CA2094642C - Distributed switching in bidirectional multiplex section-switched ring transmission systems - Google Patents
Distributed switching in bidirectional multiplex section-switched ring transmission systemsInfo
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- CA2094642C CA2094642C CA002094642A CA2094642A CA2094642C CA 2094642 C CA2094642 C CA 2094642C CA 002094642 A CA002094642 A CA 002094642A CA 2094642 A CA2094642 A CA 2094642A CA 2094642 C CA2094642 C CA 2094642C
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- 239000013307 optical fiber Substances 0.000 description 2
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- JLKIGFTWXXRPMT-UHFFFAOYSA-N sulphamethoxazole Chemical compound O1C(C)=CC(NS(=O)(=O)C=2C=CC(N)=CC=2)=N1 JLKIGFTWXXRPMT-UHFFFAOYSA-N 0.000 description 2
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Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J3/00—Time-division multiplex systems
- H04J3/02—Details
- H04J3/08—Intermediate station arrangements, e.g. for branching, for tapping-off
- H04J3/085—Intermediate station arrangements, e.g. for branching, for tapping-off for ring networks, e.g. SDH/SONET rings, self-healing rings, meashed SDH/SONET networks
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J2203/00—Aspects of optical multiplex systems other than those covered by H04J14/05 and H04J14/07
- H04J2203/0001—Provisions for broadband connections in integrated services digital network using frames of the Optical Transport Network [OTN] or using synchronous transfer mode [STM], e.g. SONET, SDH
- H04J2203/0028—Local loop
- H04J2203/0039—Topology
- H04J2203/0042—Ring
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J2203/00—Aspects of optical multiplex systems other than those covered by H04J14/05 and H04J14/07
- H04J2203/0001—Provisions for broadband connections in integrated services digital network using frames of the Optical Transport Network [OTN] or using synchronous transfer mode [STM], e.g. SONET, SDH
- H04J2203/0057—Operations, administration and maintenance [OAM]
- H04J2203/006—Fault tolerance and recovery
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J2203/00—Aspects of optical multiplex systems other than those covered by H04J14/05 and H04J14/07
- H04J2203/0001—Provisions for broadband connections in integrated services digital network using frames of the Optical Transport Network [OTN] or using synchronous transfer mode [STM], e.g. SONET, SDH
- H04J2203/0089—Multiplexing, e.g. coding, scrambling, SONET
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- Engineering & Computer Science (AREA)
- Computer Networks & Wireless Communication (AREA)
- Signal Processing (AREA)
- Small-Scale Networks (AREA)
- Time-Division Multiplex Systems (AREA)
Abstract
Long delays in bidirectional multiplex section-switched self-healing ring transmission systems are avoided by eliminating looping of communications signals when restoring them in response to a failure in the ring and by distributing switching of paths to be protected to ring nodes other than those immediately adjacent the failure. This is realized by provisioning each node in the bidirectional multiplex section-switched ring transmission system with a map of its traffic pattern (all active tributaries) and the relative position of each ring node in the ringtransmission system, and allowing the ring node, if it has communications traffic affected by the failure, to bridge and switch to and from the protection path.
Description
209464~
-DISTRIBUTED SWITCHING IN BIDIRECTIONAL MULTIPLEX
SECTION-SWITCHED RING TRANSMISSION SYSTEMS
Technical Field This invendon relates to ring tr~n~mi~sion ~y~t~ s and, more 5 pardcularly, to bidirecdonal muldplex secdon-switched ring transmission ~y~le Background of the Invention In prior known bidirecdonal muldplex secdon-switched self-healing ring trAn~mission systems, bridging and switfhing, in the presence of a fault, was restricted to switching ring nodes imm~ tçly adjacent to the fault. A problem with 10 such an arr~ngem~nt, in long ~ t~n-~e networks, is that the ~ olation path ise~ mely long. The extremely long ~ uldlion path is a consequence of the fact that only the ring nodes ~ljacent to the fault are allowed to bridge, switch and loop the restored traffic. In certain applicadons, for examples, transoceanic bidirection~l muldplex section-switched ring trAn~mi~sion sy~ s, the length of the l~ ulalion 15 path would be extremely long, cAnsing long delays and degraded system p~lro~ An~e. The extremely long length of the l~ luldlion path results from the looping which causes it to traverse the ocean three dmes for pardcular fault condidons. It is the looping aspect of the restored path that causes the system h~ai,lL~nt. The long delays and degraded service is extremely undesirable.
20 Summary of the Invention The problems resulting from prior bidirection~l muldplex section-switched ring tr~n~mi~sion system leslolation techniques are o~,e~(jllle, in accordance with the principles of the invendon, by eliminAting looping in the ring nodes imm~-liAtely ~ ent to the failure and by, ~rlflitionAlly, distribudng switching 25 of the paths to be protected to ring nodes other than those imm~di~tely adjacent to the failure. This is realized by provi~ioning each node with a map of its traffic pattern (all active tribu~ics), the identitiçs of all the ring nodes and the relative position of each ring node in the bidirecdonal mnltirl~x section-switched ring tr~nsmission system and allowing the ring node, if it has co..~ tions traffic 30 affected by the failure, to bridge and switch directly to and frûm the protecdûn path.
Techni~l advantages of this invendon are: that misconnection~ of co.~ irati-~ns circuits, previously resuldng in squelching of the circuits, are elimin~tecl the resuldng restored paths are shorter; and, since, only affected col-~""-~ tions traffic is bridged and switched, only portions of the protection facility are used, so-called part-time service can be re-established on the protection facility, where applicable.
In accordance with one aspect of the present invention there is provided a bidirectional multiplex section-switched ring tr~n~mi~ion system including: a plurality of 5 ring nodes; a first tr:~n~mi~ion path including a service path and a protection path interconnecting said plurality of ring nodes and transporting communications signals around the ring tran.~mi.~.~ion system from ring node to ring node in a first direction of tr~n~mi~ion; a second tr~n.~mis.~ion path including a service path and a protection path interconnecting said plurality of ring nodes and transporting communications circuits 10 around the ring tr~n~mi.~ion system from ring node to ring node in a second direction of tr~n~mi~ion opposite the first direction of tr~n~mi~sion; each of said plurality of ring nodes comprising: means for storing entries identifying communications tributaries active in the ring node and for storing entries identifying all the ring nodes and their relative positions in the bidirectional multiplex section-switched ring tr~n~mi~ion system; means for 15 monitoring protection switch messages incoming to the ring node to determine whether any changes in the protection switch messages have occurred indicating that one or more failures exist in a tr~n~mi~.cion path between this ring node and any other ring node in the bidirectional multiplex section-switched ring tr~n~mi~sion system; means responsive to any changes in said protection switch messages for determining which of said active 20 communications tributaries in the ring node are affected by the failure in a tr~n~mi~ion path; and means for directly bridging and switching to and from, respectively, said protection paths said affected communications tributaries having a t~rmin~tion in this ring node, which ring node is not necessarily adjacent the failure in a tr~n.cmis~ion path and wherein the shortest direct restoration path is attained between ring nodes and loop-back 25 switching of communications tributaries in any ring node is elimin~ted.
In accordance with another aspect of the present invention there is provided in a bidirectional multiplex section-switched ring tr~n~mi.~ion system including: a plurality of ring nodes; a first tr:~n~mi~ion path including a service path and a protection path interconnecting said plurality of ring nodes and transporting communications circuits 30 around the ring tr~n~mi~sion system from ring node to ring node in a first direction of tr~n~mi.~ion; and a second tr~n~mi~ion path including a service path and a protection path interconnecting said plurality of ring nodes and transporting communications circuits ~' ' -~ ~ ~ 4 ~ 4 ~
-2a-around the ring tr~n~mi~ion system from ring node to ring node in a second direction of tr~n~mi~ion opposite the first direction of tr:~n.~mi~ion; a method of redirecting communications signals comprising the steps of: storing in each of said plurality of ring nodes entries identifying communications tributaries active in the ring node and for storing 5 entries identifying all the ring nodes and their relative positions in the bidirectional multiplex section-switched ring tr~n~mi~.~ion system; monitoring protection switch messages incoming to the ring node to determine whether any changes in the protection switch messages have occurred indicating that one or more failures exist in a tr~n~mi~ion path between this ring node and any other ring node in the bidirectional multiplex 10 seetion-switched ring tr~n~mi~ion system; in response to any ehanges in said protection switch messages, detennining which of said active communications tributaries in the ring node are affected by the failure; and in response to said determination that communications tributaries active in the ring node are affected by the failure, directly bridging and switching to and from, respectively, said protection paths the affected tributaries having a 15 t~rmin:~tion in the ring node, which ring node is not necessarily adjacent the failure and wherein the shortest direct restoration path is attained between ring nodes and loop-back switching of the affected eommunieations tributaries is elimin~ted.
Brief Des~ ;l,lion of the Dr,~ .gs FIG. 1 shows, in simplified block diagram form, bidirectional multiplex 20 section-switched ring tr:~n~mi~ion system 100 including ring nodes 101 through 104 incorporating the invention;
FIG. 2 shows, in simplified block diagram form, details of a ring node including an embodiment of the invention;
FIG. 3 shows, in simplified block diagram form, details of a receiver used in 25 the ring node of FIG. 2;
FIG. 4 shows, in simplified block diagram form, details of a transmitter used in the ring node of FIG. 2, FIG. 5 is an exemplary ring node ID map included in memory of the controller of FIG. 2;
FIG. 6 is an exemplary ring node communications tributary traffic pattern table also ineluded in memory of the eontroller of FIG. 2 for ring node 104;
-2b- ~ 4 ~
FIG. 7 is an exemplary ring node communications tributary traffic pattern table also included in memory of the controller of FIG. 2 for ring node 102;
FIG. 8 is a flow chart illustrating the bridge and switch operation of the controller of FIG. 2;
FIG. 9 is a table illustrating the switch request message (Kl) and switch acknowledgment message (K2) tr~n.~mis~ion for ring nodes 101 through 104 for an idle condition of the bidirectional multiplex section-switched ring tr~n.~mi~ion system 100;
FIG. 10 is a table illustrating the initial switch request message (Kl) and switch acknowledgment message (K2) tr~n~mi~sion for ring nodes 101 through 104 for a complete fiber cut fault between ring nodes 101 and 104 bidirectional multiplex section-switched ring tr~n~mi~.~ion system 100;
FIG. 11 is a table illustrating the switch request message (Kl) and switch acknowledgment message (K2) tr~n~mi~.~ion resulting in the communication tributary traffic pattern in bidirectional multiplex section-switched ring tr~n~mis.~ion system 100 shown in FIG. 12 by employing the invention; and FIG. 12 shows, in simplified block diagram form, the co~ ic~tions tributary traffic pattern resuldng in bidirecdonal multiplex section-switched ring tr~n~mi~sion system 100 by employing the principles of the invendon for a fault between ring nodes 101 and 104.
S Detailed Des~ tion FIG. 1 shows, in simplified form, bidirecdonal muldplex section-switched ring tr~n~mi~sion system 100, which for brevity and clarity of exposidon is shown as incl~lfling only ring nodes 101 through 104, each incorporadng an embofl;..-~nl of the invendon. It will be al~p~nt that ~kliti~n~l or fewer ring nodes 10 and dirrele.~t orient~tion of ring nodes may be employed, as desired. Ring nodes 101 through 104 are int~c-~l-l-ect~d by tr~n~mi~siQn path 110, inf~lu~ing service path 110-S and protection path 110-P, in a counter-clockwise direction, and by tr~nsmi~sion path 120, in~ fling service path 120-S and protection path 120-P, in a clockwise direcdon. In this ex~mple, tr~n~mi~ion paths 110 and 120 are each 15 comprised of two (2) opdcal fibers. It will be a~a~e.~t7 however, and each oftr~n~mission paths 110 and 120 could be c~mpri~ed of a single opdcal fiber. That is, bidirection~l muldplex secdon-switched ring tr~n~mi~ion system 100 could be either a two (2) opdcal fiber or a four (4) optical fiber system. In a two (2) optical fiber system, each of the fibers in tr~n~mi~sion paths 110 and 120 incl~ldes service 20 bandwidth and protecdon bandwidth. In the four (4) opdcal fiber system shown,each of tr~n~mi~ion paths 110 and 120 includes an opdcal fiber for service bandwidth and a sepal~le opdcal fiber for pr~t~lion bandwidth. Such bidirecdonalmuldplex secdon-~wilched ring transmission ~yst~ms are known. In this example, tr~nsmi~ion of digital signals in the CCll-r Synchronous Digital Hierarchy (SDH)25 digital signal format is ~ss~m~d However, it will be a~al~nt that the invendon is equally applicable to other digital signal f~ at~, for example, the ANSI SONET
digital signal format. In this example, it is a~sllm~l that an opdcal STM-N SDH
digital signal format is being utilized for tr~nsmission over trAn~mi~sion paths 110 and 120. In one example, N=16. Details of the SDH digital signal f~llllaLs are 30 described in CClTI' Reco..",.~ tions G.707, G.708 and G.709 endtled "Synchronous Digital Hierarchy Bit Rates", "Netw~lk Node Tnterf~ce For The Synchronous Digital Hierarchy" and "Synchronous Muldplex Structure", respecdvely.
It is noted that requests and acknowledgm~nt~ for protecdon switch 35 acdon are L~ .,.iLIed in an Al1tom~tic Protecdon Switch (APS) ch~nnel in the SDH
muldplex secdon overhead accompanying the pl~tecLion paths 110-P and 120-P on each of tr~n~mi~sion paths 110 and 120. The APS channel, in the SDH format, compri~es the Kl and K2 bytes in the SDH overhead of each of protection paths l lO-P and 120-P. The Kl byte in~ir~tes a request of a c~.. ,.. .-it~*ons tributary for switch action. The first four (4) bits of the Kl byte in~lir~te the switch request S priority and the last four (4) bits in~ t~. the ring node iden*fi~tion (ID) of the destination ring node. The K2 byte in-lir~tes an acknowledg_ent of the requestedpr~>lcclion switch action. The first four (4) bits of the K2 byte inrlil~te the ring node ID of the source ring node and the last 4 bits in-lic~e the action taken. For pull~oses of this description, a "co.. i~ a*ons circuit" is considered to be a AU-4 SDH
10 digital signal having its entry and exit points on the ring.
Each of ring nodes 101 through 104 con~liSeS an add-drop multiplexer (ADM). Such add-drop multiplexer arrang~,~el.t~ are known. For generic ~uu~_l~nls of a SDH based ADM see ccm Rec~................... ld~tion G.7~2. In this eY~mrl~, the ADM o~ tes in a tr~n~mission sense to pass, i.e., express, signals 15 through the ring node, to add signals at the ring node, to drop signals at the ring node, and to bridge and switch signals, during a protection switch at the ring node.
Note that, there is no looping of the affected signals in ring nodes ~ cent the failure, as was ~uil~,d in prior bidirection~l multiplex section-switched ring tr~n~mi~ion Sy~ S.
FIG. 2 shows, in simplified block diagram form, details of ring nodes 101 through 104, inçlu-ling an embo~lim~nt of the invention. In this example, a west (W)-to-east (E) digital signal tr~n~mi~si~ n direction is ~sllm~d in the service path l lO-S and the protec~ion path l lO-P on tr~n~m~ Qn path 110. It will be appa~ tthat operation of the ring node and the ADM therein would be similar for an east (E) 25 - to - west (W) digital signal tr~nsmi~siQn direction in the service path 120-S and the plut~lion path 120-P on tr~n~mi.~ion path 120. Speçifir~lly~ shown are service path llO-S and p ut~lion path llO-P entering the ring node from the west (W) and supplying STM-N SDH optical signals to receiver 201-S and receiver 201-P, ~e~livt;ly~ where N is, for example, 16. Similarly, shown are service path 120-S30 and protection path 120-P entt~ring the ring node from the east (E) and supplying STM-N SDH optical signals to receiver 202-S and ~ceiver 202-P, l~,speclively, where N is, for example, 16. Details of receivers 201 and 202 are identir~l~ and are shown in FIG. 3, to be described below.
The SDH STM-N optical signals exit the ring node on service path 110-35 S as an output from tr~n~mitter 203-S, on service path 120-S as an output from tr~n~mittçr 204-S, on protec~ion path l lO-P as an output from tr~n~mitter 203-P and on protection path 120-P as an output from transmitter 204-P. Details of transmitters 203 and 204 are identical and are shown in FIG. 4, to be described below.
AU-4 SDH output signals from receiver 201-S are routed under control of controller 210 either to transmitter 203-S, i.e., expressed through to service path 110-S, to interface 206-S to be dropped, also to interface 206-S for protection switching to interface 206-P where it will be dropped or to transmitter 203-P to be supplied to protection path 110-P. In similar fashion, AU-4 SDH output signals from receiver 202-S are routed under control of controller 210 either to transmitter 204-S, i.e., expressed through to service path 120-S, to interface 207-S to be dropped, also to interface 207-S for protection switching to interface 207-P where it will be dropped or to transmitter 204-P to be supplied to protection path 120-P. Note that there is no looping back of the AU-4 SDH signals to either protection path 110-P or protection path 120-P, in accordance with the invention. The AU-4 signals from receiver 201-P are supplied either to transmitter 203-P, i.e., expressed through to protection path 110-P, to interface 206-P to be dropped or to transmitter 203-S to be supplied to service path 110-S. In sim;lar fashion, AU-4 signals from receiver 202-P are routed under control of controller 210 either to transmitter 204-P, i.e., expressed through to protection path 120-P, to interface 207-P to be dropped or to transmitter 204-S to be supplied to service path 120-S. Again, note that there is no looping back of the AU-4 SDH
signals to either service path l lO-S or service path 120-S, in accordance with the invention.
AU-4 SDH signals being added and dropped via interface 206-S can be bridged to transmitter 203-P and, hence, protection path l l O-P and can be s~vitched from receiver 202-P
and, hence, from protection path 120-P, all under control of controller 210. Similarly, AU-4 SDH signals being added and dropped via interface 207-S can be bridged to transmitter 204-P and, hence, protection path 120-P and can be switched from receiver 201-P and, hence, from protection path l l O-P, all under control of controller 210.
As indicated above, elimin~ting the looping of signals in ring nodes adjacent the failure, minimi7es the length of the restored path and, additionally, elimin~tescommunications circuit misconnections which, in turn, elimin~tes squelching of those clrcuits.
Interfaces 206-S, 206-P, 207-S and 207-P are employed to interface to particularduplex links 216-S, 216-P, 217-S and 217-P, respectively, and could include any desired arrangement. For example, interfaces 206 and 207 could include a CEPT-4 digital signal interface to a DSX, a STM-lE (electrical) SDH digital signal interfacing to a DSX, an optical extension interface to an STM-1 SDH optical signal 209~6~2 or the like. Such intçf~ce arrangel.lenLs are known. Controller 210 controls theadding and dropping of the signals via int~ ces 206 and 207, as well as, the direct bridging and switching of the AU-4 tribu~ics being added and dropped to and fromprotection paths 110-P and 120-P. Controller 210 also monitors the status of 5 interfaces 206 and 207 and the digital signals supplied thereto via the control bus arr~n~çm~nt Specific~lly, controller 210 lllonilul~ c.r~ S 206 and 207 for loss-of-signal, loss-of -frame, coding violations and the like, i.e., a signal failure condition.
Controller 210 operates to effect the brid~ing and switching of 10 co... -ir~tions tributaries at ring nodes other than thos¢ adjacent the failure, if necessary, in accordance with the principles of the inwntion. Controller 210 cG... nir~tes with ~~cei~cr~ 201 and 202, ~i.n~ e~ 203 and 204 and int~rf~res 206 and 207 via a control bus arr~ng~ment Specifir~lly, controller 210 monitors the incoming digital signals to d~t~lmine loss-of-signal, SDH format K bytes and the15 like. Arlflition~lly~ controller 210 causes the insertion of al~pl~liate K byte m~ssages for ~lulec~ion s~itclling purposes, examples of which are described below.
To realize the desired bridging and switching of the co-- ..~ tion~ tributaries,controller 210 is advantageously provisioned via bus 212 with the identities (IDs) of of all the cG....-~ .;r~*ons tribu~ies passing through the ring node, as well as, those 20 co~ nic~ti~ ns tributaries being added andlor dropped at the ring node, the identities of all the ring nodes in bidirectional multiplex section-switched ring 100 and the positions of the ring nodes in bidirection~l muldplex secdon-switched ring 100. The bridging and ~witching of co.~ -ic~tion~ tributaries under control of controller 210 to effect the invendon is described below.
FIG. 3 shows, in simplified form, details of receivers 201 and 202 of FIG. 2. The receiver include~s an opticaVelectrical (O/E) int~rf~ce 301, demultiplexer (DEMUX) 302 and driver and router 303. An STM-N SDH opdcal signal is supplied to OIE 301 which con~ it to an electrical STM-N signal. In turn, DEMUX 302 dem~lltiplexes the STM-N signal, in known f~hion, to obtain up to N
30 AUG SDH signal, namely, AUG (1) through AUG (N). Again, in this example, N=16. The AUG (1) through AUG (N) signals are supplied to driver and router 303 where they are routed under control of controller 210 via the control bus as AU-4 (1) through AU4 (M) SDH signals. As in~iic~ted above, each STM-N signal can include N AUG tributaries, in this example. The AU-4 (1) through AU-4 (M) 35 signals are routed under control of controller 210, as described above regarding FIG.2. DEMUX 302 also removes STM overhead (OH), and supplies the APS
20g46~2 ch~nn~ol K bytes to controller 210 via the control bus.
FIG.4 shows, in simplified form, details of l~ cn~ 203 and 204 of FIG. 2. The tr~ncmi~er includes select unit 401, multiplexer (MUX) 402 and çlectric~voptical interf~e (EJO) 403. The AU-4 (1) throu~h AU-4 (M) signals are 5 supplied to select unit 401 where the particular tribu~ics AUG (1) through AUG(N) are selected under control of controller 210 to be suppli~d to MUX 402. Again, in this example, N=16. The AUG tribu~ies are supplif d to MUX 402 where o~ellle~d (OH) is added to yield an electrical STM-N SDH signal. In turn E/O
interface 403 con~e,ls the STM-N into an optical STM-N for tr~ncmiscion on the 10 coll~;,~nding fiber tr~n~micsio~ path. MUX 402 also in~;erts a~lupliate K byte mPs~s under control of controller 210 via the control bus.
FIG. 5 is a ring node map table including the iden~ifi~tion (ID) of and relative loc~tion of each of ring nodes 101 through 104 ir bidirection~l multiplex section-swilched ring tr~n~mi~ion system 100. The ring node IDs are stored in a 15 look-up table which is provisioned via 212 in ~ Ol~ of controller 210. As in-lir~tPA above, the ring node IDs are 4 bit words and are included in the second 4 bits of the Kl bytes and the first 4 bits of the K2 bytes in the .APS ch~nnPl FIG. 6 is illustrative of a table including the identifi~tion of the ring node co.. ~ni~tion~ traffic, i.e., the active coi--.n~fi~tian~ tributaries, in a ring 20 node, in this example, ring node 104, for the clockwise ~CW) direction and the counter-clockwise (CCW) direction of tr~nsmi~sion through ring nodes 101 through104. The active c~ ni~tion~ tribu~ies include those being added, dropped or e,.~lessed through ring node 104. The table inclurling the IDs of the active co....~ tion~ tribu~ics in the ring node are provisioned via 212 in a look-up 25 table in memul~ of controller 210. Shown in the table of FIG. 6 are the AU-4 tributary identifir~ti-ms, i.e., the AU-4 (#). In this example, the number of AU-4 tribu~ies can be up to 16. Thus shown, are the AU-4 trib~ics (a) and (b) being .A in ring node 104 in the clockwise (CW) direction and AU-4 tributaries (c) and (d) being tr~n~mittPA in the counter-clockwise (CClW) direction. The CW
30 destination for AU-4 tributary (a) is ring node 101. The CW destin~tion for AU-4 tributary (b) is ring node 102. The CCW destination for trlbutary (c) is ring node 103. Finally, the CCW destination for AU-4 tributary (d) is ring node 102.
FIG. 7 is illustrative of a table including the i~Pntifir~tion of the ring node co.. nic~tions trafficj i.e., the active c(~ ni~tions tributaries, in a ring 35 node, in this example, ring node 102, for the clockwise (CW) direction and the counter-clockwise (CCW) direction of transmission through ring nodes 101 through 2094~42 104. The active co.. ~ hons trib~ies include those xing added, dropped or e~ ,sed through Ang node 102. The table incl~lfling the IDs of the acdve co..~ tions tAbu~ics in thê Ang node are provision~d via 212 in a look-up table in ~emol~ of controller 210. Shown in the table of FIG. 7 are the AU-4 5 tributary identifi~ahon~, i.e., the AU-4 (#). In this example, the nUIllbe~ of AU-4 tributaries can be up to 16. Thus shown, are the AU-4 trbu~ics (a), (b) and (d) being tr~n~ d in ring node 102 in the clockwise (CW) direction and AU-4 tributaries (b) and (e) being tl~ l in the counter-clockwise (CCW) direction.
The CW deshn~hon for AU-4 tributary (a) is ring node 103. The CW deshn~hon for 10 AU-4 tributary (b) is ring node 103. The CW ~lestin~hion for tributary (d) is ring node 104. The CCW destin~hon for tributary (b) is ring node 104. Finally, the CCW destin~hon for AU-4 tributary (e) is ring node 101.
FIG. 8 is a flow chart illustrating the opxration of controller 210 in controlling the operation of the ring nodes in order to effect the bridging and 15 switching of tributary traffic paths in the presence of a failu e. being transported on the protection path is l,l~e.l~led upon detection of the f ilure. Specifically, the process is entered via step 801. Then, operational block 802 causes the K bytes of an incoming STM-N signal to be observed. Then, con~iitional ~ranch point 803 tests to ~iete ,.,ine if the observed K bytes inllir~te a change from ar idle state. If no change 20 from the idle state is inflir~t~l control is le~ull,cd to step 802. If the observed K
bytes in~iicate switch request mpss~gçs have been l~,ce;~,ed, con-lition~l branch point 804 tests to dete.,-,ine if co-----~ C~tion~ traffic for this ring node is affected by the switch request. If the test result is NO, control is l~,lullled to step 802. If the test result in step 804 is YES, operational block 805 directly bridges and switches the 25 affected tributary traffic paths from and to the appl~liate protection path.
Thereafter, the process is ended in step 806.
FIG. 9 is a table illustrating the switch request mtoss~ge (K1) and switch acknowled~m~nt m~ss~ (K2) tr~n~mi~sion for ring nodes 101 through 104 for an idle con-liti~n of the bidirectional multiplex section-~wit,hed ring tr~nsmi.~ion 30 system 100. As in~ ted above, the K1 byte lldns~ll~ any switch request mçss~ges in the APS of the ~~ pl;ate pr~l~lion path. Th~ K2 byte transports acknowledgem~nt mlo.ss~ges In the idle state, i.e., no switch being requested, the K1 byte includes an idle code in the first four (4) and the desti l~tion ID in the second four (4) bits. The K2 byte incl~ldes the source ID in the first four (4) bits, short path 35 code bit in the fifth (5) bit and sign~ling/idle code in the last three (3) bits. Note that the K1 and K2 bytes for each of service paths 110-S and 120-S are tr~n~mi~ed in the ;~ 2094642 g APS channel of p~l~lion paths 120-P and llO-P, lespecLvely. The particular Kl and K2 byte idle state mpss~gçs for nodes 101 through 104 ~mployed in bidirecti~?n~l multiplex section-swil,hed ring tr~n~mi~sion system 100 are shown in FIG. 9.
FIG. 10 is a table illustrating the initial switch rrquest mrss~gç (Kl) and 5 switch acknowledgement mPssa~ (K2)tr~n~mi~sion for rin ~ nodes 101 through 104for a complete fiber cut fault belwcell ring nodes 101 and 104 bidirectional multiplex section-switched ring ~ n~n~ssion system 100. Thus, ring nodes 101 and 104 insert switch request mPss~ges in the Kl bytes in both plole~;~ion paths llO-P and 120-P.
The switch request mPss~gç in~iir~t~ps a signal failure and tne destination ring node.
10 ~d-lition~lly, an acknowledgP.mPnt mPss~e is inserted in the K2 bytes of bothpr~t~;lion paths llO-P and 120-P. The acknowledgPmPnt mpssag~p~ inserted in pathllO-P includes the source ID, long path bit and si n~lin~ldle. The acknowledgemPnt mçss~ inserted in path 120-Pincludes -he source ID, short path bit and sign~ling/FERF (far end l~cei~,d failure). Ring rode 104 inserts similar15 switch request and acknowlPdgemPnt mess~P,s in the Kl and K2 bytes of paths llO-P and 120-P, except the acknowlP~1gPm~nt mPss~e inserted in path llO-P
in-lir~tes short path and sign~lin~/FERF and the acknowle~l~,P~mPnt mP.ss~ge inserted in path 120-Pindic~tes long path and sign~ling/idle. Again, note that the Kl and K2 bytes for each of service paths llO-S and 120-S are tr~n~ c-1 in the APS channelof protection paths 120-P and llO-P, respectively. The pa-ticular Kl and K2 bytemçss~ges for nodes 101 through 104 employed in bidi~Lional multiplex section-switched ring tPn~mission system 100 upon initi~ting a switch are shown in FIG.
10.
FIG. 11 is a table illustrating the switch request mçss~ (Kl) and switch acknowhP~gPmP-nt mess~ (K2) tr~n~mi~sion resulting in the co.~ ir~tion~ t~ibut~ry traffic pattern in bidirectional multiplex section-swi~ched ring l,i nc~ sion system 100 shown in FIG. 12 by employing the invention. Again,ring nodes 101 and 104 insert switch request mçss~ges in the Kl bytes in both p~lion paths llO-P and 120-P. The switch request mPss~ge in-lir~tes a signal 30 failure and the ~lestin~tion ring node. Thus, ring node 101 inserts a switch request mess~gç in the Kl byte of the APS in the clockwise (CW~ direction in plolecLion path 120-P and in the counter-clockwise (CCW) direction in pl~teclion path 110-P.
The switch request mPss~ in-lir~tes a signal failure and idi- n~ s ring node 104 as the destin~tion ring node. The Kl byte on protection p~th 120-P is e~ ssed 35 through ring nodes 102 and 103 and arrives at ring node lC4. Since ring node 104 has detected loss-of-signal and the switch request mP~ss~~es inch1des its 20946~
identifiç~tion~ it knows that the fault is in the path be~ween ing nodes 101 and 104.
Similarly, ring node 104 inserts a switch request m~ss~ in the K1 byte of the APS
in the clockwise (CW) direction in l)lvlec~ioll path 120-P and in the counter-clockwise (CCW) direction in pl~t~,clion path llO-P. Th~ Kl byte on protection S path l lO-P is e~ ssed through ring nodes 103 and 102 and arrives at ring node 101.
Since ring node 101 has ~i~tecteA loss-of-signal and the switch request mpss~gesinrludes its identifir~tion it knows that the fault is in the path between ring nodes 101 and 104. Both of ring nodes 101 and 104 insert acknowled~m~nt m~ss~ges in the APS K2 byte both protection paths l lO-P and 120-P. Again, the K2 10 asknowled~m~nt mpss~ge from ring node 101 is e~pn,ss~d through ring nodes 102and 103 to ring node 104, while the K2 acknowl~1g~m~nt ~ess~ge from ring node 104 is e~p~sscd through ring nodes 103 and 102 to ring nod~. 101.
Recallse of the provicioning of eash ring node, e -sh of the ring nodes by obse,~ g the K byte mess~s knows if any co~ ir~tion~ tributary that is 15 t~ ed in the ring node is ~ffect~d by the failure. If so, tne ring node will bridge and switch the ~ffçcted tributary to and from the appropriate plut~;~-on path, in acc~l~lce with the invention.
FIG. 12 shows, in simplified block ~ ~m form, the resulting AU-4 tributary traffic pattern in bidirection~l multiplex section-sw tshed ring tr~ncmiccion 20 system 100 for a fault bel~ e.l ring nodes 101 and 104 for th~ pro*.ci~ ning as shown in FlGs. 5, 6 and 7. It is noted that all so-called part-time coll~ lni~ ~tion~ traffic being transported on the protection paths llO-P and 120-P nust be removed beforeany protection switching astivity. Thus, in ring node 101, STM-l tributary (a) inten(1ed for ring node 104 in the counter-clockwise (CCW) direction is directly25 bridged and swilched to and from protection paths llO-P and 120-P, while STM-l tributary (e) intended for ring node 102 in the clockwise (CW) direction is lln~ffectPA In ring node 102, STM-l tributary (b) int~nded for ring node 104 in the cowlt.,.-clockwise direction is directly hr~gt~A and switched to and from protection paths l lO-P and 120-P, while STM-l tribu~ics (e) intended for ring node 101 in the 30 CCW direction, (a) and (b) inten-led for ring node 103 and (d3 intended for ring node 104 in the CW direction are unaffected. In ring node 103, STM-l tributaries (a), (b), and (c) are unaffected. In ring node 104, STM-l tribu~ics ~a) and (b) intended for ring node 101 and 102, respectively, in the CW direction ;~re directly bridged awd switched to and from protection paths l lO-P and 120-P, whi e STM-l tributaries (c) 35 and (d) inten~ for ring nodes 103 and 104, respectively, in the CCW direction are unaffected. As indiç~ted above, since the affected STM-l tribu~;cs are directly 20946~ ~
bridged and ~witched to and from the protection paths at itr termin~tion ring nodes, which are not n~ess~rily ~jacent the failure, looping is e imin~tçcl, in accordance with the invention. Additionally, the elimin~tion of looping now frees up portions of the protection paths and so-called part-time co.-.. ni~ions traffic can be S transported over those freed up portions of the protection~ p~ths.
The above-described arrangell-ellls are, of cour~e, merely illustrative of the appli~tion of the principles of the invention. Othe- arrangements may be devised by those skilled in the art without departing from tle spirit or scope of the invention.
-DISTRIBUTED SWITCHING IN BIDIRECTIONAL MULTIPLEX
SECTION-SWITCHED RING TRANSMISSION SYSTEMS
Technical Field This invendon relates to ring tr~n~mi~sion ~y~t~ s and, more 5 pardcularly, to bidirecdonal muldplex secdon-switched ring transmission ~y~le Background of the Invention In prior known bidirecdonal muldplex secdon-switched self-healing ring trAn~mission systems, bridging and switfhing, in the presence of a fault, was restricted to switching ring nodes imm~ tçly adjacent to the fault. A problem with 10 such an arr~ngem~nt, in long ~ t~n-~e networks, is that the ~ olation path ise~ mely long. The extremely long ~ uldlion path is a consequence of the fact that only the ring nodes ~ljacent to the fault are allowed to bridge, switch and loop the restored traffic. In certain applicadons, for examples, transoceanic bidirection~l muldplex section-switched ring trAn~mi~sion sy~ s, the length of the l~ ulalion 15 path would be extremely long, cAnsing long delays and degraded system p~lro~ An~e. The extremely long length of the l~ luldlion path results from the looping which causes it to traverse the ocean three dmes for pardcular fault condidons. It is the looping aspect of the restored path that causes the system h~ai,lL~nt. The long delays and degraded service is extremely undesirable.
20 Summary of the Invention The problems resulting from prior bidirection~l muldplex section-switched ring tr~n~mi~sion system leslolation techniques are o~,e~(jllle, in accordance with the principles of the invendon, by eliminAting looping in the ring nodes imm~-liAtely ~ ent to the failure and by, ~rlflitionAlly, distribudng switching 25 of the paths to be protected to ring nodes other than those imm~di~tely adjacent to the failure. This is realized by provi~ioning each node with a map of its traffic pattern (all active tribu~ics), the identitiçs of all the ring nodes and the relative position of each ring node in the bidirecdonal mnltirl~x section-switched ring tr~nsmission system and allowing the ring node, if it has co..~ tions traffic 30 affected by the failure, to bridge and switch directly to and frûm the protecdûn path.
Techni~l advantages of this invendon are: that misconnection~ of co.~ irati-~ns circuits, previously resuldng in squelching of the circuits, are elimin~tecl the resuldng restored paths are shorter; and, since, only affected col-~""-~ tions traffic is bridged and switched, only portions of the protection facility are used, so-called part-time service can be re-established on the protection facility, where applicable.
In accordance with one aspect of the present invention there is provided a bidirectional multiplex section-switched ring tr~n~mi~ion system including: a plurality of 5 ring nodes; a first tr:~n~mi~ion path including a service path and a protection path interconnecting said plurality of ring nodes and transporting communications signals around the ring tran.~mi.~.~ion system from ring node to ring node in a first direction of tr~n~mi~ion; a second tr~n.~mis.~ion path including a service path and a protection path interconnecting said plurality of ring nodes and transporting communications circuits 10 around the ring tr~n~mi.~ion system from ring node to ring node in a second direction of tr~n~mi~ion opposite the first direction of tr~n~mi~sion; each of said plurality of ring nodes comprising: means for storing entries identifying communications tributaries active in the ring node and for storing entries identifying all the ring nodes and their relative positions in the bidirectional multiplex section-switched ring tr~n~mi~ion system; means for 15 monitoring protection switch messages incoming to the ring node to determine whether any changes in the protection switch messages have occurred indicating that one or more failures exist in a tr~n~mi~.cion path between this ring node and any other ring node in the bidirectional multiplex section-switched ring tr~n~mi~sion system; means responsive to any changes in said protection switch messages for determining which of said active 20 communications tributaries in the ring node are affected by the failure in a tr~n~mi~ion path; and means for directly bridging and switching to and from, respectively, said protection paths said affected communications tributaries having a t~rmin~tion in this ring node, which ring node is not necessarily adjacent the failure in a tr~n.cmis~ion path and wherein the shortest direct restoration path is attained between ring nodes and loop-back 25 switching of communications tributaries in any ring node is elimin~ted.
In accordance with another aspect of the present invention there is provided in a bidirectional multiplex section-switched ring tr~n~mi.~ion system including: a plurality of ring nodes; a first tr:~n~mi~ion path including a service path and a protection path interconnecting said plurality of ring nodes and transporting communications circuits 30 around the ring tr~n~mi~sion system from ring node to ring node in a first direction of tr~n~mi.~ion; and a second tr~n~mi~ion path including a service path and a protection path interconnecting said plurality of ring nodes and transporting communications circuits ~' ' -~ ~ ~ 4 ~ 4 ~
-2a-around the ring tr~n~mi~ion system from ring node to ring node in a second direction of tr~n~mi~ion opposite the first direction of tr:~n.~mi~ion; a method of redirecting communications signals comprising the steps of: storing in each of said plurality of ring nodes entries identifying communications tributaries active in the ring node and for storing 5 entries identifying all the ring nodes and their relative positions in the bidirectional multiplex section-switched ring tr~n~mi~.~ion system; monitoring protection switch messages incoming to the ring node to determine whether any changes in the protection switch messages have occurred indicating that one or more failures exist in a tr~n~mi~ion path between this ring node and any other ring node in the bidirectional multiplex 10 seetion-switched ring tr~n~mi~ion system; in response to any ehanges in said protection switch messages, detennining which of said active communications tributaries in the ring node are affected by the failure; and in response to said determination that communications tributaries active in the ring node are affected by the failure, directly bridging and switching to and from, respectively, said protection paths the affected tributaries having a 15 t~rmin:~tion in the ring node, which ring node is not necessarily adjacent the failure and wherein the shortest direct restoration path is attained between ring nodes and loop-back switching of the affected eommunieations tributaries is elimin~ted.
Brief Des~ ;l,lion of the Dr,~ .gs FIG. 1 shows, in simplified block diagram form, bidirectional multiplex 20 section-switched ring tr:~n~mi~ion system 100 including ring nodes 101 through 104 incorporating the invention;
FIG. 2 shows, in simplified block diagram form, details of a ring node including an embodiment of the invention;
FIG. 3 shows, in simplified block diagram form, details of a receiver used in 25 the ring node of FIG. 2;
FIG. 4 shows, in simplified block diagram form, details of a transmitter used in the ring node of FIG. 2, FIG. 5 is an exemplary ring node ID map included in memory of the controller of FIG. 2;
FIG. 6 is an exemplary ring node communications tributary traffic pattern table also ineluded in memory of the eontroller of FIG. 2 for ring node 104;
-2b- ~ 4 ~
FIG. 7 is an exemplary ring node communications tributary traffic pattern table also included in memory of the controller of FIG. 2 for ring node 102;
FIG. 8 is a flow chart illustrating the bridge and switch operation of the controller of FIG. 2;
FIG. 9 is a table illustrating the switch request message (Kl) and switch acknowledgment message (K2) tr~n.~mis~ion for ring nodes 101 through 104 for an idle condition of the bidirectional multiplex section-switched ring tr~n.~mi~ion system 100;
FIG. 10 is a table illustrating the initial switch request message (Kl) and switch acknowledgment message (K2) tr~n~mi~sion for ring nodes 101 through 104 for a complete fiber cut fault between ring nodes 101 and 104 bidirectional multiplex section-switched ring tr~n~mi~.~ion system 100;
FIG. 11 is a table illustrating the switch request message (Kl) and switch acknowledgment message (K2) tr~n~mi~.~ion resulting in the communication tributary traffic pattern in bidirectional multiplex section-switched ring tr~n~mis.~ion system 100 shown in FIG. 12 by employing the invention; and FIG. 12 shows, in simplified block diagram form, the co~ ic~tions tributary traffic pattern resuldng in bidirecdonal multiplex section-switched ring tr~n~mi~sion system 100 by employing the principles of the invendon for a fault between ring nodes 101 and 104.
S Detailed Des~ tion FIG. 1 shows, in simplified form, bidirecdonal muldplex section-switched ring tr~n~mi~sion system 100, which for brevity and clarity of exposidon is shown as incl~lfling only ring nodes 101 through 104, each incorporadng an embofl;..-~nl of the invendon. It will be al~p~nt that ~kliti~n~l or fewer ring nodes 10 and dirrele.~t orient~tion of ring nodes may be employed, as desired. Ring nodes 101 through 104 are int~c-~l-l-ect~d by tr~n~mi~siQn path 110, inf~lu~ing service path 110-S and protection path 110-P, in a counter-clockwise direction, and by tr~nsmi~sion path 120, in~ fling service path 120-S and protection path 120-P, in a clockwise direcdon. In this ex~mple, tr~n~mi~ion paths 110 and 120 are each 15 comprised of two (2) opdcal fibers. It will be a~a~e.~t7 however, and each oftr~n~mission paths 110 and 120 could be c~mpri~ed of a single opdcal fiber. That is, bidirection~l muldplex secdon-switched ring tr~n~mi~ion system 100 could be either a two (2) opdcal fiber or a four (4) optical fiber system. In a two (2) optical fiber system, each of the fibers in tr~n~mi~sion paths 110 and 120 incl~ldes service 20 bandwidth and protecdon bandwidth. In the four (4) opdcal fiber system shown,each of tr~n~mi~ion paths 110 and 120 includes an opdcal fiber for service bandwidth and a sepal~le opdcal fiber for pr~t~lion bandwidth. Such bidirecdonalmuldplex secdon-~wilched ring transmission ~yst~ms are known. In this example, tr~nsmi~ion of digital signals in the CCll-r Synchronous Digital Hierarchy (SDH)25 digital signal format is ~ss~m~d However, it will be a~al~nt that the invendon is equally applicable to other digital signal f~ at~, for example, the ANSI SONET
digital signal format. In this example, it is a~sllm~l that an opdcal STM-N SDH
digital signal format is being utilized for tr~nsmission over trAn~mi~sion paths 110 and 120. In one example, N=16. Details of the SDH digital signal f~llllaLs are 30 described in CClTI' Reco..",.~ tions G.707, G.708 and G.709 endtled "Synchronous Digital Hierarchy Bit Rates", "Netw~lk Node Tnterf~ce For The Synchronous Digital Hierarchy" and "Synchronous Muldplex Structure", respecdvely.
It is noted that requests and acknowledgm~nt~ for protecdon switch 35 acdon are L~ .,.iLIed in an Al1tom~tic Protecdon Switch (APS) ch~nnel in the SDH
muldplex secdon overhead accompanying the pl~tecLion paths 110-P and 120-P on each of tr~n~mi~sion paths 110 and 120. The APS channel, in the SDH format, compri~es the Kl and K2 bytes in the SDH overhead of each of protection paths l lO-P and 120-P. The Kl byte in~ir~tes a request of a c~.. ,.. .-it~*ons tributary for switch action. The first four (4) bits of the Kl byte in~lir~te the switch request S priority and the last four (4) bits in~ t~. the ring node iden*fi~tion (ID) of the destination ring node. The K2 byte in-lir~tes an acknowledg_ent of the requestedpr~>lcclion switch action. The first four (4) bits of the K2 byte inrlil~te the ring node ID of the source ring node and the last 4 bits in-lic~e the action taken. For pull~oses of this description, a "co.. i~ a*ons circuit" is considered to be a AU-4 SDH
10 digital signal having its entry and exit points on the ring.
Each of ring nodes 101 through 104 con~liSeS an add-drop multiplexer (ADM). Such add-drop multiplexer arrang~,~el.t~ are known. For generic ~uu~_l~nls of a SDH based ADM see ccm Rec~................... ld~tion G.7~2. In this eY~mrl~, the ADM o~ tes in a tr~n~mission sense to pass, i.e., express, signals 15 through the ring node, to add signals at the ring node, to drop signals at the ring node, and to bridge and switch signals, during a protection switch at the ring node.
Note that, there is no looping of the affected signals in ring nodes ~ cent the failure, as was ~uil~,d in prior bidirection~l multiplex section-switched ring tr~n~mi~ion Sy~ S.
FIG. 2 shows, in simplified block diagram form, details of ring nodes 101 through 104, inçlu-ling an embo~lim~nt of the invention. In this example, a west (W)-to-east (E) digital signal tr~n~mi~si~ n direction is ~sllm~d in the service path l lO-S and the protec~ion path l lO-P on tr~n~m~ Qn path 110. It will be appa~ tthat operation of the ring node and the ADM therein would be similar for an east (E) 25 - to - west (W) digital signal tr~nsmi~siQn direction in the service path 120-S and the plut~lion path 120-P on tr~n~mi.~ion path 120. Speçifir~lly~ shown are service path llO-S and p ut~lion path llO-P entering the ring node from the west (W) and supplying STM-N SDH optical signals to receiver 201-S and receiver 201-P, ~e~livt;ly~ where N is, for example, 16. Similarly, shown are service path 120-S30 and protection path 120-P entt~ring the ring node from the east (E) and supplying STM-N SDH optical signals to receiver 202-S and ~ceiver 202-P, l~,speclively, where N is, for example, 16. Details of receivers 201 and 202 are identir~l~ and are shown in FIG. 3, to be described below.
The SDH STM-N optical signals exit the ring node on service path 110-35 S as an output from tr~n~mitter 203-S, on service path 120-S as an output from tr~n~mittçr 204-S, on protec~ion path l lO-P as an output from tr~n~mitter 203-P and on protection path 120-P as an output from transmitter 204-P. Details of transmitters 203 and 204 are identical and are shown in FIG. 4, to be described below.
AU-4 SDH output signals from receiver 201-S are routed under control of controller 210 either to transmitter 203-S, i.e., expressed through to service path 110-S, to interface 206-S to be dropped, also to interface 206-S for protection switching to interface 206-P where it will be dropped or to transmitter 203-P to be supplied to protection path 110-P. In similar fashion, AU-4 SDH output signals from receiver 202-S are routed under control of controller 210 either to transmitter 204-S, i.e., expressed through to service path 120-S, to interface 207-S to be dropped, also to interface 207-S for protection switching to interface 207-P where it will be dropped or to transmitter 204-P to be supplied to protection path 120-P. Note that there is no looping back of the AU-4 SDH signals to either protection path 110-P or protection path 120-P, in accordance with the invention. The AU-4 signals from receiver 201-P are supplied either to transmitter 203-P, i.e., expressed through to protection path 110-P, to interface 206-P to be dropped or to transmitter 203-S to be supplied to service path 110-S. In sim;lar fashion, AU-4 signals from receiver 202-P are routed under control of controller 210 either to transmitter 204-P, i.e., expressed through to protection path 120-P, to interface 207-P to be dropped or to transmitter 204-S to be supplied to service path 120-S. Again, note that there is no looping back of the AU-4 SDH
signals to either service path l lO-S or service path 120-S, in accordance with the invention.
AU-4 SDH signals being added and dropped via interface 206-S can be bridged to transmitter 203-P and, hence, protection path l l O-P and can be s~vitched from receiver 202-P
and, hence, from protection path 120-P, all under control of controller 210. Similarly, AU-4 SDH signals being added and dropped via interface 207-S can be bridged to transmitter 204-P and, hence, protection path 120-P and can be switched from receiver 201-P and, hence, from protection path l l O-P, all under control of controller 210.
As indicated above, elimin~ting the looping of signals in ring nodes adjacent the failure, minimi7es the length of the restored path and, additionally, elimin~tescommunications circuit misconnections which, in turn, elimin~tes squelching of those clrcuits.
Interfaces 206-S, 206-P, 207-S and 207-P are employed to interface to particularduplex links 216-S, 216-P, 217-S and 217-P, respectively, and could include any desired arrangement. For example, interfaces 206 and 207 could include a CEPT-4 digital signal interface to a DSX, a STM-lE (electrical) SDH digital signal interfacing to a DSX, an optical extension interface to an STM-1 SDH optical signal 209~6~2 or the like. Such intçf~ce arrangel.lenLs are known. Controller 210 controls theadding and dropping of the signals via int~ ces 206 and 207, as well as, the direct bridging and switching of the AU-4 tribu~ics being added and dropped to and fromprotection paths 110-P and 120-P. Controller 210 also monitors the status of 5 interfaces 206 and 207 and the digital signals supplied thereto via the control bus arr~n~çm~nt Specific~lly, controller 210 lllonilul~ c.r~ S 206 and 207 for loss-of-signal, loss-of -frame, coding violations and the like, i.e., a signal failure condition.
Controller 210 operates to effect the brid~ing and switching of 10 co... -ir~tions tributaries at ring nodes other than thos¢ adjacent the failure, if necessary, in accordance with the principles of the inwntion. Controller 210 cG... nir~tes with ~~cei~cr~ 201 and 202, ~i.n~ e~ 203 and 204 and int~rf~res 206 and 207 via a control bus arr~ng~ment Specifir~lly, controller 210 monitors the incoming digital signals to d~t~lmine loss-of-signal, SDH format K bytes and the15 like. Arlflition~lly~ controller 210 causes the insertion of al~pl~liate K byte m~ssages for ~lulec~ion s~itclling purposes, examples of which are described below.
To realize the desired bridging and switching of the co-- ..~ tion~ tributaries,controller 210 is advantageously provisioned via bus 212 with the identities (IDs) of of all the cG....-~ .;r~*ons tribu~ies passing through the ring node, as well as, those 20 co~ nic~ti~ ns tributaries being added andlor dropped at the ring node, the identities of all the ring nodes in bidirectional multiplex section-switched ring 100 and the positions of the ring nodes in bidirection~l muldplex secdon-switched ring 100. The bridging and ~witching of co.~ -ic~tion~ tributaries under control of controller 210 to effect the invendon is described below.
FIG. 3 shows, in simplified form, details of receivers 201 and 202 of FIG. 2. The receiver include~s an opticaVelectrical (O/E) int~rf~ce 301, demultiplexer (DEMUX) 302 and driver and router 303. An STM-N SDH opdcal signal is supplied to OIE 301 which con~ it to an electrical STM-N signal. In turn, DEMUX 302 dem~lltiplexes the STM-N signal, in known f~hion, to obtain up to N
30 AUG SDH signal, namely, AUG (1) through AUG (N). Again, in this example, N=16. The AUG (1) through AUG (N) signals are supplied to driver and router 303 where they are routed under control of controller 210 via the control bus as AU-4 (1) through AU4 (M) SDH signals. As in~iic~ted above, each STM-N signal can include N AUG tributaries, in this example. The AU-4 (1) through AU-4 (M) 35 signals are routed under control of controller 210, as described above regarding FIG.2. DEMUX 302 also removes STM overhead (OH), and supplies the APS
20g46~2 ch~nn~ol K bytes to controller 210 via the control bus.
FIG.4 shows, in simplified form, details of l~ cn~ 203 and 204 of FIG. 2. The tr~ncmi~er includes select unit 401, multiplexer (MUX) 402 and çlectric~voptical interf~e (EJO) 403. The AU-4 (1) throu~h AU-4 (M) signals are 5 supplied to select unit 401 where the particular tribu~ics AUG (1) through AUG(N) are selected under control of controller 210 to be suppli~d to MUX 402. Again, in this example, N=16. The AUG tribu~ies are supplif d to MUX 402 where o~ellle~d (OH) is added to yield an electrical STM-N SDH signal. In turn E/O
interface 403 con~e,ls the STM-N into an optical STM-N for tr~ncmiscion on the 10 coll~;,~nding fiber tr~n~micsio~ path. MUX 402 also in~;erts a~lupliate K byte mPs~s under control of controller 210 via the control bus.
FIG. 5 is a ring node map table including the iden~ifi~tion (ID) of and relative loc~tion of each of ring nodes 101 through 104 ir bidirection~l multiplex section-swilched ring tr~n~mi~ion system 100. The ring node IDs are stored in a 15 look-up table which is provisioned via 212 in ~ Ol~ of controller 210. As in-lir~tPA above, the ring node IDs are 4 bit words and are included in the second 4 bits of the Kl bytes and the first 4 bits of the K2 bytes in the .APS ch~nnPl FIG. 6 is illustrative of a table including the identifi~tion of the ring node co.. ~ni~tion~ traffic, i.e., the active coi--.n~fi~tian~ tributaries, in a ring 20 node, in this example, ring node 104, for the clockwise ~CW) direction and the counter-clockwise (CCW) direction of tr~nsmi~sion through ring nodes 101 through104. The active c~ ni~tion~ tribu~ies include those being added, dropped or e,.~lessed through ring node 104. The table inclurling the IDs of the active co....~ tion~ tribu~ics in the ring node are provisioned via 212 in a look-up 25 table in memul~ of controller 210. Shown in the table of FIG. 6 are the AU-4 tributary identifir~ti-ms, i.e., the AU-4 (#). In this example, the number of AU-4 tribu~ies can be up to 16. Thus shown, are the AU-4 trib~ics (a) and (b) being .A in ring node 104 in the clockwise (CW) direction and AU-4 tributaries (c) and (d) being tr~n~mittPA in the counter-clockwise (CClW) direction. The CW
30 destination for AU-4 tributary (a) is ring node 101. The CW destin~tion for AU-4 tributary (b) is ring node 102. The CCW destination for trlbutary (c) is ring node 103. Finally, the CCW destination for AU-4 tributary (d) is ring node 102.
FIG. 7 is illustrative of a table including the i~Pntifir~tion of the ring node co.. nic~tions trafficj i.e., the active c(~ ni~tions tributaries, in a ring 35 node, in this example, ring node 102, for the clockwise (CW) direction and the counter-clockwise (CCW) direction of transmission through ring nodes 101 through 2094~42 104. The active co.. ~ hons trib~ies include those xing added, dropped or e~ ,sed through Ang node 102. The table incl~lfling the IDs of the acdve co..~ tions tAbu~ics in thê Ang node are provision~d via 212 in a look-up table in ~emol~ of controller 210. Shown in the table of FIG. 7 are the AU-4 5 tributary identifi~ahon~, i.e., the AU-4 (#). In this example, the nUIllbe~ of AU-4 tributaries can be up to 16. Thus shown, are the AU-4 trbu~ics (a), (b) and (d) being tr~n~ d in ring node 102 in the clockwise (CW) direction and AU-4 tributaries (b) and (e) being tl~ l in the counter-clockwise (CCW) direction.
The CW deshn~hon for AU-4 tributary (a) is ring node 103. The CW deshn~hon for 10 AU-4 tributary (b) is ring node 103. The CW ~lestin~hion for tributary (d) is ring node 104. The CCW destin~hon for tributary (b) is ring node 104. Finally, the CCW destin~hon for AU-4 tributary (e) is ring node 101.
FIG. 8 is a flow chart illustrating the opxration of controller 210 in controlling the operation of the ring nodes in order to effect the bridging and 15 switching of tributary traffic paths in the presence of a failu e. being transported on the protection path is l,l~e.l~led upon detection of the f ilure. Specifically, the process is entered via step 801. Then, operational block 802 causes the K bytes of an incoming STM-N signal to be observed. Then, con~iitional ~ranch point 803 tests to ~iete ,.,ine if the observed K bytes inllir~te a change from ar idle state. If no change 20 from the idle state is inflir~t~l control is le~ull,cd to step 802. If the observed K
bytes in~iicate switch request mpss~gçs have been l~,ce;~,ed, con-lition~l branch point 804 tests to dete.,-,ine if co-----~ C~tion~ traffic for this ring node is affected by the switch request. If the test result is NO, control is l~,lullled to step 802. If the test result in step 804 is YES, operational block 805 directly bridges and switches the 25 affected tributary traffic paths from and to the appl~liate protection path.
Thereafter, the process is ended in step 806.
FIG. 9 is a table illustrating the switch request mtoss~ge (K1) and switch acknowled~m~nt m~ss~ (K2) tr~n~mi~sion for ring nodes 101 through 104 for an idle con-liti~n of the bidirectional multiplex section-~wit,hed ring tr~nsmi.~ion 30 system 100. As in~ ted above, the K1 byte lldns~ll~ any switch request mçss~ges in the APS of the ~~ pl;ate pr~l~lion path. Th~ K2 byte transports acknowledgem~nt mlo.ss~ges In the idle state, i.e., no switch being requested, the K1 byte includes an idle code in the first four (4) and the desti l~tion ID in the second four (4) bits. The K2 byte incl~ldes the source ID in the first four (4) bits, short path 35 code bit in the fifth (5) bit and sign~ling/idle code in the last three (3) bits. Note that the K1 and K2 bytes for each of service paths 110-S and 120-S are tr~n~mi~ed in the ;~ 2094642 g APS channel of p~l~lion paths 120-P and llO-P, lespecLvely. The particular Kl and K2 byte idle state mpss~gçs for nodes 101 through 104 ~mployed in bidirecti~?n~l multiplex section-swil,hed ring tr~n~mi~sion system 100 are shown in FIG. 9.
FIG. 10 is a table illustrating the initial switch rrquest mrss~gç (Kl) and 5 switch acknowledgement mPssa~ (K2)tr~n~mi~sion for rin ~ nodes 101 through 104for a complete fiber cut fault belwcell ring nodes 101 and 104 bidirectional multiplex section-switched ring ~ n~n~ssion system 100. Thus, ring nodes 101 and 104 insert switch request mPss~ges in the Kl bytes in both plole~;~ion paths llO-P and 120-P.
The switch request mPss~gç in~iir~t~ps a signal failure and tne destination ring node.
10 ~d-lition~lly, an acknowledgP.mPnt mPss~e is inserted in the K2 bytes of bothpr~t~;lion paths llO-P and 120-P. The acknowledgPmPnt mpssag~p~ inserted in pathllO-P includes the source ID, long path bit and si n~lin~ldle. The acknowledgemPnt mçss~ inserted in path 120-Pincludes -he source ID, short path bit and sign~ling/FERF (far end l~cei~,d failure). Ring rode 104 inserts similar15 switch request and acknowlPdgemPnt mess~P,s in the Kl and K2 bytes of paths llO-P and 120-P, except the acknowlP~1gPm~nt mPss~e inserted in path llO-P
in-lir~tes short path and sign~lin~/FERF and the acknowle~l~,P~mPnt mP.ss~ge inserted in path 120-Pindic~tes long path and sign~ling/idle. Again, note that the Kl and K2 bytes for each of service paths llO-S and 120-S are tr~n~ c-1 in the APS channelof protection paths 120-P and llO-P, respectively. The pa-ticular Kl and K2 bytemçss~ges for nodes 101 through 104 employed in bidi~Lional multiplex section-switched ring tPn~mission system 100 upon initi~ting a switch are shown in FIG.
10.
FIG. 11 is a table illustrating the switch request mçss~ (Kl) and switch acknowhP~gPmP-nt mess~ (K2) tr~n~mi~sion resulting in the co.~ ir~tion~ t~ibut~ry traffic pattern in bidirectional multiplex section-swi~ched ring l,i nc~ sion system 100 shown in FIG. 12 by employing the invention. Again,ring nodes 101 and 104 insert switch request mçss~ges in the Kl bytes in both p~lion paths llO-P and 120-P. The switch request mPss~ge in-lir~tes a signal 30 failure and the ~lestin~tion ring node. Thus, ring node 101 inserts a switch request mess~gç in the Kl byte of the APS in the clockwise (CW~ direction in plolecLion path 120-P and in the counter-clockwise (CCW) direction in pl~teclion path 110-P.
The switch request mPss~ in-lir~tes a signal failure and idi- n~ s ring node 104 as the destin~tion ring node. The Kl byte on protection p~th 120-P is e~ ssed 35 through ring nodes 102 and 103 and arrives at ring node lC4. Since ring node 104 has detected loss-of-signal and the switch request mP~ss~~es inch1des its 20946~
identifiç~tion~ it knows that the fault is in the path be~ween ing nodes 101 and 104.
Similarly, ring node 104 inserts a switch request m~ss~ in the K1 byte of the APS
in the clockwise (CW) direction in l)lvlec~ioll path 120-P and in the counter-clockwise (CCW) direction in pl~t~,clion path llO-P. Th~ Kl byte on protection S path l lO-P is e~ ssed through ring nodes 103 and 102 and arrives at ring node 101.
Since ring node 101 has ~i~tecteA loss-of-signal and the switch request mpss~gesinrludes its identifir~tion it knows that the fault is in the path between ring nodes 101 and 104. Both of ring nodes 101 and 104 insert acknowled~m~nt m~ss~ges in the APS K2 byte both protection paths l lO-P and 120-P. Again, the K2 10 asknowled~m~nt mpss~ge from ring node 101 is e~pn,ss~d through ring nodes 102and 103 to ring node 104, while the K2 acknowl~1g~m~nt ~ess~ge from ring node 104 is e~p~sscd through ring nodes 103 and 102 to ring nod~. 101.
Recallse of the provicioning of eash ring node, e -sh of the ring nodes by obse,~ g the K byte mess~s knows if any co~ ir~tion~ tributary that is 15 t~ ed in the ring node is ~ffect~d by the failure. If so, tne ring node will bridge and switch the ~ffçcted tributary to and from the appropriate plut~;~-on path, in acc~l~lce with the invention.
FIG. 12 shows, in simplified block ~ ~m form, the resulting AU-4 tributary traffic pattern in bidirection~l multiplex section-sw tshed ring tr~ncmiccion 20 system 100 for a fault bel~ e.l ring nodes 101 and 104 for th~ pro*.ci~ ning as shown in FlGs. 5, 6 and 7. It is noted that all so-called part-time coll~ lni~ ~tion~ traffic being transported on the protection paths llO-P and 120-P nust be removed beforeany protection switching astivity. Thus, in ring node 101, STM-l tributary (a) inten(1ed for ring node 104 in the counter-clockwise (CCW) direction is directly25 bridged and swilched to and from protection paths llO-P and 120-P, while STM-l tributary (e) intended for ring node 102 in the clockwise (CW) direction is lln~ffectPA In ring node 102, STM-l tributary (b) int~nded for ring node 104 in the cowlt.,.-clockwise direction is directly hr~gt~A and switched to and from protection paths l lO-P and 120-P, while STM-l tribu~ics (e) intended for ring node 101 in the 30 CCW direction, (a) and (b) inten-led for ring node 103 and (d3 intended for ring node 104 in the CW direction are unaffected. In ring node 103, STM-l tributaries (a), (b), and (c) are unaffected. In ring node 104, STM-l tribu~ics ~a) and (b) intended for ring node 101 and 102, respectively, in the CW direction ;~re directly bridged awd switched to and from protection paths l lO-P and 120-P, whi e STM-l tributaries (c) 35 and (d) inten~ for ring nodes 103 and 104, respectively, in the CCW direction are unaffected. As indiç~ted above, since the affected STM-l tribu~;cs are directly 20946~ ~
bridged and ~witched to and from the protection paths at itr termin~tion ring nodes, which are not n~ess~rily ~jacent the failure, looping is e imin~tçcl, in accordance with the invention. Additionally, the elimin~tion of looping now frees up portions of the protection paths and so-called part-time co.-.. ni~ions traffic can be S transported over those freed up portions of the protection~ p~ths.
The above-described arrangell-ellls are, of cour~e, merely illustrative of the appli~tion of the principles of the invention. Othe- arrangements may be devised by those skilled in the art without departing from tle spirit or scope of the invention.
Claims (10)
1. A bidirectional multiplex section-switched ring transmission system including:
a plurality of ring nodes;
a first transmission path including a service path and a protection path interconnecting said plurality of ring nodes and transporting communications signals around the ring transmission system from ring node to ring node in a first direction of transmission;
a second transmission path including a service path and a protection path interconnecting said plurality of ring nodes and transporting communications circuits around the ring transmission system from ring node to ring node in a second direction of transmission opposite the first direction of transmission;
each of said plurality of ring nodes comprising:
means for storing entries identifying communications tributaries active in the ring node and for storing entries identifying all the ring nodes and their relative positions in the bidirectional multiplex section-switched ring transmission system;
means for monitoring protection switch messages incoming to the ring node to determine whether any changes in the protection switch messages have occurred indicating that one or more failures exist in a transmission path between this ring node and any other ring node in the bidirectional multiplex section-switched ring transmission system;
means responsive to any changes in said protection switch messages for determining which of said active communications tributaries in the ring node are affected by the failure in a transmission path; and means for directly bridging and switching to and from, respectively, said protection paths said affected communications tributaries having a termination in this ring node, which ring node is not necessarily adjacent the failure in a transmission path and wherein the shortest direct restoration path is attained between ring nodes and loop-back switching of communications tributaries in any ring node is eliminated.
a plurality of ring nodes;
a first transmission path including a service path and a protection path interconnecting said plurality of ring nodes and transporting communications signals around the ring transmission system from ring node to ring node in a first direction of transmission;
a second transmission path including a service path and a protection path interconnecting said plurality of ring nodes and transporting communications circuits around the ring transmission system from ring node to ring node in a second direction of transmission opposite the first direction of transmission;
each of said plurality of ring nodes comprising:
means for storing entries identifying communications tributaries active in the ring node and for storing entries identifying all the ring nodes and their relative positions in the bidirectional multiplex section-switched ring transmission system;
means for monitoring protection switch messages incoming to the ring node to determine whether any changes in the protection switch messages have occurred indicating that one or more failures exist in a transmission path between this ring node and any other ring node in the bidirectional multiplex section-switched ring transmission system;
means responsive to any changes in said protection switch messages for determining which of said active communications tributaries in the ring node are affected by the failure in a transmission path; and means for directly bridging and switching to and from, respectively, said protection paths said affected communications tributaries having a termination in this ring node, which ring node is not necessarily adjacent the failure in a transmission path and wherein the shortest direct restoration path is attained between ring nodes and loop-back switching of communications tributaries in any ring node is eliminated.
2. The invention as defined in claim 1 wherein said communications tributaries are AU-4 synchronous digital hierarchy tributaries.
3. The invention as defined in claim 1 wherein said means for directly switching and bridging switches and bridges said affected communications tributaries so that they are transported on the protection paths in a direction in the bidirectional multiplex section-switched ring to avoid interruption of the paths by a transmission path failure.
4. The invention as defined in claim 3 wherein the entries stored in said means for storing include the identities of communication tributaries to be expressed through the ring node, communication tributaries to be added at the ring node and communication tributaries to be dropped at the ring node.
5. The invention as defined in claim 4 wherein said means for monitoring includes means for observing K bytes of synchronous digital hierarchy STM-N signals incoming to the ring node to determine if a change from an idle state has occurred which thereby indicates that a path failure exists and said means for determining includes means for observing switch request messages in said K bytes for determining if any of the tributaries active in the ring node are affected by the failure.
6. In a bidirectional multiplex section-switched ring transmission system including:
a plurality of ring nodes;
a first transmission path including a service path and a protection path interconnecting said plurality of ring nodes and transporting communications circuits around the ring transmission system from ring node to ring node in a first direction of transmission;
and a second transmission path including a service path and a protection path interconnecting said plurality of ring nodes and transporting communications circuits around the ring transmission system from ring node to ring node in a second direction of transmission opposite the first direction of transmission;
a method of redirecting communications signals comprising the steps of:
storing in each of said plurality of ring nodes entries identifying communications tributaries active in the ring node and for storing entries identifying all the ring nodes and their relative positions in the bidirectional multiplex section-switched ring transmission system;
monitoring protection switch messages incoming to the ring node to determine whether any changes in the protection switch messages have occurred indicating that one or more failures exist in a transmission path between this ring node and any other ring node in the bidirectional multiplex section-switched ring transmission system;
in response to any changes in said protection switch messages, determining which of said active communications tributaries in the ring node are affected by the failure;
and in response to said determination that communications tributaries active in the ring node are affected by the failure, directly bridging and switching to and from, respectively, said protection paths the affected tributaries having a termination in the ring node, which ring node is not necessarily adjacent the failure and wherein the shortest direct restoration path is attained between ring nodes and loop-back switching of the affected communications tributaries is eliminated.
a plurality of ring nodes;
a first transmission path including a service path and a protection path interconnecting said plurality of ring nodes and transporting communications circuits around the ring transmission system from ring node to ring node in a first direction of transmission;
and a second transmission path including a service path and a protection path interconnecting said plurality of ring nodes and transporting communications circuits around the ring transmission system from ring node to ring node in a second direction of transmission opposite the first direction of transmission;
a method of redirecting communications signals comprising the steps of:
storing in each of said plurality of ring nodes entries identifying communications tributaries active in the ring node and for storing entries identifying all the ring nodes and their relative positions in the bidirectional multiplex section-switched ring transmission system;
monitoring protection switch messages incoming to the ring node to determine whether any changes in the protection switch messages have occurred indicating that one or more failures exist in a transmission path between this ring node and any other ring node in the bidirectional multiplex section-switched ring transmission system;
in response to any changes in said protection switch messages, determining which of said active communications tributaries in the ring node are affected by the failure;
and in response to said determination that communications tributaries active in the ring node are affected by the failure, directly bridging and switching to and from, respectively, said protection paths the affected tributaries having a termination in the ring node, which ring node is not necessarily adjacent the failure and wherein the shortest direct restoration path is attained between ring nodes and loop-back switching of the affected communications tributaries is eliminated.
7. The invention as defined in claim 6 wherein said communications tributaries are AU-4 synchronous digital hierarchy tributaries.
8. The invention as defined in claim 6 wherein said steps of directly switching and bridging switches and bridges said affected communications tributaries so that they are transported on the protection paths in a direction in the bidirectional multiplex section-switched ring to avoid interruption of the paths by a transmission path failure.
9. The invention as defined in claim 8 wherein the entries being stored include the identities of communication tributaries to be expressed through the ring node, communication tributaries to be added at the ring node and communication tributaries to be dropped at the ring node.
10. The invention as defined in claim 9 wherein said step of monitoring includes observing K bytes of synchronous digital hierarchy STM-N signals incoming to the ring node to determine if a change from an idle state has occurred which thereby indicates that a path failure exists and said step of determining includes observing switch request messages in said K bytes for determining if any of the tributaries active in the ring node are affected by the failure.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US07/892,079 US5341364A (en) | 1992-06-02 | 1992-06-02 | Distributed switching in bidirectional multiplex section-switched ringtransmission systems |
| US892,079 | 1992-06-02 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2094642A1 CA2094642A1 (en) | 1993-12-03 |
| CA2094642C true CA2094642C (en) | 1999-06-15 |
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ID=25399330
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002094642A Expired - Fee Related CA2094642C (en) | 1992-06-02 | 1993-04-22 | Distributed switching in bidirectional multiplex section-switched ring transmission systems |
Country Status (5)
| Country | Link |
|---|---|
| US (1) | US5341364A (en) |
| EP (1) | EP0573211B1 (en) |
| JP (1) | JP3195465B2 (en) |
| CA (1) | CA2094642C (en) |
| DE (1) | DE69326382T2 (en) |
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| US4539655A (en) * | 1982-03-16 | 1985-09-03 | Phoenix Digital Corporation | Microcomputer based distributed control network |
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| US4835763A (en) * | 1988-02-04 | 1989-05-30 | Bell Communications Research, Inc. | Survivable ring network |
| US5218604A (en) * | 1990-08-31 | 1993-06-08 | Bell Communications Research, Inc. | Dual-hubbed arrangement to provide a protected ring interconnection |
| US5187706A (en) * | 1990-10-30 | 1993-02-16 | At&T Bell Laboratories | Dual access rings for communications networks |
| US5179548A (en) * | 1991-06-27 | 1993-01-12 | Bell Communications Research, Inc. | Self-healing bidirectional logical-ring network using crossconnects |
-
1992
- 1992-06-02 US US07/892,079 patent/US5341364A/en not_active Expired - Lifetime
-
1993
- 1993-04-22 CA CA002094642A patent/CA2094642C/en not_active Expired - Fee Related
- 1993-05-27 EP EP93304119A patent/EP0573211B1/en not_active Expired - Lifetime
- 1993-05-27 DE DE69326382T patent/DE69326382T2/en not_active Expired - Lifetime
- 1993-06-01 JP JP15257493A patent/JP3195465B2/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| JPH0637779A (en) | 1994-02-10 |
| EP0573211A2 (en) | 1993-12-08 |
| CA2094642A1 (en) | 1993-12-03 |
| US5341364A (en) | 1994-08-23 |
| DE69326382T2 (en) | 2000-05-11 |
| EP0573211A3 (en) | 1995-05-24 |
| JP3195465B2 (en) | 2001-08-06 |
| DE69326382D1 (en) | 1999-10-21 |
| EP0573211B1 (en) | 1999-09-15 |
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| EEER | Examination request | ||
| MKLA | Lapsed |