CN1269955A - Loop detection - Google Patents

Loop detection Download PDF

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Publication number
CN1269955A
CN1269955A CN 98808820 CN98808820A CN1269955A CN 1269955 A CN1269955 A CN 1269955A CN 98808820 CN98808820 CN 98808820 CN 98808820 A CN98808820 A CN 98808820A CN 1269955 A CN1269955 A CN 1269955A
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CN
China
Prior art keywords
node
information source
loop
connection oriented
network device
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Granted
Application number
CN 98808820
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Chinese (zh)
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CN1132493C (en
Inventor
G·厄斯特
J·阿克塞尔
G·哈加尔德
L·安德松
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Telefonaktiebolaget LM Ericsson AB
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Telefonaktiebolaget LM Ericsson AB
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Publication of CN1269955A publication Critical patent/CN1269955A/en
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Publication of CN1132493C publication Critical patent/CN1132493C/en
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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04Q—SELECTING
    • H04Q11/00—Selecting arrangements for multiplex systems
    • H04Q11/04—Selecting arrangements for multiplex systems for time-division multiplexing
    • H04Q11/0428—Integrated services digital network, i.e. systems for transmission of different types of digitised signals, e.g. speech, data, telecentral, television signals
    • H04Q11/0478—Provisions for broadband connections
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L12/00—Data switching networks
    • H04L12/54—Store-and-forward switching systems 
    • H04L12/56—Packet switching systems
    • H04L12/5601—Transfer mode dependent, e.g. ATM
    • H04L2012/5625—Operations, administration and maintenance [OAM]
    • H04L2012/5627—Fault tolerance and recovery
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L12/00—Data switching networks
    • H04L12/54—Store-and-forward switching systems 
    • H04L12/56—Packet switching systems
    • H04L12/5601—Transfer mode dependent, e.g. ATM
    • H04L2012/5628—Testing
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L12/00—Data switching networks
    • H04L12/54—Store-and-forward switching systems 
    • H04L12/56—Packet switching systems
    • H04L12/5601—Transfer mode dependent, e.g. ATM
    • H04L2012/5638—Services, e.g. multimedia, GOS, QOS
    • H04L2012/5646—Cell characteristics, e.g. loss, delay, jitter, sequence integrity
    • H04L2012/5652—Cell construction, e.g. including header, packetisation, depacketisation, assembly, reassembly

Abstract

The invention relates to a loop-detection means produced by a source switch AS when establishing a route to a destination switch ES wherein the loop-detection means is a loop back cell (20) having the source switch AS in both source (21) and turning point (22) fields.

Description

Loop detection
The present invention relates to be used for the communication supervisory method and apparatus of network.
The invention particularly relates to and be used for detecting the especially for example method of the loop in the connection oriented network in the ATM(Asynchronous Transfer Mode) network of network, and relate to employed in the method device.
The network that two kinds of main types are arranged, i.e. connection oriented network and connectionless networks, it is used for transmission information between network.
In the connection oriented network, for example be in the ATM network, message or information flow transmit between two end systems (for example being computer or phone etc.) that for example are A and B, and it is connected to network by setting up with being connected of maintenance during transmitting.Therefore, in office what is the need before breath can be sent out, certain occurrence logic/virtual connection is provided with the stage.During connection is provided with process, this connection is provided with process can be by the end system that passes through to signal to network or by management system or the initialization by other device, selection is by the path of network, logical channel assignment is in the path on the link between the node, resource is kept in link and the node, and logic channel is interconnected in the node, and it comprises transducer in such network.
During connection was provided with process, transducer write down the logic channel of interconnection in table, make the information of follow-up data in the stage that generally can easily transmit connection at the interconnect logic interchannel by hardware logic.
Under the situation of atm network, the information in the connection transmits with unit form, and each unit comprises 53 bytes, and wherein 5 bytes form header, and 48 bytes are pay(useful) loads.Header comprises the identifier that is used for the logic channel that connects on current link.This identifier must be changed by transducer by node and transmits on next link with the unit.Pay(useful) load comprises freely to connect the stream of transmission or the information of message.
For because of the connection setting of initialization from the result of end system signal, generally loop can not take place, because this has been stoped by the network function of handling this signal.
Correctly work in order to ensure route, the special maintenance bag that is called the loopback unit can be transmitted on the route.The loopback unit comprise wherein can identification ring receipt unit information source and the information of the destination of unit.The designator that is called the loopback designator in addition, its represent this unit be pass to or pass from loopback point/destination.Therefore, if node A wishes that the route that is checked through Node B correctly works, then its transmission has A as information source and the B loopback unit as the destination.It is non-subscriber unit that this unit comprises this unit of explanation, and specifies that it is the information of maintenance unit.Maintenance unit has indication, and it is the field (field) of loopback unit.This field notice destination transducer or node (here being Node B), it must steering unit and it is sent back information source.Therefore, check loopback point/destination field receiving loopback unit time point, see whether with this unit loopback.If it is really with this unit loopback, then its change loopback designator represents that this unit is recycled.It does not change information source identifier or loopback identifier.In the loopback unit another field can also be arranged, be called mark of correlation, it remains unchanged.If the route between A and the B correctly works, then node A will get the loopback unit from B back, and it has the loopback designator that indicating member has been diverted.This incident occurs in the loopback unit and inserts certain time afterwards.This time-dependent is in the length and appearance any queuing or other delay thereon of route.
Connection is provided with process and need uses some times, and inswept each node is wanted tens time frames to the hundreds of millisecond, has therefore introduced some stand-by period for end system.But in case set up connection, by transducer hardware, information can transmit node/transducer with effective and efficient manner.When breaking down in network, this connection generally is interrupted and has to be provided with new connection.Newly connect chosen route then so that avoid the faulty component of network.
At big connectionless networks (between the communicator fixed communication not being set but can send this information by obtainable best route this moment) by do not have connecting to be illustrated in for example in the internet, here information is at node A for example with the packets of information of separating, transmit between the B, this packets of information comprises header, header is that a part has also comprised its identifier therein, the information of its length and other useful information, it is from where (information source), and where it must arrive (destination).Each node uses Routing Protocol, so that how exchange preferably arrives the routing iinformation of other node in network.At HUITEMA, CHRISTIAN, " Routing in theInternet ", and ISBNO-13-132192-7,4.4 chapters have described the explanation of Routing Protocol in the 4.2.6 chapter, and the application quotes that it is open as a reference.When between the node in network during these packets of information of route, total possibility that loop takes place that exists.When the sealing of link in the route or node or other from when front nodal point temporarily or for good and all can not receive new packets of information, this can take place.Then in this case be stored in packets of information in its routing information protocol at front nodal point through the alternative route forward pass.But in certain stage, this alternative route might comprise the link with routing information protocol, and this routing information protocol guiding turns back to this at front nodal point.In this case, this packets of information through alternative route from selecting route to turn back at front nodal point once more at front nodal point.Therefore, formed loop.If loop forms, then owing to will waste system resource around loop unnecessary transmission on hop.Even loop interrupts, it is nugatory that the packets of information of obtaining in loop can be considered to, and they can not be delivered to their destination on the correct time.
But loop is transient problem normally.This is because routing information protocol is revised with the information of network state, so the original and alternative route of each node also is to be modified consistently.This modification can for example be finished by exchange distance vector or about the information of Link State between the node.
The distance vector comprises the information that is used for each destination of network, and in general, each destination is an element, and it is distance or " cost " that sends packets of information from specific node to that destination simultaneously.By Routing Protocol, each node adjacent node exchange whole distance vector with it.This exchange cycle ground takes place, and also is possible when causing changing the incident of its cost.The knowledge of distance vector that receives from the neighbour and relevant link cost to this neighbour is used for recomputating its distance vector by node.When reception is used for when forwarding to the packets of information of certain destination, which link corresponding distance vector table illustrates should be as forwarding this packets of information with least cost.Use path to come to be the selected route of this packets of information then with least cost.If node or in specific path, fail to the link of node, then its adjacent node indicate use this failure node or link cost as infinity and therefore must select the path of replacing.The information of relevant this failure node is by the adjacent node that sends to other with the distance vector of revising.These nodes are revised their distance vector then and they are delivered to other adjacent node etc.Therefore the information about this failure link passed network lentamente.The distance vector of each modification affects all adjacent nodes, and in distance vector convergence and new stable state by it carries out distance vector exchange many times between adjacent node before rebuliding.During this convergent cycle, be sent to the influence of the distance vector that the packets of information on the original path might be changed and in loop, finish.This loop finishes naturally when the distance vector has been restrained.But during convergent cycle, it can last till a minute magnitude, processor and bandwidth resources that waste is precious.
Another reason of loop transient state attribute is in most of connectionless networks, some agreements are arranged, wherein each packets of information has the counter in its header usually, be called " activity time " (time to live), it guarantees after passing the time of determining or is more typically after packets of information has been passed the predetermined number destination node, packets of information by under unload promptly from network damage and remove.Depend on value of " activity time " Counter Value when loop takes place and the delay in the loop, loop can exist maximum to reach one minute time cycle.In this cycle, in the aforesaid loop that is considered to valueless and is destined to abandon, wasted precious route processors resource aspect this packets of information of processing.At HUITEMA, CHRISTIAN, " Routing in theInternet " ISBNO-13-132192-7 can find the explanation of " activity time " counter in the 3.3.1 chapter " The Internet Header ", quoted by the application as reference at this.
Owing to before sending message, do not need to set up the reverse connection between information source and the destination, do not have connect be flexibly and message can be sent apace.But the great processor capacity of these network requirements is with the destination of each packets of information of determining just to be sent out, and the loop of resource can take place to waste in system.
In order to improve the performance of network, proposed to form so-called " label (label) switching network " (it is also known as " multi-protocols label switching network "), wherein connectionless networks is superimposed at connection oriented network.In other words, such as the no jockey of router be with such as for example interrelating of the transducer in atm network towards jockey.Each router uses its Routing Protocol, and to set up its routing table with destination information, it expresses the best route that promptly is called the node transmission of downstream node to each specific purpose ground, and in order to arrive desired destination, it must be communicated by letter forward.Then, for the traffic/packets of information to each destination, it must ask generally to be known as the logical channel number of " label " from this downstream neighbor point.When this node is swum neighbor point when having obtained corresponding request from it, it can order its commutator assemble these channels that interconnect.Along with this processing is carried out in the node of network, the link layer of setting up from each information source to each destination is connected.These connections will be followed the path identical with best path, and these best path have been determined by Routing Protocol and distance vector.
The problem of this label switching network is that router network can cause loop, and it is added on the connection oriented network then.Owing to lack the particular organization that is used for detection loop in connection oriented network, therefore before router network had loop with the standard mode notice, might there be the long relatively time cycle in this loop.
Have that to add on the connection oriented network that is stacked in transducer for example and/or ATM be that the existence of loop causes resource waste for the problem of the connectionless networks of router for example.The prior art Routing Protocol that is used for router network can not provide the assurance that prevents loop.They only provide status condition, and wherein protocol rule guarantees to limit the maximum life of loop.This means if loop takes place, then will waste system resource till loop reaches its maximum life or system and carries out some variations of interrupting loop by accident.
By at connection oriented network, especially at atm network and including the active device that is provided for detection loop in the network that is superimposed upon the connectionless networks on the connection oriented network and is used to interrupt loop especially, the present invention attempts to reduce resource waste when loop takes place.This realizes by the following method, and wherein when the information source transducer has been set up connection to destination transducer or node in connection oriented network, it will for example be that the loop detection means of loop detection unit is inserted in the route.This loop detection unit comprises recognition device, and it identifies the loop detection unit by information source node and whether turns back to node.If there is not loop, then this unit will proceed to the destination of its route that will be abandoned there.If loop is arranged, then the loop detection unit will turn back to information source node.It will be discerned by information source node and have loop to occur the warning letter source node, and can take action to avoid this loop, and for example, information source node can notify the network control unit of relevant for example router to have loop to occur.This advantage that has is at several millisecond rather than is approximately within one minute and can detects loop.
In the preferred embodiment of the present invention, loop detection means is the loopback unit, and wherein, in the information field of unit, information source node or transducer are information source and destination (being transition point (turning point)) of loopback unit.If there is not loop to occur, then there be not (having a mind to) to form under the situation of loop, because it transmits on the link of the destination that only causes route, the loopback unit can not turn back to information source node or transducer.If there is loop to occur, the loopback unit that then has the information source identifier in information source and destination/loopback field will return information source node or transducer.The loopback indicator table illustrates this unit and just is being sent to transformation/loopback point.By realizing it itself being the information source and the destination of loopback unit, node or transducer detect this loop.It checks that whether it is the destination of loopback unit, and it is if not the destination, and then the unit will transmit along its logic channel.In order to discern it is the originators of loopback unit, and it can use information source identifier field or correlating markings or both.It checks that also the loopback indicator table illustrates this unit and flowing on the direction of loopback point.
In an example of the present invention, be not sent to potential loop in order to ensure packets of information, after sending the loop detection unit, information source node can be lined up incoming traffic till some time of process.Select this time, if make that loop is promptly arranged really, then before past time, this loop detection unit will very likely return information source node.But, need the elapsed time necessarily can not be oversize because this cause packets of information handle in unacceptable delay and require big buffer memory.Therefore select this time according to the desired length of information type that just is being sent out and route.
In another example of the present invention, for fear of the unnecessary delay packets of information, after sending the loop detection unit, this node begins to send the packets of information that does not have delay along route.This means and do a hypothesis that promptly new route will not cause loop.To postpone be that this hypothesis is acceptable under the unacceptable situation for rare and/or packets of information at loop.
Fig. 1 is the schematic diagram of an example of the simplification network of expression according to the present invention.
Fig. 2 is an example of the loop detection unit according to the present invention.
Fig. 1, it will be used to represent basic thought of the present invention that represented the example of virtual simple connectionless networks, it is superimposed upon on the connection oriented network that is made of node A, B, C, D and E.In this example, each node has no jockey, and it is expressed as router for the purpose of example, AR, and BR, CR, DR and ER, each node also have towards jockey, and it is expressed as ATM transducer AS, BS, CS, DS and ES for the purpose of example.Naturally it may be used in the hybrid network for the present invention, no jockey wherein occurred and/or towards jockey and/or do not have and connect and towards the combination of jockey.
Router and transducer be by link L1, L2, L3, L4 and L5 interconnection.Each node A-E has route and determines device, and for example it is the form of routing table, is respectively RT A, RT B, RT C, RT D, RT E, it comprises the routing iinformation device, for example is routing iinformation inlet E A-B, E A-C, E A-D, E A-EBy the time E X-YThe form of (X is an information source here, and Y is the destination node), its expression packets of information from each node to network in addition the nodal information bag be how to select route.These inlets in the routing table are set up from route cost recognition device, and its mode is known in the prior art, for example are the form of distance vector, and its each node is sent in the network its adjacent node, and it does not here explain.As an example, for the routing table RT of node A A, its information that comprises is: to Node B, to node C, is how to transmit packets of information from node A to node D and from node A to node E from node A from node A.Note, have several modes to make node A packets of information can be sent to node E, promptly pass through link L1, L3, L4, L5 or process link L2, L4, L5.In general, node A will be through link L2, L4, L5 is sent to node E to packets of information, because therefore it provides the shortest is " the most cheap " route, (it all is identical suppose to use the cost of link all links in network), so distance E from information source node A to destination node E A-EShould have cost 3.If link L2 interrupts, then node A will use link L1, L3, and L4, L5 replaces it, and the distance from node A to node E will be increased to 4, and routing iinformation enters the mouth and will be changed to reflect it.
Similarly, Node B has to the distance E of node E B-EIf node 3 is complete, it is 3, if node 3 failures, then it rises to 4.
For node D, to the distance E of node E D-EBe 1, unless link L5 interrupts, distance becomes infinity and promptly becomes the impossible node E that arrives from node D in this case.
Router-A R-ER uses its routing table to connect by aforesaid transducer AS-ES.Therefore under normal circumstances, when hope when E sends the traffic, the label of router-A R request from node CR to E, i.e. the logical channel number CLEa-c of the traffic under the ATM situation.The destination that is received by A is that the packets of information of E will send to C forward by that channel then.
Router CR will require the label CLEc-d to the traffic of E of D, and can order its transducer CS with the interconnection of CLEc-d with CLEa-c, allow the traffic from A to E to be handled by transducer CS thus, and the therefore resource among bypass and the saving router CR.
In an identical manner, for the upstream node X to the A of the traffic of E will ask label CLEx-a to A, it allows AR to order its transducer AS to interconnect with CLEa-c and CLEx-a then.
To follow the path of in router, determining by these connections of aforementioned foundation by routing table RTx.If some incidents cause these routers and produce loop that then this will cause linkloop.
If for example consider in link L4, to have when interruption what happens.This will be detected by router CR, and it will manage to notify its neighbour's router-A R and BR, and its distance to D and E is infinitely-great.If under any circumstance should arrive the information drop-out of B, then AR will be sure of that it can arrive D with cost 3 through B, and AR notifies C with this.This causes route loop.
Before this incident, A has the channel CLEa-c to C, is used for the traffic to E, and B has corresponding channel CLEb-c, is used for its traffic to E.
As the result of this incident, node A discharges its channel to C, and replace to B request channel to B, promptly CLEa-b is used for the traffic to E.BS will interconnect therewith with existing channel CLEb-c.C will be used for channel CLEc-a to the traffic of E to A request.With the CLEa-b CLEc-a that interconnects, router CR with the CLEc-a CLEb-c that interconnects, therefore forms command converter CS loop and connects router-A R with command converter AS.As long as loop exists, will in loop, circulate and cause the waste of link and translator resource to all packets of information of E, and finally cause the problem of overflowing such as in transducer buffer memory etc.
The present invention has reduced the waste problem of resource by loop detection means is provided.In preferred embodiment of the present invention shown in Figure 2, what loop detection means comprised specific modification safeguards loopback unit 20, and it is to produce and send by transducer when the communication channel of setting up another transducer.Unit 20 has header 18 and pay(useful) load 19.This loop detection unit 20 has the transducer of starting, and it is discerned as information source and in transition point field 22 in information source field 21.This unit 20 can also have loopback indicator field 23, and whether its expression unit loopback.Therefore, if transducer AS will set up and the communicating by letter of transducer ES, it produces loop detection unit 20, and wherein this unit will comprise as the AS of information source with as the AS of transition point.This unit 20 is sent on the route that should cause transducer ES then, and generally it does not return transducer AS.If transducer AS then regains any unit, it comprises AS and has loopback designator 23 among both in information source and transition point field (21,22), if its expression unit has not had loopback, it means and has formed loop.Information source can also be by some other information source field identification, and for example this information source field is specific correlating markings 24 in the ITU-T610 rule.Transducer AS can take suitable effect with the loop that prevents from just be used and/or interrupt loop and/or give a warning from network then.In this manner, detection loop immediately, and the loop detection unit is skipped at the loop of newly setting up in the route.In general, can think that loop only comprises several nodes and link.Therefore, the time that loop is skipped in the loop detection unit generally will be short, and loop will detect apace with the method according to this invention.
If there is not loop, then the loop detection unit will proceed to the destination node and be abandoned, and perhaps have the loopback designator loopback that changes to " by loop " possibly.
If loop is arranged, then the loop detection unit was lost before turning back to the transducer that produces it or is disappeared, and this loop removes in official hour with standard mode then.
In the preferred embodiment according to the inventive method, the transducer hypothesis that produces the loop detection unit is without any appearing at the loop on the route and after sending the loop detection unit packets of information being forwarded on route.If this has been avoided the deferred message bag loop is arranged really then may cause losing of some packets of information.But, because by using the loop detection unit can carry out loop detection quickly, if the number of lost packets will be lower than the number of being lost under any situation that does not send the loop detection unit.Therefore, this embodiment causes having improved conveying function and does not have signal delay.
In second embodiment according to the inventive method, the transducer hypothesis that produces the loop detection unit has loop to appear on the route.In this case, a timer is arranged, it is set and stops preset time at interval after the loop detection unit has been transmitted on the replacement route.The length of selecting timer is with the suitable maximum loop length of correspondence.For example, can select this maximum length will skip the loop of arbitrary number link or set the time that number transmits the cycle corresponding to packets of information.Be stored in the end of the packets of information that has the destination on the route up to this timer period.If the loop detection unit does not also return transducer, then hypothesis does not have loop to occur, and institute's canned data bag will transmit on route.This embodiment causes having improved more transmission quality, because be will not have losing of packets of information under the cost in loop in the transmission that delay is caused one or more packets of information.
Select to use which embodiment of the present invention to depend on the type of information in the packet naturally, it is acceptable postponing in transfer of data, but under the situation of the discernable loss of not bearing quality, losing of several packets of information is unacceptable, and mass loss is can be received in the telephone conversation, but transmission delay is unacceptable.Might determine to use which embodiment for node or transducer, be used for each packets of information of its reception: some will transmit other immediately and then will postpone.
In the third embodiment of the invention that does not illustrate, the loop detection unit be programming in advance or preset time produce under at interval.
In the fourth embodiment of the invention that does not illustrate, the loop detection unit is not to produce in each time that route is set up, but after route has been established pre-programmed or predetermined times after produce.
The present invention is not limited to the network that only has 5 nodes and 5 links naturally, but is suitable for the network of any size.
Although notion of the present invention is illustrated by the example that is superimposed upon the connectionless networks on the connection oriented network, can imagines at pure connection oriented network certainly and comprising in the network of connection oriented network or transducer and use the present invention.
The present invention is not limited to the loop detection means based on the loopback unit, but can use any other unit, and this unit can suitably be designed or improve, and can notify originators device loop to exist.

Claims (6)

1. detect the method for network intermediate ring road, this network comprises the link (L1-L5) of node (A-E) and the described node of interconnection, and wherein at least one node comprises the connection oriented network device, for example, is transducer (AS-ES), is characterised in that step:
Whenever a) information source connection oriented network device for example is a transducer (AS), for example sets up communicate by letter route for transducer (ES) at itself and destination connection oriented network device, generation loop detection instrument (20);
B) described information source connection oriented network device (AS) sends described loop detection instrument through described communication route to described destination connection oriented network device (ES); With
C) if described loop detection instrument returns described information source connection oriented network device (AS), described information source connection oriented network device (AS) determines that loop occurs.
2. according to the method for claim 1, be characterised in that step:
D) at above-mentioned steps b) time or afterwards, described information source connection oriented network device (AS) starts the loop detection timer;
E) described information source connection oriented network device (AS) storage is used for the packets of information of described destination connection oriented network device (ES) till described timer expiration; With
F) before the timer expiration, if described loop detection instrument does not return described information source connection oriented network device (AS), described information source connection oriented network device (AS) sends described packets of information through described communication route.
3. according to the method for claim 1 or 2, be characterised in that described loop detection instrument is the loopback unit that is produced by described information source connection oriented network device (AS), described loopback unit has the field of the described information source connection oriented network device of identification (AS) as information source and transition point.
4. according to any one method of aforementioned claim, be characterised in that described network comprises at least one node (A-E), this node comprise the connection oriented network device (AS, BS, CS, DS, ES) and the connectionless networks device (AR, BR, CR, DR, ER).
5. loop detection unit (20), it for example has for the information source recognition device of information source field (21) and/or correlating markings (24) and for example is the transition point recognition device of transition point field (22), be characterised in that: the device (AS-ES) of identification is identical with the device (AS-ES) of identification in described transition point identification (22) in described information source recognition device (21,24).
6. according to the loop detection unit (20) of claim 5, be characterised in that: whether it comprises such as being the loopback designator device of loopback field (23), be used to indicate described unit by loopback.
CN 98808820 1997-07-04 1998-07-03 loop detection Expired - Fee Related CN1132493C (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE9702604A SE512055C2 (en) 1997-07-04 1997-07-04 Detection of loop
SE97026041 1997-07-04

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CN1269955A true CN1269955A (en) 2000-10-11
CN1132493C CN1132493C (en) 2003-12-24

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GB (1) GB2343085B (en)
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CN1734991B (en) * 2004-08-13 2010-08-18 中兴通讯股份有限公司 Method for detecting multi-service transmission platform device service loopback
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CN100344116C (en) * 2004-04-20 2007-10-17 北京润光泰力科技发展有限公司 A method and apparatus for Ethernet converter line side loop back detection
CN1734991B (en) * 2004-08-13 2010-08-18 中兴通讯股份有限公司 Method for detecting multi-service transmission platform device service loopback
CN100403705C (en) * 2006-03-30 2008-07-16 华为技术有限公司 Loopback detecting method for PPP package interface
US9584399B2 (en) 2013-04-28 2017-02-28 Hewlett Packard Enterprise Development Lp Preventing a loop in a vertical stack network

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GB2343085A8 (en) 2000-05-18
SE9702604D0 (en) 1997-07-04
JP2002510454A (en) 2002-04-02
GB9930819D0 (en) 2000-02-16
GB2343085A (en) 2000-04-26
CA2294807A1 (en) 1999-01-14
SE512055C2 (en) 2000-01-17
CN1132493C (en) 2003-12-24

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