r-to Onc- thlJ occur-, th- ~tat- o~
lS th- Brok r PC tran~ition~ along lln- 354 bacX into Port Idl-stat- 310 ~a~tly, and alt-rnatlv-ly, lr tho Brok-r PC, whil- ln B Chann-l ~t-ady tat- 3S0, r-c-lv-- a ~Tran ition to D Chann-l~ control ~ g ~ro~ th- ho-t co~put-r, th-n th- BroX-r PC l- to t ar down th- B ch~nn-l ~SDN acc--- path to th- ~wltch nd th-r-through to th ~-r PC and to u~- th-D chann-l conn ctlon ror ~ub~-gu nt co~ounlcatlon In thl~
; ca~-, onc- thl~ control n ~-ag i~ r c-lv d ov-r th- LAN
conn-ctlon ~ron th- ho-t conput-r, th- BroX r PC tranJ~lt- a Q 931 Dl-conn ct ~ ag- to th- ~wltch Onc- th- 8rok r PC
r-c-lv-~ ~n appropriat- Q 931 ~--ag-, ~p-cl~lcally a Q~931 -- n ~Jag a~ hown in FIG 5, ~ro~ th~ ~ltch lndlc tlng that th B chann l conn-ction l- no long-r ~unctlonal and 1- b lng r-l a--d, th n th 8rok r PC ~ nd~
~n ~Acknovl~dg n nt~ (ACX) ~ --ag to th- ho-t whlch ackno~l dg-a that th B chann-l conn ctlon no long r xl~t~
~h r ~t-~, th Bro~ r ~C r ~ ocl~t-- t~- LAN por~ ~lth th currcnt D chann-l loglc l conn-ctlon Onc- tbl- occur-, th- ~t t- o~ th Brok r PC trun~itlon~ ~long lln- 356 back into D Ch~nn-l St-~dy 8t~t- ~t~t- 330 -. . .

;~()C~5734 Now, havlng dl~cu~-d th- proc dur--, in t-rJ~ o~
stat-- and ~tat- tran-ltlon-, ~ollow d by th- U~-r ~nd Brok-r PC-, th- dl~cu--lon wlll turn to th- proc dur-~
x-cut-d by th- ho-t coJput-r Ih- ho-t co~put-r, wlth th exc-ption Or b-lng cognlz~nt o~ wh-th-r a p~rtlcul~r u--r i~
communicating to it ov-r a B or D chann-l conn-ction, op-rat-- ln ~ ntlally th- ~ r~-hion r g~rdl-~ o~ which ISDN conn-ctlon 18 b lng -ploy d to co~ounlcat- durlng a ho-t ~ lon wlth that u--r AJ uch, th-r- ~r- ---ntl~lly no dl~-r-nt tat-- that xl-t wlthln th- ho-t conput-r and sp cl~ically corr-~pond to lth-r B or D chann-l conn-ctlon~
and partlcularly ch~ng-- occurring th r b-tw -n, a~ w-r-d-~ln d ~nd dl-cu---d ~bo~ in con~unctlon~wlth th- U--r and ~rok r PC-In partlcular, th- ho-t co~put-r ~lr-t alloc~t-~
and ub--qu-ntly r-cognlz-~ varlou~ pr -d-~ln d L~N
addr ~ , wh n ~N conn ctlon- ar ~lr~t -t~bll-h d, a~
tho~ that r gulr- a conn-ctlon through a BroX-r PC to r-ach a u--r At th- lnc-ptlon o~ uch a conn-ctlon, th ho-t coaput-r -nd~ tandard ~UNIX~ ~logln~ and ~pa- word~
~-gu nc-~, 1 - r qu~at~ng u~-r ntry o~ account nuab-r- and pa~ word~ th-rn-t L~N pacX~to ov-r thl~ ~aN conn-ctlon to th Brok r PC. ~h- ~rok~r PC -r-ly r lay~ th-~-2 u nc ~ contaln-d wlthln th- Eth-rn t pacX t to th- ~SDN
~wltch ao X 2~ p~cX t- whlCh, ln turn, r-lay~ th ~-~agu nc~a wlthln l~llar X 25 p~o~t~ to th- u~-r ~tatlonod at th ~ r PC. ~n thl- nann r, th- hoat co-put-r r--pond-to thl- ~tt- pt d u--r conn-ctlon occurrinq through th-Bro~ r PC ln uch th- an- ~nn-r a- th ho-t couput-r would r-~pon~ to ~ dlr ct ~logln~ ~tt-npt by lth-r ~ u--r ltu t d ~t ~ r ot- t-ruln~l or ~ dl~ r nt r--at ly ~ltuat d ho-t co put-r . .

. .
.

~" 2005734 ~ h- ho-t coaput-r utlllz-- a p-clal ho-t protocol ~or co~munlcatlon occurrlng b-tw--n th- ho-t cc~put~r and carri-d through a 8roX-r PC to a U--r PC 8p-cl~ically, th~
ho~t comput-r ~J abl- to tr~n-~lt thr-- di~-r-nt typ-~ o~
S ~o~ages ov-r a ~AN conn-ctlon to th- BroX-r PC data m-~-ag-~, I/0 ~lnput/output) control a!~ag-~ and tran~itlon r~qu-~t m ~-ag-- Flr~t, data a ~ag-- orlglnatlng ~ro~ tho ho~t which includ- appropriat- tor~attlng co~ and~ ~or a - glv-n t-~lnal ~ulatlon progr~ b lng x-cut d by th- u--r, Q g a D~C VT-100 t-rulnal or th- llk , ar- pa~ d un~odi~i d by th- BroX-r PC to th- wltch and th-r by to th U~-r PC ~or local dl~play th-r-at Tn lnv-ntlv- y~t-a 5, th- ho~t co~put-r, u-r ly to i pli~y th ~l-pl-D-ntat$on, ~alntaln- th- lz- o~ ach data --ag- that i- nt to th-Brok-r PC ~- ~th-rn-t ~AN pack~t- that hav- a lz- qual to or 1--- than th- ~xlaun pack t lz- allow d by th- D
chann!l X 25 p~ck t n twork, 1 -. ~128~ oct-t- T~ any d~ta --ag- 1- larg-r tban thl- iz-, th- ho-t co~put-r wlll approprlat-ly par~- thl~ J-~-ag- lnto cont$guou~ Eth-rn~t LAN pacX t- that ach conta$n- a d~ta a--~ag- b-ing gual to or 1-~- than ~128~ oct-t~ $n ~ h--- ~aint-nanc- and par-$ng runct$on- could alt-rnatl~-ly b iapl- -nt-d $n th-Brok r PC by ult~bly nod$~ylng lt- o~twar-. 8-cond, V
control ~ --ag-- ar g n-rat d by th- ho-t ~or $nt-rpr t tlon by th- U -r PC. ~h--- control n --ag - ar-g-n-rat d by t~ ho-t conput-r $n ord-r to ~-ra$t th ho-t conput-r to control t-ralnal ulatlon ~nd th X 3 and X 29 PAD Sunctlon~, uch a- loc l buS~-rlng ~nd charac*-r cholng, t~t x-cut- at th U -r PC Th- BroX r PC D r-ly r-l-y th ~0 control n -ag-- w$thout uod$Slcatlon to th vitcb whlch, $n turn, tran- lt- th ~- D ~ag-~ to t~-U--r FC. Thlrd, th ho-t gon r~t-- tran-ltlon r qu--t u --ag--, $.-. ~Sr~n~lt$on to ~ Ch~nn l~ and ~Tr~n~$tlon to D Ch~nn l~ ag-~ a- d$-¢uJ~ d ~bov-, to th- Brok-r PC
- 35 wh$ch $n-truct th- ~roX-r PC to chang th- I~DN acc--- p~th .
- , ' ' ' ' ~ - , , ., ' ,, ~00S73~

curr-ntly b-lng u~-d b-tw -n a D chann-l pacX-t ~wltch-d conn-ctlon and a B chann-l clrcult wltch d conn-ct$on ~nd vico v-rsa Tho-- tran~ltlon r-qu--t ~ ~ag-~ ~r-int~rpr~t-d by th- BroX r PC a- dl-cu-~ d abov to S dyn~ically ~nag- th- ISDN conn-ctlon by -tabll~hlnq th-approprlat- ISDN acc-~- patb curr-ntly b-lng r-qu-~t-d by th- ho-t .
A~ part o~ t~lJ ~p~¢lal ho-t proto¢ol, th- ho-t couputor can r-c-iv thr-- typ - Or ~---ag-- ov r a ~N
conn-ctlon ~ro~ a Brok r PC d~ta ~ --ag--, op ratlng ~y-t~
~-lgnal~ ~o--ag-~ and tran-ltlon r--pon--- Plr-t, data m --ag-~ ~-r-ly conta$n charact-r- that w ~ lnltlally typ-d by a u--r ltuat d at th- u--r ~ ybo-rd o~ a corr--ponding lS U -r PC Th- ho-t protocol -r-ly d-llv r- th -- charact-r-to a partlcular ho-t appllc-tlon th t th- u--r 1- curr ntly -x-cutlng wlthln th- ho-t conput-r and whlch approprlat-ly lnt-rpr t~ th--- ch-ract-r-. 8-cond, th- ho-t conput-r can r~c-lv- op ratlng ~y~t-~ ~-lgn l~ -g-~, uch a- ~Br-ak~
conJ-nd-, th e w r- g n rat d by th u--r to t- por~rlly t-ralnat- a ho-t appllcatlon nd g-ln th- att ntion o~ th-~UN~X~ op ratlnq y-t- curr ntly x cutlnq wlthln th- ho-t couput-r ln ord-r to ~ub--qu ntly ln truct th- ho~t co~put-r accordlngly to x-cut a ~ub--qu nt ho-t appllcatlon~
2~ Thlrd, th ho~t conput-r c~n r c lv tran ltlon r -pons-ag ~ Acknowl dg-~ nt~ (ACX) and ~Non--ckno~l dq n nt~ ~NAX) ~o--~g ~, ~ron th- Brok-r PC
Th-~ r ~ponJ- ~---aq-~, a- dl-cu---d a~ov-, r part wh th r a tr~n-ltlon in th I8DN acc--- path, 1 - ~rou a B to a D
chann l ¢onn ctlon or vlc- ~ r ~, tbat ba- ~u-t b -n r qu tod by th ho-t cooput-r, through a corr--pondlng tran~ltlon r qu -t ~ --ag-, ba- ucc---~ully oc¢urr d or ~all-d .

~,, , " , ... . . ..
, , , ,, " , .
, ' ' -, , ', ',, ; ,:' ' '' ' ~ ~ ',' ," ' ,' , , 200573~

Th- ho-t comput-r c~n r-qu-~t ~ tr~n~lt~on ln ~n ISDN acc--~ path throu~h two ~ thod-s through ~ d~r-ct op-r~tlng ~y-t-u c~ll or indlr-ctly b~-d upon thc n~tur 4~
ho~t application curr-ntly x-cuting during th- ho-t ~ ion with a u~er Fir~t, th- ~UNIX~ op-r~tlng ~y~t~ o~ th- ho~t can b- r-~dily ~odi~i d to cont~in an addition~l op-rating syJt~n call whlch c~n b- dlr-ctly ln--rt~d a~ a progra~
st~t-~-nt by an appllc~tlon- progr~m~ r lnto a ho~t applic~tlon progr~n ~hi- p-¢i~i¢ c~ll, wh-n r-ach-d in th- progran, would ~ppropri~t-ly in truct th- ho-t op-rating Jy-t-o to g-n-r~t- ~nd tr~n-ait ~n ~ppropri~t- tr~n~ition r-qu--t m-~ag-, i - ~Tr~n-ition to ~ Ch~nn-l~ or NTr~n~ition to D Ch~nn-l~, b~- d upon wh~t`th- progr~ r nvi~ionJ th- co~ounic~tion r-gulr-~ nt~ o~ th- ~ppll¢~tlon progr~ to b- ~t th~t polnt ln th- progr~ Wh n-v-r thl~
c~ r-~ch-d ln th- progruo, th- c~ll would ~x-¢ut- to initl~t- ~ ch~ng- ln th- I8DN ~cc-~- p~th and th-n r-turn control to th- ~ppllc~tlon~ progr~ onc- th- ho-t co~put-r r c-l~-d ~ tr~n~ltlon r -pon~-, lth-r ACX or NAX, ~ro~ th Brok r PC Alt-rn~tl~ ly, th- ho-t couput-r could lnltlato a tr~n~itlon in ~n I8DN ~cc-~ p~th through ~n lndlr-ct t~od wh-r-ln th ho-t co~put r r~cognlz~- tho~-appll¢~tlon~ wh-r- chopl-Y 1~ llX-ly to o¢cur H r-, th-~UNIX~ op ratlng y~t-- wlthln ho~t couput-r could ~lly b-~odl~l-d to lnoorpor~t- ~ t bl- tb~t ld ntltl d tho--~p-cltlc ho-t ~ppl~c~tlon- vhlch could g n rat-ob~-ctlon~bl- chopl-x, g ~ ~UN~X~ ~vi~ dltor In u--, th- ho t co put-r vould -r ly p rtor~ ~ ~lnpl- tabl- look up op r~Slon vh n v-r ~ u~-r ln truct-d th- ho~t co put-r to x ¢Ut ~ n v ho~t ~ppllc~tlon ~N~, prlor to Y-cutlng that p cl~lo ~ppllc~tlon, th n lnltl~t- ~n ~pproprla~-tr n d tlon ln tb- ~N ~cç--~ path 1~ th n~ - or oth-r ld ntltylng lndlcl~ ot t~t ~ppllcstlon ~pp-sr~d ln th-Wbl- ~hl~ t~bl- voul~ b~ po~ul~t d ~y ~ y-t-u 3S adnlnl~tr~tor of th~ ho-t corput-r b~-~d u~on co~ unlc~tlon ~` 200~i734 -~3-r~qulre~ent~ Juppll-d by th- appllcatlon progra~-4r~
Wh~n-v~r ~uch a progra~m-r d-v-lop-d ~ n-w ho-t ~ppllcatlon, tho ~yst-u ad~lnl-trator would b approprl~t-ly ln~or~ d who would th-n add ~ corro-pondlng ntry ~or lt to th- tabl-, S includlng th- ~ppl$catlon n~ and corr-~ponding tyF- ~
ISDN acc--- path th~t lt r-qulr-- So~ appllc~tlon progr~m~ xhlblt ~-chopl-x~ ch~r~ct-rl-tlc- throuqh only portlon~ o~ th-lr ~ull Y-cutlon cycl- Sp cl~lc~lly, th-~-portlon~ occur wh-n ~n ~ppllcatlon progr~ ha- turn d orr th- local cho ~nd lln- bu~-rlnq runctlon- dl-cu---d pr-vlou~ly An incr-~-d d-gr-- Or pr cl-lon ln ~tchlng th- ISDN co~ounic~tlon r--ourc- to th n -d o~ uch an appllcatlon progr~ could b- obtaln d by t~lgg-rlng a tran~ltlon to chang- th- I8DN acc--J p~th on not only th n~n- or typ o~ th~ ~ppllcatlon progr~ b-lng x-cut~d, ~uch a- throuqh a t~bl- look up op ratlon, but ~l-o on ~ny ch~ngo o~ th- loc~l cho ~nd lln- bu~-rlng tunctlon~ provld d by th~t ~ppllc~tlon progr~o Althouqh th ~lr-t ~ thod lluln~t-- th n- d rOr t~bl- loo~ op-ratlon~, lt do--r-qulr- ~odl~lcatlon to appllcatlon ourc- cod- lna-uuch ~- th- look-up op r~tlon- con-u~ ~ n ql~glbl- u~ount Or ho-t proc---lng tlu , th- -cond n-thod 1- pr-r-rr-d ln ~o~t ln-t~nc-~ ln~-uuch ~- lt llnln~t-- th- n--d to ~X- ourc-cod- nodl~lcatlon- to xl-tlng ~ppllcatlon progrun~
Alt-rnatlv ly, th- ho~t co put r could an~lyz- th~ actual co- unlcatlon occurrlng b-tw n lt~ and a u--r and d-cld-, ba~-~ upon varloua pr~-d-tln d rul-~ that ~p cl~y ~p cl~lo t~Y hold~ ~or g duratlon and/or aaount Or con unl¢~tlon ~lowlng ln ach dlr-ctlon b-t~ -n th- w or and th ho~t co put r, whlch typ- o~ ~ -- path hould b ~t bll~h d ~or ~ny glv n altuatlon an~ th n, ba- d upon wh th r th ~- thr hold- ~ r- xco d-d or not, dynuolc~lly chang th typ o~ I8DN a ~ path ~ccordlngly .

. ,; . ~
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, ' " ' ' "' , ' , ,, -`` 200573~
-4~-~ avlng now dl-eu~-~d th~ proe-dur ~ und-rtaX-n by th- U~-r PC, th- Brok-r PC and th- ho-t eo~put-r, th dlscus~lon wlll now hlSt to d--erlblng th- lllu tratlv co~unlç~tlon ~-gu-nc-- th~t oceur a~ong th- ~a~or S component~ of sy-t-u S und-r v~rlou~ ~x~pl~ry ~y~t-~condltlon- eJtabll-hing a ho-t -A-lon, ~ovlng a bo~t ~ lon fron a 8 ch~nn-l elreult wlteh d eonneetlon to a D
chann-l pack t ~wltch-d conn-etlon, ~ovlng ~ ho~t s-~lon ~ro~ a D ch~nn-l pacX t wltch-d conn ctlon to ~ B cb~nn-l elreult wltch-d conn-ctlon and t-r~ln~tlng a ho-t -J~lon through a ~ lon lnltlat~d dlJeonn-et Th--- lllu-tr~tlv-s-gu nc-- ar- ~hown ln P~C- 4 - 7 ~h- p~rtleular portlon-Or th- -qu ne-~ hown ln th--- rlgur-~ wh~ch lnvolv th-~wltch ar- ~ r ly lllu-tratlv-~ ln ract, th- tlnlng at whlch th- wlteh r-e-l~-~ and tr~n--lte a---ag b-tw -n lt ~nd th U -r and Brok r PC~ ean b- dlr~ r nt rrO~ that hown provld-d that tb- U -r and BroX r PC th-nJ-lv-- r-c-lv ~---ag-- ln th- -qu-ne- ~hown ln tb-~- flgur -~n partlcul~r, P~ 4 d-plet- th- eo~ounle~tlon s-qu-ne- that oceur- anong U--r 81t- 20 (th~t eontaln~ th-U~-r PC x-cutlnq ~ t-rnln ~ -ul~tlon progr~a), I~DN wltch 3~, BroX-r PC ~0 Icont lnlnq lt~ t-raln l ad~pt-r ~nd LAN
lnt-rr~e-) and hoet y~t-a 701, tor -t~bl$~hl~g a ho-t ~ ion b~t~ -n th- ho-t y-t a ~nd th- U--r PC
8p elrle~11y, to t~bll-h ueh ~ ---lon, ~ u--r rlr t lnvok-~ th t-r ln~l aulatlon proqru wlthln th U -r PC a-y boll~od by lin ~10 ~h r rt-r, ona- thl- proqran 1 Y cutlng, th progr~n tranJ~it- ~n X ~S ~11 R-~u--t p~ck~t, ~ lndlc~t d by lln 4~0, to th- I8DN vltch to ~tabll~h ~ D ch~nn l p~Ckot wltCh-d conn Gtlon th r-b-tv n. I~ tbl- D ch nn-l conn-ctlon 1- ucc --rully -t~bll h d, th n th ~SDN ~ltch tr nJ-lt-, ~- lndl Q t~d by lln 430, an X ~S ~nco lng C ll pack t to th Brok r PC to 3S p clry th~t th- l~tt-r h~- an inc~ ~ng pAek-t c~ r th-~ ,." ", , ." , .. . . ...
,, , ~005734 - 8roX-r PC 1- abl- to ~tabll~h a D chann~l conn-ctlon to th switch and th-r-throUsh acc-pt th- lnco~ing pack~t c~ll, th 8rok r PC tr~n-~lt-, a- lndlc~t~d by lln- 440, an X 2~ Call AccQpt p~ck-t back to th- TSDN ~witch Th- ~witch, in turn, trans~its, a~ lndlcat-d by lln- 4S0, an X 25 Call Conn-ct-d packot bacX to th- U~-r PC At thl~ point an X 2~ pack t conn-ction 1J ~tabllJh d b-tw -n th- BroX-r PC, through th-ISDN ~wltch, and th- U-or PC Th BroX r PC n-xt stabli~h~ AN conn-ctlon to t~- ho~t co~put-r To do lo thl~, t~- Brok-r PC rlr~t tran~uit-, a~ hown by lln- 460, a ~CP/IP Sync ~ g- a- ~n ~th-rn-t LAN pacX t ov-r th- LAN
to th- ho~t co~put-r ~ th- ho~t conput-r i- ~bl- to ~tabll-h a L~N conn-ctlon, th- ho-t co~put-r th-n tran-~lt-, a- lndl¢at-d by lln- ~70, a TCP/TP 8ync AcXnowl-dg- ~ --ag- a- an ~th-rn-t LAN pack-t back ov-r th-~AN conn-ction to th- Brok r PC Tt, tor any r-a-on, th-Brok r PC can not -tabli-h a LAN conn-ctlon v$th th- ho-t co~put-r, th-n th- Brok r PC tran-nit~ an X 25 Cl-ar ~ --ag (not hown) to th- T8DN vltch to t-ar down th- D chAnn l ~--conn-ction that wa~ ~uJt nad- How v-r, lt th ~AN
conn-ction i~ ucc-J-tully ~ad~ to th- ho-t co~put-r and th-Brok r PC r-c-iv d th ~CP/TP 8ync Acknowl-dg ~ ago th-r-ov-r, th n th- Brok r PC ~ r ly tran--$t~ indlcat-d by lin 480, a ~CP/T~ 8ync ~cknovl-dg ~ --ag a~ anoth r Eth rn-t IAN p~ck t back to th- ho t conput-r At thi~
po$nt, not only i~ th- V r PC and th- Brok r RC in an X 25 Data ~r~nJt r Jtat-, a~ hovn, 1 - abl- to tran t-r pa¢k t data ov an X.25 conn ction -tabliah d th r-b t~ n, but al o t~ ho~t 1- ¢onn ct-d to th- Brok-r PC an~ c~n co- unlc t- th r through wlth th V--r PC~ A~ u~h, wlth th L~ conn ctlon nov t~bllah~d, ~h- bo-t conput r ndJ
approprlat- ~logln~ qu nc-~, aa indlcat d by lin 490, o~-r th- L~N conn ctlon to th- BroX-r PC tor ~ ntu~l r-c-ption at and di-play by th U -r PC gy-t-n 5 now - -r--id-- in th- D C~h-l gt-ady ~tat- condltlon Th- ho-t :, ;
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--~c--~ ion i~ ostablish-d onc- th- u~-r ucc-s~rully co~pl-t-~th- appropriat~ ~UNIX~ ~log$n~ proc~dur-: F~G. 5 d~plct- a co~-unlcatlon ~qu-nc- th~t occur- among U~-r Slt- 20 ~that contaln~ th- U~-r PC
ex~cuting a t-r~lnal ~ulation progra~ SDN Jvltch 3S, Brok-r PC 50 (containlng it~ t-rJ$nal adapt-r and LAN
int-r~ac-) and ho-t y-t-a 701 ror w vlng a hoat ~ ion rrO~ a B chann-l circult wltch d conn-ctlon to a D chann-l pack t ~witch-d conn-ctlon Sp clrlcally, a- di-cu~- d abov-, a~ long a- a ho-t --alon 1~ ~tabll~h d, an X 25 Data Tran-~-r ~tat-, 1 - an actl~ D chann-l pack-t ~wltch d conn-ctlon, a- lndic t-d by lln- 503, xl-t-b-tw -n th- U~-r PC and th 8rok-r PC ~ n though no 1~ conuunlcatlon l- b lng carrl d t~-r-o~-r whl-- th- B chann-l conn-ctlon 1- ln u-- Furth-r or-, durlng th- xl-t nc- o~
a B chann-l conn-ctlon b-tw n th U -r PC and th- Brok-r PC, th- B chann-l co~aunlcatlon path -t~bll-h-d th-r b-tw -n xl-t- ln a Q.931 Actl~ tat-, a- indlc~t d by lln- S05, wlth cornunlcatlon carrl d th-r-ov-r u-$ng th-V.120 protocol At th an~ tin~, a LAN conn-ctlon, y bollz d by lin- 507, ~or th carrlag- o~ Eth-rn-t I~N
pack t- xl~t- b tw n th Brok r PC and th- ho-t co~put-r Now, to chang th- I~DN acc--- path ~ro~ B ¢hann l to D
chann-l, th ho-t ¢o-put-r l--u - a ~Tran-ltlon to D
Chann-l~ -ag and tranJJlt , ~- lndlcat d by lln~ 5~0, thl- n---aq wlthln an ~th rn-t L~N pack t to th- Brok~r PC
Upon r c l~t o~ thl- p~cX t, th- BroX r PC tran-~lt-, a~
lndl Q t-d by lln 5~0, Q 931 Dl~conn-c~ ~ J-ag- to th-~D~ vltch. Th- vltch, ln turn, tran-nlt- a Q 931 Dl~¢onn ct ~aJ-ag , a- lndlc~t-d by lln 530, to th- U--r PC. In r -pon - to thl- dl-conn ct ~ --ag-, th- U--r PC
c a-- to tran~alt turth r dat~ ov r th- B chann-l, r-l a~--th- B chann-l conn ctlon and to lgnlty thl- tranJ~lt-, a-lndlcat-d ~y lln- S~0, a Q.931 ~ -- ~ ---g to tho ISDN

,, ,,, . ., ,, , , .. ~ , ;~OO.j734 ~wltch Th- ~wltch, $n turn, tr~n--lt-, a~ lndlc~t-d by lin- SS0, a Q 931 R-l-a~ ag- to th- Brok-r PC
s~gn$~ylng that it i- c-~-lng to tran~lt d~t~ ov r th- B
ch~nn-l and 1- r-l-a-lng thl- ch~nn~l Th- Brok-r PC, upon s it~ r~c~ipt Or thl~ r~ go, tr~nJ~lt~, a~ indlc~t-d by lln- 560, a Q 931 R l-~J- Conpl-t- ~-s~g- to th- ~wltch to ~p-cl~y to th- ~wltch th~t th- broX r h~- now tot~lly r-l-~--d (torn down) th- B ch~nn-l conn-ctlon Th-r-~t-r, a- lndlcat-d by lln- S6S, th- BroX r PC tr~n~lt- ~n "AcXnowl-dg-~ nt~ (ACX) ~ --~g- ~- un Eth-rn-t ~N p~ck t to th- ho-t co~put-r ~- ~n ~cXnowl dg-~ nt th~t th- B ch~nn l i- no long-r ln u-- Th- wltch, ln turn, trunJ-lt-, a-lndlc~t d by l~n- 570, ~ Q 931 R l-~- Co pl-t- J ~-~g to th- U -r PC to ~p cl~y to ~h- U--r PC that th- ~vltch ha~
now tot~lly r-l-~--d th- B chann-l conn-ctlon At thl-point, th- B chann-l conn-ctlon b tw -n th- U -r PC ~nd th ~ro~ r PC 1- co~l-t-ly torn down ~nd ~11 th~t r -~ln~
th-r-b tw -n 1- th- D c~nn l conn ctlon wlth y~t-~ S nov r-~ldlnq ln th- D Cb~nn-l 8t-~dy ~t~t- ~t~t-, ~ lndlc~t~d by lln- S80 ~ a. 6 d-plct- ~ co~ unlc~tlon -qu nc- th~t occur- ~ ong U--r ~lt- 20 ~that contaln~ th U -r PC
eY-cutlng a t-ralnal ulatlon progran), ~DN ~ltch 35, ~rok r PC 50 (contalnlnq lt~ t- D lnal adapt-r ~nd L~N
int-r~ac-t and host y-t-- 701 ~or uovlng a ho-t ---lon ~ron a D cbonn l p~ck t ~wltch-d conn-ctlon to a B chann-l circ~lt vltcb-~ conn ctlon. A~ long a- ~ D cbann-l conn ctlon 1- b lng w d to carry a ho-t -~lon b~tw~-n tb-U~ r P~ and th- Brok-r PC, th- D c~ann l co~ unicatlon path t~bllab d tb r b tw n xl-t- ln a X 25 D~ta Tran~-r tat , a- indlc~t-d by lin- 603, vlth ¢o~nunlc~tlon carri-d th r ov r a- X 25 pacX~t-. At th- a~- t~, a ~AN
conn ctlon, ~y~boliz~d by lln 60S, ror th- carrlag~ o~
~th rn t LAN pack-t~ xl-t- b-tw n th- ~rok r PC und th~

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~ ' . ~ , , , : 200S~34 , -~8-ho-t co~put-r Now, a--u~- that th- ho-t co~put-r h~
~lnlshed a curr~nt ta~k ~or th- u--r ~nd 1~ now pro~ptlng th- us-r ~or th- n-xt t~k In thl- caz-, th- ~UNIX~
- op~rating ~y-t-~ x-cutlng ln th ho-t co~put-r wlll g~n-rat-, as symboliz~d by lin- 607, a u--r pro pt sy~bol, typlcally a ~S~ charact-r, and th-n tr~n~nlt, a~ lndlcat~d by lin- 610, that pronpt sy~bol wlthln an Eth-rn-t ~AN
; pack-t to th- ~roX-r PC Th- Brok-r PC wlll, ln turn, plac~
th~t pro~pt ~y~bol withln ~n X 25 pack-t and tr~n~lt, a~
lndic~t~d by lln- 615, th~t p~cX-t to th- lSDN ~witch Th-~wltch, upon r-c-lpt o~ that X 25 pack-t ~ro~ th- BroX r Pc, wlll rorw~rd, ~- lndlcat-d by lln- 620, that pack t ov r th D chann-l conn-ctlon to th- U~-r PC Th U--r PC wlll, a~
sy bollz-d by lln- 625, dl~ - bl- th- pacX-t ~nd dl~pl~y lS th- u~-r pro~pt ~y bol on th- u--r cr--n ~ltuat d th-r-~t Th u--r --lng th pronpt y bol ~y lllu-tratlv-ly d-cld-to lnvok th- cr--n dltor ~unctlon at thlo polnt ln th ho-t ~ lon A~ not d abov-, th cr -n dltor 1- ~ r-ly on- o~ pot-ntlally ~any ho-t runctlOn that cau-- chopl-x to occux aNd h nc~ hown ln ~Ia 6 n~r ly ~or lllu-tr~ - purpo--- Thu-, to lnvok th- ~UNIX~ cr--n dltor, th- u~-r typ-- an ntry cont lnlnq th- con-~nd ~vl~
~ollow d by a carrl~q- r turn, a- ynbollz-d by lln- 630, lnto th- u~-r k yboard In r ~pon~- to thl- co~a~nd, tho U--r PC tran nlt-, a- lndlcat-d by l~n 635, ~n X 2S data - pack-t, that contaln- th u~-r ntryO to th ~wltch In r~-pon - to th r c-lpt o~ thl- p~ck t, th- ~ltch trun~-lt~ indlc~t-d by lln 6~0, ~ r X.25 p~ck-t contalnlnq thl- u -r ntry to th Brok r PC. Th Bro~ r PC
nov tranJ~ r th w r ntry lnto an Etb rn-t LAN pack-t ~nd tr nJ~lt- tbl- I~N pack t, a- lndlcnt-d by lln- 6~, oY-r th ~aN conn ctlon to th- bo-t conput-r ~or proc---lng Th-ho-t couput-r r cognl~lng, t~rough pr ~-rably a tabl- look -- up op r~tlon, ~- dl-c w d ~bov-, tb~t thl- con~nd wlll lnvok ~ ho-t appll~tlon th~t g n r~t-- chopl-x, g n-rat~

--` 2005734 a "Tr~n-ltlon to B Chann-l~ control a-~ag-, a- y~bollz-d by lln- 648, to ln-truct th- BroX-r PC and th-r-through th ~wltch and U~-x PC to ch~ng- th- ISDN acc-~- path ~ro- a D
chann-l pack-t conn-ctlon to a B chann-l c~rcult ~wltch d s connQctlon Th- ho~t th-n tr~n~nit-, a- lndlcat d by lln-6S0, thl- control ~-~-ag- wlthln an Eth-rn t LAN pack t to th- Brokor PC Th- BroX-r PC th n l~-uo~, a- lndlcat~d by lln- 6SS, ~ Q 931 S-tup u---~g ov r th- D ch~nn-l to th-ISDN ~wltch to -tabll-h ~ B ch~nn-l clrcult wltch d conn-ctlon to th~ wltch Upon r c lpt o~ thl- ~-tup g-, th- ~SDN wltch, ln turn, l--u--, ~- ~ndlc~t-d by lln- 660, ~ Q 931 ~-tup u --~g- ov-r th- D chann-l to th-U--r PC to -t~bll-h a B ch nn-l clrcult ~wltch d conn-ctlon th-r b-tw--n I~ th- U -r PC 1- ~bl- to -t~bll-h ~ B
1~ chann-l clrcult wltch d conn ctlon to th- wltch, th n th-U--r PC tr~n-nlt-, ~- lndlcat d by lln- 66S, ~ Q 931 Conn ct ~-n--~g- to th- wltch, and th- wltch l--u--, ~- lndlc~t d by lln- 670, a Q 931 Conn ct n-~-~g to th- BroX-r PC. Th-Brok r PC th n acknowl d g-- th- --t~bll-hn nt o~ a B chann-l clrcult ~vltch d conn-ctlon to th- vltch by tr~n--lttlng, a- lndlcat-d by lln- 675, a Q.931 Conn-ct Acknovl-dg g to th wltch ~h vltch th n acXnowl dg-- th- 8 ch~nn l conn-ctlon -tabll-h-d b tv -n lt an th- U--r PC by tr~nJnlttlng, a- indlcat-d by lin 680, a Q 931 Conn-ct AcXnovl dg ~ --~g to th U -r ~C. Nov, with a ~unctlonlng B chann-l clrcult vltch d conn ctlon -t~bli-h~d b-tw n th- U -r PC nd th Brok r PC, th- U -r PC and Brok r PC
both ~nltlat Y cutlon o~ th- V.120 protccol ~nd ~tt--pt lnltlall~atlon th o~ ln ord r to ub--gu-ntly und - --accurat ly carry co~ unlcatlon ov r thl- conn-ctlon onco thl~ pro~ocol 1- ucc rully lnltlall~-~, t~ ~ro~r tr~n olt-, a- lndlc~t-d by lln ~8S, n AcXnovl dg-~ nt ~ACX) a~ g ~- ~n ~th rn-t L~ p~ck t to th- ho-t co put-r, to ~lgnl~y that tho ~ cb nn l l- ucc--~tully 3S op~r~tlng ~nd c~n c~r'ry coa unlcAtion th-roov-r At thi-.. . ..
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, Z0057~4 --~o--polnt, y~t-~ S now r--ld-- ~n th- B Ch~nn-l 8t-ady ~tat-stat~, as indlcat-d by lln- 690 ; FIG 7 d-plct~ a co~unlcatlon -gu-nc- that occur- among U--r 81t- 20 ~that contaln~ th- U~-r PC
Qx-cutlng a t-r~lnal nulatlon pro~ra~), ISDN Jwitch 35, BroX-r PC So ~contalnlng lt~ t-r~lnal adapt-r and LAN
lnt-rrac-) and ho~t ~y-t-~ 701 ~or lnvoXlng a ~ lon lnltlat-d dl~conn-ct ln ord r to t-ralnat- a ho~t J-~lon A ~ lon lnltlat-d dl~conn-ct can arl~- whll- th- ho-t s---lon 1- b-lng carrl-d ov r ith-r a B or D chann-l conn-ctlon A uch, an lllu tr~tlv- co~aunlcatlon ~-gu-nc-that occur~ to cau-- a dl-conn ct ~or ach~o~ th--- two dl~-r nt conn-ctlon- wlll b- -parat-ly dl-cu-- d ~5 Sn partlcular, 1~ th ho-t ---lon 1- pr - ntly b lng carrl d ov-r a D chann-l pacX t wltch~d conn ctlon, th-n ~y-t-a 5 xl-t- ln th- D Chann-l 8t-ady Jtat- tat- a-lndlcat-d by lln- 703 ln Psa. 7 AJ-u - th u~-r nt-r-, a~
~y bollz d by lln- 705, a ~p cl~la ntry, g. ~^D~ rollov d by a carrlag- r-turn, through tho u~-r X yboard at th- U~-r PC to ln~truct th ho~t to t-r~lnat- th- hoat ~ lon In r ~pon - to thl~ ntry, th U- r PC tran~lt~ lndlcat-d by lln 710, an X 2S p cX~t tbat contaln- thl- ntry ov~r th D chann-l ~ac~ t conn~ctlon to th- wltch. ~h- wltch, ln turn, aa lndlcat-d by lln ?~S, tran~ lta a l~llar X 25 pacX t cont lnlng thl~ ntry ov r a D chann 1 pacX t conn ctlon to th Brok~r PC. ~h Bro~4r PC, ln r--pon~- to th r c lpt o~ thl~ pacX-t ~OD an Eth~rn t ~AN pacX t cont lnlng thl- ntry and tran~alt- thl- ~N pacX t, a~
lndlc~t d by lln 718, ov r th IAN conn-ctlon to th- ho~t coJput-r In r ~pona- to thla pa¢X t, th ho-t co put-r t-rnlnat-- th- hoat --alon, tor ulat-- a TCP/I~ dl~conn ct ~ g to dl-conn ct th ~AN conn ctlon snd tra~JJlt- thl-3S dl conn-ct ~ -~ag-,'a~ lndlcat-d by lln- 720, a~ an ~tb rn-t 2005~34 ~AN p~cX-t to th- Brok-r PC rn r-~pon-- to thi- di~¢onn ct m--sag-, th- Brok-r PC and ub--gu-ntly th- swltch t-~r down th- D ch~nn-l conn ction Sp-cl~lc~lly, a~t-r th- BroX r PC
r-c-lv ~ th- TCP/~P dl~conn-¢t ~ --~g- ~ro~ th~ ho~t S comput-r, th- BroX r PC tr~n-ult~, a~ lndlcat d by lln- 725, ~n X 2S Cl-~r R-qu-~t p~ck-t to th- ~wltch to dl~conn ct th-curr~nt D ch~nn-l conn ¢tlon xl~tlng th-r-b-tw--n onc-th- s~ltch dl~conn-ct~ th- D ch nn-l conn-¢tlon to th-Brok r PC, th- wltch th n trun~lt-, ~- lndlc~t-d by lln-730, ~n X 2S Cl-~r Indl¢~tlon pa¢X t to th- U--r PC to lndlc~t- th~t ~ D ch~nn-l conn ctlon no long-r ~xl~t~ ~rou th- U~-r PC to th- BroX r PC and th-r-through, vla ~ IAN
conn-ctlon, to th- ho-t couput-r In r--pon~- to th$~
pack t, th- U~-r PC dl~conn-ct- lt- D chann-l conn-ction to 1~ th- wltch ~nd ub--Qu-ntly r-turn- to lt- T-r~ln~l ~dl-~t~t~ t~t- 210 hown ln P~- 2A ~ d 2B

Now, ~lt-rn~tlv ly, 1~ th ho~t ~ lon 1-pr ~ ntly b lng c~rrl-~ ov r a B oh nn l clrcuit ~wltch-d conn otlon, th n y-t-n 5 Yl~t~ ln th- B Ch~nn-l 8t-~dy St~t- ~tat- ~- lndlc~t d by lln 733 ln Pl¢ 7 Agaln ~un th- u~-r nt-r-, ~- y bollz~d by lln- 73S, th-~pproprl~t ntry, g ~^D~ rolloN~d by ~ c~rrl~q r-turn, through th- u~-r k ybo rd ~t t~ U -r PC to in truct th-2S ho-t to t-r~ln~t th ho t -~-lon ~n r ~pon~ to thl~
i ntry, th U~-r PC tran~nlt~, a~ l d lc~t d by lln- 7~0, ~
g th~t cont ln~ thl~ ntry ~ V 120 d t~ ov r th- 8 chann l clrcult wltch d conn-ctlon to th wltch Th wltc~, ln turn, a~ lndlcat d by lln 74S, trun nlt~ ~ -~lnll~r ~ --ag cont lnlng thl~ ntry ov r a B ch nn-l conn ctlon to th Brok r PC. Th Brok-r PC, ln r -pon-- to th r c lpt o~ thl- V ~20 data ~oru~ an ~th-rn-t ~AN p~ck-t cont lnlng thl~ ntry ~nd tranJ lt~ thl~ ~AN p ck t, a-lndlcat d by lln- 7S0, ov r t~ LAN conn-ctlon t~ th- ho-t 3S conput-r. In r -pon - to thl- pack-t, th- ho-t co put~r ~, :, ., ;, . ,.. ~, ~
, ,, , :

, ~ ., , ,., ~ ' - ~0~5~34 t-r~lnat-~ th- ho-t ~-J~lon, ror ulat-- ~ TCP/~P di-conn~ct mes~ag- to diJconnect th- LAN conn-ctlon and tr~n~Dit~ thl-di~connect ~s~sag-, a- indlcat-d by lin- 755, a- an ~th-rn~t LAN pack-t to th- BroX~r PC Th 8roX r PC ror~ulat-~ a Q 931 Di~conn-ct ~e~ag- and trans~lt~ thi~ ag-, a~
indicat~d by lin- 760, to th- ~wltch to lnitiat-disconn~ction o~ th- curr-nt 8 chann-l conn-ction exi~ting th-rob~tw -n and through th- wltch to th- U--r PC Th-~itch, in re-pon~- to th- di~conn-ct ~-s~ag-, ror~ulat-- a ~i~ilar Q 931 Dl-conn-ct ~ ag- and tran~it~ thl~ g-, a- indicat-d by lin 765, to th- U~-r PC ln ord-r to in~truct th- latt-r to lnitiat- di-conn-ction Or th- curr-nt B chann-l sonn-ction xi-ting th-r b-tw n~ ~n r-~pon~- to thl- dl~conn-ct ~ --ag-, th- U--r PC ¢-a~-- to tran-~it rurth-r data ov-r th- B chann-l, r-l-a--- th- B chann-l conn ction and to lgnl~y thl- tran-~it-, a- lndlcat-d by lln- 770, a Q 931 R l-~-- n --ag- to th- I8DN wltch Th-witch tran-alt-, a- indlcat-d by lln- 775, a Q 931 R-l-a--n---ag- to th- Brok r PC lgnlrylng that th- ~wltch 1-c-a-lng to tran-~lt data ov r th- B chann-l and i- r-l-a-ing thi- chann-l Th-r-art-r, th BroX r PC tranJ~lt~
indlcat-d by lln- 780, a Q 931 R-l-a-- Conpl-t- n---ag- to th- wltch to p clry to th~ wltch that th- BroX r PC h~-now totally r-l-a-~d (torn down) th- ~ chann l conn-c~lon 2S ~h- wltch trunJ~$t-, a- lndlcat d by lln 785, a Q 931 R-l-a~- Co~pl-t- ~-~ag to tho U -r PC to p cl~y to th U -r PC that th vltch ha~ nov totally r l-a~-d th B
chunnci conn ctlon. At thl- polnt, th- B chann-l conn-ctlon b tv on th- V~-~ PC and th- Brok-r PC 1- conpl-t-ly torn dovn and all that r aln- to ~ don- 1- to t-ar down th- D
ch nn l conn ctlon xl-tlng b tw n th- 8rok-r und U--r PCJ
To acco pll-b thl-, hortly art-r th Brok ~ PC haJ
tr~n~altt-d a Q 931 R l-a~- Co-pl-t- n-~-ag to th- wltch, th- 8rok r ~C tran-olt-, a- lndlc t~d by lln 790, ~n X 25 Cl--r R-qu--t p~ck t'to th- w$tch to dl-conn-ct th curr nt ~` ZOOS73~

D ch~nn-l conn-ctlon xl~ting th-r-b-tw~-n Onc- th- ~wltch dl~conn-ct- tho D chann-l conn-ctlon to th- BroX-r PC, th ~witch th-n tr~n-nlt-, a- indicat~d by l~n- 795, an X 25 Clo~r Indlc~tlon packot to th- U~-r PC to indicato that a D
chann-l conn-ction no lonq-r ~Yi~t~ through th- U~-r PC to th- Broker PC and th-r~through, v$a a ~AN conn~ctlon, to th-ho~t co~put-r In r-~pon-- to thi~ pacX t, th- U~-r PC
dl~conn-ct~ it- D chann-l conn-ction to th- ~witch and ~ub~-qu-ntly r-turn~ to lt- T-r~lnal ~dl- tat-, 1 ~ ~tat-lo 210 hown ln P~G~ 2A and 2B

With th- abov di~cuJ-ion now ln ulnd, t~-~rchlt-ctur- Or our lnv-ntiv- ~y~t-~, g ~y~t-n ~ ~hown ln F~a~ 1, can b- r-~dlly xt-nd~d and g-n-rall~-d to a lS nultl-brok r approach Thl- appro~ch utlllz-- a group o~
brok-r~, in whlch ~ch broX r c~n ~tabll~h acc-~ lnto th-I8DN and th r-through -tabli h an ISD~ conn-ctlon to any oth-r broX r ln th- qroup AJ ucb, a w -r ltuat d at on-broX r, 1 - th ~orlglnatlng~ broX r, can -tabll-h an I8DN
call, ~la th~ ~8DN, uch ~- tbrouqh a k~-lc I8DN 2~B~I~D~
acc--~ path, to anoth-r broX r, 1 - th- ~d-~tlnatlon~
brok-r, to -tabll h a ho~t --~lon wlth a r-uot- ho-t co~put-r ltuat-d at tb- latt-r broX r In thl- appro~ch lth-r o~ th-- t~o co4 unlcatlng brok-r- c~n dyn~lcally 2S chang- an lJDN acc-~ path that conn~ctJ tb~-- brok-r~ ~
b tw -n ~ ¢$rcult wltch d conn ctlon and pack t wltch d conn ctlon accordlng to th co- unlc~tlon d--~nd- th~t occur durlng thc ~o t --lon A block dl~gran o~ ~n ~bodi~ nt, 1 -. ~ultl-brokor y t-n 300, that ~ pl-~ nt- thl- ~pproach 1J hoHn ln ~sa. 8 Sn lt- lrpl--t ibodl~ont, y-t-~ 800 ~- ~hown ln YSC. 8 contaln two brok r- 820 and 8~0 t~at ~r both conn ct-d tc~SS~N 830 vl~ SSDN acc--~ lln-~ 8~S and 835, 3S r--p ctl~ ly Brok r 820, ~l-o r ~ rr-~ to ~ Brok-r A or ,, , , , . . .
, . . ..

~OOS734 th- oriqinating brok-r, ~x-cut-~ u~r proc--~ 810, al~o r~rorr~d to ~ us~r proc-~- A, whlch 2ay b- ~ t~r~ln~l ~mulation progra~ For xa~pl-, ~ u--r sltu~t d at a dl~play ~cr--n ~nd ~ k-yboard ~--oclat-d wlth thl- brok-r s ~-r-ly ln~oX-- th- ~ul~tlon progr~o to -t~bli~h and th-rea~t-r conduct ~ ho~t ~ lon with a r-~ot- ho-t co~put-r onc- th- t-r~lnal uulatlon prograo 1- x cutlng within orlglnatlng brok-r 820 ~nd th u~-r nter a co~and th-r-~t to initlato a ho-t ---lon, orlqln~tlng brok-r 820 th-n ~tabllsh-- ~n ISDN ~cc--- p~th through I8DN 830 to anoth-r broX-r, 1 ~ d--tlnatlon brok-r 840, ~l-o ro~-rr d to ~- 8rok-r B rn ro-pon-- to th- -tabll~h~ nt o~ an r8DN
D chunn-l p~ck-t ~wltch d conn ctlon b-tw-~n th--- two brok r-, th- d--tinatlon brok r -tabll-h-~ a conn-ctlon to lS a conput-r ltu~t d t~-r-at to lnvok- u--r pro¢--~ 850, ~l~o r-~-rr-d to ~ u--r pro¢--- ~ U--r proc-~- 850 ~y lllu-tratlv-ly b- a ~UNlX~ ho-t op ratlng y-t~ uch ~-that d--crlb-d abov A~ u¢h, y-too 5 ~hown ln ~lG 1 1-a p clrlc l~pl-o-ntatlon Or ~y-t-o 800 hown ln Pr~ 8 D p nding upon th- ~p cl~lc conput-r ltuat d at th-orlgln~tlng ~nd d--tlnatlon brok r-, ~ch brok-r ~y includ-a ~AN conn-ctlon, u¢h a- th t d -¢rlb d abov , to th-corr--pondlng conput-r or a dlr ct conn-ctlon ~uch ~-through ~ hlgA p--d p~r-ll-l or -rlal port into th-co put-r ltuat d th-r-at nd a-~ocl~t d th-r-wlth Cl-~rly, wlth thl~ ~pproach v r~l broX r- ~not hown) could b conn-ct-d through -p~rat- or brldg-d ~8DN
conn-4tlon~ to -tabll-h ~ n-tworX th r u~ong througA whlch any on brok-r c~n bl-dir ctlonally connunlcato with ~-vor~l dl~ r nt r- ot-ly ltuat-d ho-t co~put-r~ to ~t~bll-h and condu4t concurr nt ho-t ---lon- th r-~lth ln ord-r to lnvok ~nd lnultan ou ly proc--- varlou dl~-r-nt corr -pondlng ho~t appllcatlonJ. Non th~ ach ho~t s---lon ln~olv-- a ~lngl- orlgln~t~ng broX-r, i - that whlch orlglnat-d th~ -lon, ~nd a lngl- d--tlna~lon ;~OOS734 brok-r, i e th~t brok-r whlch 1~ ocl~t-d with a glv n - rQ~ot- ho-t coaput-r Por purpo~-- o~ pll~ylng th-dr~wlng and th- n-ulng dl-cu--ion, only on- ho-t ---lon wlll b~ u~ d to occur b-tw -n a lngl- p-lr of brok-r~s orlgln~ting brok-r 820 ~nd d-~tln~tlon brok r 840, ~- ~hown, - wh-rein eith-r on- Or th-~- brok-r- h~- th- c~p~bility to ; dyn~ic~lly chang- th- ISDN ~cc--- path u~ d to c~rry th~t ~e~-ion b-two-n ~ B ch nn l clrcult wltch d conn-ctlon and a D chann-l pack-t wltch d conn-ction in th- v nt that brok-r d-t-rDln-- tb~t ~ ch~ng h~ occurr d ln th-co~unlc~tion r-qulr 4 nt~ o~ that ~ lon or th~t broX-r h~ b- n ~p-cl~ic~lly ln-truct d to ch~ng th- ch~nn-l, through u~-r proc--- 8~0 ~or brok r 820 or~u--r proc--- 850 ~or brok r 8~0 lS
A t~t- dl~gr~a o~ th- o~tw~r- ~h~t 1-inpl-~-nt-d withln any bro~ r, .g. broX r 820, t~t ~or~ -~ultl-brok r y~t-a 800 hown ln ~IC. 8 nd u~ d in con~unctlon wlth dyn~ lcally an~ging ~ lngl- I8DN ~cc---p~th pp ~rlng th-r ln 1~ coll-ctlv ly d-plct-d ln P~C~ 9A
~nd 9Bt th- prop r allgn nt o~ th dr~wlng h--t- ~or th---~lgur ~ 1- hown ln P~a. 9 ~n~ uch ~ brokor 8~0, hown ln P~G 8, ~- ltu~t d ~t an oppo-lt- nd o~ th- I8DN ~cc-~-p~th ~ brok r 820, brok r 8~0 wlll b- r r rr d to ~ th-~p--r~ broX r tbrougbout th rollo~ing di-cu ~lon ~h-proc dur Y cut d by brok r 820 r qulr-- th- -t~bli-hJ nt o~ -t-r/-l~v ~ r l~tlon hlp b tw -n thl- brok r ~nd lt~
p -r brok-r in ord r ~o ~ur th t only on clr~ult - wltch d conn ctlon 1~ ~t bll h d b tw -n tb two bro~ r~
~hould both brok-r~ ~tt apt to tr~n-ltlon l~ult~n-ou-ly ~roa ~ D ch nn l to ~ ~ ch nn-l conn ctlon. Wh n tho inltl~l X 2S conn ctlon 1~ -t~bll h~d b ~w -n th- two brok r~, th~t brok r wblc~ l- tb r clpl-nt Or tb-conn-ctlon 1~ d ~ln~d to b th- ~-t-r broX-~ whll- th-3S oth-r brok r whlcb l~lti~t th conn ctlon 1~ d-rln~d to b ~005734 -~6-th- ~lav- brok-r Thl- d-~lnltlon onC- o-tabli~h d r~ln~
con-tant throughOUt th- re~lnd-r Or th- 18D~ csnn-ction establl~h-d b-tw--n th- two broX r- ~h- d-~lnltlon 1~ only us-d, a~ ~-t torth b-low, wh-n th- u--r proc~ - occurring at both broX-rs ~r- att-~ptlng to ~lmultaneou d y ~t~bll~h B
channel connectlon~ b-tw--n both brok-r- ~nd provid-~ a a~ch~nl~ to s-l-ct whlch on- Or th- two brok-r~ i~
p-r~itt-d to ~t~bll-h ~ 8 ch~nn-l conn~ctlon wlth th- oth-r brok-r In p~rtlcul~r, th B ch~nn-l ¢onn-ctlon th~t th-a~-t-r brok-r 1- ~tt-~ptlnq to -t~bll-h t~k-- pr-c-d-nc-ov-r th- B ch~nn-l conn-ctlon th~t th- l~v- brok-r i~
si~ultan-ou~ly ~tt-~ptlng to -t~bll-h A~ uch, both brok r- wlll contlnu- Q 931 -t~bl~-h~ nt ~roc-dur - ror B
ch~nn-l conn-ction inltl~t-d by th- a~-t-r brok r whll-~bortlng th- D ch~nn-l conn-ctlon lnltl~t d by th~ v-brok r A~ hown ln ~C- 9a ~nd 9B, lr brok r 820 1- not w tlv-ly c~rrylng ~ ho-t ~ lon, th n ~h~t brok r r-~ln-ln Idl- ~t~t- 910 untll ~ D chunn-l conn-ction i- to b--t~bll-h d wlth th- p -r brok r ~o -t~bll-h uch conn-ctlon, ~ u~-r lnvok-- ~ t-ruln~ ul~tlon progr~
wlthln brok r 820 ~hlch ub--qu ntly, ln turn, tr~n ~lt- ~n X 25 Call R-gu-Jt p~c~ t through th- TSDN ~nd p clrl-~ th-p -r brok r ~ lt- d--tln~tlon. In th- v nt th~t th- I~DN
i- un~bl- to conn ct tho c~ll, th-n th I8DN r-turn ~n X 2S
Cl-ar pack-t to brok r 820 to t-rJlnat- th- call att-Jpt In thlJ c~- , brokor 8ao r-~ln-, a- lndlc~t-d by lln- 913, ln tat- 910. Alt-rnatlv ly, 1~ brok r ~20 r-c lv-- ~n X 2S
C~ll Conn ct p~ck t rrO~ th I~DN, th-r by lgnl~ying that th~ call att-npt wa- ucc---rul, and brokor 820 through ~
u--r proc-~- x cutlng th-r-~t w~- th- brok~r that lnltlat d th- call att-npt, th n ~ok r 820 1~ d rln d ~ lnq th-~lav brok~r_ ~, on th oth-r h~nd, th~ ~ucc~ ul c~ll 3~ att~pt lnltlat~d w~th a w -r proc--- x-cutlng at th- p--r ,' '' -~7-broX-r, l e brok-r 840, th-n brokor 820 1~ d-~ln-4 a- b ing th- ~t-r brok-r A~ not-d ~bov-, ach broX-r ~intain~
thl- d-finitlon throughout th- r ~ind-r o~ lt~ ~DN
conn-ct~on wlth th- oth-r b~oX-r Onc- b~ok r 820 ha~
d-~inQd lt~ ~tatuJ a- ~a~t-r or lav-, th- ~tat- ot thl~
brok-r tran~ltlon- along lln- 917 lnto D Chann-l 8t-ady Stat- stat- 920 -Whll- ln th- D Chann l ~t-ady St~t- ~tat-, brok-r 10 820 and lt~ p--r broX-r acc-pt and pa~ X 2S pack t~
t~-r b-tw -n b-tw~ n u--r proc--~ 810 through tb- ISDN and u~-r proc--- 850 tor proc---lng BroX-r 820 wlll l-av ~tat- 920 und-r varlou- condltlon s an X 2~S Cl-~r ~ --ag 1-r-c-lv-d tro~ th ~DN to dl-conn-ct th- D chann-l lS conn-ctlon~ th u~-r proc---, 1 -. u--r proc--- 810 hown ln FIG 8, x-cutlng at th~t broX r r gu -t~ ~ tran-ltlon ~ro~
a D to B chann-l conn ctlon and~or th- u--r proc---x-¢utlng at th- p--r bro~ r, 1 -. u- r proc--- 850, r gu--t~ a tr~n~ltlon ~roa D to B cbann-l conn ctlon ~ -20 ~p cl~lcally, 1~ bro~or 820 r c lv an X 2S Cl ar p~ck t - ~roa th- ISDN to dl-conn ct th- D ch~nn-l conn-ctlon, th n tha~ brok-r, 1~ lt 1- ~ a-t-r, ~lr t dl-conn-ct- any ho-t conn ctlon lt -t~bll h d to lt a--oal~t-d co-put-r rollow d by tran ltlonlng lt- tat-, ~- lndlcat d by lln-2S 928, bacX lnto ~dl- atat 910. U t rnatlv-ly, 1~ brok-r 820 r-c-lv - a Q 931 8-tup x-- ag ~roa th ISDN and th orlgln~tor o~ thl- -J ag 1- not th p -r brok r, th n thl~ -n---ag 1- rron ou ~n thl- c~ roX r 820 wlll ~-nd a corr -pondlng Q.931 Dl conn ct n--~ag to th- I~DN to 30 t r lnat- thl- att- pt d B chann l conn-ctlon ~nd wlll th r ~t-r ro ~ln, a- lndlc~t d by lln 9~, ln D Chann-l St-~dy ~tat- t t- 920 No~, ln tb ~ nt th t brok r 820 r~c-lv - a Q 931 S-tup no--~g to ~tabli-h a B chann-l conn ctlon to lt- p- r brok r, th t~t- oS thl- brok r wlll 35 tran ltlon lnto on 'o~ two tran lto~y ~t~t-~, ~p cl~lc~lly , , , : , .
, ........ . . . .

, . . . . . ... . ...
, . . .
.

X00~i73~

~nltlatlng Tran~ltlon to B Chann-l tat- 930 or Acc ptlng * TranJitlon to ~ Chann-l tat- 9~0, d-~-ndlng u~on vh th-r brok-r 820 lAltlat-d that Q 931 ~ --aq- or r c lv~d lt ~ro lt~ p~ roX-r, broX-r 8~0 In th- v nt that broX r 820 lnltlat-d th- r-qu ~t to tr~n~ltlon to a ~ chann-l conn-ctlon, uch a~ throuqh a us-r r-gy--t nt-r d at thl- broX r, th- ~tat- o~ broX r 820 th n tran-ltlon~ along lln 924 lnto ~nltlatlnq ~ran-ltlon to B Chann-l tat- 930 Qt t 930 1- a tran~$tory tat- and i- ---ntlally ld-ntlcal to B Chann-l ~ t~bll hn nt tat-230, dl-cu---d ~bov- ln con~unctlon vlth F~Ga. 2A and 2~, wlth th- addlt`lon ot tvo addltlonal tr n~l~lon rout--.
~roX-r 820 vlll xl-t vlthln t t- 930 tor a v-ry hort lS p-rlod ot ti~ Whll- ln t~l- t t-, broX r 820 vlll no~
tran-alt any d ta nJ--ag ~ to th 18DN. Hov v r, brok r 820 vlll acc-pt any X ybc~rd lnput tro~ th- uJ-r an~ locally butt r t~l- data tor uba-qu nt tranJ~ lon. ~ any X 25 pack-t~ ar- r-c-lv d troa th- I8DN, th n broX r 820 vlll locally dl-play th data contaln d vlthln th-~- pack tJ and ~pproprlat-ly proc--- any PAD con aAd~ contaln d vlthln th--- p~cX t- accordlng to th- X.3 and X 29 PAD
R-cona-ndatlono. Al o, ln t~ v nt any ~ ch nn l data 1-r c lv~4, broX-r 8~0 vlll appro~rl~t-ly butt r thl~ data tor 2~ ub--qu nt dl-play. Now, ba~ d upon vh th r bro~ r 820 can ucc---tully at bll-h a B chann l conn ctlon (a~ a ~tlrJt~
uch conn ctlon) to th 18DN, or ~h th r a ~ cond r qu-~t tor ~ 8 chann l conn-ctlon w a r c l~ d prlor to th-ucc w ~ul -t bll-h~nt ot th- tlr t 8 a~nn l conn-ctlon and bro~ r 820 lo a a-~-r or ~la~ broX r, th-n broX r 820 tr nJltlon- lnto on ot rour tat-~s D Ch~nn-l 8t-~dy Stat-tat- 9~0, ~ r lnal Idl- tat 910, Acc-ptlng ~r~n ltlon to 8 Chann-l ~tat- 940 or 8 Ch nn-l 8t-ady St~t- tat 950.

.
, ," , ,' : ,'' .' , ,:
, ,, ' '' ' ~ . .' ' .. . ..
,, ~ , , ;~005734 , Ir b~Ok-~ 820 r--ld-- ln ~tat- 930 and 1~
att-~ptlng to -t~bll-h ~ B chann-l conn-ctlon wlth th~ ~gDN
but th- ~SDN 1- un bl- to ~ovld- thl~ conn ctlon to brok~
820, th~n thl- brok-r th n r-c l~ Q 931 Dl~conn ct ~ g- rrO~ th- lgDN ln r-~pon ~ to thl~ g , th-stat~ Or broX-r 820 tr~n~itlon along lln- 939 back lnto D
Ch~nnel St-~dy Stat- t t 920 in ord-r ror thl~ brok r to c~rry ~ub~-gu-nt con unlcatlon~J X 25 pack t tra~rlc to lt~
p -r brok-r ov-r th- Yi~ting D ch nn l conn-ctlon to th ISDN ~lt-rnatlv-ly, lr . B ch~nn-l conn ction ha- b- n ~t~bll~h-d b-t~ n t~ 18DN ~nd brok-r B20 but th- V 120 protocol h~ th-n r~il d to prop rly initi~llz-, th n brok-r 820 l~-u-- ~ Q;931 Di-conn-ct ~---g to th ~DN to t-~r down thl- conn-ctlon. Onc- thl- dl-conn-ct ~ g- 1J
1~ g n-r~t d, th- tat- Or brok r 820 ~l-o ~r~n~ltlon~ ~long lln- 939 b~ck to tata 920.

Now, lr broX r 820 la in t~- proc--~ Or -t bll-hlng a ~ chann 1 conn ction ov r t~ DN to it~
p--r brok r ~- ~ rt Or t t 930 and th n r-c i~-~ a Q 931 S-tup ~ g- ~ro~ th p -r bro~ r, thi~ n~ g- lndlc~t--that both brok~r~ ar nov ~tt ptlng to l-ult~n-ou-~y lnltl~t- S ch~nn l call conn otlon-~ ~o a~ur that only on B ch nn-l conn ¢tlon 1- t bll-h d aa th r--ult o~
th - two ¢all att-Jpt~, only on~ o~ th-~- ~tt- pt- wlll b-- ~u¢¢-~ul d p ndlng upon ~h th r b~ok r 8~0 h~J a ~-t~r or d a~ tatu~, di~cu~--d ~bov . ~n p~rtlcular, th-~a~t-r~-lav tatuJ Or brok r n 0 d-t roln ~ ~hi¢h on or t~o t t -, ~t t~ 9~0 or 950, thla brok-~ a-~u~--. Th r~at r brok~r v111 b p r~ltt d to -tabll~h it~ B cb~nn l conn ction t~roug~ th- ~DNt ~hll- th conn-ct~on whlCh th d av brok-r i~ atta ptinq to ~t~bll-h will b- abort-d Sp cl~ic lly~ 1~ brok~r 8~0 h~- th t tUJ ~- th 3~ ~a~t r brok r and i-'att--ptin~ to t~bll~h ~ ~ ch~nn l ... .
.

,, ,: ~ ', ' ~ " , . ., ~

~OS73'~

conn-ctlon wlthln tat- 930 and ~laultan-ouJly r-c-lv-~ a Q 931 S-tup ~-~sag- ~roa lt- p -r brok-r, th-n, ln r -ponJ-to thl~ s~tup ~ s-~g-, brok r 820 wlll tran~lt a Q 931 Dlsconn~ct m~ g- to th- TSDN ln-tructlng th- n-twork to disconnoct th- B ch~nn-l conn-ctlon whl¢h lt~ p--r, l - th-~lav- broX r, l- ~tt-~ptlng to - W bll-h Thl~ dl~conn-ct ~-sag- wh-n x-cut-d by th- I~DN ~f ctlv-ly t-ralnat-~ th-B chann-l c~ -tup ~tt-4pt th n b lng und-rt~k n by th p~-r broX-r and p-r~lt~ th- ISDN to ~ucc-~fully ~tabll~h th- B chann-l conn-ctlon ~hlch broX r 820, ~ t-r broX r, h~ lnltlat-d ~n p~rtlcul~r, onc- thl~ dl~conn-ct ~ ~ag-l~ tr~n-~ltt-d, brok~r 820 r--~ln~ lndlc~t d by lin~
931, ln ~nltl~tlng Tran-itlon to B Ch~nn~ t~t- 930 Th-r-~t-r, brok r 820, ~ t-r broX r, proc--d~ to ~lnl~h ~t~bll~hlng lt~ B ch nn-l conn-~tlon through th ISDN to th- p--r brok r In o dolng on~o broX r 820 r-c-lv-- ~ Q 93~ Conn-ct a --~g froa t~ ~DN ~nd obt~ln~
an lndlc~tlon that th V 120 psotocol ha~ ~ro~ rly lnltl~llz-d ov r thl~ conn ctlon-and h~- r c-lv d a ~-~llng ~ g- ln ~n X ~5 p~cX-t ov r th D ch~nn-l conn-ctlon, brok r 820 wlll r l-a~- ny pr vlou ly buff r d d~ta r c-lv d o~-r th- B ch~nn-l conn-ctlon to th u~-r Jcr--n - a-~ocl~t d th-r vltb. Onc thl- occur-, tho ~t~t- o~ brok-r 820 tr~n ltlonJ ~long lln 935 lnto 8 Ch nn-l 8t-a~y gt~t-~t~t- 950 Alt rn tlv ly, 1~ broX r 8~0 ha- th- ~t~tu~ ~ th-v brok r n~ 1J tt nptlns to ~t~kll-b ~ ~ ch~nn conn ctlon vlthln t~t 930 and ~lault~n ou ly r c-lY~- ~
Q 931 8-tu~ u~ g- ~ron lt- p -~ ~roX-r, th-n, ln r JponJ-to thl- -tup n~J~g , brokor 820 vlll tr n lt ~ Q 931 Dl conn ct ~ ag to th ~8D~ ln tructinq tho n-twork to dlJconn-ct th- B cb nn-l conn ctlon vhlch ~ro~ r a20, 1 -th- l~v bro~ r, 1- ~tt--ptlng~to -t bllah ln ~vor o~
3S p r lttlng th- 18DN to ucc--~ully -t~blldh ~ B ch~nn-l .: .:, : ,,.
, :, , ' .

~005~73~

conn-ctlon whlch th~ r broX-r, ~ t-r brok r, h~
in~tl~t-d A~ ~uch, broX-r 820 -nd- a Q 931 Dl conn-ct ~-s~ag- to th- SSDN to t-rsln~t- th- B chann-l conn-ctlon att-~pt $~t h~- lnitl~t d onc- thl- h~- occurr d, th tat-S o~ brok-r 820 tran-itlon~ along lln- 937 lnto Acc-ptlng ~ran-ltlon to B Chann-l tAt- 940 8tat- 940 1~ al-o ~
tr~n-ltory ~tat- and 1~ ntl~lly ld ntlc~l to B Ch~nn-l E~t~bllsh~-nt ~tat- 230, dl~cu~- d abov ln con~unctlon ~lth FIC~ 2A and 28 Wlthln t~t- 940, broX-r 820 wlll proc-~d to ~ln~-h -tabll~lng ~ B ch nn-l conn-ctlon wlth lt- p--r, brok-r, h-r- th- ~a~t-r brok-r Sn ~o dolng onc- brok-r 820 r-c-iv-~ a Q 931 Conn-ct ~ g rrO~ th 18DN and obtaln~
an lndlcatlon that th- V 120 protocol ha~ ~rop rly $nltializ-d ov r thl- conn-ctlon and ha~ r c lv d allng ~ ~ag- ln an X 25 F~ck-t ov-r th D chann-l conn-ctlon, brok r 820 vlll r-l a~- ~ny pr vlou ly burr r d data r c-lv d ov-r th B chann-l conn ctlon to th- u--r cr- n a~oclat~d th-r-at onc thl- o¢cur~, th~ ~t~t- Or broX~r 8~0 tran~lt~on- along lln 94~ lnto ~ Ch-nnol 8t-~dy Stat-~t~t- 9S0 Alt-rn tlv ly, lr broX r 8~0 1- un~bl- to -~rully ~t~bllah B ¢h nn-l conn ctlon wlth ~nd lnltlat d by lt- p brok r, thon brok r 820, d p ndlng upon th- n---~g- lt r c lv ~ troa th- S8DN, tr~nJltlon- back into D Ch~nn l 8t-~dy 8tat- t~t- 920 or Sdl- ~t t- 910 8p ¢l~l¢~llr, 1~ brok~r 820 r-¢ lY ~ Q 931 Dl~¢onn ct ~ag-, th- ~tat ot broX r 820 tr n ltlon~ ~long lln 9~C
bacX lnto D Cbann l St-~dy 8tat- t~t- 920 ln ord-r ~or brok-r 820 to c r~y ~ub ~u nt oo-aunlcatlon ~ X 25 pack-t t~t~lc to lt~ p -r broX-r ov r th xl~tlng D ch~nn-l conn-¢tlon to th- ~8DN. Alt-rn~tlv-ly, 1~ ~ ~ ch nn~l conn~ctlon hn- ~o~n -t bllah d b t~ n th ~8DN und brok-r 820 but th- V 120 proto¢ol h~ th-n ~all d to prop rly lnltlall~-, th n brok r 820 l~-u - ~ Q 931 Dl-conn-ct ~ --ag- to th- 18DN to t-ar do~n thl- B ch~nn-l aonn-ctlon onc- thl- dl-conn-ctq~ J-ag 1~ g n r~t-d, th- tat- o~

brok r 820 alJo tran-ltlon- alon~ lln- 9~6 ba¢k to ~t~t 920 Alt-rnatlv-lY, lr broX-r 820, whll- ln tat- 9~0, r-c-lv-~ an X 2S Cl-ar pack t ~ro~ th- ISDN, th-r by indlcatlng that th- D chann l pack t conn-ctlon hould b torn do~n, brok-r 820 ~ub~-qu-ntly tranJ~lt~ a Q 931 Dl~conn~ct ~ ~ag- to th- I8DN to t~ar down th- D chann l conn-ctlon onc- thl~ oc ~, th ~tat- or brok r 820 tran~ltlon~, along lln- 944, back to ~dl- ~tat- 910 Now, lt bro~ r 820, ~hll- ln tat- 930, r-c-~v--an X ~5 Cl-~r pack-t ~ro~ th- I~DN, th r-by lndlc~tlng that th- D chann-l pack t oonn-ction hould b- torn do~n, brok r 820, lr lt i~ a a~t-r, dl~conn-ct~ any conn-¢tlon lt ha~
~tabll-h-d to lt~ ho~t co~put-r rOr th- p--r broX r and ~ub--gu-ntly tran-nlt- a Q.931 Dl~conn-ct ~ ~ag to th-~8DN to t-ar down th B chann-l conn-ctlon onc- th$-occur-! th tat- Or broX r 820 tr~n~ltlon , along lln- 933, bac~ to Idl- tat- 910.

Whll- ln B C~ann-l 8t ady 8tat- ~t~t- 950, broX-r 820 acc-pt- and pa-~-c data ln Y.l~0 ro~n ov r th- B chann-l clrcult wltch d conn ctlon throuqh th 28DN b tw -n lt~-lr and lt~ p--r broX r rOr proo --ln~ by th- r -p ctl~ uJ-r proc ~ cutln~ th r at. In thl- tat- and a-ld- rrO~
2S any protocol conv r lon that ~y occur, broXo~ 820 ~ r-ly pa---~ dat~ wlt~out ~lt~rln4 lt~ cont nt BroX-r 820 r~ alna ln tat- 9S0 untll th I~DN dl-conn-ct- th D
ch nnol ¢onn ctlon, or th- p--r broX r or th u~-r proc-~-x cutlng at brokor 8~0 r qu -tJ ~ trun~ltlon in th curr0nt ~8D~ a¢o ~ p~th ~ro- a B to ~ D ch nn-l conn-¢tlon. ~n pa~tlcul~r, 1~ brok r 820, ~h~l- r -ldlng ln 8 C~nn-l St dy 8tat t t- 950, r ~ iY ~ ~ ~.931 Dl-conn-ct ~ ~-ag-~ron th- ~DN ov r th D Cb~nnol conn-ctlon, tbl- lndl¢~t ~ i that th p ~r ~rok-r 1- r gu -t~ng a tran ltion ~ro~ a 8 to 3S a D ch~nn l conn ctlon. ~ ~uch, th tat- ot broX r 820 !

. .
.
, . .. ..
., . , ~ . .

, ;~)OS'734 tran-$tlon~ ~lonq lln- 957 b~oX to D Ch-nn-l ~t~dy 8t~t-st~t- 920 ln ord-r rOr broXor 820 to c~rry ~ub~-qu-nt co~unlc~tlon a- X 25 p~cx t tr~tfl¢ to lt- p--r broX-r ov r th- xl~tlnq D ch~nn-l conn-ctlon to th- I~DN.
Alt-rn~tiv-~y~ uA-r proc--~ x cutlnq wlthln broX-r 820 r-qu-~t~ a B to D chann-l tran~ltlon, th-n brok-r 820 tr~n~lt~ ~ Q 931 Dl-connoct ~ ~g- to th- r8DN to t~ar down th- curr nt B ch4nn-1 conn~ctlon. Onc- broX-r 820 r-c-lv~ ult~bl- Q 931 ~ - Co~pl-t- ~ ~ag fro~ th ISDN p-clfylng th~t th- B chann-l conn-ctlon no long-r xl-t-, th-n th- t~t- of broX r 820 ~l-o tr~n ltlon~ ~long lln- ss7 bacX to D Ch~nn-l St-~dy St t ~t~t- 920. I~tly, lr broX-r 820, whll- ln t~t- 950, r o-lv - ~n X 25 Cl-ar pacX t fron th 18DN, th-r by lndlo tlng th~t th- ~ chann l lS p~oX t conn~otlon houl~ bo torn dovn, broX-r 8~0, 1~ lt l-t-r, dl-conn-ct~ ~ny conn ctlon lt h~n t~bll hod to ltn ho-t conput-r ~or th- p- r broX r nd ub~-qu ntly tranJnlt~ ~ Q 93~ Dl~conn ct n-~g- to th- ~8DN to t-~r down th- B ch~nn-l conn ctlon. Onc- thl~ oocur~, th- ~tat-of broX-r 820 tran ltlon , long lln 9S3, back to Tdl-- ~t~t- 910 Cl arly, tho~ ~klll-d ln t~o ~rt r cognlz- th t ~lthough lnv ntlv ~y~t-o 5, hovn ln F~a. 1, h4- b- n hown 2S ~nd d-~crlb d - lnt r-connoctlng ~ BroX r PC to ~ nu~b r ot ~ r~t- ho-t co put-r~ by ~ ~N, ~ch ot th ho-t conput r do ~ not n d to b ltu~t d in t~c vlclnlty o~ -t~o ~ro~or PC. Tn t4ct, th L~N can xt-nd gult ~ooo dl~t~nc to r ch ~ ho-t co~put r. Por ho-t co~ut~r- th4t ar dl~p-r~-d ov r a r l~tlv-ly vld- g-oqr~phlc ar ~, ~h-- L~N could b dv nt~g-ou ly r-~l~cod vlth ~ n-tropolltan ar-~ n twork ~AN) or wlth ~ny on o~ v~rlo w oth-r typ o~ -w ll Xnown hlg~ p d dlglt l conput-r llnk~ t~ t int r-conn-c~ th-~- ho~t co p~t r~ w~lth t~- BroX-r PC.

- , ;~OOS734 -6~-In addltiOn, th- lnv ntl~- ~y-t-n could ~-lly ~unctlon wlth oth-r ~or~ Or I8DN acc~ uch ~ pri~ry rat- ISDN acco--, in whlc~ ~ ~ultltud- o~ 8 chann~l p~th~, ~ g 23 B chann-l p~th~, xl~t rOr v ry on- D chann-l path.
Through us- or ~uch ~or~ Or I8DN ~cc--~ ch brok r would b- abl- to upport ~n lncr ~--d nu~b-r or U~-r PC than that d-~crlb-d abov- Th- runctlon- p rror~-d by ~ch U~-r ~nd BroX-r PC ~ould b~ ub-t~ntl~lly ld~ntl¢~l to tho~-d~-crlb-d ~bov-Furth-~or-, th- ho-t co~put-r could ~ploy sult~bl- ~lgorlth~ wblch t~tl-tlcally d~t-rnln-~ on glob~l b~ , b~ upon lllu tr~tlv-ly qu-u-- Or ~ g ~nd p~ck6t- ~wAltlng tr~n-port through th- I~DN, ~rr~v~l r~t-~ Or ~ g - ~nd p~ck tJ ~t th-lr d~tln~lon- ~nd~or ongolng dl-trlbutlon Or tr~rla ~low tbroughout th ~DN, wh-th-r ~ B or D ch~nn-l ~SDN conn ctlon ~hould b- u-~ ln glv n ltu~tlon AJ uch, thl- ~lgorlthn would utlllz-rul-- th~t ~dv~ntag-ou ly ~aX ~h ~ l-ctlon Or Wh-th r to u-- ~ B or D c~nn-l ISRN conn ct~on ~-ontlally ind-p nd nt Or th curr-nt ho-t ~pplle~tlon b lng x cut d by a u~-r Ir ~ t-rnlnal adapt-r ~nd a n-tvorX t-r-~n~tlon w r- to b-conn-¢t d dlr otly to tho ho-t Go put-r, th-n thl- ho~t - conput~r oould b- dlr atly lnt r~e~d to a ~B~D~ ba~lc ace-~ path ln th- IJD~ notwork ~nd, at th approprl~t-tluo~, g-n-ra~- pproprl~t Q 931 control ~ g - and X 25 p~cX~t~ to dyn~ lcally ~b~nq a eurr nt I~DN conn-etlon whlc~ ~ r ot- u~-r 1~ ~ploylng durlng a ho-t ~ lon In~J ueh a~ th ~DN lnt-rrae~ runetlon- ~rovld~ by ~-broX r vould, through uCh u~- Or a t r lnal ~d~pt r, b lncorpor~t d lnto th ~o-t co ~ut r, thl~ would ~dvant~g-oualy ~nd ~ub-t~ntl~lly l~aln~t th- n- d to u~
~-Far~t- broX r wlth th~t ~o-t coo~ut-r. ~n ~ddltlon, th brok-r or ~ r ly lt- ~unctlonallty could b~ r-~d$1y ~5 $ncorpor~t d lnto th~ ~8DN lt--l~, ~nd pr ~ ~bly w$thln an ~ " . ' ', . .
,, , .

;~005~

, ~SDN ~w$tch, ln ord-r to p-r~lt un ntlty th~t 1-co~unlcatlng ov-r an ~SDN acc--- path provld d by th-switch and whlch i~ conn-ct d to ~n nd o~ that path to dyn~lcally man~g- that path ln accordanc- wlth th-S co~unlcation r-gulr~ nt- o~ a ta~k curr-ntly b lng ox-cut~d at oith-r nd o~ that path durlng a ho~t ~ lon involv$ng th~t ~ntlty Mor-ov-r, ~lthough th u~r h~ b- n d-~cr$b d ~-b-ing an lndl~$dual that u~r-ly Y cut-- a t-r~$n~1 ~ulatlon progr~a at a U -r PC ln ~y~t-a 5 ~hown ln ~Ta. 1 or a broX-r in cy-t-a 800 bown ln FTa 8, th u r n-~d not b- ~o con~tra$n-d In ~act, th- w r can ~- ~noth conput-r that pro~ld o a r gul-lt- a ount ot r ~ot- data proc-~lng durlng th- ho-t ~--clon, vlth tb- u~ount ~ lng d-p nd-nt upon th- pro¢-~lng ¢apablllty at th- uJ-r lo¢atlon and lto a~allablllty th-r at 8uch ho~t ~-~clon~
t~at bl~ur¢at- pro¢-c~$ng r cpon lbllltl-~ b-t~- n ~wo ~-parat- coDput-rc lnt rconn ct-d througb a tran~ lon ~ dla, ~uch a~ ~n T8D~ conn ctlon, can rro4u ntly arl~- ln dl~trlbut d proc---lng appllc~tlon-. On- uch llluJtrativ-~ppll¢-tlon lnvolv - a co-put-r lnt grat-~ anu~acturlnq ~C~ y-t-~ that lnt grat-- an~ p r lt- d~t~ tr-n~ r b-t~ -n ~-v ral g oqra p lcally dl~p r d co put-rlz d 2~ ~y-t-n~ q. a co~put r ald d d--lgnlng (C~D) ~nq~or a conput-r ald d ngln -rlng ~Ca~) y t-~ ltu~tad at ~n ngln--rlng loc tlon, a co~put r ald d ~nu~cturlng (CAN~
~ndJor a co put~ d ~nvontory y t-- ~ltuat d at a plant locatlon, and/or v rlou- co put r a--l-t-d accountlng, ~ch-dullng ~nd~or ~anag ~ nt y t-- ~ltuatod at a h-adgy4rt r~ lo¢ tlon.

A~oug~ varlou -bodl~oAt~ o~ th- pr-- nt 1 m ntlon hav b -n J~own Dnd d--or~b d in d tall h-r ln, _ ;~0057 6~
m~ny oth-r v~rl-d obodlr-nt~ th-t lncorpor~t- ~b- t- chlnqJ
Or th- pr-~-nt lnv ntlon ~y ~ lly ¢on truc~-d by tho~
~klll-d ln th- ~rt.

.. . .

.

"''' ,.', , , ,~ .: . ' ' ~' ''., '. ' ' .

,' , ' ' , ' . ', ~, .
' ' , ' , ' ' ' , .: . ' ' , :,

Claims (16)

1. Apparatus for dynamically changing an access path having a plurality of different attributes between a first connection having one of said attributes and a second connection having a different one of said attributes during an ongoing host session carried over said access path in order to provide the particular one of said first and second connections that is most suited to the current communication needs of said session, said apparatus comprising:
means for connection to one end of said access path and to a host computer for instructing a communication system that provides said access path to change a connection provided over said access path between said first and second connections in response to a command received from the host computer during execution of said host session, said instructing means comprising:
means for establishing an interface to the host computer to begin said host session and for maintaining the interface substantially throughout the remainder of the host session; and means, responsive to said interface and for connection to said one end of the access path, for receiving a command over said interface from said host computer requesting a change in the connection provided over the access path between said first and second connections and for supplying the command over said access path in a pre-defined form as an instruction to said communication system so as to effectuate said requested change.

2. The apparatus in claim 1 wherein said instructing means further comprises means, responsive to communication containing a message to establish a host session and received over said access path and originating at an opposite end thereof, for instructing said interface establishing and maintaining means to establish said interface to the host computer and initiate said session.

3. The apparatus in claim 2 wherein said communication system is an ISDN network having at least one ISDN switch and said access path is an ISDN access path, wherein said first connection is an ISDN circuit switched B channel connection and said second connection is an ISDN D channel packet switched connection.

4. The apparatus in claim 3 wherein the D channel packet switched connection is maintained throughout the duration of said host session and the B channel circuit switched connection is established or torn down in accordance with the command issued by the host computer requesting a change in the connection provided over the ISDN access path.

5. The apparatus in claim 4 wherein said B channel carries V.120 data messages and said D channel carries both X.25 data and control packets and Q.931 messages and wherein the instruction to said ISDN network is in the form of a pre-defined Q.931 message.

6. The apparatus in claim 5 wherein said instructing means further comprises means, responsive to V.120 data messages, Q.931 messages and X.25 data packets received over said access path and communication received over said interface from the host computer, for converting protocols therebetween so as to permit the host computer to bi-directionally communicate over said ISDN access path to a user situated at the opposite end of said path and to instruct said ISDN network to effectuate the requested change.

7. The apparatus in claim 4 wherein the host computer issues the command in response to a corresponding call statement embedded within and encountered by the host computer during execution of a host application program, a result of a table look-up operation undertaken by the host computer given a name of a current host application program that is to be currently executed by the host computer, or whenever the host computer detects that the host application program currently executing has terminated line buffering and local echo functions.

8. The apparatus in claim 4 wherein said instructing means further comprises an ISDN network termination for providing a physical ISDN link to said command receiving means from a corresponding ISDN access line provided by the ISDN network.

9. The apparatus in claim 8 wherein the ISDN access path is a basic ISDN access path containing two B channels and one D channel.

10. A method for dynamically changing an access path having a plurality of different attributes between a first connection having one of said attributes and a second connection having a different one of said attributes during an ongoing host session carried over said access path in order to provide the particular one of said first and second connections that is most suited to the current communication needs of said session comprising the steps of:
instructing a communication system that provides said access path to change a connection provided over said access path between said first and second connections in response to a command received from the host computer during execution of said host session, said instructing step comprising:

establishing an interface to the host computer to begin said host session;
maintaining the interface substantially throughout the remainder of the host session;
receiving a command over said interface from said host computer requesting a change in the connection provided over the access path between said first and second connections; and supplying the command over said access path in a pre-defined form as an instruction to said communication system so as to effectuate said requested change.

11. The method in claim 10 wherein said instructing step further comprises the step of instructing, in response to communication containing a message to establish a host session and received over said access path and originating at an opposite end thereof, said interface establishing and maintaining means to establish said interface to the host computer and initiate said session.

12. The method in claim 11 wherein said communication system is an ISDN network having at least one ISDN switch and said access path is an ISDN access path, wherein said first connection is an ISDN circuit switched B channel connection and said second connection is an ISDN D channel packet switched connection.

13. the method in claim 12 wherein the instructing step further comprises the steps of:
maintaining the D channel packet switched connection throughout the duration of said host session; and establishing or tearing down the B channel circuit switched connection in accordance with the command issued by the host computer requesting a change in the connection provided over the ISDN access path.

14. The method in claim 13 wherein said B channel carries V.120 data messages and said D channel carries both X.25 data and control packets and Q.931 messages and wherein the instruction to said ISDN network is in the form of a pre-defined Q.931 message.

15. The method in claim 14 wherein said instructing step further comprises the step of converting, in response to V.120 data messages, Q.931 messages and X.25 data packets received over said access path and communication received over said interface from the host computer, protocols therebetween so as to permit the host computer to bi-directionally communicate over said ISDN access path to a user situated at the opposite end of said path and to instruct said ISDN network to effectuate the requested change.

16. The method in claim 13 wherein the host computer is ?
the command in response to a corresponding call statement embedded within and encountered by the host computer during execution of a host application program, a result of a table look-up operation undertaken by the host computer given a name of a current host application program that is to be currently executed by the host computer, or whenever the host computer detects that the host application program currently executing has terminated line buffering and local echo functions.