CN101237399A - Method, system and device for obtaining label switching path - Google Patents

Abstract

The invention discloses a method, system and equipment for obtaining a label switching path, belonging to the communication field. The method includes: receiving a path calculation request, in which the request carries a destination address, basic constraints and hop number constraints; according to the network topology and the destination address in the request, calculating a path that satisfies the basic constraints; from the calculated path Select the path whose hop count satisfies the hop count constraint condition; return the selected path to the sender of the path calculation request. The system includes: a path calculation request device and a path calculation device. The device includes: a message extension module, a path calculation request sending module and a receiving module. The present invention also provides another device, including: a path calculation request receiving module, a path calculation module, a path selection module and a sending module. The present invention improves the reliability of the calculated path by adding the number of hops as a constraint during path calculation.

Description

Method, system and device for obtaining label switching path

technical field

The present invention relates to the communication field, in particular to a method, system and equipment for obtaining a label switching path.

Background technique

Traffic engineering focuses on the optimization of the overall performance of the network. Its main goals are to provide efficient and reliable network services, optimize the use of network resources, and optimize network traffic. Traffic engineering is specifically divided into two levels: one is traffic-oriented, that is, it focuses on how to improve the service quality of the network; the other is resource-oriented, that is, it focuses on how to optimize the use of network resources, and the most important thing is how to effectively use bandwidth resources. With the expansion of network deployment and the development of GMPLS (General Multiple Protocol Label Switch, general multi-protocol label switching) technology, inter-domain traffic engineering will span different operators and cover GMPLS networks.

CSPF (Constraint-based Shortest Path First, constraint-based shortest path first) calculation is an important part of MPLS (Multiple Protocol Label Switch, multi-protocol label switching) and GMPLS traffic engineering, multi-AS (Autonomous Systems, autonomous system) Path calculation is very complicated and may require the cooperation of computing entities in different ASs to complete it together. In addition, the constrained path calculation method based on the PCE (Path Computation Element, Path Computation Node) model can also be applied to inter-domain traffic engineering. This calculation method does not affect the use of the calculated path, such as LSP (Label Switching Path, label switching path) establishment, maintenance and dismantling.

The calculation method of the constraint path based on the PCE model is as follows:

When PCC (Path Computation Client, path computing client), such as ingress LSR (ingress LabelSwitch Router, ingress label switching router) establishes an LSP path, it sends a request to PCE through PCEP protocol message, and the request information will contain the destination address of the path and various constraints and other basic information.

According to the network topology information in TED (Traffic Engineering Database, traffic engineering database), PCE calculates the path that satisfies the constraints in the request, and returns it to PCC through the response message as the ERO (Explicit Route Object, Explicit Route Object) for establishing LSP. path object) parameters, the calculation result can contain precise nodes (a router) and loose nodes (a network segment, an area or an AS).

The calculation range that a PCE is responsible for is generally one AS. This is because the scope of IGP (Interior Gateway Protocol, Interior Gateway Protocol) diffusion TED information is one AS. When the destination of the calculation request is another AS, a different AS is required. The PCEs cooperate among them to complete the calculation of a path. The PCE is not limited to a specific implementation form, and may be implemented in a router or a designated server.

There are two basic agreements in the PCE model:

PCED (Path Computation Element Discovery Protocol, PCE Discovery Protocol), responsible for PCC to discover the existence and computing capabilities of PCE, when PCC has a computing request, according to the information obtained by the protocol, select the appropriate PCE to send computing requests for computing;

PCEP (Path Computation Element communication Protocol, PCE communication protocol), is responsible for transmitting calculation request and response information between PCC and PCE. When PCC sends calculation requests, it includes various constraints. When a PCE calculation requires other PCEs to assist, Communication between PCEs also requires the support of this communication protocol.

The PCEP protocol message uses TLV (Type, Length, Value, type, length, value) to carry various information, and the encapsulation format is as follows:

0 1 2 2 3

0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- +-+-+-+-+-+-+-+

| Object-Class | OT | Res | P |I| Object Length(bytes) |

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- +-+-+-+-+-+-+-+

| | | |

// (Object body) (Object body) //

| | | |

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- +-+-+-+-+-+-+-+

The meaning of each field is as follows:

Object-Class: object type;

Object-Type: object type;

Res: Reserved field;

P: processing rule field, when set, it means that the constraints described by this object must be processed;

I: ignore field, when set, indicates whether the constraints described by the object are ignored during calculation;

Object Length: the length of the entire object;

Object body: The content of the object.

Among them, Object-Class and Object-Type uniquely represent an object. When the Object-Class and Object-Type are determined, the content of the Object body is also determined.

When establishing an LSP path, more than one path satisfying the constraint condition is obtained. For example, referring to Figure 1, there are five nodes R1, R2, R3, R4 and R5 in the network, among which, the TE cost between R1-R2, R2-R4, R4-R5 is 10, R1-R3, R3- The TE cost of R5 is 15; now it is necessary to establish a TE path from R1 to R5, assuming that the bandwidth information on each link is exactly the same and the constraint conditions are met. According to the current topology, there are two paths: R1-R2- The total TE cost of R4-R5 and R1-R3-R5 is 30, so it can be considered as two equivalent paths.

However, if you need to find a more reliable path, you should choose R1-R3-R5. Assuming that each node and each link has the same probability of failure, it can be known from the perspective of probability that R1-R2-R4-R5 should have a higher probability of failure than R1-R3-R5. That is to say, the fewer links and nodes passed, the more reliable the path is.

In the process of realizing the present invention, the inventor finds that there are at least the following problems in the prior art:

Only the path that satisfies the existing constraints can be selected, so the selected path is not optimized enough and has poor practicability.

Contents of the invention

In order to find a better LSP path, embodiments of the present invention provide a method, system and device for obtaining a label switching path. Described technical scheme is as follows:

An embodiment of the present invention provides a method for obtaining a label switching path, the method comprising:

receiving a path calculation request, the request carrying a destination address, basic constraints and hop constraints;

calculating a path that satisfies the basic constraints according to the network topology and the destination address in the request;

Selecting a path whose hop count satisfies the hop count constraint condition from the calculated paths;

Return the selected path to the sender of the path calculation request.

An embodiment of the present invention provides a system for obtaining a label switching path, and the system includes:

a path calculation request device, configured to send a path calculation request, where the request carries a destination address, basic constraints, and hop count constraints;

a path calculation device, configured to receive the path calculation request sent by the path calculation requesting device, calculate a path that satisfies the basic constraints according to the network topology and the destination address in the request, and select from the calculated paths A path whose hop count satisfies the hop count constraint condition, and returns the selected path to the path calculation requesting device.

An embodiment of the present invention provides a device, which includes:

A message extension module, configured to extend the communication protocol message of the path computation node, and carry a hop number constraint condition in the message;

A path calculation request sending module, configured to send a path calculation request using the path calculation node communication protocol message expanded by the message expansion module, the message carrying a destination address, basic constraints, and hop number constraints;

The receiving module is configured to receive the path calculated by the path calculation device.

Further, an embodiment of the present invention also provides a device, which includes:

A path calculation request receiving module, configured to receive a path calculation request, where the request carries a destination address, basic constraints, and hop count constraints;

A path calculation module, configured to calculate a path that satisfies the basic constraints according to the network topology and the destination address in the request received by the path calculation request receiving module;

a path selection module, configured to select a path whose hop count satisfies the hop count constraint condition from the paths calculated by the path computation module;

A sending module, configured to return the path selected by the path selection module to the path calculation requesting device.

The beneficial effects of the technical solution provided by the embodiments of the present invention are:

By introducing the hop count object in the PCEP message, when the PCC establishes the LSP path, the hop count is added as a new constraint condition. When other constraint conditions are satisfied, the path with the smallest hop count is selected. If the number of hops is less, the reliability of the path is higher. Therefore, when the number of hops is used as a constraint condition, a better LSP path can be obtained.

Description of drawings

FIG. 1 is a schematic diagram of a TE path node in the prior art;

FIG. 2 is a flow chart of a method for obtaining a label switched path provided by Embodiment 1 of the present invention;

FIG. 3 is a structural diagram of a system for obtaining a label switched path provided by Embodiment 2 of the present invention;

Fig. 4 is a structural diagram of the equipment provided by Embodiment 3 of the present invention;

Fig. 5 is a structural diagram of a device provided by Embodiment 4 of the present invention.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the implementation manner of the present invention will be further described in detail below in conjunction with the accompanying drawings.

In the embodiment of the present invention, by introducing the hop count object in the PCEP protocol message, the hop count is used as a constraint condition for CSPF calculation, and when other constraint conditions are satisfied, the path with the least hop count is selected.

Example 1

An embodiment of the present invention provides a method for obtaining a label switching path, which is completed through a PCE, including:

Receive a path calculation request, the request carries the destination address, basic constraints and hop constraints;

According to the network topology and the destination address in the request, calculate the path that satisfies the basic constraints;

Select a path whose hop count satisfies the hop count constraint condition from the calculated paths;

Return the selected path to the sender of the path calculation request.

The PCE in this embodiment may be a router or a designated server, which is used to receive the path calculation request information of the PCC, and calculate the LSP path satisfying the constraints.

Referring to FIG. 2, the above-mentioned method for obtaining a label switching path specifically includes the following steps:

Step 101: Extending the PCEP protocol message, introducing a new hop count object, ie MAX-HOPObject, into the PCEP protocol message, using the hop count as a constraint condition when obtaining the LSP path.

The Object-Class and Object-Type of the newly introduced hop object need to be applied separately to distinguish it from some existing objects. The object body format of the hop object is as follows:

0 1 2 2 3

0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- +-+-+-+-+-+-+

| R | S | hop-value |

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- +-+-+-+-+-+-+-+

Among them, the meanings of each field in the above-mentioned newly applied hop count object are as follows:

S (Scope): Indicates the meaning of the hop count, whether it is Node Hop (node hop count), Area Hop (domain hop count), or AS Hop (AS hop count), and the S field occupies 3 bits.

R: flag bit, can be set to 1 or 0. It can be set to 1, indicating that the PCC wants to know the actual hop count of the path; by setting it to 0, it means that the PCC does not want to know the actual hop count of the path, and there is no need for the PCE to return.

hop-value: Indicates the actual hop count of the path calculated by the PCE. For example, if the hop-value is 3, it means that the hop count of the path calculated by the PCE is 3. You can determine which hop-value specifically represents based on the setting value of the S field. class hop count.

1) When the PCC needs to set up an LSP path, send an extended PCEP protocol message to the PCE, set a maximum acceptable hop count as a constraint condition for the PCE, for example, set the maximum acceptable hop count to 5, If the PCE cannot calculate a path that satisfies the specified hop count, that is, when no path with a hop count within 5 is found, it will notify the PCC of the calculation failure;

2) If PCE fails to calculate because of the number of hops, it can return the minimum number of hops in the actual path for PCC's reference in the response message sent by PCE to notify PCC that the calculation failed. For example, the minimum number of hops in the actual path is 7, and PCE By setting the bits in the hop count object, the minimum hop count 7 is returned to the PCC in the response message sent by the PCE to notify the PCC of the calculation failure;

3) The PCC does not use the hop count as a constraint when the PCE calculates the path, but requires the PCE to return the hop count as a part of the result to the PCC after calculating the path.

Step 102: When the PCC establishes an LSP path, it sends a path calculation request to the PCE.

In an AS, there may be one or more PCEs. When there are multiple PCEs, the PCC can select an appropriate PCE according to the computing capability of each PCE before sending the PCEP message to the PCE.

The path calculation request carries constraints and the information of the destination address of the path to be established by the PCC. The constraints include basic constraints such as bandwidth, prohibited nodes, and management groups. In this embodiment, the constraints include a hop count constraint. condition, that is, when other constraint conditions are satisfied, the PCE is required to select the path with the smallest number of hops.

The path calculation request can have various forms. In this embodiment, the message is taken as an example for illustration. The PCC sends the extended PCEP protocol message to the PCE. For the newly added constraints, the extended PCEP protocol message can be set The bits of the hop count object are used to set the hop count required by the PCC, for example, set the maximum acceptable hop count to 5.

Step 103: After receiving the path calculation request sent by the PCC, the PCE calculates a path satisfying the basic constraints in the request according to the information in the TED.

The topology information synchronized with the network is stored in the TED. According to the destination address of the path in the received message and the network topology information, the PCE calculates the path that satisfies the basic constraints in the message through the CSPF algorithm. Select the path whose hop count satisfies the hop count constraint condition in the path of the condition.

Step 104: Judging whether there is a path satisfying the constraint condition, if yes, go to step 105; otherwise, go to step 106.

Step 105: The PCE sends a PCEP response message to the PCC, and the response message carries a group of information such as LSR addresses of path nodes satisfying the constraint conditions, and then performs step 107.

The calculation result of the CSPF algorithm is to output an external route, which contains a group of LSR addresses of the shortest path nodes satisfying the constraints, and the PCE can use the calculated LSR address information of the path nodes satisfying the constraints as ERO The encoding method is returned to the PCC. For example, in Figure 2, if two suitable paths are found based on bandwidth constraints: R1-R2-R4-R5 and R1-R3-R5, then compare the hops of the two paths and choose the one with the smallest hops The path is R1-R3-R5, and then the PCE returns the result to the PCC through a response message.

When the PCE calculates multiple paths satisfying the constraints, it will select the optimal path and return the selected path to the PCC.

Step 106: The PCE sends a PCEP response message to the PCC, notifying the PCC that the calculation fails, that is, there is no path satisfying the current constraint.

When the calculation of the PCE fails due to the number of hops, that is, when the PCE fails to select a path satisfying the hop number constraint from the calculated paths satisfying the basic constraint conditions, judge according to the flag bit R in the PCEP protocol message sent by the PCC Whether to return the hop count of the calculated path to PCC. For example, the maximum acceptable hop count required in the request message is 5, and the minimum hop count of the calculated actual path is 7. When the R bit is 1, the minimum hop count 7 is returned to PCC is used as a reference, when the R position is 0, no hop count information is returned.

Step 107: After receiving the response message sent by the PCE, the PCC extracts the path node information in the message, uses it as the ERO parameter for establishing the LSP, initiates the signaling for establishing the LSP, and establishes the LSP path.

If the response message received by the PCC is to notify that the calculation has failed, it can wait for a period of time to calculate again, or reduce the constraint conditions and request to calculate a new path again. The method is the same as above, and will not be repeated here.

Example 2

Referring to Fig. 3, an embodiment of the present invention provides a system for obtaining a label switching path, which specifically includes:

The path calculation request device 201 is configured to send a path calculation request, and the request carries a destination address, basic constraints and hop count constraints;

The path calculation device 202 is configured to receive the path calculation request sent by the path calculation request device 201, calculate a path that satisfies the basic constraints according to the network topology and the destination address in the request, and select the number of hops from the calculated path to satisfy the hop count requirement. The route calculation request device 201 returns the selected route to the route calculation requesting device 201.

Further, the path calculation request device 201 may specifically include:

The message extension module is used to expand the path calculation node communication protocol message, and carries the hop number constraint condition in the message;

The path calculation request sending module is used to send a path calculation request using the path calculation node communication protocol message extended by the message expansion module, and the message carries a destination address, basic constraints and hop limit constraints.

The path calculation device 202 may specifically include:

a path calculation request receiving module, configured to receive the path calculation request sent by the path calculation request device 201;

A path calculation module, configured to calculate a path satisfying basic constraints according to the network topology and the destination address in the request received by the path calculation request receiving module;

A path selection module, configured to select a path whose hop count satisfies the hop count constraint condition from the paths calculated by the path computation module;

A sending module, configured to return the path selected by the path selection module to the path calculation requesting device 201 .

Example 3

Referring to FIG. 4, an embodiment of the present invention provides a device. The device provided in this embodiment can be used to send a path calculation request when establishing an LSP path, specifically including:

A message extension module 301, configured to extend the communication protocol message of the path computation node, and carry the hop number constraint condition in the message;

The path calculation request sending module 302 is configured to use the path calculation node communication protocol message extended by the message extension module 301 to send a path calculation request, and the message carries a destination address, basic constraints and hop number constraints;

The receiving module 303 is configured to receive the path calculated by the path calculation device.

Example 4

Referring to FIG. 5 , an embodiment of the present invention also provides a device. The device provided in this embodiment can be used to receive a path calculation request, and calculate a path that satisfies the constraints in the request according to the request, specifically including:

The path calculation request receiving module 401 is configured to receive a path calculation request, and the request carries a destination address, basic constraints, and hop count constraints;

A path calculation module 402, configured to calculate a path satisfying basic constraints according to the network topology and the destination address in the request received by the path calculation request receiving module 401;

A path selection module 403, configured to select a path whose number of hops satisfies the constraint condition of the number of hops from the paths calculated by the path calculation module 402;

The sending module 404 is configured to return the path selected by the path selection module 403 to the path calculation requesting device.

The embodiment of the present invention can be implemented by software, and the corresponding software can be stored in a readable storage medium, such as a hard disk, a floppy disk, or an optical disk of a computer, or a network device such as a router.

The embodiment of the present invention introduces the hop count object in the PCEP message. When the PCC establishes the LSP path, the hop count is used as a constraint condition. When other constraints are all satisfied, the path with the minimum hop count is selected. The fewer the nodes, the more reliable it is relatively speaking. Therefore, after the number of hops is used as a constraint condition, a better LSP path can be obtained.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection of the present invention. within range.

Claims (8)

1. a method of obtaining label switched path is characterized in that, described method comprises:

RX path computation requests, described request are carried destination address, basic constraints and jumping figure constraints;

According to the destination address in network topology structure and the described request, calculate the path of satisfying described basic constraints;

The path of from the path that is calculated, selecting jumping figure to satisfy described jumping figure constraints;

The path of selecting is returned to the path computing request transmit leg.

2. the method for obtaining label switched path according to claim 1 is characterized in that, described path computing request is specially the path computing node communication protocol massages that carries jumping figure constraints.

3. the method for obtaining label switched path according to claim 1 is characterized in that, described method also comprises:

When not satisfying the path of described jumping figure constraints in the path that is calculated, return the calculating failure notification to the path computing request transmit leg.

4. a system that obtains label switched path is characterized in that, described system comprises:

Path computing request equipment is used for path computation request, and described request is carried destination address, basic constraints and jumping figure constraints;

Path computation equipment, be used to receive the path computing request that described path computing request equipment sends, according to the destination address in network topology structure and the described request, the path of described basic constraints is satisfied in calculating, the path of from the path that is calculated, selecting jumping figure to satisfy described jumping figure constraints, and the path of selecting returned to described path computing request equipment.

5. the system that obtains label switched path according to claim 4 is characterized in that, described path computing request equipment comprises:

The message expansion module is used for extensions path computing node communication protocol message, carries jumping figure constraints in described message;

The path computing request sending module is used to use the path computing node communication protocol massages path computation request after described message expansion module is expanded, and described message carries destination address, basic constraints and jumping figure constraints.

6. the system that obtains label switched path according to claim 4 is characterized in that, described path computation equipment comprises:

The path computing request receiver module is used to receive the path computing request that described path computing request equipment sends;

Path calculation module is used for the destination address according to the request of network topology structure and the reception of described path computing request receiver module, calculates the path of satisfying described basic constraints;

Path selection module, the path that the path that is used for calculating from described path calculation module selects jumping figure to satisfy described jumping figure constraints;

Sending module is used for the path that described path selection module is selected is returned to described path computing request equipment.

7. an equipment is characterized in that, described equipment comprises:

The message expansion module is used for extensions path computing node communication protocol message, carries jumping figure constraints in described message;

The path computing request sending module is used to use the path computing node communication protocol massages path computation request after described message expansion module is expanded, and described message carries destination address, basic constraints and jumping figure constraints;

Receiver module is used for the path that the RX path computing equipment calculates.

8. an equipment is characterized in that, described equipment comprises:

The path computing request receiver module is used for the RX path computation requests, and described request is carried destination address, basic constraints and jumping figure constraints;

Path calculation module is used for the destination address according to the request of network topology structure and the reception of described path computing request receiver module, calculates the path of satisfying described basic constraints;

Path selection module, the path that the path that is used for calculating from described path calculation module selects jumping figure to satisfy described jumping figure constraints;

Sending module is used for the path that described path selection module is selected is returned to path computing request equipment.

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