CA2042402C - Automatic fault recovery in a packet network - Google Patents
Automatic fault recovery in a packet networkInfo
- Publication number
- CA2042402C CA2042402C CA002042402A CA2042402A CA2042402C CA 2042402 C CA2042402 C CA 2042402C CA 002042402 A CA002042402 A CA 002042402A CA 2042402 A CA2042402 A CA 2042402A CA 2042402 C CA2042402 C CA 2042402C
- Authority
- CA
- Canada
- Prior art keywords
- virtual
- node
- fault
- affected
- fault indication
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
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Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L41/00—Arrangements for maintenance, administration or management of data switching networks, e.g. of packet switching networks
- H04L41/06—Management of faults, events, alarms or notifications
- H04L41/0654—Management of faults, events, alarms or notifications using network fault recovery
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L45/00—Routing or path finding of packets in data switching networks
- H04L45/02—Topology update or discovery
- H04L45/10—Routing in connection-oriented networks, e.g. X.25 or ATM
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L45/00—Routing or path finding of packets in data switching networks
- H04L45/22—Alternate routing
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L45/00—Routing or path finding of packets in data switching networks
- H04L45/28—Routing or path finding of packets in data switching networks using route fault recovery
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04Q—SELECTING
- H04Q3/00—Selecting arrangements
- H04Q3/0016—Arrangements providing connection between exchanges
- H04Q3/0062—Provisions for network management
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L41/00—Arrangements for maintenance, administration or management of data switching networks, e.g. of packet switching networks
- H04L41/40—Arrangements for maintenance, administration or management of data switching networks, e.g. of packet switching networks using virtualisation of network functions or resources, e.g. SDN or NFV entities
Abstract
A transmission is disclosed for recovering from faults in transmission equipment or facilities forming so-called virtual circuits for transmitting packets in a network. Faults are detected in transmission paths associated with a network node and an individual fault indication message is generated for each network facility that has at least one virtual circuit affected by the fault. Each fault indication message includes the identity of each virtual circuit on the associated network facility affected by the fault. The message is transmitted in-band on at least one of the affected virtual circuits on the associated network facility.
If affected virtual circuits are terminated in the node, they are switched to alternate virtual circuits. Otherwise, the fault indication messages are transmitted over the identified facilities to other unknown nodes. A node receiving a fault indication message determines which virtual circuits identified in the message are terminated in the node and which virtual circuits pass through the node. The virtual circuits that are terminated in the node are switched to alternate virtual circuits. For virtual circuits passing through the node, the network facilities associated with them are identified and a new fault indication message is generated for each of the identified facilities. Each of the generated fault indication messages is transmitted in-band on at least one virtual circuit on the, respective, identified network facility. (FIG. 2)
If affected virtual circuits are terminated in the node, they are switched to alternate virtual circuits. Otherwise, the fault indication messages are transmitted over the identified facilities to other unknown nodes. A node receiving a fault indication message determines which virtual circuits identified in the message are terminated in the node and which virtual circuits pass through the node. The virtual circuits that are terminated in the node are switched to alternate virtual circuits. For virtual circuits passing through the node, the network facilities associated with them are identified and a new fault indication message is generated for each of the identified facilities. Each of the generated fault indication messages is transmitted in-band on at least one virtual circuit on the, respective, identified network facility. (FIG. 2)
Description
-
2~2~
AUTOMATIC FAULT RECOVERY IN A PACKET NETWORK
Technical Field This invenion relates to packet i systems and/or networks and, more I ' 'y, to automatic recovery from faults in the system andlor 5 network.
' of the Inven~ion Prior packet L~ and switching systems and/or networks included fault recovery r--n~, One such prior: ~ required a so-called centralized network ~ function to analyze reported faults and to 10 reconfigure the network as required. ('~ 1 ~y, the centralized network ,, function needed knowledge of tne entire network and ~I~y to each node in the network. Such ^ ~ are slow to respond to faults and are also susceptible to faults irl the network and in the ., -~,,. " .~ function itself.
In another prior fault recovery ~ t, each node in the network 15 required knowledge of the netwo}k .. ,., riCI 11 A 1 ;l ~.. and of faults occurring in the network In such an ~ t, each node must store additional network c~ r~c~ data other than that needed for ~ of packets in the particular node~ Any change in the network conficll~tir~n may require a change in the i.,r.,..., -~;"n oeing stored in the node. Both the storing and updating of the 20 c~) - cc~ ;"r .. ) I -1;.... in the node is ~ . and expensive to implement.
More recently, recovery from faults in a packet network has been realized by detecting faults in the ~ I path associated with a network node and ~ e a fault indication message for each virtual circuit which is passing (i.e., switched) through the node and is affected by the fault. Each of the fault 25 indication messages is transmitted in-band on each of the affected virtual circuits and is ad~ , utilized to switch the affected virtual circuits to alternate virtual circuits. Althoughthis All C~-~ll'''1l functions~ rAl1lll;Iy inmany Alllll;l^lill--~> it may not function r~Atjr~fA~t~lily in others. Indeed, a problem with such an A I ) ~- ~ IC~ is that a large number of fault indication messages may have to be 30 generated and transmitted by the particular node. This may require a significant amount of time, thereby delaying the desired recovery from the fault.
2~ 2 Summary o~ the Invention These and other problems and limitations of prior automatic packet fault recover ,, are overcome, in accordance with an aspect of the invention, by detecting faults in ~ . paths associated with a network node and, then, S generating an individnal fault indication message for each network facility connected to some other unknown node from this node that has at least one virtual circuit affected by a detected fault. Each fault indication message includes the identity of each virtual circuit on the associated network facility affected by the fault and is transmitted in-band on a virtual circuit on the associated network facility. If the 10 node terminates any of the affected virtual circuits, no fault indication message is generated for those virtual circuits and they are switched to alternate virtual circuits.
A node receiving such a fault indication message detern~ines which virtual circuits are terminated, i.e., exit the network, at the node and which virtual circuits pass through this node to some other unknown node in the network. Virtual 15 circuits that are terminated in the node are switched to alternate virtual ciTcuits. For virtual circuits passing through the node, the network facilities associated with them are identified and a fault indication message is generated for each of the identified network facilities. These fault indication messages inclnde the identity of each of the virtual circuits passing through the node that were included in the received fault 20 indication messages. Each of these fault indication messages is transmitted in-band on a virtual circuit on the, respective, identified network facilities.
Brief Description of the Drawin~s In the drawings:
FIG. I shows, in simplified form, a packet ~ system and/or 25 network including an ~ of the invention;
FIG. 2 depicts, in simplified block diagram form, details of a packet node used in the system and/or network of FIG. 1;
FIG. 3 shows, in simplified block diagram form, details of the fault recovery unit employed in the node of FIG. 2;
FlGs. 4 and 5 when connected as shown, form a flow chart of a sequence of operations effected by the fault indication message receiver of FIG. 3;
FlGs. 6 and 7 when connected as shown, form a flow chart illustrating a sequence of operations effected by the fault indication message generator of FIG. 3;
FIG. 8 is a flow chart illustrating a sequence of operations effected by 35 the access circuit mapping unit of FIG. 2;
~ 20~2~2
AUTOMATIC FAULT RECOVERY IN A PACKET NETWORK
Technical Field This invenion relates to packet i systems and/or networks and, more I ' 'y, to automatic recovery from faults in the system andlor 5 network.
' of the Inven~ion Prior packet L~ and switching systems and/or networks included fault recovery r--n~, One such prior: ~ required a so-called centralized network ~ function to analyze reported faults and to 10 reconfigure the network as required. ('~ 1 ~y, the centralized network ,, function needed knowledge of tne entire network and ~I~y to each node in the network. Such ^ ~ are slow to respond to faults and are also susceptible to faults irl the network and in the ., -~,,. " .~ function itself.
In another prior fault recovery ~ t, each node in the network 15 required knowledge of the netwo}k .. ,., riCI 11 A 1 ;l ~.. and of faults occurring in the network In such an ~ t, each node must store additional network c~ r~c~ data other than that needed for ~ of packets in the particular node~ Any change in the network conficll~tir~n may require a change in the i.,r.,..., -~;"n oeing stored in the node. Both the storing and updating of the 20 c~) - cc~ ;"r .. ) I -1;.... in the node is ~ . and expensive to implement.
More recently, recovery from faults in a packet network has been realized by detecting faults in the ~ I path associated with a network node and ~ e a fault indication message for each virtual circuit which is passing (i.e., switched) through the node and is affected by the fault. Each of the fault 25 indication messages is transmitted in-band on each of the affected virtual circuits and is ad~ , utilized to switch the affected virtual circuits to alternate virtual circuits. Althoughthis All C~-~ll'''1l functions~ rAl1lll;Iy inmany Alllll;l^lill--~> it may not function r~Atjr~fA~t~lily in others. Indeed, a problem with such an A I ) ~- ~ IC~ is that a large number of fault indication messages may have to be 30 generated and transmitted by the particular node. This may require a significant amount of time, thereby delaying the desired recovery from the fault.
2~ 2 Summary o~ the Invention These and other problems and limitations of prior automatic packet fault recover ,, are overcome, in accordance with an aspect of the invention, by detecting faults in ~ . paths associated with a network node and, then, S generating an individnal fault indication message for each network facility connected to some other unknown node from this node that has at least one virtual circuit affected by a detected fault. Each fault indication message includes the identity of each virtual circuit on the associated network facility affected by the fault and is transmitted in-band on a virtual circuit on the associated network facility. If the 10 node terminates any of the affected virtual circuits, no fault indication message is generated for those virtual circuits and they are switched to alternate virtual circuits.
A node receiving such a fault indication message detern~ines which virtual circuits are terminated, i.e., exit the network, at the node and which virtual circuits pass through this node to some other unknown node in the network. Virtual 15 circuits that are terminated in the node are switched to alternate virtual ciTcuits. For virtual circuits passing through the node, the network facilities associated with them are identified and a fault indication message is generated for each of the identified network facilities. These fault indication messages inclnde the identity of each of the virtual circuits passing through the node that were included in the received fault 20 indication messages. Each of these fault indication messages is transmitted in-band on a virtual circuit on the, respective, identified network facilities.
Brief Description of the Drawin~s In the drawings:
FIG. I shows, in simplified form, a packet ~ system and/or 25 network including an ~ of the invention;
FIG. 2 depicts, in simplified block diagram form, details of a packet node used in the system and/or network of FIG. 1;
FIG. 3 shows, in simplified block diagram form, details of the fault recovery unit employed in the node of FIG. 2;
FlGs. 4 and 5 when connected as shown, form a flow chart of a sequence of operations effected by the fault indication message receiver of FIG. 3;
FlGs. 6 and 7 when connected as shown, form a flow chart illustrating a sequence of operations effected by the fault indication message generator of FIG. 3;
FIG. 8 is a flow chart illustrating a sequence of operations effected by 35 the access circuit mapping unit of FIG. 2;
~ 20~2~2
- 3 -FIG. 9 is a flow chart showing a sequence of operations effected by the frame relay unit of FIG. 2;
FIG. 10 is a graphic IO~ of a LAPD frame; and FlGs. I l and 12 are graphic illllCh~hOnc of fault indication messages 5 employed in this P..,1~l;.... of the invention.
Detailed Description FIG. 1 shows, in simplified form, details of 1,~ . system andlor network 100 employing an ~ ' of the invention. A~ , shown are a plurality of system andlor network nodes, namely, nodes 101-1 through 101-N.
10 Herdnafter all references will be made to network nodes, etc. Also shown are a number of network facilities (NFs) connecting nodes 101 and access facilities (AFs) connected to particular ones of nodes 101. Network facilities carry virtual links (VLs) between nodes inside the network. Access facilities carry access circuits from the network to outside of the network and, conversely, from outside of the network 15 to the network. In this example, some of nodes 101 are identical and others are not depending on their particular function in the network. That is, some of nodes 101 have access facilities connectPd to them while others do not. It will also bo apparent that particular ones of nodes 101 may have a plurality of access facilities. Similarly, particular ones of nodes 101 may interface with a plurality of network facilities 20 connecting them to one or more other nodes. In this specific example, it is assumed that the network facilities are either T1, CEPT1, or T3 i facilities using non-~ ISDN packet mode framing formats, e.g., LAPD, protocols, and procedures. In some different ~ , other facilities may be employed, for example, local area networks, wide area networks, RS232 and the like. Each 25 network facility carries one or more virtual links. The access facilities are assumed to be Tl or ISDN basic rate interface (BRI) facilities. Each access facility carries one or more access circuits. In a network node, an access circuit may be connected to a virtual link or a virtual link may be connected to another virtual link. A virtual circuit for a call comprises a local access circuit, one or more virtual links connected 30 through one or more nodes and at least one remote access circuit. It will bô apparent to those skilled in the art that other ~ -: .. . facilities and other packet protocols may equally be employed in pracdcing the invention.
For the purposes of illustrating the fault recovery operation of network 100, in accordance with an aspect of the invention, it is assumed that a primary35 virtual circuit, shown in dashed outline, is ~JV ' between an access crrcuit carried on the access facility (AF) shown connected to node 101-1 and an access 2~2402
FIG. 10 is a graphic IO~ of a LAPD frame; and FlGs. I l and 12 are graphic illllCh~hOnc of fault indication messages 5 employed in this P..,1~l;.... of the invention.
Detailed Description FIG. 1 shows, in simplified form, details of 1,~ . system andlor network 100 employing an ~ ' of the invention. A~ , shown are a plurality of system andlor network nodes, namely, nodes 101-1 through 101-N.
10 Herdnafter all references will be made to network nodes, etc. Also shown are a number of network facilities (NFs) connecting nodes 101 and access facilities (AFs) connected to particular ones of nodes 101. Network facilities carry virtual links (VLs) between nodes inside the network. Access facilities carry access circuits from the network to outside of the network and, conversely, from outside of the network 15 to the network. In this example, some of nodes 101 are identical and others are not depending on their particular function in the network. That is, some of nodes 101 have access facilities connectPd to them while others do not. It will also bo apparent that particular ones of nodes 101 may have a plurality of access facilities. Similarly, particular ones of nodes 101 may interface with a plurality of network facilities 20 connecting them to one or more other nodes. In this specific example, it is assumed that the network facilities are either T1, CEPT1, or T3 i facilities using non-~ ISDN packet mode framing formats, e.g., LAPD, protocols, and procedures. In some different ~ , other facilities may be employed, for example, local area networks, wide area networks, RS232 and the like. Each 25 network facility carries one or more virtual links. The access facilities are assumed to be Tl or ISDN basic rate interface (BRI) facilities. Each access facility carries one or more access circuits. In a network node, an access circuit may be connected to a virtual link or a virtual link may be connected to another virtual link. A virtual circuit for a call comprises a local access circuit, one or more virtual links connected 30 through one or more nodes and at least one remote access circuit. It will bô apparent to those skilled in the art that other ~ -: .. . facilities and other packet protocols may equally be employed in pracdcing the invention.
For the purposes of illustrating the fault recovery operation of network 100, in accordance with an aspect of the invention, it is assumed that a primary35 virtual circuit, shown in dashed outline, is ~JV ' between an access crrcuit carried on the access facility (AF) shown connected to node 101-1 and an access 2~2402
- 4 -circuit carried on the access facility (AF) shown connected to node 101-N. The primary virtual circuit is ca~ried from originating node 101-1 to desination node 101-N through a prima}y path includingnodes 101-2, 101-3 and lbl-4 and virtual links (VLs) carried on the assvciated
5 network facilities (NFs). ~ " an altemate virtual circuit, shown in dot-dashed outline, is ~vv I between the access circuit carried on the access facility (AE~) connected to node 101-1 and the access circuit ca~ried on the access facility (AF) connected to node 101-N on an altemate path passing through node 101-5 and virtual links carried on the associated network facilities (NFs). Although 10 only one primary virtual circuit and one altemate virtual circuit are shown, there may be a plurality of such virtual circuits vetween node 101-1 and node 101-N.
Moreover, it is important to note that none of nodes 101 in network 10v has knowledge of any other node in the network. Each of nodes iol, only knows its own mappings of access circuits to virtual links and virtual links to virtual links. It is 15 further noted that a fault can occur in the node equipment itself or in one or more network facilities connecting nodes. In this example, it is assumed that a faultoccurs somewhere in the i path between nodes 101-3 and 101-4.
When a fault occurs, there is a disruption in the primary virtual circuits along the primary path between node 101-1 and node I01-N. Upon detecting the0 fault, each of nodes 101-3 and 101-4 detemlines which virtual circuits and q v network facilities that are affected by the fault. Node 101-3 generates a fault indication message for all the affected virlual circuits on a network facility and supplies it as an output on at least one of the affected virtual circuits to node 101-2. Alternatively, a specific virtual link ID (DLCI) can be designated to transport 25 the fault indication messages. In this example, a separate such fault indication message is generated for each network facility connected to node 101-3. In this example, only one such network facility is connected to node 101-3. In this example, the fault indication message is a LAPD frame a;lGS. I l and 12) using aXID format. (See CCITT Rr~ Q.921, pages 4248, and Committee T1 30 (' ' "Explicit Congestion avoidance indication as part of Link Layer , TIS1.1-89/339, T1S1.2-89/240, July 17-21, 1989, pages 1-14. for an ., ' of the LAPD frame and XID format). Similarly, node 101-4 generates a fault indication message for all the effected vir~ual circuits on a network facility and supplies it as an output on at least one of the affected virtual circuits to node 101-N.
35 In this example, a separate such fault indication message is generated for each network facility connected to node 101-4. Again, it is noted that neither node 101-3 ~ 24~2 nor node 101-4 has knowledge of other nodes in the path or of the end points of the affected virlual circuit. Nodes 101-3 and 101-4 include; r~ .. relating only to the virtual link to virtual link mapping of the virtual circuit. Upon receiving any of the fault indication messages, node 101-2 dete~rnines if any of the affected virtual S circuits are terminated in this node. Since none of the virtual circuits are terrninated, node 101-2 then determines which network facility and virtual link that the incoming virtual link of the affected virtual circuit is connected to for all of the affected virtual circuits. Fault indication messages arc generated, as described above, for all the affected virtual circuits on a network facility and relayed over at least one virtual 10 link on the network facility to a connected node, in this exarnplc, node 101-1. In this example, this relaying of the fault indication message is realized by employing the known LAPD frarne relay procedures. (See articles entitled "Frame Relay: Protocols and Private Network Al.l.l;.-l;. ,..~", Fr. . f IEEE lNFOCOM 89, April 23-27,1989, pages 676-685 and "Frame Relaying Service: An Overview", l~u~I;
f IEEE lNFOCOM 89, April 23-27, 1989, pages 608-673 for an; 1 of frame relay). When node 101-1 receives the fault indication message it determines that the fault indication message applies to virtual circuits that are terrninated at this node. Then, node 101-1 switches the virtual circuit from its primary path that was disrupted by the fault to its alternate path that passes through node 101-5. Similar 20 actions to those effected in node 101-1 are taken by node 101-N upon receiving the fault indication message that was originated by node 101-4. Thus, it is seen that, in accordance with an aspect of the invention, the network has recovered from the fault on the affected virtual circuits. r. ~ , it can be seen that, in accordance withan aspect of the invention, this recovery is ~ 1 without any node having 25 ;.. r.. ~ relating to the network topology other than for the network facilities that terminate at individual ones of nodes 101.
FIG. 2 shows, in simplified block diagram form, the general ,u~,lut~
of nodes 101. It is to be noted that the cnnfil of specific ones of nodes 101 may include an interface to at least one network facility and may not include any 30 access facilities. However, a typical one of nodes 101 includes one or more receive access facilities 201-1 through 201-M, and a CU~ " 3 number of transmit access facilities 202-1 through 202-M. It is noted that pairs of receive access facilities 201-1 through 201-M and transmit access facilities 202-1 through 202-M, respectively, forrn the access facilities (AFs) shown in FIG. 1. As indicated above, 35 the signals received and transmitted on the access links may take any desired form.
In this example, it is assumed that the access facility signals are non-packetized T-` ~ 204~02`
Moreover, it is important to note that none of nodes 101 in network 10v has knowledge of any other node in the network. Each of nodes iol, only knows its own mappings of access circuits to virtual links and virtual links to virtual links. It is 15 further noted that a fault can occur in the node equipment itself or in one or more network facilities connecting nodes. In this example, it is assumed that a faultoccurs somewhere in the i path between nodes 101-3 and 101-4.
When a fault occurs, there is a disruption in the primary virtual circuits along the primary path between node 101-1 and node I01-N. Upon detecting the0 fault, each of nodes 101-3 and 101-4 detemlines which virtual circuits and q v network facilities that are affected by the fault. Node 101-3 generates a fault indication message for all the affected virlual circuits on a network facility and supplies it as an output on at least one of the affected virtual circuits to node 101-2. Alternatively, a specific virtual link ID (DLCI) can be designated to transport 25 the fault indication messages. In this example, a separate such fault indication message is generated for each network facility connected to node 101-3. In this example, only one such network facility is connected to node 101-3. In this example, the fault indication message is a LAPD frame a;lGS. I l and 12) using aXID format. (See CCITT Rr~ Q.921, pages 4248, and Committee T1 30 (' ' "Explicit Congestion avoidance indication as part of Link Layer , TIS1.1-89/339, T1S1.2-89/240, July 17-21, 1989, pages 1-14. for an ., ' of the LAPD frame and XID format). Similarly, node 101-4 generates a fault indication message for all the effected vir~ual circuits on a network facility and supplies it as an output on at least one of the affected virtual circuits to node 101-N.
35 In this example, a separate such fault indication message is generated for each network facility connected to node 101-4. Again, it is noted that neither node 101-3 ~ 24~2 nor node 101-4 has knowledge of other nodes in the path or of the end points of the affected virlual circuit. Nodes 101-3 and 101-4 include; r~ .. relating only to the virtual link to virtual link mapping of the virtual circuit. Upon receiving any of the fault indication messages, node 101-2 dete~rnines if any of the affected virtual S circuits are terminated in this node. Since none of the virtual circuits are terrninated, node 101-2 then determines which network facility and virtual link that the incoming virtual link of the affected virtual circuit is connected to for all of the affected virtual circuits. Fault indication messages arc generated, as described above, for all the affected virtual circuits on a network facility and relayed over at least one virtual 10 link on the network facility to a connected node, in this exarnplc, node 101-1. In this example, this relaying of the fault indication message is realized by employing the known LAPD frarne relay procedures. (See articles entitled "Frame Relay: Protocols and Private Network Al.l.l;.-l;. ,..~", Fr. . f IEEE lNFOCOM 89, April 23-27,1989, pages 676-685 and "Frame Relaying Service: An Overview", l~u~I;
f IEEE lNFOCOM 89, April 23-27, 1989, pages 608-673 for an; 1 of frame relay). When node 101-1 receives the fault indication message it determines that the fault indication message applies to virtual circuits that are terrninated at this node. Then, node 101-1 switches the virtual circuit from its primary path that was disrupted by the fault to its alternate path that passes through node 101-5. Similar 20 actions to those effected in node 101-1 are taken by node 101-N upon receiving the fault indication message that was originated by node 101-4. Thus, it is seen that, in accordance with an aspect of the invention, the network has recovered from the fault on the affected virtual circuits. r. ~ , it can be seen that, in accordance withan aspect of the invention, this recovery is ~ 1 without any node having 25 ;.. r.. ~ relating to the network topology other than for the network facilities that terminate at individual ones of nodes 101.
FIG. 2 shows, in simplified block diagram form, the general ,u~,lut~
of nodes 101. It is to be noted that the cnnfil of specific ones of nodes 101 may include an interface to at least one network facility and may not include any 30 access facilities. However, a typical one of nodes 101 includes one or more receive access facilities 201-1 through 201-M, and a CU~ " 3 number of transmit access facilities 202-1 through 202-M. It is noted that pairs of receive access facilities 201-1 through 201-M and transmit access facilities 202-1 through 202-M, respectively, forrn the access facilities (AFs) shown in FIG. 1. As indicated above, 35 the signals received and transmitted on the access links may take any desired form.
In this example, it is assumed that the access facility signals are non-packetized T-` ~ 204~02`
- 6 -carrier in the known DS1 format. Thus, in this example, an access facility carries up to 24 access circuits. Signals obtained from receive access facilities 201-l through 201-M are supplied via digital line interface (DLI) units 203-1 through 203-M, ,ly, to packetizer 204. Each of digital line interfaces 203 are of a type well 5 known in the art for interfacing the DS 1 signals being supplied via the receive access facilities 201. Packetizer 204 forms incoming voice or data ;..r.., .. ~ into a packet format. Such packetizers are known in the art. In this example, the LAPD
format is used for l ' L; The LAPD layer 2 data unit is known as a frame, and the layer 3 data unit is known as a packet. Thus, throughout this example, the 10 term "rrame" is used instead of "packet". The LAPD frames (I;IG. 10) generated in packetizer 204 are supplied to access circuit mapping unit 205. Access circuit mapping unit 205 also obtains received frames from receive frame bus 206.
Additionally, remap control signals are supplied to access circuit mapping unit 205 via circuit path 220 from fault recovery unit 207. The remap control signals control 15 remapping of access circuits carried on receive access facitilies 201 to virLual links carried on transmit network facilities 212, and the remapping of virtual links carried on receive network facilities 211 to the original access circuits carried on transmit access facilities 202. Access circuit mapping unit 205 yields so-called terminated frames which are supplied to il. 1~ L_l;,. .. 208, and so-called transmit frames which 20 are supplied to transmit frame bus 209. Operation of access circuit mapping unit 205 is described below in ." , :- with FIG. 8. D~ ;,. . 208 ICUUII~LIU~,L~ the voice or data digital signals from the terminated LAPD frames. These signals aresupplied via digital line interface (DLI) units 210-1 through 210-M to transmit access facilities 202-1 through 202-M, ~ ,Li~.~.ly. Again, such digital line 25 interface units and such .1. ~ L .-1;,. .. ` are known in the art.
Received LAPD frames from receive network facilities 211-1 through 211-Y are supplied to digital line interface (DLI) units 213-1 through 213-Y, l~Li~ . Each of digital line interface units 213 is of a type well known in the art for interfacing DS 1 digital signals. In this example, each of digital line interface 30 (DLI) units 213 generates a facility failure signal in well known fashion. The facility failure signals from digital line interfaces 213-1 through 213-Y each indicate whether a red, yellow, blue, or 1,. ' alarm has occurred and are supplied via circuit paths 217-1 through 217-Y, I~ ,Li~,ly, to fault recovery unit 207. Each of digital line interface units (DLI) 213-1 through 213-Y supplies the received LAPD
35 frames to receive frame bus 206. The received frames can be of many types, including received fault indication messages as shown in FIGs. 11 and 12. Fault 2~424~2
format is used for l ' L; The LAPD layer 2 data unit is known as a frame, and the layer 3 data unit is known as a packet. Thus, throughout this example, the 10 term "rrame" is used instead of "packet". The LAPD frames (I;IG. 10) generated in packetizer 204 are supplied to access circuit mapping unit 205. Access circuit mapping unit 205 also obtains received frames from receive frame bus 206.
Additionally, remap control signals are supplied to access circuit mapping unit 205 via circuit path 220 from fault recovery unit 207. The remap control signals control 15 remapping of access circuits carried on receive access facitilies 201 to virLual links carried on transmit network facilities 212, and the remapping of virtual links carried on receive network facilities 211 to the original access circuits carried on transmit access facilities 202. Access circuit mapping unit 205 yields so-called terminated frames which are supplied to il. 1~ L_l;,. .. 208, and so-called transmit frames which 20 are supplied to transmit frame bus 209. Operation of access circuit mapping unit 205 is described below in ." , :- with FIG. 8. D~ ;,. . 208 ICUUII~LIU~,L~ the voice or data digital signals from the terminated LAPD frames. These signals aresupplied via digital line interface (DLI) units 210-1 through 210-M to transmit access facilities 202-1 through 202-M, ~ ,Li~.~.ly. Again, such digital line 25 interface units and such .1. ~ L .-1;,. .. ` are known in the art.
Received LAPD frames from receive network facilities 211-1 through 211-Y are supplied to digital line interface (DLI) units 213-1 through 213-Y, l~Li~ . Each of digital line interface units 213 is of a type well known in the art for interfacing DS 1 digital signals. In this example, each of digital line interface 30 (DLI) units 213 generates a facility failure signal in well known fashion. The facility failure signals from digital line interfaces 213-1 through 213-Y each indicate whether a red, yellow, blue, or 1,. ' alarm has occurred and are supplied via circuit paths 217-1 through 217-Y, I~ ,Li~,ly, to fault recovery unit 207. Each of digital line interface units (DLI) 213-1 through 213-Y supplies the received LAPD
35 frames to receive frame bus 206. The received frames can be of many types, including received fault indication messages as shown in FIGs. 11 and 12. Fault 2~424~2
- 7 -recovery unit 207 obtains the received fault indication messages from receive frame bus 206 via circuit path 218, in well known fashion. An equipment failure signalindicating the failure of any unit in this node in the path of any virtual circuit is supplied via circuit path 216 to fault recovery unit 207. Fault recovery unit 207 S generates transmit fault indication messages which ate supplied via circuit path 219 to transmit frame bus 209 and receive fault indication messages which are supplied via circuit path æl to frame relay unit 214. Frame relay unit 214 obtains the received frames from receive frame bus 206. .A.' ~ y~ frarne relay unit 214 relays transmit frames from receive frame bus 206 to transmit frame bus 209. To 10 this end, frame relay unit 214 employs the known LAPD frame relay procedure to remap these incoming frames into transtnit frames that are supplied to transmit frame bus 209. The relayed frames include appropriate address mapping for each virtual circuit. That is to say, LAPD frames that are passing through this node are frame relayed from receive frame bus 206 to transmit frame bus 209. The operation 15 of frarne relay unit 214 is described below in c~ , with FIG. 9. In turn, thea~ V~JI;...4 transrnit frames are obtained from transmit frame bus 209 by digital line interface units (DLI) 215-1 through 215-Y and, then, supplied to transmit network facilities 212-1 through 212-Y, l~ia~fi~ . Pairs of receive network facilities 211-1 through 211-Y and transmit network facilities 212-1 through 212-Y form the20 network facilities (NFs) shown in FIG. 1.
Fault recovery unit 207 monitors for fault indication messages (FlGs. 11 and 12) on receive frame bus 206. This is achieved by monitoring received framesfor those that match a prescribed format. To this end, control fields in the received frames are monitored to determine if the frame includes a control message. In this 25 example, the prescribed format is the so-called LAPD XID frame format denoting fault indication messages for either a fault condition or a clear condition, as indicated in FIG. 11 and FIG. 12, respectively. As shown in FIG. 11 and FIG. 12 the IDs (DLCls) of the affected virtual circuits are included in fields of the r - field of the LAPD frame, an indication (in this example, 10101111) that the LAPD frame30 is an XID frame is inc~uded in the XID field, an indication that this XID frame is a fault indication message, in accordance with an aspect of the invention, is included in the FI field and an indication, in accordance with another aspect of the invention, of whether the fault indication message denotes a fault or a clear condition is included in the GI field. Thus, in this example, as shown in FIG. I l, the indication 35 11111010 in the GI field denotes a fault condition and, as shown in FIG. 12, the indication 11110000 in the GI field denotes a clear condition. It is further noted that ~, 2~2402
Fault recovery unit 207 monitors for fault indication messages (FlGs. 11 and 12) on receive frame bus 206. This is achieved by monitoring received framesfor those that match a prescribed format. To this end, control fields in the received frames are monitored to determine if the frame includes a control message. In this 25 example, the prescribed format is the so-called LAPD XID frame format denoting fault indication messages for either a fault condition or a clear condition, as indicated in FIG. 11 and FIG. 12, respectively. As shown in FIG. 11 and FIG. 12 the IDs (DLCls) of the affected virtual circuits are included in fields of the r - field of the LAPD frame, an indication (in this example, 10101111) that the LAPD frame30 is an XID frame is inc~uded in the XID field, an indication that this XID frame is a fault indication message, in accordance with an aspect of the invention, is included in the FI field and an indication, in accordance with another aspect of the invention, of whether the fault indication message denotes a fault or a clear condition is included in the GI field. Thus, in this example, as shown in FIG. I l, the indication 35 11111010 in the GI field denotes a fault condition and, as shown in FIG. 12, the indication 11110000 in the GI field denotes a clear condition. It is further noted that ~, 2~2402
- 8 -the fault conditdon or clesr condition indicated in the GI field is for all the affected virtual circuit DLCIs in the i r, " ", -: ;.... field. It will be apparent to those skilled in the art that other signaling - .~ ,c,.... ~ may equally be employed to indicate the presence of a fault indicatdon message. Upon obtaining a fault indication message, 5 fault recovery unit 207 either sends a remap control signal to access circuit mapping unit 205 causing it to switch a ~UllC~IJVll~lil.g access circuit to a virtual link included in the alternate virtual circuit, in accordance with an aspect of the invention, or sends a C~ r '- g receive fault indication message via circuit path 221 to frame relayunit 214. In tum, frame relay unit 214 supplies the fault indicaion message to 10 anothcr node on a virtual link included in the primary virtual circuit. Additionally, fault recovery unit 207 monitors for facility or equipment failures, and either orders access circuit mapping unit 205 via remap control signals to switch the affcctedaccess circuits to alternate virtual circuits and/or generates transmit fault indication messages to be passed via transmit frame bus 209 and appropriate ones digital line 15 interface units 215-1 through 215-Y and transmit network facilities 212-1 through 212-Y, IC~ , to other ones of nodes 101 in network 100 (E~IG.l). Further details regarding operation of fault recovery unit 207 are discussed below in with FlGs. through 7.
FIG. 3 depicts, in simplified block diagrarn form, details of fault 20 recovery unit 207 of FIG. 2. Accordingly, shown are fault indication message receiver 301 and fault indication message generator 302. Fault indication message receiver 301 obtains received fault indication messages via circuit path 218 from receive frame bus 206. If the received fault indication message is for an accesscircuit in this node, the remap control signal for that access circuit is activated. If a 25 receivcd fault indication message is not for an access circuit in this node, it is supplicd as an output unchanged to frame relay unit 214. The operation of fault indication message receiver 301 is shown in the flow chart of FIGs. 4 and 5 and described below. Fault indicadon message generator 302 is responsive to either afacility failure signal or an equipment failure signal becoming active or inactive.
30 When either failure signal becomes active, fault indication message generator 302 determines if the failure affects an access crrcuit terminated in this node. If an access circuit terrninated in this node is affected, a remap control signal for the access circuit is activated. If the affected access circuit is not in this node, a transmit fault indication message including a fault indication (E~IG. 11) is generated for the 35 affected access circuit. Similarly, when the fault is cleared, either the remap control signal is deactivated or a transmit fault indication message including a clear ~ 2~42~2 g indication (FIG. 12) is generated. Operation of fault indication message generator 302 is described below in ~,~ with the flow chart shown in FIGS. 6 and 7.
FIGS. 4 and 5,when connected as shown, form a flow chart showing a sequence of operations effected in fault indication message receiver 301 of FIG. 3.
5 Accordingly, the sequence is entered via step 401. Thereafter, conditional branch point 402 tests to determine if there is a received fault indication message on receive frame bus 206 (FIG. 2). If the test result is NO, the sequence is exited via step 403.
If the test result in step 402 is YES, operational block 404 deter~nines all the virtual link ' ~ from the received fault indication message atld stores them in a 10 received list. In the LAPD format the virtual link ' ~ aD) is known as the DLCI. It is noted that although the virtual links are hereinafter designated "receive"
and "transmit" they provide two-way i i.e., incoming and outgoing.
Operational block 405 obtains a first receive virtual link ID (DLCI) from the received list. Then, conditional branch point 406 tests to determine if this receive 15 virtual link ID (DLCI) is mapped to an access circuit in this node. If the test result in step 406 is NO, operational block 407 determines the transmit virtual link ID aDLCI) that this receive virtual link ID (DLCI) is connected to and the networl~ facility that the transmit virtual link is on. Operational block 408 stores this receive virtual link ~D aDLCI) and the determirled virtual link ID aDLCI) in a list for the riPt. nnin~-A
20 network facility. Then, conditional branch point 409 tests to determine if this receive virtual link ID aDLCI) is the last one stored in the received list. If the test result in step 409 is NO, control is supplied to operational block 410.
Returning to step 406, if the test result is YES, this receive virtual link ID (DLCI) is mapped to an access circuit in this node, i.e., the virtual circuit is 25 terminated at this node. ~ ' ' branch point 411 tests to determine if the received fault indication message indicates the presence of a fault. or the clearing of a fault. If the test result in step 411 is YES, indicating the activation of a fault, operational block 412 supplies as an output an activated remap control signal for this receiv~ virtual link ID aDLCI) to access circuit mapping unit 205 (I;IG. 2).
30 Thereafter, control is supplied to step 409. If the test result in step 411 is NO, indicating clearing of a fault, operational block 413 supplies as an output a de,~tiv ' remap control signal for this receive virtual link ID (DLCI) to accesscircuit mapping unit 205 (FIG. 2). Thereafter, control is supplied to step 409.
Returning to step 410, it causes a next virtual link ID aDLCI) to be 35 obtaining from the received list. Then, appropriate ones of steps 406 through 413 are iterated until step 409 yields a YES result, indicating that the last virtual link ID
~ 2~42402 ~DLCl) has been reached in the received list.
C l branch point 414 tests to determine if any of the network lists formed in step 408 includes a transmit virtual link ID (DLCI). If the test result in step 414 is NO, the sequence is exited via step 403. If the test result in step 414 is 5 YES, operational block 415 causes a first one of the network facility lists to be obtained. Then, operational block 416 generates a fault indication message including all the transmit vi~tual link IDs (DLCIs) in the current network facility list (FIG. 11). Operational block 417 selects at least one receive virtual link ID (DLCI) from the current network facility list for use as the address for the fault indication 10 message generated in step 416. It is noted that frame relay unit 214 (E;IG. 1) will map the at least one selected receive virtual link ID (DLCI) to the a~
transmit virtual link ID (DLCI). In this example, only one such fault indicationmessage is being generated. However, it may be desirable for ' ' ~ to generate a plurality of such fault indication messages using a different receive virtual 15 ~ink ID (DLCI) for the address of each such message. Again, if desired, a specific virtual link ID ~LCI) can be designated to transport the fault indication messages.
It will be apparent to those skilled in the art how to expand this ~....l.. l; ....l for generating such a plurality of fault indication messages. Op.~ inn~l block 418 causes the fault indication message to be supplied to frame relay unti 214 (E~IG. 2).
20 Then, conditional branch point 419 tests to determine if the current network facility list is the last such list. If the test result in step 419 is YES, the sequence is exited via step 403. If the test result in step 419 is NO, operational block 420 obtains a next network faci!ity list from those generated in step 408. Thereafter, steps 416 through 420 are iterated until step 419 yields a YES result and, then, the sequence is exited 25 via step 403.
FIGs. 6 and 7, when connected as shown, form a flow chart of a sequcnce of operations effected by fault indication message generator 302 of FIG. 3.
" the sequence is entered via step 601. Thereafter, conditional branch point 602 tests changes in the state of either the facility failure signal or equipment 30 failure signal. The active state indicates that a fault has occurred and the inactive state indicates that no fault is present. If there is no change in the state of these failure signals, the sequence is exited via step 603. If there is a change in the state of either of the failure signals, conditional branch point 604 tests to determine if the change of state in either of the &ilure signals affects any virn~al link that is mapped 35 to an access circuit at this node. If the test result in step 604 is NO, control is supplied to conditional branch point 605 (FIG. 7). If the test result in step 604 is 2~2~
YES, operational block 606 determines which access circuits are affected. It is noted that more than one access circuit may be affected. Then, operational block 607 determines the virtual link ID (DLCI) for each affected access circuit. C
branch point 608 tests to deterrnine if the change in state of either failure signal is 5 from inactive to active. If the test result in step 608 is YES, operational block 609 activates the rernap control signal for this virtual link ID (DLCI). Then, control is supplied to conditional branch point 605 (FIG. 7). If the test result in step 608 is NO, operational block 610 deactivates the temap control signal for this virtual link ID (DLCI). Thereafter, control is supplied to conditional branch point 605 (FIG. 7).
10 ~'I ' ' branch point 605 tests to detertnine if the change in state of either failure signal affects any so-called frame relay rnnn~rtinn~ i.e., virtual link to virtual link It is notcd that an affected frame relay connection includes a faulted or cleared virtual link and a connected virtual link. If the test result in step 605 is NO, the sequence is exited via step 603 (FIG. 5). lf the test result in step 605 is YES, 15 operational block 611 determines which framc relay are affected by the fault. Operational block 612 determines the virtual link ID (DLCI) and the network facility of the connected virtual link for each affected virtual link. C~ - ' block 613 causes the virtual link ID (DLCI) deter~nined in step 612 to be stored in a list for the, , " ,, network facility. Operational block 614 causes a fault indication 20 message to be generated for each network facility list. Each such fault indication message includes all the virtual link IDs (DLCIs) from the ~,ull -r " 'J networkfacility list and uses one virtual link ID (DLCI) from the ~ c~ " g list as the message address. Again, a plurality of fault indication messages could be generated for each network facility list each using a different virtual link ID (DLCI) for its 25 address. (-'n- 1itinn ~1 branch point 615 tests to determine whether the change in state of either failure signal is from inactive to active. If the test result in step 615 is YES, operational block 616 causes the fault indication message(s) generated in block 614 to indicate "fault" (E;IG. 11). E the test result in step 615 is NO, operational block 617 causes the fault indication message generated in block 614 to indicate "clear"
30 (FIG. 12). Thereafter, operational block 618 supplies as an output the fault indication message(s) to transmit frame bus 209 (E;IG. 2). Then, the sequence isexited via step 603 (E~IG. 6).
FIG. 8 is a flow chart of a sequence of operations effected by access circuit mapping unit 205 of FIG. 2. Accordingly, the sequence is entered via step 35 801. Thereafter, conditional branch point 802 tests to determine if a received frame is present on receive frame bus 206 (FIG. 2). If the test result in step 802 is YES, :
~ 2~42402 operational bloc_ 803 determines the virtual linL: ID (DLCI) for the received frame.
sl branch point 804 tests to determine if the remap control signal is active for this virtual link ID (DLCI). If the test result in 804 is YES, operational block 805 causes the virtual link ID (DLCI) determined in step 803 to be modified to aS DLCI for the appropriate virtual lin_ ID of the primary virtual circuit. If the test result in step 804 is NO, no action is taL en to change the virtual link ID (DLCI) and operational block 806 supplies the received framc to d~l L ~, . 208 (FIG. 2).
Tnereafter, the sequence is exited via step 807. Returning to step 802, if the test result is NO, conditional branch point 808 tests to determine if there is a generated 10 frame from packetizer 204 (FIG. 2). If the test result in step 808 is NO, the sequence is exited via step 807. If the test result in step 808 is YES, operational block 809 determines the virtual link ID (DLCI) for the generated frame. Then, conditionalbranch point 810 tests to determine if the remap control signal is active for this virtual linL- ID (DLCI). If the test result in 810 is YES, operational blocL 81115 changes the virtual link ID (DLCI) in the generated frame to the alternate virtual link ID (DLCI) for the appropriate virtual link in the alternate virtual circuit (E71G. 1).
Then, operational block 812 supplies as an output the generated frame to transmit frame bus 209 (FIG. 2). Thereafter, the sequence is exited via step 807. Returning to step 810, if the test result is NO, the generated frame DLCI is not changed and 20 steps 812 and 807 are iterated.
FIG. 9 is a flow chart of a sequence of operations effected in f}ame relay unit 214 of FIG. 2. This flow chart does not completely describe the LAPD frame relay function known to the art but only those functions necessary to this b. of the invention. Accordingly, the sequence is entered via step 901.
25 Then, conditional branch point 902 tests to determine if there is a received frame on receive frame bus 200 (E~IG. 2). If the test result in step 902 is NO, conditional branch point 903 tcsts to determine if there is a receive fault indication message on receive fr. me bus 206 (E~IG. 2). If the result in step 903 is NO, the sequence is exited via step 904. If the test result in either step 902 or step 903 is YES, 30 operational block 905 determines the virtual link ID (DLCI) for the received frame.
Operational block 906 determines the virtual link ID (DLCI) for the coMected virtual link, i.e., the frame relay cr~ r~inn Operational block 907 changes the virtual link ID (DLCI) of the received frame to the virtual link ID (DLCI) for the coMected virtual link. Operational block 908 supplies as an output the modified 35 "received" frame to the transmit frame bus 209 (FIG. 2). Thereafter, the sequence is exited by step 904.
2042~02 Although this ~ ' of the invention has been described in t~r~ns of so-called ~ ,v ' virtual circuits and frame-relay, it will be apparent to those skilled in the art that thc invention is equally applicable to switched virtual circuits and to frarne switching ,,
FIG. 3 depicts, in simplified block diagrarn form, details of fault 20 recovery unit 207 of FIG. 2. Accordingly, shown are fault indication message receiver 301 and fault indication message generator 302. Fault indication message receiver 301 obtains received fault indication messages via circuit path 218 from receive frame bus 206. If the received fault indication message is for an accesscircuit in this node, the remap control signal for that access circuit is activated. If a 25 receivcd fault indication message is not for an access circuit in this node, it is supplicd as an output unchanged to frame relay unit 214. The operation of fault indication message receiver 301 is shown in the flow chart of FIGs. 4 and 5 and described below. Fault indicadon message generator 302 is responsive to either afacility failure signal or an equipment failure signal becoming active or inactive.
30 When either failure signal becomes active, fault indication message generator 302 determines if the failure affects an access crrcuit terminated in this node. If an access circuit terrninated in this node is affected, a remap control signal for the access circuit is activated. If the affected access circuit is not in this node, a transmit fault indication message including a fault indication (E~IG. 11) is generated for the 35 affected access circuit. Similarly, when the fault is cleared, either the remap control signal is deactivated or a transmit fault indication message including a clear ~ 2~42~2 g indication (FIG. 12) is generated. Operation of fault indication message generator 302 is described below in ~,~ with the flow chart shown in FIGS. 6 and 7.
FIGS. 4 and 5,when connected as shown, form a flow chart showing a sequence of operations effected in fault indication message receiver 301 of FIG. 3.
5 Accordingly, the sequence is entered via step 401. Thereafter, conditional branch point 402 tests to determine if there is a received fault indication message on receive frame bus 206 (FIG. 2). If the test result is NO, the sequence is exited via step 403.
If the test result in step 402 is YES, operational block 404 deter~nines all the virtual link ' ~ from the received fault indication message atld stores them in a 10 received list. In the LAPD format the virtual link ' ~ aD) is known as the DLCI. It is noted that although the virtual links are hereinafter designated "receive"
and "transmit" they provide two-way i i.e., incoming and outgoing.
Operational block 405 obtains a first receive virtual link ID (DLCI) from the received list. Then, conditional branch point 406 tests to determine if this receive 15 virtual link ID (DLCI) is mapped to an access circuit in this node. If the test result in step 406 is NO, operational block 407 determines the transmit virtual link ID aDLCI) that this receive virtual link ID (DLCI) is connected to and the networl~ facility that the transmit virtual link is on. Operational block 408 stores this receive virtual link ~D aDLCI) and the determirled virtual link ID aDLCI) in a list for the riPt. nnin~-A
20 network facility. Then, conditional branch point 409 tests to determine if this receive virtual link ID aDLCI) is the last one stored in the received list. If the test result in step 409 is NO, control is supplied to operational block 410.
Returning to step 406, if the test result is YES, this receive virtual link ID (DLCI) is mapped to an access circuit in this node, i.e., the virtual circuit is 25 terminated at this node. ~ ' ' branch point 411 tests to determine if the received fault indication message indicates the presence of a fault. or the clearing of a fault. If the test result in step 411 is YES, indicating the activation of a fault, operational block 412 supplies as an output an activated remap control signal for this receiv~ virtual link ID aDLCI) to access circuit mapping unit 205 (I;IG. 2).
30 Thereafter, control is supplied to step 409. If the test result in step 411 is NO, indicating clearing of a fault, operational block 413 supplies as an output a de,~tiv ' remap control signal for this receive virtual link ID (DLCI) to accesscircuit mapping unit 205 (FIG. 2). Thereafter, control is supplied to step 409.
Returning to step 410, it causes a next virtual link ID aDLCI) to be 35 obtaining from the received list. Then, appropriate ones of steps 406 through 413 are iterated until step 409 yields a YES result, indicating that the last virtual link ID
~ 2~42402 ~DLCl) has been reached in the received list.
C l branch point 414 tests to determine if any of the network lists formed in step 408 includes a transmit virtual link ID (DLCI). If the test result in step 414 is NO, the sequence is exited via step 403. If the test result in step 414 is 5 YES, operational block 415 causes a first one of the network facility lists to be obtained. Then, operational block 416 generates a fault indication message including all the transmit vi~tual link IDs (DLCIs) in the current network facility list (FIG. 11). Operational block 417 selects at least one receive virtual link ID (DLCI) from the current network facility list for use as the address for the fault indication 10 message generated in step 416. It is noted that frame relay unit 214 (E;IG. 1) will map the at least one selected receive virtual link ID (DLCI) to the a~
transmit virtual link ID (DLCI). In this example, only one such fault indicationmessage is being generated. However, it may be desirable for ' ' ~ to generate a plurality of such fault indication messages using a different receive virtual 15 ~ink ID (DLCI) for the address of each such message. Again, if desired, a specific virtual link ID ~LCI) can be designated to transport the fault indication messages.
It will be apparent to those skilled in the art how to expand this ~....l.. l; ....l for generating such a plurality of fault indication messages. Op.~ inn~l block 418 causes the fault indication message to be supplied to frame relay unti 214 (E~IG. 2).
20 Then, conditional branch point 419 tests to determine if the current network facility list is the last such list. If the test result in step 419 is YES, the sequence is exited via step 403. If the test result in step 419 is NO, operational block 420 obtains a next network faci!ity list from those generated in step 408. Thereafter, steps 416 through 420 are iterated until step 419 yields a YES result and, then, the sequence is exited 25 via step 403.
FIGs. 6 and 7, when connected as shown, form a flow chart of a sequcnce of operations effected by fault indication message generator 302 of FIG. 3.
" the sequence is entered via step 601. Thereafter, conditional branch point 602 tests changes in the state of either the facility failure signal or equipment 30 failure signal. The active state indicates that a fault has occurred and the inactive state indicates that no fault is present. If there is no change in the state of these failure signals, the sequence is exited via step 603. If there is a change in the state of either of the failure signals, conditional branch point 604 tests to determine if the change of state in either of the &ilure signals affects any virn~al link that is mapped 35 to an access circuit at this node. If the test result in step 604 is NO, control is supplied to conditional branch point 605 (FIG. 7). If the test result in step 604 is 2~2~
YES, operational block 606 determines which access circuits are affected. It is noted that more than one access circuit may be affected. Then, operational block 607 determines the virtual link ID (DLCI) for each affected access circuit. C
branch point 608 tests to deterrnine if the change in state of either failure signal is 5 from inactive to active. If the test result in step 608 is YES, operational block 609 activates the rernap control signal for this virtual link ID (DLCI). Then, control is supplied to conditional branch point 605 (FIG. 7). If the test result in step 608 is NO, operational block 610 deactivates the temap control signal for this virtual link ID (DLCI). Thereafter, control is supplied to conditional branch point 605 (FIG. 7).
10 ~'I ' ' branch point 605 tests to detertnine if the change in state of either failure signal affects any so-called frame relay rnnn~rtinn~ i.e., virtual link to virtual link It is notcd that an affected frame relay connection includes a faulted or cleared virtual link and a connected virtual link. If the test result in step 605 is NO, the sequence is exited via step 603 (FIG. 5). lf the test result in step 605 is YES, 15 operational block 611 determines which framc relay are affected by the fault. Operational block 612 determines the virtual link ID (DLCI) and the network facility of the connected virtual link for each affected virtual link. C~ - ' block 613 causes the virtual link ID (DLCI) deter~nined in step 612 to be stored in a list for the, , " ,, network facility. Operational block 614 causes a fault indication 20 message to be generated for each network facility list. Each such fault indication message includes all the virtual link IDs (DLCIs) from the ~,ull -r " 'J networkfacility list and uses one virtual link ID (DLCI) from the ~ c~ " g list as the message address. Again, a plurality of fault indication messages could be generated for each network facility list each using a different virtual link ID (DLCI) for its 25 address. (-'n- 1itinn ~1 branch point 615 tests to determine whether the change in state of either failure signal is from inactive to active. If the test result in step 615 is YES, operational block 616 causes the fault indication message(s) generated in block 614 to indicate "fault" (E;IG. 11). E the test result in step 615 is NO, operational block 617 causes the fault indication message generated in block 614 to indicate "clear"
30 (FIG. 12). Thereafter, operational block 618 supplies as an output the fault indication message(s) to transmit frame bus 209 (E;IG. 2). Then, the sequence isexited via step 603 (E~IG. 6).
FIG. 8 is a flow chart of a sequence of operations effected by access circuit mapping unit 205 of FIG. 2. Accordingly, the sequence is entered via step 35 801. Thereafter, conditional branch point 802 tests to determine if a received frame is present on receive frame bus 206 (FIG. 2). If the test result in step 802 is YES, :
~ 2~42402 operational bloc_ 803 determines the virtual linL: ID (DLCI) for the received frame.
sl branch point 804 tests to determine if the remap control signal is active for this virtual link ID (DLCI). If the test result in 804 is YES, operational block 805 causes the virtual link ID (DLCI) determined in step 803 to be modified to aS DLCI for the appropriate virtual lin_ ID of the primary virtual circuit. If the test result in step 804 is NO, no action is taL en to change the virtual link ID (DLCI) and operational block 806 supplies the received framc to d~l L ~, . 208 (FIG. 2).
Tnereafter, the sequence is exited via step 807. Returning to step 802, if the test result is NO, conditional branch point 808 tests to determine if there is a generated 10 frame from packetizer 204 (FIG. 2). If the test result in step 808 is NO, the sequence is exited via step 807. If the test result in step 808 is YES, operational block 809 determines the virtual link ID (DLCI) for the generated frame. Then, conditionalbranch point 810 tests to determine if the remap control signal is active for this virtual linL- ID (DLCI). If the test result in 810 is YES, operational blocL 81115 changes the virtual link ID (DLCI) in the generated frame to the alternate virtual link ID (DLCI) for the appropriate virtual link in the alternate virtual circuit (E71G. 1).
Then, operational block 812 supplies as an output the generated frame to transmit frame bus 209 (FIG. 2). Thereafter, the sequence is exited via step 807. Returning to step 810, if the test result is NO, the generated frame DLCI is not changed and 20 steps 812 and 807 are iterated.
FIG. 9 is a flow chart of a sequence of operations effected in f}ame relay unit 214 of FIG. 2. This flow chart does not completely describe the LAPD frame relay function known to the art but only those functions necessary to this b. of the invention. Accordingly, the sequence is entered via step 901.
25 Then, conditional branch point 902 tests to determine if there is a received frame on receive frame bus 200 (E~IG. 2). If the test result in step 902 is NO, conditional branch point 903 tcsts to determine if there is a receive fault indication message on receive fr. me bus 206 (E~IG. 2). If the result in step 903 is NO, the sequence is exited via step 904. If the test result in either step 902 or step 903 is YES, 30 operational block 905 determines the virtual link ID (DLCI) for the received frame.
Operational block 906 determines the virtual link ID (DLCI) for the coMected virtual link, i.e., the frame relay cr~ r~inn Operational block 907 changes the virtual link ID (DLCI) of the received frame to the virtual link ID (DLCI) for the coMected virtual link. Operational block 908 supplies as an output the modified 35 "received" frame to the transmit frame bus 209 (FIG. 2). Thereafter, the sequence is exited by step 904.
2042~02 Although this ~ ' of the invention has been described in t~r~ns of so-called ~ ,v ' virtual circuits and frame-relay, it will be apparent to those skilled in the art that thc invention is equally applicable to switched virtual circuits and to frarne switching ,,
Claims (16)
1. Apparatus in a packet node for recovering from faults in transmission paths including at least one virtual circuit in a network including a plurality of packet nodes, comprising, means for detecting faults in any transmission paths associated with the node, each of said transmission paths including at least one network facility at least one virtual circuit, the apparatus being CHARACTERIZED BY
first means for determining if any virtual circuit affected by a detected fault is terminated in the node, first means for generating a fault indication message for each network facility transporting a virtual circuit that is affected by the detected fault and including an identity of each virtual circuit affected by the detected fault being transported on said network facility that is not terminated in the node, first means for transmitting said generated fault indication messages, each generated fault indication message being transmitted on at least one of theaffected virtual circuits being transported by a corresponding network facility away from the fault to some other node in the network, and means for switching any affected virtual circuits determined to be terminated in the node to associated alternate virtual circuits for transmission toward a destination node.
first means for determining if any virtual circuit affected by a detected fault is terminated in the node, first means for generating a fault indication message for each network facility transporting a virtual circuit that is affected by the detected fault and including an identity of each virtual circuit affected by the detected fault being transported on said network facility that is not terminated in the node, first means for transmitting said generated fault indication messages, each generated fault indication message being transmitted on at least one of theaffected virtual circuits being transported by a corresponding network facility away from the fault to some other node in the network, and means for switching any affected virtual circuits determined to be terminated in the node to associated alternate virtual circuits for transmission toward a destination node.
2. The apparatus as defined in claim 1 CHARACTERIZED BY
means for receiving fault indication messages including second means for determining if any virtual circuits identified in a received fault indication message are terminated in the node, second means for generating a fault indication message for each network facility including virtual circuits affected by a detected fault and not terminated in the node, each of said generated fault indication messages including an identity of each virtual circuit affected by the fault being transmitted on said network facility and not terminated in the node, and second means for transmitting said fault indication messages generated by said second generating means, each of said generated fault indication messages being transmitted on at least one of said affected virtual circuits on a corresponding network facility to some other node in the network.
means for receiving fault indication messages including second means for determining if any virtual circuits identified in a received fault indication message are terminated in the node, second means for generating a fault indication message for each network facility including virtual circuits affected by a detected fault and not terminated in the node, each of said generated fault indication messages including an identity of each virtual circuit affected by the fault being transmitted on said network facility and not terminated in the node, and second means for transmitting said fault indication messages generated by said second generating means, each of said generated fault indication messages being transmitted on at least one of said affected virtual circuits on a corresponding network facility to some other node in the network.
3. The apparatus as defined in claim 2 CHARACTERIZED BY each of said virtual circuits comprises a first access circuit at an originating node, a second access circuit at a destination node and at least one virtual link.
4. The apparatus as defined in claim 3 CHARACTERIZED BY said each of said received fault indication messages for a corresponding network facility includes identities of virtual links in corresponding virtual circuits being transmitted on said corresponding network facility, and CHARACTERIZED IN THAT said second means for determining includes means for generating a control signal representative of whether a virtual link identified in the received fault indication message is mapped to an access circuit in the node and said means for switching is responsive to said control signal for changing the identity of said virtual link to an alternate virtual link identity when said control signal indicates that said virtual link is mapped to an access circuit in the node, wherein said access circuit is mapped to an alternate virtual circuit for transmission to said destination access circuit.
5. The apparatus as defined in claim 3 CHARACTERIZED IN THAT
said first means for determining includes means for identifying access circuits in the node that are affected by the detected fault, means for identifying an associated virtual link for each access circuit in the node which is affected by the detected fault and means for generating a first control signal representative that a corresponding access circuit is mapped to a virtual link that is affected by the detected fault, and wherein said means for switching includes means responsive to said first controlsignal for changing the identity of said virtual link associated with the identified access circuit to an alternate virtual link identity, wherein said access circuit is mapped to an alternate virtual circuit.
said first means for determining includes means for identifying access circuits in the node that are affected by the detected fault, means for identifying an associated virtual link for each access circuit in the node which is affected by the detected fault and means for generating a first control signal representative that a corresponding access circuit is mapped to a virtual link that is affected by the detected fault, and wherein said means for switching includes means responsive to said first controlsignal for changing the identity of said virtual link associated with the identified access circuit to an alternate virtual link identity, wherein said access circuit is mapped to an alternate virtual circuit.
6. The apparatus as defined in claim 3 CHARACTERIZED BY said each of said virtual circuits may include a virtual link being mapped to another virtual link in a node, and CHARACTERIZED IN THAT said first means for generating a fault indication message includes means for identifying a virtual link to which a virtual link affected by the detected fault is mapped to and means for including the identity of the identified virtual link in the fault indication message being generated for the corresponding network facility having at least one affected virtual circuit, and wherein said first means for transmitting supplies said generated fault indication message as an output on at least one affected virtual circuit being transported on said corresponding network facility.
7. The apparatus as defined in claim 3 CHARACTERIZED IN THAT
said second means for generating includes means for determining an identity of avirtual link in said received fault indication message, means for determining anidentity of an associated virtual link to which said identified virtual link is to be connected to, means for including the virtual link identification of the associated virtual link in the fault indication message, and wherein said second means for transmitting includes means for supplying the fault indication message includingidentities of all associated virtual links as an output on at least one affected virtual circuit being transported on said corresponding network facility.
said second means for generating includes means for determining an identity of avirtual link in said received fault indication message, means for determining anidentity of an associated virtual link to which said identified virtual link is to be connected to, means for including the virtual link identification of the associated virtual link in the fault indication message, and wherein said second means for transmitting includes means for supplying the fault indication message includingidentities of all associated virtual links as an output on at least one affected virtual circuit being transported on said corresponding network facility.
8. The apparatus as defined in claim 3 CHARACTERIZED BY said fault indication message comprises a frame including a plurality of fields, a predetermined field including identities of all virtual links of corresponding virtual circuits affected by the detected fault being transported by a corresponding network facility and a field including an indication of whether a fault condition exists.
9. The apparatus as defined in claim 8 CHARACTERIZED By a field in said frame includes an indication representative that the frame is a fault indication message.
10. The apparatus as defined in claim 9 CHARACTERIZED BY said frame being a LAPD XID frame having a field including an indication that the frame is an XID frame.
11. A method for recovering from faults in transmission paths associated with a packet node including at least one virtual circuit associated with a packet node in a network including a plurality of packet nodes, comprising the step of, detecting faults in any transmission paths associated with the node, each of said transmission paths including at least one network facility transporting at least one virtual circuit, the method being CHARACTERIZED BY determining if any virtual circuit affected by a detected fault is terminated in the node, generating a fault indication message for each network facility transporting a virtual circuit that is affected by the detected fault and including an identity of each virtual circuit affected by the detected fault being transported on said network facility that is not terminated in the node, transmitting said generated fault indication messages, each generated fault indication message being transmitted on at least one of the affected virtual circuits being transported by a corresponding network facility away from the fault to some other node in the network, and switching any affected virtual circuits determined to be terminated in the node to associated alternate virtual circuits for transmission toward a destination node.
12. The method as defined in claim 11 CHARACTERIZED BY the steps of receiving fault indication messages including the step of determining if any virtual circuits identified in a received fault indication message are terminated in the node, generating a fault indication message for each network facility including virtual circuits affected by a detected fault and not terminated in the node, each of said generated fault indication messages including an identity of each virtual circuit affected by the fault being transmitted on said network facility and not terminated in the node, and transmitting said fault indication messages generated by said second generating means, each of said generated fault indication messages being transmitted on at least one of said affected virtual circuits on a corresponding network facility to some other node in the network.
13. The method as defined in claim 12 CHARACTERIZED BY each of said virtual circuits comprises a first access circuit at an originating node, a second access circuit at a destination node and at least one virtual link.
14. The method as defined in claim 13 CHARACTERIZED BY said fault indication message comprises a frame including a plurality of fields, a predetermined field including identities of all virtual links of corresponding virtual circuits affected by the detected fault being transported by a corresponding network facility and a field including an indication of whether a fault condition exists.
15. The method as defined in claim 14 CHARACTERIZED BY a field in said frame includes an indication representative that the frame is a fault indication message.
16. The method as defined in claim 15 CHARACTERIZED BY said frame being a LAPD XID frame having a field including an indication that the frame is an XID frame.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US431,796 | 1986-11-06 | ||
| US07/431,796 US5016243A (en) | 1989-11-06 | 1989-11-06 | Automatic fault recovery in a packet network |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2042402A1 CA2042402A1 (en) | 1991-05-07 |
| CA2042402C true CA2042402C (en) | 1996-11-19 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002042402A Expired - Fee Related CA2042402C (en) | 1989-11-06 | 1990-11-02 | Automatic fault recovery in a packet network |
Country Status (8)
| Country | Link |
|---|---|
| US (1) | US5016243A (en) |
| EP (1) | EP0452479B1 (en) |
| JP (1) | JP2533998B2 (en) |
| AU (1) | AU626745B2 (en) |
| CA (1) | CA2042402C (en) |
| DE (1) | DE69017193T2 (en) |
| IL (1) | IL96256A0 (en) |
| WO (1) | WO1991007040A1 (en) |
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- 1989-11-06 US US07/431,796 patent/US5016243A/en not_active Expired - Lifetime
-
1990
- 1990-11-02 JP JP3500823A patent/JP2533998B2/en not_active Expired - Lifetime
- 1990-11-02 CA CA002042402A patent/CA2042402C/en not_active Expired - Fee Related
- 1990-11-02 DE DE69017193T patent/DE69017193T2/en not_active Expired - Lifetime
- 1990-11-02 WO PCT/US1990/006546 patent/WO1991007040A1/en active IP Right Grant
- 1990-11-02 AU AU68886/91A patent/AU626745B2/en not_active Ceased
- 1990-11-02 EP EP91900115A patent/EP0452479B1/en not_active Expired - Lifetime
- 1990-11-06 IL IL96256A patent/IL96256A0/en unknown
Also Published As
| Publication number | Publication date |
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| WO1991007040A1 (en) | 1991-05-16 |
| JP2533998B2 (en) | 1996-09-11 |
| IL96256A0 (en) | 1991-08-16 |
| AU6888691A (en) | 1991-05-31 |
| DE69017193T2 (en) | 1995-06-29 |
| CA2042402A1 (en) | 1991-05-07 |
| EP0452479A1 (en) | 1991-10-23 |
| DE69017193D1 (en) | 1995-03-30 |
| US5016243A (en) | 1991-05-14 |
| AU626745B2 (en) | 1992-08-06 |
| EP0452479B1 (en) | 1995-02-22 |
| JPH05502347A (en) | 1993-04-22 |
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