WO2009043256A1

WO2009043256A1 - Method, system and device for obtaining label switched path

Info

Publication number: WO2009043256A1
Application number: PCT/CN2008/072260
Authority: WO
Inventors: Hongmiao Xia
Original assignee: Huawei Technologies Co., Ltd.
Priority date: 2007-09-28
Filing date: 2008-09-03
Publication date: 2009-04-09
Also published as: CN101237399A

Abstract

A method, system and device for obtaining label switched path are provided. The method includes steps of: receiving a path computation request carrying destination address, basic constraint condition and hop count constraint condition; computing paths that meet basic constraint condition based on a network topology structure and the destination address; selecting a path with hop count meeting the hop count constraint condition from the computed paths; returning the selected path to a path computation request sending part. The system includes path computing request device and path computing device. The device includes message extending module, path computation request sending module and receiving module. Another device that includes path computation request receiving module, path computing module, path selecting module and sending module is also disclosed. This invention improves the reliability of the calculated path by adding the hop count constraint condition during the path calculation.

Description

Method, system and device for obtaining label switching path

The present invention relates to the field of communications, and in particular, to a method, system, and device for acquiring a label switching path. Background art

TE (Traffic Engineering) focuses on the optimization of overall network performance. Its main goal is to provide efficient and reliable network services, optimize the use of network resources, and optimize network traffic. Traffic engineering is divided into two levels: First, it is traffic-oriented, that is, how to improve the service quality of the network; Second, it is resource-oriented, that is, how to optimize the use of network resources, the most important thing is how to effectively use bandwidth resources. With the expansion of network deployment and the development of GMPLS (Genneral Multiple Protocol Label Switch) technology, inter-domain traffic engineering will span different operators, covering GMPLS networks.

CSPF (Constraint-based Shortest Path First)

MPLS (Multiple Protocol Label Switch) and GMPLS traffic engineering are important components. The path calculation between multiple ASs is very complex. It may require the computing entities of different ASs to cooperate and work together. In addition, the constrained path calculation method based on the PCE (Path Computation Element) model can also be applied to inter-domain traffic engineering. This calculation method does not affect the use of calculated paths, such as LSP (Label Swithing Path). Path) establishment, maintenance and removal.

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

When the LSP path is established by the ingress label switch (PC), the inbound label switching router (PCC) sends a request to the PCE through the PCEP protocol packet. The destination information is included in the request information. Basic information such as address and various constraints.

Based on the network topology information in the TED (Traffic Engineering Database), the PCE calculates the path that satisfies the condition of the request, and returns the response packet to the PCC as the ER0 (Explicit Route Object). Path object) parameters, the calculation results can contain precise nodes (a router) and loose nodes (a network segment, a region or an AS).

The calculation range that a PCE is responsible for is generally an AS. This is because the range of the TED information spread by the IGP (Interior Gateway Protocol) is an AS. When the destination of the calculation request is another AS, PCE collaboration between different ASs is required to complete the calculation of a path. The PCE is not limited to a specific implementation, and may be implemented in a router or in a designated server.

There are two basic protocols in the PCE model:

The PCE (Path Computation Element Discovery Protocol) is responsible for PCC's discovery of the existence and computing power of the PCE. When the PCC has a calculation request, according to the information obtained by the protocol, the PCE is selected to send a calculation request for calculation;

PCEP (Path Computation Element Communication Protocol), which is responsible for transmitting calculation request and response information between PCC and PCE. When sending a calculation request, PCC contains various constraints. When a PCE calculation requires other PCEs for assistance, Communication between PCEs also requires this communication protocol support.

The PCEP protocol carries various information in the form of TLV (Type, Length, Value, Type, Length, and Value). The encapsulation format is as follows:

0 1 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 | 0T Res | P | I Object Length (bytes)

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

(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, indicates that the constraint described by the object must be processed;

I: Ignore the field, when set, indicates whether the constraint described by the object is ignored during the calculation;

Object Length: the length of the entire object;

Object body: The content of the object.

Among them, Object-Class and Object-Type only represent 'objects, and when 0b ject-Class and 0b ject-Type are determined, the contents of the Object body are determined.

When the LSP path is established, more than one path is obtained that satisfies the constraint. For example, see Figure 1, there are 5 in the network. Nodes R1, R2, R3, R4, and R5, where the TE cost between R1-R2, R2-R4, and R4-R5 is 10, and the TE cost of Rl-R3 and R3-R5 is 15; Establish a TE path from R1 to R5. Assume that the bandwidth information is complete on each link and meets the constraints. The current topology shows that there are two paths: R1-R2-R4-R5 and R1-R3-R5 The total TE cost is 30, so you can think of this 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 have 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. In other words, the fewer links and nodes that pass, the more reliable the path is.

In the process of implementing the present invention, the inventors have found that the prior art has at least the following problems:

When establishing an LSP path, it is impossible to select a more reliable LSP path from the obtained path that satisfies the existing constraint, so that the selected path is not optimized enough and the practicability is poor. Summary of the invention

In order to find a better LSP path, an embodiment of the present invention provides a method, system, and device for acquiring a label switching path. The technical solution is as follows:

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

Receiving a path calculation request, the request carrying a destination address, a basic constraint condition, and a hop count constraint condition; calculating a path that satisfies the basic constraint condition according to a network topology structure and a destination address in the request; Selecting a path in which the number of hops satisfies the hop limit constraint;

Return the selected path to the path calculation request sender.

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

a path calculation requesting device, configured to send a path calculation request, where the request carries a destination address, a basic constraint, and a hop limit constraint;

a path calculation device, configured to receive a path calculation request sent by the path calculation requesting device, calculate a path that satisfies the basic constraint condition according to a network topology structure and a destination address in the request, and select a path selected from the calculated path The hop counts the path satisfying the hop limit constraint, and returns the selected path to the path calculation requesting device.

The embodiment of the invention provides a device, and the device includes:

a packet extension module, configured to extend a path calculation node communication protocol packet, and carry the hop limit constraint condition in the packet;

a path calculation request sending module, configured to use the path calculation node communication protocol packet sending path calculation request extended by the packet extension module, where the packet carries a destination address, a basic constraint condition, and a hop limit constraint condition;

The receiving module is configured to receive a path calculated by the path computing device. Further, the embodiment of the present invention further provides a device, where the device includes:

a path calculation request receiving module, configured to receive a path calculation request, where the request carries a destination address, a basic constraint condition, and a hop limit constraint condition;

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

a path selection module, configured to select, from the path calculated by the path calculation module, a path whose hop count satisfies the hop limit condition;

And 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 solutions provided by the embodiments of the present invention are:

By introducing a hop object in a PCEP packet, when the LSP path is established on the PCC, the hop count is increased as a new constraint. If other constraints are met, the path with the smallest hop count is selected, and the path passes through the node. The less the path, the higher the reliability of the path. Therefore, after the hop count is used as the constraint, a better LSP path can be obtained. DRAWINGS

1 is a schematic diagram of a ΤΕ path node in the prior art;

2 is a flowchart of a method for acquiring a label switching path according to Embodiment 1 of the present invention;

3 is a structural diagram of a system for acquiring a label switching path according to Embodiment 2 of the present invention;

4 is a structural diagram of an apparatus according to Embodiment 3 of the present invention;

Figure 5 is a structural diagram of an apparatus according to Embodiment 4 of the present invention. detailed description

In order to make the objects, the technical solutions and the advantages of the present invention more apparent, the embodiments of the present invention will be described in detail below.

In the embodiment of the present invention, the hop count object is introduced into the PCEP protocol packet, and the hop count is used as the constraint condition of the CSPF calculation. When other constraints are met, 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 implemented by a PCE, and includes: receiving a path calculation request, where the request carries a destination address, a basic constraint, and a hop limit constraint; according to the network topology and the request Destination address, calculate the path that satisfies the basic constraints;

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

Return the selected path to the path calculation request sender. The PCE in this embodiment may be a router or a designated server, configured to receive path calculation request information of the PCC, and calculate an LSP path that satisfies the constraint condition.

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

Step 101: Extend the PCEP protocol packet, and introduce a new hop count object, that is, a MAX-H0P Object, into the PCEP protocol packet, and use the hop count as a constraint condition for obtaining the LSP path.

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

0 1 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 I S hop-value

+-+ -+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+- +-+-+-+-+-+-+-+ Among them, the meanings of the fields in the hop count object of the above new application are as follows:

S (Scope): Indicates the meaning of the hop count, whether it is a Node Hop or an Area Hop, or an AS Hop (AS hops) field that occupies 3 bits.

R: Flag bit, which can be set to 1 or 0. It can be set to 1, indicating that the PCC needs to know the actual hop count of the path; by setting it to 0, the PCC does not need to know the actual hop count of the path, and the PCE does not need to return.

Hop-value: Indicates the actual hop count of the path calculated by the PCE. For example, the hop-value is 3, which indicates that the hop count of the path calculated by the PCE is 3. You can determine which hop-value is specified based on the set value of the S field. The number of hops.

1) When the PCC needs to establish an LSP path, send the extended PCEP protocol packet to the PCE, and set the 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 the path that meets the specified hop count, that is, if the path with the hop count is less than 5, the PCC is notified that the calculation fails;

2) If the PCE fails to calculate due to the hop count, the PCE can return the minimum hop count in the actual path for PCC reference in the response message sent by the PCE to notify the PCC that the packet fails to be calculated. For example, the minimum hop count in the actual path is 7, PCE By setting the bit 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 that the calculation fails.

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

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

Within an AS, there may be one or more PCEs. When there are multiple PCEs, the PCC is sending PCEP to the PCE. Before the message, you can select a suitable PCE based on the computing power of each PCE.

The path calculation request carries the information of the constraint and the destination address of the path to be established by the PCC. The constraint includes a basic constraint such as a bandwidth, a forbidden node, and a management group. In this embodiment, the hop limit is also added to the constraint. The condition, that is, when other constraints are met, the PCE is required to select the path with the smallest number of hops.

The path calculation request can be in various forms. In this embodiment, the packet is used as an example. The PCC sends the extended PCEP protocol packet to the PCE. For the newly added constraint, the extended PCEP protocol packet can be set. The number of hops of the object is set to set the number of hops required by the PCC. For example, the maximum acceptable number of hops is set to 5.

Step 103: After receiving the path calculation request sent by the PCC, the PCE calculates a path that satisfies the basic constraint condition in the request according to the information in the TED.

The TED stores the topology information of the same network. The PCE calculates the path that satisfies the basic constraints in the packet according to the destination address and network topology information of the received packet. In the path of the constraint, select the path whose hop count satisfies the hop constraint.

Step 104: Determine whether there is a path that satisfies the constraint, and if yes, execute step 105; otherwise, execute step 106.

Step 105: The PCE sends a PCEP response message to the PCC, where the response message carries information such as an LSR address of the path node that meets the constraint condition, and then performs step 107.

The calculation result of the CSPF algorithm is to output an external path, which includes a set of LSR addresses of the shortest path nodes satisfying the constraint conditions, and the PCE can encode the calculated LSR address information of the path nodes satisfying the constraint condition by ER0. The way to return to the PCC. For example, in Figure 2, if two suitable paths are found with the constraints of bandwidth, etc.: R1-R2-R4-R5 and R1_R3_R5, then compare the hop count of the two paths and select the path with the smallest hop count, ie R1 -R3-R5, then PCE returns this result to the PCC via the response message.

When the PCE calculates a number of paths that satisfy the constraint, it will pick the optimal path and return the selected path to the PCC.

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

When the calculation of the PCE fails due to the hop count, that is, the PCE does not select a path that satisfies the hop limit constraint in the calculated path that satisfies the basic constraint condition, it is determined according to the flag bit R in the PCEP protocol packet sent by the PCC. Whether to return the calculated number of hops of the path to the PCC. For example, the maximum acceptable hop count required in the request message is 5, and the calculated minimum hop count of the actual path is 7. When the R position is 1, the minimum hop count 7 is returned to the response message. PCC is used as a reference. When the R position is 0, the hop count information is not returned.

Step 107: After receiving the response message sent by the PCE, the PCC extracts the path node information in the packet and uses it as a construction. Establish the ELSP parameters of the LSP, initiate signaling to establish an LSP, and establish an LSP path.

If the response packet received by the PCC is a notification that the calculation fails, it can wait for a period of time to calculate again, or reduce the constraint condition and request to calculate a new path again. The method is the same as above, and will not be described here.

In this embodiment, the hop count object is introduced in the packet by extending the PCEP protocol packet. When the PCC establishes the LSP path, the hop count is used as a constraint condition, and if other constraints are satisfied, the path with the smallest hop count is selected. The fewer the nodes passing through the path, the more reliable it is. Therefore, after the hop count is used as the constraint, a better LSP path can be obtained.

Example 2

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

The path calculation requesting device 201 is configured to send a path calculation request, where the request carries a destination address, a basic constraint, and a hop limit constraint;

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

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

a message extension module, configured to extend a path calculation node communication protocol packet, and carry a hop count constraint condition in the packet; the path calculation request sending module, and the path calculation node communication protocol packet sent by using the ten-use message extension module The path calculation request carries the destination address, the basic constraint, and the hop limit constraint.

The path computing device 202 can specifically include:

a path calculation request receiving module, configured to receive a path calculation request sent by the path calculation requesting device 201, and a path calculation module, configured to calculate a destination address in the request received by the request receiving module according to the network topology structure and the path, and calculate a basic constraint condition Path

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

And 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 an apparatus. The device provided in this embodiment may be used to send a path calculation request when establishing an LSP path, and specifically includes:

The message expansion module 301 is configured to: extend the path calculation node communication protocol message, and carry the hop limit constraint condition in the message; the path calculation request sending module 302 is configured to use the path expansion node communication protocol extended by the message expansion module 301. The packet is sent to the path calculation request, and the packet carries the destination address, the basic constraint, and the hop limit constraint. The receiving module 303 is configured to receive a path calculated by the path computing device. Example 4

Referring to FIG. 5, an embodiment of the present invention further provides an apparatus. The device provided in this embodiment may be configured to receive a path calculation request, and calculate a path that meets a constraint condition in the request according to the request, and specifically includes:

The path calculation request receiving module 401 is configured to receive a path calculation request, where the request carries a destination address, a basic constraint condition, and a hop limit constraint condition;

The path calculation module 402 is configured to calculate a destination address in the request received by the request receiving module 401 according to the network topology and the path, and calculate a path that satisfies the basic constraint condition;

The path selection module 403 is configured to select, from the path calculated by the path calculation module 402, a path whose hop count satisfies the hop constraint condition;

The sending module 404 is configured to return the path selected by the path selecting module 403 to the path calculation requesting device. The embodiments 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. In the embodiment of the present invention, a hop count object is introduced in a PCEP packet. When the PCC establishes an LSP path, the hop count is used as a constraint condition, and if other constraints are satisfied, the path with the smallest hop count is selected, and the ώ path is passed. The fewer the nodes, the more reliable they are. Therefore, after the hop count is used as a constraint, a better LSP path can be obtained. The above is only the preferred embodiment of the present invention, and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., which are within the spirit and scope of the present invention, should be included in the protection of the present invention. Within the scope.

Claims

Claim

A method for obtaining a label switching path, the method comprising:

Return the selected path to the path calculation request sender.

The method for obtaining a label switching path according to claim 1, wherein the path calculation request is specifically a path calculation node communication protocol message carrying a hop limit constraint condition.

The method for obtaining a label switching path according to claim 1, wherein the method further comprises: when there is no path that satisfies the hop limit constraint in the calculated path, requesting a sender to the path calculation request Return to the calculation failure notice.

A system for obtaining a label switching path, the system comprising:

The system for obtaining a label switching path according to claim 4, wherein the path calculation requesting device comprises:

The path calculation request sending module is configured to use the path calculation node communication protocol packet sending path calculation request extended by the packet extension module, where the packet carries a destination address, a basic constraint condition, and a hop limit constraint condition.

The system for acquiring a label switching path according to claim 4, wherein the path computing device comprises: a path calculation request receiving module, configured to receive a path calculation request sent by the path calculation requesting device, and a path calculation module, configured to calculate a destination address in the request received by the request receiving module according to the network topology structure and the path calculation The path of the basic constraint;

7. A device, characterized in that the device comprises:

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

8. A device, wherein the device comprises: