WO2008000125A1

WO2008000125A1 - A method, system and apparatus for discovering path computation element

Info

Publication number: WO2008000125A1
Application number: PCT/CN2007/000947
Authority: WO
Inventors: Renhai Zhang
Original assignee: Huawei Technologies Co., Ltd.
Priority date: 2006-06-22
Filing date: 2007-03-23
Publication date: 2008-01-03
Also published as: CN101094168A

Abstract

A method of path computation element (PCE) discovery involves acquiring path computation capability information of every PCE in the networks by label switching router (LSR) in the networks when path computation is requested, and then discovering PCE based on the acquired capability information. Thereby only LSR which has path computation request, viz. path computation client (PCC), does PCE discovery, avoiding PCE discovery executed by LSRs which have no path computation request, decreasing network flow and improving efficiency of PCE discovery.

Description

TECHNICAL FIELD The present invention relates to a MPLS (Multiple Protocol Label Switch) technology, and more particularly to a method, system, and apparatus for a Path Computation Element (PCE). BACKGROUND OF THE INVENTION The calculation of constraint-based shortest paths, that is, constrained path computation, is an important component of MPLS technology and generalized multi-protocol label switching (GMPLS, General MPLS) technology traffic engineering (TE, Traffic Engineering). Currently, the constraint path calculation adopts a PCE-based mode, that is, a Path Computation Client (PCC), such as a Label Switching Router (LSSR), needs to establish a Label Switched Path (LSP). The LSR sends a path calculation request to the PCE, and includes destination and constraint information in the request. After receiving the path calculation request, the PCE calculates the satisfaction according to the topology structure and the TE data synchronized with the network. The path calculates the path of the constraint in the request, and may include, in the calculation result, an accurate node such as a router, and a loose node such as a network segment, a region, and an autonomous system, and then the PCE returns the calculation result to the corresponding response message through the response message. The LSR, as an explicit path object (ERO) parameter that establishes the LSP.

Generally, an autonomous system can have one or more PCEs. When there is only one PCE in an autonomous system, it belongs to a centralized path calculation method, that is, all path calculation requests in the autonomous system are sent to the PCE, and then The PCE completes the calculation of all the paths, and returns the corresponding calculation result to the corresponding LSR, which is a relatively large amount of calculation in the path. In this case, it is easy to cause PCE blocking, which eventually leads to the failure of path calculation. When there are multiple PCEs in an autonomous system, all the paths in the autonomous system can be calculated and distributed on different PCEs, so that the load of the calculation load can be shared, and the possibility of path calculation failure caused by PCE blocking can be reduced. For such a method in which multiple PCEs exist in an autonomous system, the LSR needs to know or discover multiple PCEs in the system and computing power information of each PCE before sending the path calculation request, including: Quality of Service (QoS) ) Computational ability, whether it is possible to calculate protection link and load sharing path, traffic engineering database (TED, TE Database) synchronization capability and speed, etc., so that the PCE that best meets the current path calculation requirements sends a corresponding path calculation request, that is, it is found. PCE.

Currently, the discovery of the PCE in the autonomous system is implemented by using an Internal Gateway Protocol (IGP), such as Open Shortest Path First (OSPF) or IS-IS. The following is an example of extending the OSPF routing protocol. That is, the network nodes in the network establish neighbor relationships according to the OSPF routing protocol, and then each network node passes its own information such as location, link state, and network segment through the opaque chain. The Opaque LSA message is periodically broadcasted over the entire network, and each PCE node in the network needs to further carry its own path calculation capability information in the broadcast message, when other network nodes receive After the corresponding broadcast message is sent, the information of the corresponding node is maintained locally. For the PCE node, the path calculation capability information needs to be further maintained. When the LSR in the network needs to perform path calculation, according to the information of the corresponding PCE node maintained locally, a PCE node that meets the current path calculation requirement is selected from multiple PCE nodes, and then the corresponding path is sent to the PCE node. Calculate the request and complete the corresponding path calculation.

This way of discovering PCE by extending IGP enables all LSRs in the network to participate in transmitting and maintaining message information related to the PCE discovery protocol. However, in a network, only a few LSRs usually have path calculation requests. At this time, for those who do not have a path calculation please In the case of LSRs, maintaining and publishing this information is an unnecessary overhead, and it also increases the burden of IGP and the overhead of network bandwidth resources. SUMMARY OF THE INVENTION Embodiments of the present invention provide a method, system, and apparatus for discovering a path calculation unit PCE, so as to reduce network overhead and improve discovery efficiency of a PCE.

The method for discovering the PCE of the embodiment of the present invention includes:

The label switching router in the network obtains the path computing capability information of each PCE in the network when path calculation is required, and discovers the PCE based on the obtained path computing capability information.

A system for discovering PCE, including: PCE, label switching router LSR;

The LSR obtains the path computation capability information of each PCE in the network when the path calculation is needed, and selects the PCE whose path computation capability is most consistent with the current path calculation requirement from the PCEs as the discovered PCE according to the acquired path computation capability information.

A label switching router LSR includes one or more units for acquiring path calculation capability information of each PCE in the network when path calculation is required, and selecting the path calculation capability from each PCE according to the acquired path calculation capability information. The PCE that meets the current path calculation requirements is used as the discovered PCE.

In summary, the embodiment of the present invention discloses a method, a system, and a device for discovering a PCE. The method adopts: when an LSR in a network needs to perform path calculation, acquiring path calculation capability information of each PCE in the network, and according to The obtained path calculation capability information is found in the PCE. Therefore, only the LSR with the path calculation request performs the PCE discovery, which avoids the LSR without the calculation request and also performs the PCE discovery, reduces the network traffic, and further improves the discovery efficiency of the PCE. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a message flow chart of discovering a PCE according to an embodiment of the present invention.

2 is a flow chart of a method of discovering a PCE in accordance with an embodiment of the present invention. BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be further described in detail below with reference to the accompanying drawings.

The message flow chart of the PCE is shown in FIG. 1 . In the embodiment of the present invention, the LSR in the network obtains the path calculation capability information of each PCE in the network when the path calculation is required, and discovers the PCE according to the acquired path calculation capability information, so that only the LSR having the path calculation request is performed. PCE found that it avoids the LSR without calculation request and also performs PCE discovery, which reduces network traffic and improves the discovery efficiency of PCE.

The method for discovering a PCE in the embodiment of the present invention is described in detail below by using a specific embodiment. The process of the method is as shown in FIG. 2, and specifically includes the following steps:

Step 201: The LSR in the network maintains location information of each PCE in the network.

The location information of the PCE may specifically include, for example, IP address information or other location information. Moreover, the foregoing step 201 can be implemented by pre-configuring the location information of the PCE on the LSR in the network, or the PCE can send the location information to all the LSRs in the network by using the LSA diffusion mechanism of the IGP, for example, The node can receive and maintain the location information of the PCE. In the latter mode, the PCE can send the Opaque LSA packet to all the LSRs in the network, and the Opaque LSA packet carries the type length value (TLV) field of the IP address information of the PCE. . In addition, other entities that can obtain PCE location information, such as a neighbor node of the PCE, may send location information of the PCE to the LSR in the network. Step 202: The LSR in the network sends a path calculation capability query message to each PCE in the network according to the PCE location information maintained by the LSR in the network.

The LSR in the network needs to perform path calculation, for example: after receiving other entities in the network, such as: after the path establishment request sent by the client.

Step 203: After receiving the path calculation capability query message, the PCE returns its path calculation capability information to the corresponding LSR.

The foregoing step 202 and step 203 can be implemented by extending an existing PCE communication protocol. For the sake of clarity, the following is a brief introduction to the existing PCE communication protocol. The existing PCE communication protocol uses the Transmission Control Protocol (TCP) as the transport layer protocol, which is mainly used for communication between the LSR and the PCE. The types of packets defined in the protocol are: 1. Start message (Open), used to establish a connection between the PCC and the PCE, negotiate parameters and notify the computing power; 2. Keepalive message, used to maintain the protocol at both ends of the communication protocol. connection. 3. A path calculation request message (PCReq) for transmitting a calculation request to the PCE at the end having the calculation request. 4. The path calculation response message (PCRep) is used by the PCE to return the calculation result; 5. The notification message (PCNtf) is used for both ends of the communication protocol to notify the other party of the specific event; 6. The error message (PCErr) is used to notify the protocol. Error; 7, close the message (Close), used to close the connection.

The foregoing extension of the existing PCE communication protocol specifically means that two types of packets are set based on the existing PCE communication protocol: a PCE calculation capability query message and a PCE calculation capability response message, which are used for the path between the LSR and the PCE. Computational capabilities query and response. The foregoing step 102 and step 103 can be implemented as follows: First, the LSR that needs to perform path calculation sends a path calculation capability query message to the corresponding PCE according to the PCE location information maintained by the PC. The PCE receives the path calculation capability. After the packet is queried, the path calculation capability response packet carrying the path calculation capability information is returned to the LSR. In addition, it is also possible not to set the above-mentioned discovery computing capability query message and calculation energy in the existing PCE communication protocol. The power response message is used to implement the PCE discovery, but the PCE discovery is realized by extending the function of the original message in the existing PCE communication.

Step 204: The LSR in the network selects, according to the received path computing capability information, the PCE whose path computation capability is most consistent with the current path calculation requirement from each PCE as the discovered PCE, and then sends a corresponding path calculation request to the PCE.

The path calculation capability of each PCE in the network is different, and the LSR in the network has different calculation requirements for each path. Therefore, the LSR needs to calculate the capability information according to the received path of each PCE, and select a path calculation from all PCEs. A PCE that matches the current path computation requirements and then sends a path computation request to the PCE.

The method for discovering a PCE according to an embodiment of the present invention is described. In the foregoing method, when an LSR in a network needs to perform path calculation, a path computation capability query message is sent to each PCE in the network, and then according to each PCE. The returned path computing capability information is selected from the PCE that meets the current path calculation requirements for the current path calculation. In addition, the path calculation capability information of each PCE in the network is obtained and saved by the LSR in the network when the path calculation is needed for the first time, and the PCE is found according to the acquired path calculation capability information, and when path calculation is needed later, The PCE is found directly based on the path calculation capability information of the saved PCE. Moreover, when the path computation capability of a certain PCE in the network changes, the PCE may send a notification message including its path computation capability change information to the LSR that maintains a protocol connection with itself and/or registers its location information itself; The LSR in the network maintains the path computation capability information of the PCE saved by itself according to the received notification message. In this way, the LSR in the network can synchronize the path calculation capability information of the corresponding PCE, so that when the path calculation is needed, the appropriate PCE is accurately selected to send the corresponding path calculation request.

The LSR in the network can perform PCE discovery according to the path calculation capability information of the PCE, and can also perform PCE discovery according to the state information of the PCE. For example: In the above steps In 203, in addition to returning the path calculation capability information of the LSR to the LSR, the PCE also returns its own state information; thus, the LSR can comprehensively receive the received PCE path calculation capability information and state information to determine an appropriate PCE, that is, the PCE is found. For example: In some cases, although the path computation capability of the PCE complies with the current path calculation requirements, the PCE may be in a blocked state or a large traffic state. In this case, it may be considered to select a path computation capability that conforms to or conforms to the current path. The PCE, which is required to calculate, but is in an idle or low traffic state, acts as the discovered PCE, and then sends a corresponding path calculation request to the PCE.

For the above situation, in the specific implementation, the LSR in the network can obtain and save the state information of the corresponding PCE from each PCE. The status information of the PCE may specifically include, for example, idle, large traffic (which may include information such as specific traffic values), and information such as congestion (which may include specific congestion duration and the like). When the LSR in the network performs the PCE discovery, the following may be performed: First, the PCE whose current state meets the current path calculation requirement is selected from each PCE according to the state information of each PCE, and then the path calculation capability is further selected from the selected PCE. The PCE that best meets the current path calculation requirements is used as the discovered PCE, and sends a path calculation request to the PCE. Or adopting: Firstly, according to the acquired path calculation capability information, the PCE whose path calculation capability meets the current path calculation requirement is selected from each PCE, and then the PCE whose current state is most consistent with the current path calculation requirement is further selected from the selected PCE as the discovery. PCE. Therefore, the LSR in the network can not only select the PCE according to the received path computing capability information, but also can select a more suitable PCE by considering the state of the corresponding PCE.

In addition, when the state of a certain PCE in the network changes, the PCE may actively send a notification message including its state change information to the LSR that maintains a protocol connection with itself and/or has registered its location information. The LSR maintains the state information of the PCE saved by itself according to the received notification message. In this way, the LSR in the network can synchronize the status information of the corresponding PCE, so that when the path calculation is needed, the appropriate selection can be accurately performed. The PCE sends the corresponding path calculation request.

The above is only the preferred embodiment of the present invention, and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the present invention. Within the scope of protection.

Claims

Claim

A method for discovering a path calculation unit PCE, the method comprising: obtaining, by a label switching router LSR in a network, path calculation capability information of each PCE in the network, and calculating according to the acquired path The capability information found PCE.

The method according to claim 1, wherein the LSR acquires path computation capability information of each PCE in the network, including:

Maintain the location information of each PCE in the network;

Sending a path calculation capability query message to each PCE in the network according to the maintained PCE location information when path calculation is required;

Receives its own path calculation capability information returned by the PCE.

The method according to claim 2, wherein the location information of each PCE in the maintenance network is: pre-configure location information of each PCE on the LSR.

The method according to claim 2, wherein the location information of each PCE in the maintenance network includes:

Each PCE sends its own location information to the LSR;

The LSR saves the received location information of each PCE.

The method according to claim 4, wherein each PCE sends its own location information to the LSR as follows: Each PCE sends an opaque link state broadcast Opaque LSA message to the LSR, and reports the Opaque LSA in the Opaque LSA. The text carries the type length value TLV field of the IP address information of the PCE.

The method according to claim 2, wherein the LSR sends a path calculation capability query message to each PCE in the network according to the maintained PCE location information, including: the LSR sends the PCE location information to the PCE according to the PCE location information maintained by the LSR. Path calculation capability query message; The path calculation capability information returned by the receiving PCE includes: receiving a path calculation capability response message that is returned by the PCE and carrying the path calculation capability information of the path.

The method according to any one of claims 1 to 6, wherein the step of discovering the PCE according to the acquired path calculation capability information comprises: selecting a path calculation from each PCE according to the acquired path calculation capability information. The PCE with the ability to best meet the current path calculation requirements is the discovered PCE.

The method according to claim 1, further comprising: saving path calculation capability information of each PCE in the obtained network;

The LSR obtains the path computation capability information of each PCE in the network as follows: The LSR obtains the path computation capability information of the saved PCE.

The method according to claim 8, wherein the method further comprises: the PCE that changes the path computation capability in the network to maintain a protocol connection with itself and/or the LSR that has registered its location information itself includes The notification message of the path calculation capability change information; the LSR in the network maintains the path calculation capability information of the PCE saved by itself according to the received notification message.

The method of claim 1, wherein the method further comprises: acquiring, by the LSR in the network, the state information of each PCE in the network, and selecting the current state from each PCE according to the state information of each PCE. The PCE required for the current path calculation; the step of discovering the PCE according to the acquired path calculation capability information includes: selecting, from the PCE selected according to the state information of each PCE, a PCE whose path calculation capability best meets the current path calculation requirement as a discovery PCE.

The method according to claim 1, wherein the method further comprises: acquiring, by the LSR in the network, the state information of each PCE in the network;

The step of discovering the PCE according to the acquired path calculation capability information includes: selecting a path calculation capability from each PCE according to the acquired path calculation capability information, and calculating according to the current path The required PCE is selected from the selected PCEs as the PCE of the current state that best meets the current path calculation requirements.

The method according to claim 10 or 11, wherein the method further comprises: transmitting, by the PCE whose state changes in the network, a protocol connection with itself and/or an LSR that has registered its location information by itself The notification message of the state change information; the LSR in the network maintains the state information of the PCE according to the received notification message.

A system for discovering a path calculation unit PCE, comprising: a PCE, a label switching router LSR;

The system according to claim 13, wherein the LSR further comprises one or more units for maintaining location information of each PCE in the network, and according to the maintained PCE location information when path calculation is required. Each PCE in the network sends a path computation capability query message;

The PCE further includes one or more units for returning its own path computation capability information to the LSR after receiving the computing capability query message.

The system according to claim 14, wherein the location information of the PCE is pre-configured on the LSR.

16. The system according to claim 14, wherein the PCE further comprises one or more units for transmitting its own location information to an LSR in the network; the LSR further one or more units, It is used to save the location information of each received PCE.

The system according to claim 13, wherein the LSR further includes one or more units, configured to save path calculation capability information of the acquired PCE, and When path calculation is required in the future, the PCE is found based on the path calculation capability information of the saved PCE.

18. The system according to claim 17, wherein the PCE further comprises one or more units for maintaining a protocol connection with itself and/or registering itself when its path computational capability changes. The LSR of the location information sends a notification message including its path calculation capability change information;

The LSR further includes one or more units for maintaining path calculation capability information of the PCE saved by itself according to the received notification message.

The system of claim 13, wherein the LSR further comprises one or more units for acquiring and saving state information of each PCE in the network, and selecting from each PCE according to status information of each PCE. The current state meets the PCE of the current path calculation requirement; and then selects the PCE whose path calculation capability best meets the current path calculation requirement from among the PCEs selected according to the state information of each PCE as the discovered PCE.

The system of claim 13, wherein the LSR further comprises one or more units, configured to acquire and save state information of each PCE in the network, and calculate capability information from each PCE according to the acquired path. The PCE whose path calculation capability meets the current path calculation requirement is selected, and the PCE whose current state is most consistent with the current path calculation requirement is selected from the selected PCEs as the discovered PCE.

21. The system according to claim 19 or 20, wherein the PCE further comprises one or more units for maintaining a protocol connection with itself and/or registering itself when its status changes. The LSR that has passed its location information sends a notification message containing its state change information; the LSR further includes one or more units for maintaining state information of the PCE according to the received notification message.

A label switching router (LSR), comprising: one or more units, configured to acquire path calculation capability information of each PCE in the network when path calculation is required, and According to the obtained path calculation capability information, the PCE whose path calculation capability best meets the current path calculation requirement is selected from each PCE as the discovered PCE.

The LSR according to claim 22, wherein the LSR further includes one or more units for maintaining location information of each PCE in the network, and according to the maintained PCE location information when path calculation is required. Each PCE in the network sends a path computation capability query message.

The LSR according to claim 23, wherein the LSR is pre-configured with location information of the PCE.

The LSR according to claim 22, wherein the LSR further includes one or more units, configured to save path calculation capability information of the acquired PCE, and when the path calculation needs to be performed later, according to the saved PCE's path computation capability information found PCE.

The LSR according to claim 22, wherein the LSR further includes one or more units, configured to acquire and save state information of each PCE in the network, and select from each PCE according to status information of each PCE. The current state meets the PCE of the current path calculation requirement; and then selects the PCE whose path calculation capability best meets the current path calculation requirement from among the PCEs selected according to the state information of each PCE as the discovered PCE.

The LSR according to claim 22, wherein the LSR further includes one or more units, configured to acquire and save state information of each PCE in the network, and calculate capability information from each PCE according to the acquired path. The PCE whose path calculation capability meets the current path calculation requirement is selected, and the PCE whose current state is most consistent with the current path calculation requirement is selected from the selected PCEs as the discovered PCE.