WO1999009702A2 - Distributed method and system for excluding components from a restoral route in a communications network - Google Patents
Distributed method and system for excluding components from a restoral route in a communications network Download PDFInfo
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- WO1999009702A2 WO1999009702A2 PCT/US1998/016226 US9816226W WO9909702A2 WO 1999009702 A2 WO1999009702 A2 WO 1999009702A2 US 9816226 W US9816226 W US 9816226W WO 9909702 A2 WO9909702 A2 WO 9909702A2
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- WIPO (PCT)
- Prior art keywords
- path
- segment
- paths
- failed
- restoration
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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
- H04Q3/0075—Fault management techniques
- H04Q3/0079—Fault management techniques involving restoration of networks, e.g. disaster recovery, self-healing networks
Definitions
- the present invention relates to communication networks and, in particular, to the restoration of failed communication networks.
- a communications network consists of a collection of transmission links, also known as segments, that are interconnected at network nodes.
- the segments include transmission lines, fiber optic cables, microwave links, and other such transmission medium. Traffic is transmitted on the network from one endpoint to another endpoint through a current route or "trunk,” which is a network path of segments that interconnect the endpoints.
- the network nodes may serve a variety of functions such as amplifying the network traffic for transmission down the next segment in the route or establishing an interconnection between two segments connected to the node (i.e., a switch).
- Each node is located at an installation, and several nodes may be located within a single installation.
- the restoration nodes can be controlled locally or from a remote computer system to connect or to disconnect segments that are connected to the node. Segments are connected to individual ports of a restoration node.
- the components (e.g., nodes and segments) of the communications network may occasionally fail.
- a segment that is a buried fiber optic cable may fail as a result of being inadvertently severed by someone digging near the buried cable. If one or more of the cables fail, massive disruption of services to a large number of network customers could result. Therefore, telecommunications carriers strive to quickly and economically route the network traffic around such failed components by establishing a "restoral" route.
- a restoral route is a combination of segments between the endpoints that does not include the failed component.
- the establishing of a restoral route generally involves: (1) detecting that a component on the current route has failed, (2) identifying the location of the component, (3) selecting a restoral route to bypass the failed component, and (4) implementing the selected restoral route.
- the reliability of telecommunication networks depends in large part on the ability to detect such failures and implement the restoral route with minimal impact on network customers.
- a plan that identifies which restoration nodes are to be switched to bypass one or more specific failed components is called a "restoration plan.”
- Communications networks typically have excess capacity that can be used to bypass a failed component.
- the segments of a network that are currently being used to bear traffic are referred to as active segments, and the segments that are not being currently used to bear traffic (i.e., excess capacity) are referred to as spare segments.
- Restoral routes are implemented by identifying spare segments and incorporating certain of those spare segments into the network.
- segments are often physically collocated in larger components such as cables.
- one segment of the larger component fails, it is likely that the remaining segments of the larger component will also fail within a reasonably short amount of time. For example, if a cable catches on fire, the cable may end up being burned through, damaging all the segments within the cable. Initially, as the cable is being burned, perhaps only one or two segments on the periphery of the cable will be burned. As the heat intensifies and the fire progresses, the remaining segments will each be successively burned through and fail. It would be desirable for communications carriers to devise restoration plans in which spare segments that are not physically collocated with a failed segment are used to build a restoral route. The use of such spare segments would decrease the chance that the restoral route identified in the restoration plan will itself fail due to cascading failures of a cable that includes both the failed segment and the spare segment.
- the present invention provides a distributed method and system for excluding segments from use in restoring a communications network following a failure.
- the restoration system of the present invention starts the restoration process when a failure of a segment in the communications network is detected. Each restoration node is notified of the segment that failed.
- the restoration system at each node then identifies each segment that is connected to the restoration node and that is collocated with at least a portion of the failed segment. Segments are collocated when they traverse at least one common pair of installations.
- the restoration system at each node then excludes from using in restoring the communications network the identified segments.
- the restoration system at a central location identifies each path in the communications network. A path is a unique sequence of installations that a segment traverses.
- the restoration system then creates a mapping of the ports of the restoration nodes to the paths of the segments connected to each port.
- the restoration system identifies for each path the set of paths that are interdependent. A pair of paths are interdependent when both paths traverse a common pair of installations.
- the restoration system downloads to each restoration node a mapping of its ports to the path of the segments connected to the restoration node and the identification of the interdependent paths for the path of each segment that is connected to the restoration node.
- the restoration system uses the port on which the failure was detected and uses the mapping to identify the path of the segment that failed.
- the restoration system then excludes each restoral route that includes a segment that has a path that is interdependent with the failed segment.
- Figure 1 illustrates an example communications network comprising installations, restoration nodes, and segments.
- Figures 2A-2B illustrate the port/path table for the example network.
- Figures 3A-3B illustrate the interdependent path table for the example network.
- Figure 4 illustrates the various groups of interdependent paths.
- Figure 5 illustrates a table of restoral routes to bypass active segment b.
- Figure 6 is a flow diagram of the set-up component.
- Figure 7 is a flow diagram of the exclusion component.
- Figure 8 is a flow diagram of a routine that identifies the groups of failed paths.
- the present invention provides a distributed method and system for excluding network components that may fail when restoring a failed communications network.
- a failure occurs in a component (e.g., network segment)
- the restoration system of each restoration node is notified and attempts to identify between which two installations in the communications network the segment has failed.
- the restoration system at each restoration node identifies the spare segments that are connected to the restoration node and for which at least a portion of the segment traverses those two identified installations.
- the restoration system at each restoration node excludes the identified spare segments from use in building the restoral route. In this way, if a cable that contains multiple segments is damaged (e.g., the cable is burning), then all spare segments within that cable are assumed to also have failed.
- the restoration system may not be able to pinpoint the failure to between which two installations. For example, if a segment traverses several installations and an alarm is detected for that segment, the failure could have occurred between any two of the several adjacent installations. In such a case, the restoration system assumes that a failure has occurred between each pair of adjacent installations. The restoration system, thus, excludes from the restoration process all segments that also traverse at least one of the pairs of adjacent installations. The distributed restoration system then builds a restoral route without the excluded segments.
- the restoration system at each restoration may be able to eliminate certain of the pairs of adjacent installations as possible locations of the failure. For example, portions of two segments may traverse the same two installations, but another portion of each segment may also traverse different pairs of adjacent installations. If a failure is detected for only one of the segments, the restoration system cannot pinpoint between which pair of adjacent installations. However, when a failure is detected on both of these segments, then the restoration system can pinpoint that the failure occurred between the pair of adjacent installations that both failed segments traverse. In this way, the restoration system limits the segments that are excluded from possible restoral routes to only those segments that traverse the identified pair of installations.
- the restoration system preferably at a central location initially identifies all paths within the communications network.
- Each path has a path route that identifies the installations that the segments of that path traverse. For example, if a segment starts at inst lation A ' , passes through installation B ' , and ends at installation C, then the path route is A ' -B ' -C.
- the restoration system then identifies for each path the set of paths that have at least one pair of adjacent installations in common with the path. For example, a path with a path route of B'-C'-D' shares adjacent installations B ' -C with the path with a path route A'-B'-C.
- each path has a set of interdependent paths (including the path itself) such that, if a segment on the path fails, then segments on all the paths in the set are excluded from possible restoral routes (unless the failure can be pinpointed more precisely).
- the restoration system at the central location downloads to each restoration node the identification of the paths that are interdependent with each segment connected to the restoration node.
- the restoration system at each restoration node determines whether the two paths are interdependent based on information stored locally. If the two paths are interdependent, then the restoration system then analyzes the sets of interdependent paths for the two failed paths. The restoration system determines whether there are any paths in the sets of interdependent paths that are common to each set. If so, then the restoration system excludes the segments in those common paths from the restoration process. So, in general, if a failure is detected on two segments, then any paths that may traverse a pair of installations that both segments also traverse is excluded.
- Figure 1 illustrates an example communications network comprising installations, restoration nodes, and segments.
- the network includes 7 installations A'-G ' and 6 restoration nodes A-F.
- Each restoration node includes the distributed portion of the restoration system and is included in an installation.
- restoration nodes B and C are in installations B' and C, respectively.
- Installations may contain telecommunications equipment other than restoration nodes.
- installation G' contains no restoration node but may contain a regenerator to amplify the transmission.
- the segments of the network appear as lines labeled with the lower-case letters a-k within a circle.
- segment e connects restoration node A with restoration node E through port 1 and port 4.
- Each pair of installations has an inter-installation cable 103-112.
- inter- installation cable 103 connects installation A'-E '
- inter-installation cable 104 connects installations A ' and G ' .
- the inter-installation cables 106-109 are shared by various segments.
- inter-installation cable 109 is shared by segments f and g.
- Each of the paths of the network are identified by a primed lower-case letter.
- the path between restoration nodes A and E is identified as path e ' , as indicated by the e ' next to the port numbers 1 and 4. Since segments h and i connect restoration nodes E and F, they both are on the same path h'.
- the network shown in Figure 1 has many interdependent paths.
- the network connects restoration node A to restoration node D.
- the active segments of the network are segments a-c. If cable 107 that contains segment b is being bumed through, then segments d, f, .and g, which .are physically collocated with segment b, should not be included in a restoral route because they will probably fail as well. Instead, a restoral route through restoration nodes E and F should be chosen.
- the restoration system detects that path b' has failed (e.g., through an alarm at port 16), it identifies the interdependent paths as d ' , f , and g ' .
- FIGS. 2A-2B illustrate the port/path table for the example network.
- Figure 2A illustrates a combined port/path table for all the restoration nodes
- Figure 2B illustrates the port/path table for restoration node C.
- the port/path table contains an entry for each port in the network that is connected to a segment. The entry identifies the path of the segment that is connected to the port.
- port 1 in restoration node A is connected to segment e. Since segment e is on path e', the entry for port 1 in the port/path table identifies path e'. Similarly, port 4 in restoration node E is also connected to segment e. Therefore, the entry in the port/path table for port 4 identifies path e ' .
- the restoration system maintains a table that identifies sets of interdependent paths, referred to as the interdependent path table.
- Figures 3A and 3B illustrate the interdependent path table for the example network.
- Figure 3A illustrates the combined interdependent path table for all restoration nodes
- Figure 3B illustrates the interdependent path table for restoration node C.
- the table contains an entry for each path in the network.
- the entry contains the identification of the path, the path route of the path, and the set of interdependent paths.
- path d' starts at installation A ' , passes through installations G' and B', and ends at installation C. Therefore, the entry for path d ' identifies A'-G'-B'-C as its path route.
- the related paths for path d ' are d ⁇ b ⁇ f , and g ' .
- Figure 4 illustrates the various groups of interdependent paths.
- a group of paths is any set of paths that have at least one pair of installations that are common to each path in the group.
- the paths b ' , d ' , and f form a group because each traverses installations B ' and C.
- the restoration system detects a failure on several paths that form a group, then the failure can be pinpointed to pairs of installations that are common to each path in the group.
- Each group is identified by the paths in the group.
- the restoration system identifies the paths in a group by comp.aring sets of interdependent paths. If the sets of interdependent paths of two paths have paths in common, then those two paths are in the same group.
- the set of interdependent paths for path b ' is (b ⁇ d', f , g ' ).
- path d ' is (d ⁇ b ' , , g ' ), and for path f is (f, b ' , d', g'). Since these sets of interdependent paths have paths in common (i.e., b ' , d ' , f, g'), then paths b ' , d ' , and f form a group as shown in entry 401.
- the paths that are common to the sets of interdependent paths for each path in the group are excluded from restoration.
- paths b ' , d', , and g ' are common to the sets of interdependent paths for paths b ' , d ' , and f. Thus, if a failure is detected on each of paths b', d', and f , then the common set of paths are excluded.
- Figure 5 illustrates a table of restoral routes to bypass active segment b.
- the restoration system identifies from the network topology these possible restoral routes to bypass segment b. If the restoration system had no way of determining whether a spare segment was collocated with failed segment b, then it might choose any of the seven restoration routes depending on the variety of criteria including cost of the restoral route, difficulty in implementing the restoral route, or other such considerations. However, by using the information contained in the interdependent paths table and the port/path table, the restoration system excludes restoral routes 501-503, which include segments that are collocated with segment b. When a failure is detected at port 16, the restoration system uses the port/path table to identify that the failure is on path b'.
- path b ' Since path b ' is the only path that has failed, it forms a group of one path. Path b' is interdependent with paths b ' , d', f, and g ' as indicated by the interdependent path table. Since path b ' is the only path in the group, then paths b', d', , and g' are common to the one set of interdependent paths. Thus, paths b', d', f , and g' are excluded. Since segments b, d, f, .and g, which are on those excluded paths, restoral routes 501, 502, and 503, which include segments f. d, and g, respectively, are excluded.
- Restoral routes 504-507 do not include segments on paths b ' , d ' , , and g ' , and thus are available to be used in the restoration process. These four restoral routes extend from restoration node A, pass through restoration nodes E and F, and terminate at restoration node D, bypassing failed path b ' and bypassing all other segments located within cable 107.
- the restoration system comprises a set-up component and exclusion component.
- the set-up component analyzes the network and generates the path/port tables and interdependent path tables for each restoration node.
- the set-up component then downloads the tables to the restoration nodes.
- the exclusion component executes at each restoration node after a failure is detected and identifies those segments that are connected to the restoration node that should be excluded.
- Figure 6 is a flow diagram of the set-up component.
- the component analyzes the network topology to identify all the paths.
- steps 602-604 the component loops assigning a unique path identifier to each path.
- the component selects the next determined path, starting with the first one.
- step 603 if all paths have already been selected, then the component continues at step 605, else the component continues at step 604.
- the component assigns the next path identifier to the selected path.
- steps 605-607 the component initializes the port/path table.
- step 605 the component selects a next port from the network topology, starting with the first port.
- step 606 if all the ports have already been selected, then the component continues at step 608, else the component continues at step 607.
- step 607 the component identifies the path corresponding to the segment connected to that port and stores the path identification in the port/path table for the selected port.
- steps 608-610 the component loops identifying sets of interdependent paths.
- step 608 the component selects the next path, starting with the first.
- step 609 if all the paths have already been selected, then the component is done, else the component continues at step 610.
- step 610 the component identifies all the paths that are interdependent with the selected path. If a path has a pair of adjacent installations in common with the selected path, the path is interdependent. The component then stores the path identifier of the interdependent paths in the interdependent path table. The set-up component then downloads the tables to the restoration nodes.
- Figure 7 is a flow diagram of the exclusion component.
- the exclusion component executes when a restoration node determines that restoration should proceed.
- the component invokes a routine to identify the groups that are defined by the failed paths.
- the routine loops selecting each identified group and determining the paths that are common to each set of interdependent paths of the paths in the group.
- the routine selects the next group starting with the first.
- the routine continues at step 708. else the routine continues at step 704.
- the routine initializes a common set to all the interdependent paths of a path in the selected group.
- steps 705-707 the routine loops selecting each other path in the selected group and identifies those paths that are common to the current common set and the interdependent paths of the selected path.
- step 705 the routine selects another path in the selected group.
- step 706 if all the paths in the selected group have already been selected, then the routine loops to step 702 to select the next group, else the routine continues at step 707.
- step 707 the routine sets the current common set to the intersection of the common set and the interdependent paths of the selected paths and loops to step 705 to select another path in the selected group.
- the routine excludes all paths in each common set from the restoral process.
- Figure 8 is a flow diagram of a routine that identifies the groups of failed paths.
- the routine checks each possible combination of failed paths to determine whether they define a group. If one combination is a group that is a subset of another combination that is a group, then the subset is disregarded.
- the number of possible combinations of failed paths is 2 N , where N is the number of failed paths.
- the routine checks the combinations in order based on the number of failed paths in the combination. In step 801, the routine selects the next combination of failed paths starting with a combination that includes all the failed paths. In step 802, if all possible combinations have already been selected, then the routine retums, else the routine continues at step 803.
- step 803 if the selected combinations of paths form a group, then the routine continues at step 804, else the routine loops to step 801 to select the next combination.
- step 804 if the group is a subset of a previously defined group then the routine loops to step 801 to select the next combination, else the routine continues at step 805.
- step 805 the routine defines the selected combination of failed paths as a group and loops to step 801 to select the next combination of failed paths.
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US08/910,912 | 1997-08-13 | ||
US08/910,912 US5941992A (en) | 1997-08-13 | 1997-08-13 | Distributed method and system for excluding components from a restoral route in a communications network |
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WO1999009702A2 true WO1999009702A2 (en) | 1999-02-25 |
WO1999009702A3 WO1999009702A3 (en) | 1999-05-14 |
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PCT/US1998/016226 WO1999009702A2 (en) | 1997-08-13 | 1998-08-04 | Distributed method and system for excluding components from a restoral route in a communications network |
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WO (1) | WO1999009702A2 (en) |
Families Citing this family (27)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB2318262B (en) * | 1996-10-08 | 2000-11-08 | Ibm | Bypass circuit for data processing system |
US6052796A (en) * | 1997-06-30 | 2000-04-18 | Mci Communications Corporation | Method and system for augmenting communications network with spare capacity |
US6347074B1 (en) * | 1997-08-13 | 2002-02-12 | Mci Communications Corporation | Centralized method and system for excluding components from a restoral route in a communications network |
US6856627B2 (en) * | 1999-01-15 | 2005-02-15 | Cisco Technology, Inc. | Method for routing information over a network |
US6859431B1 (en) * | 2000-01-28 | 2005-02-22 | Ciena Corporation | System and method for calculating protection routes in a network prior to failure |
US6550024B1 (en) * | 2000-02-03 | 2003-04-15 | Mitel Corporation | Semantic error diagnostic process for multi-agent systems |
US6850997B1 (en) * | 2000-09-27 | 2005-02-01 | International Business Machines Corporation | System, method, and program for determining the availability of paths to a device |
US6745347B1 (en) * | 2000-09-27 | 2004-06-01 | International Business Machines Corporation | System, method and program for determining the availability of interfaces to a device from information provided by the device |
US6748557B1 (en) * | 2000-09-27 | 2004-06-08 | International Buisness Machines Corporation | System, method, and program for determining the availability of interfaces to a control unit |
US6982951B2 (en) * | 2000-12-21 | 2006-01-03 | At&T Corp. | Method for selecting a restoration path in a mesh network |
WO2002099946A1 (en) * | 2001-06-05 | 2002-12-12 | Stern Thomas E | A system and method of fault restoration in communication networks |
US7652983B1 (en) | 2001-06-25 | 2010-01-26 | At&T Intellectual Property Ii, L.P. | Method for restoration and normalization in a mesh network |
US6931564B2 (en) * | 2001-07-13 | 2005-08-16 | International Business Machines Corporation | Failure isolation in a distributed processing system employing relative location information |
US6735718B2 (en) | 2001-12-21 | 2004-05-11 | Hubbell Incorporated | Protection switch to support redundant application of converter units |
JP2005031928A (en) * | 2003-07-11 | 2005-02-03 | Hitachi Ltd | Storage system and method for specifying failure of storage system |
US7428214B2 (en) * | 2004-03-04 | 2008-09-23 | Cisco Technology, Inc. | Methods and devices for high network availability |
US7489639B2 (en) * | 2005-03-23 | 2009-02-10 | International Business Machines Corporation | Root-cause analysis of network performance problems |
US8516444B2 (en) | 2006-02-23 | 2013-08-20 | International Business Machines Corporation | Debugging a high performance computing program |
JP5068023B2 (en) * | 2006-03-29 | 2012-11-07 | 株式会社日立製作所 | Computer system and logical path switching method |
US7796527B2 (en) * | 2006-04-13 | 2010-09-14 | International Business Machines Corporation | Computer hardware fault administration |
US9330230B2 (en) * | 2007-04-19 | 2016-05-03 | International Business Machines Corporation | Validating a cabling topology in a distributed computing system |
US8204980B1 (en) * | 2007-06-28 | 2012-06-19 | Emc Corporation | Storage array network path impact analysis server for path selection in a host-based I/O multi-path system |
US7831866B2 (en) * | 2007-08-02 | 2010-11-09 | International Business Machines Corporation | Link failure detection in a parallel computer |
JP2015056748A (en) * | 2013-09-11 | 2015-03-23 | 富士通株式会社 | Network design device, network design method and network design program |
US9608874B2 (en) * | 2013-12-05 | 2017-03-28 | At&T Intellectual Property I, L.P. | Methods and apparatus to identify network topologies |
US9258242B1 (en) | 2013-12-19 | 2016-02-09 | Emc Corporation | Path selection using a service level objective |
RU2013156784A (en) | 2013-12-20 | 2015-06-27 | ИЭмСи КОРПОРЕЙШН | METHOD AND DEVICE FOR SELECTING THE READING AND WRITING DATA ROUTE |
Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4920529A (en) * | 1987-02-27 | 1990-04-24 | Hitachi, Ltd. | Network control method and apparatus therefor |
WO1991015066A1 (en) * | 1990-03-27 | 1991-10-03 | Bell Communications Research, Inc. | Distributed protocol for improving the survivability of telecommunications trunk networks |
US5435003A (en) * | 1993-10-07 | 1995-07-18 | British Telecommunications Public Limited Company | Restoration in communications networks |
Family Cites Families (15)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4577066A (en) * | 1983-08-03 | 1986-03-18 | At&T Bell Laboratories | Telephone interexchange call routing |
US5146452A (en) * | 1990-10-26 | 1992-09-08 | Alcatel Network Systems, Inc. | Method and apparatus for rapidly restoring a communication network |
US5182744A (en) * | 1991-01-03 | 1993-01-26 | At&T Bell Laboratories | Telecommunications network restoration architecture |
US5187740A (en) * | 1991-10-01 | 1993-02-16 | Mci Communications Corporation | Method and apparatus for telephone call reorigination |
JP3071007B2 (en) * | 1991-10-22 | 2000-07-31 | 富士通株式会社 | Communication network control method |
US5335268A (en) * | 1992-10-22 | 1994-08-02 | Mci Communications Corporation | Intelligent routing of special service telephone traffic |
US5333130A (en) * | 1993-05-18 | 1994-07-26 | Alcatel Canada Wire, Inc. | Self-healing drop and insert communication network |
CA2171344C (en) * | 1993-10-07 | 2000-04-18 | David Johnson | Protection network design |
US5459716A (en) * | 1994-04-15 | 1995-10-17 | Mci Communications Corporation | Facility restoration for telecommunications networks |
US5463615A (en) * | 1994-07-07 | 1995-10-31 | At&T Corp. | Node failure restoration tool |
US5623481A (en) * | 1995-06-07 | 1997-04-22 | Russ; Will | Automated path verification for SHN-based restoration |
US5636203A (en) * | 1995-06-07 | 1997-06-03 | Mci Corporation | Method and system for identifying fault locations in a communications network |
US5646936A (en) * | 1995-06-22 | 1997-07-08 | Mci Corporation | Knowledge based path set up and spare capacity assignment for distributed network restoration |
EP0872084A1 (en) * | 1995-09-22 | 1998-10-21 | Mci Communications Corporation | Communication system and method providing optimal restoration of failed paths |
US5832196A (en) * | 1996-06-28 | 1998-11-03 | Mci Communications Corporation | Dynamic restoration process for a telecommunications network |
-
1997
- 1997-08-13 US US08/910,912 patent/US5941992A/en not_active Expired - Lifetime
-
1998
- 1998-08-04 WO PCT/US1998/016226 patent/WO1999009702A2/en active Application Filing
Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4920529A (en) * | 1987-02-27 | 1990-04-24 | Hitachi, Ltd. | Network control method and apparatus therefor |
WO1991015066A1 (en) * | 1990-03-27 | 1991-10-03 | Bell Communications Research, Inc. | Distributed protocol for improving the survivability of telecommunications trunk networks |
US5435003A (en) * | 1993-10-07 | 1995-07-18 | British Telecommunications Public Limited Company | Restoration in communications networks |
Non-Patent Citations (2)
Title |
---|
HITOSHI SHIMAZAKI ET AL: "NEOPILOT: AN INTEGRATED ISDN FAULT MANAGEMENT SYSTEM" COMMUNICATIONS: CONNECTING THE FUTURE, SAN DIEGO, DEC. 2 - 5, 1990, vol. 3, 2 December 1990, pages 1503-1507, XP000218827 INSTITUTE OF ELECTRICAL AND ELECTRONICS ENGINEERS * |
HITOSHI SHIMAZAKI ET AL: "NETWORK FAULT MANAGEMENT" NTT REVIEW, vol. 4, no. 5, 1 September 1992, pages 74-80, XP000358223 * |
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WO1999009702A3 (en) | 1999-05-14 |
US5941992A (en) | 1999-08-24 |
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