CN102420757A - Path calculation method, device and communication system - Google Patents

Abstract

The invention discloses a path calculation method. The invention also discloses a path calculation client, a path calculation unit and a communication system. The invention discloses a path calculation method, which comprises the following steps: a path computation client sends a path computation request message to a path computation unit, wherein the path computation request message carries a source node and a destination node of an access client side service and a cascade constraint condition of a path; the cascade constraints include: the method comprises the steps of (1) cascading units, cascading number and cascading type, wherein the cascading number is more than 1; and the path computation client receives a path computation response message carrying a path returned by the path computation element, wherein the path is obtained by the path computation element according to the source node, the destination node, the cascade constraint condition and the cascade capability of each interface of the nodes in the network. The technical scheme of the invention is simpler and quicker, and the complexity of concrete implementation is obviously reduced.

Description

A path calculation method, device and communication system

technical field

The present invention relates to the field of communication technology, in particular to a path calculation method, a path calculation client, a path calculation unit and a communication system.

Background technique

The physical channels provided by the service network are used to connect the devices of the client network to each other, specifically, the devices at both ends of the service network (source end and destination end) are respectively connected to two client network devices. When there is signal transmission, the source device of the service network encapsulates and adapts the customer network signal into a bearer signal that can be transmitted in the service network, and transmits it to the destination end of the service network, and the destination end of the service network restores the client signal. Send to the customer network equipment; when the customer network signal rate is greater than the service network bearer signal rate, it is necessary for the service network to combine multiple bearer signals to transmit the customer signal. Therefore, it becomes a problem to calculate a path in the service-side network that satisfies the transmission signal of the client-side network.

A solution for path calculation in the prior art: the node that receives the client-side service request is used as the head node of the path, and the head node is responsible for calculating the path of the client-side service request.

When the scale of the service-side network is very large, in order to prevent network congestion caused by excessive flooding of topology information in the network, the network is divided into multiple smaller network domains, and the topology information of each network domain will not be flooded to other network domains . Another solution for path calculation in the prior art: the node that receives the client-side service request acts as the head node in its domain to calculate the path in the domain, and the node in the domain where the head node is located and connected to other domains selects the path that satisfies The next domain node of the path required by the client-side business, the next domain node is responsible for calculating the path of this domain, and then the nodes connected to other domains in the domain where the next domain node is located select the next domain node that meets the client-side business requirements. A domain node finally calculates the cross-domain path.

However, for a path calculation solution in the prior art, each node may be responsible for calculating the path as the first node. When the network scale is very large, the path calculation will increase the burden of the node due to the limited processing capacity of the node. As for another path calculation solution in the prior art, the calculation of the cross-domain path requires the participation of multiple nodes in the network, and the solution is relatively complicated.

Contents of the invention

Embodiments of the present invention provide a path calculation method, a path calculation client, a path calculation unit, and a communication system, which can realize path calculation simply and conveniently.

An embodiment of the present invention provides a path calculation method, including:

The path calculation client sends a path calculation request message to the path calculation unit, and the path calculation request message carries the source node and destination node for accessing the client-side service, and the cascading constraints of the path; the cascading constraints include: Unit, number of cascades, and type of cascades, the number of cascades is greater than 1; the path computation client receives the path computation response message returned by the path computation unit carrying the path, and the path is determined by the path computation unit according to the The source node and the destination node, the cascading constraints, and the cascading capabilities of the interfaces of the nodes in the network are calculated and obtained.

The embodiment of the present invention also provides a path calculation method, including:

The path calculation unit receives the path calculation request message, the path calculation request message carries the source node and the destination node for accessing the client-side service, and the cascading constraints of the path; the path calculation unit according to the source node and the destination node, the The cascading constraint conditions and the cascading capability calculation path of each interface of the node in the network; wherein, the cascading capability of each interface of the node in the network is stored in the path calculation unit; the path calculation unit sends a path calculation response message, The path computation response message carries the path.

An embodiment of the present invention provides a path calculation client, including:

A module for sending a path computation request message to a path computation unit, the path computation request message carrying a source node and a destination node for accessing client-side services, and cascading constraint conditions of the path; the cascade constraint conditions include: cascading unit, number of cascades, and type of cascade, and the number of cascades is greater than 1; a module for receiving a path computation response message carrying a path returned by the path computation unit, the path being determined by the path computation unit according to The source node and the destination node, the cascading constraints, and the cascading capabilities of the interfaces of the nodes in the network are calculated and obtained.

An embodiment of the present invention provides a path calculation unit, including:

A module for receiving a path computation request message, where the path computation request message carries a source node and a destination node for accessing a client-side service, and cascading constraint conditions of a path; The cascading constraint conditions and the module for calculating the cascading capability of each interface of the node in the network; the module for storing the cascading capability of each interface of the node in the network; the module for sending a path calculation response message, the path The calculation response message carries the path.

An embodiment of the present invention provides a communication system. The communication system includes a path computation client and a path computation unit, wherein the path computation client is connected to the path computation unit, and the path computation client is the above path The calculation client, the path calculation unit is the above-mentioned path calculation unit.

It can be seen from the above technical solution that after receiving the service transmission request from the client side, the path computation request message is sent to the path computation unit, and the path computation unit calculates the cascading path; the path computation unit first receives the information of each interface sent by the nodes in the network The cascading capability calculates the path according to the source node and destination node of the client-side transmission service carried in the path calculation request message, the cascading constraint conditions of the path, and the cascading capability of each interface of the nodes in the network. Compared with the prior art, the embodiment of the present invention has a simpler and faster technical solution when calculating paths across multiple network domains in a large-scale network, and obviously reduces the complexity of specific implementation.

Description of drawings

FIG. 1 is a schematic diagram of a service-side network structure provided by an embodiment of the present invention;

Fig. 2 is a flow chart of the path calculation method provided by the first embodiment of the present invention;

Fig. 3 is a flow chart of the path calculation method provided by the second embodiment of the present invention;

FIG. 4 is a schematic structural diagram of a node device provided by a third embodiment of the present invention;

FIG. 5 is a schematic structural diagram of a path calculation unit provided by a fourth embodiment of the present invention;

Fig. 6 is a schematic structural diagram of a path calculation unit provided by a fifth embodiment of the present invention.

Detailed ways

An embodiment of the present invention provides a path calculation method. Embodiments of the present invention also provide corresponding node devices and path calculation units. Each will be described in detail below.

In a Time Division Multiplex (TDM, Time Division Multiplex) network, cascade technology can be used to use multiple bearer signals to provide signal transmission services for the client-side network. Cascading technology is divided into continuous cascading and virtual cascading. Continuous cascading uses different time slots of the same node interface to transmit signals, so the node interface is required to have continuous idle time slots to transmit signals; since continuous cascading uses two or more consecutive idle time slots of the node interface to transmit signals , so it can play a cascading role. Virtual concatenation is developed when continuous concatenation cannot meet the requirements of current network equipment. The source node of the virtual concatenation path converts the continuous concatenation path into a virtual concatenation path, and the destination node of the virtual concatenation path converts the virtual The cascading path is restored to a continuous cascading path; the virtual concatenation uses the idle time slots of different interfaces of the nodes to transmit signals. The delay of the path cannot be too large to ensure that the differential delay of each virtual concatenation path meets the differential delay constraints of the source node and the destination node of the virtual concatenation path; the differential delay constraints of the source node and the destination node are cache The delay time of data transmitted by each cascade path.

The following describes the path calculation method, node device, and path calculation unit provided by the embodiments of the present invention from the calculation of a single path, a continuous concatenated path, and a virtual concatenated path.

Embodiment one

In the embodiment of the present invention, a Synchronous Digital Hierarchy (SDH, Synchronous Digital Hierarchy) network is taken as an example to illustrate a path calculation method, a node device, and a path calculation unit. However, the path calculation method, node device, and path calculation unit provided in the embodiments of the present invention may also be applied to other TDM networks, such as an Optical Transport Network (OTN, Optical Transport Network).

In the embodiment of the present invention, a Path Computation Element (PCE, Path ComputationElement) is built in the service side network. PCE is a functional entity responsible for path computation in the network. Create a cascading path that satisfies the constraints. The PCE can be located anywhere in the network, can be integrated inside the network equipment, or can be an independent equipment. The Path Computation Client (PCC, Path Computation Client) requests the PCE to calculate the path and receives the path returned by the PCE. PCC and PCE and between PCE and PCE communicate through path computation protocol (PCEP, PCE Protocol). PCEP messages are used to submit path computation requests and obtain path computation results.

This embodiment illustrates the path calculation method provided by the embodiment of the present invention by using the calculation of the continuous concatenation path and the virtual concatenation path. In this embodiment, the path calculation request message sent to the PCE by the node transmitting the service request on the client side is received, and the message carries the cascading constraint condition for establishing the path, and the cascading constraint condition includes the cascading unit, the cascading quantity, and the cascading type; After receiving the path calculation request message, the PCE directly calculates the cascading path satisfying the requirements according to the cascading constraints.

Fig. 1 shows the structure of the service side network and the connection structure with the client side network.

Taking the SDH network as an example, the service side network is composed of 5 nodes. Each interface of the node has a corresponding interface number I1, I14, I12, I21, I23, I3, I32, I35, I53, I54, I45 and I41 ( I represents Interface), and the nodes N1 and N3 are respectively connected to the client-side network. In the network without dividing the network domain, the time slot status of the link corresponding to the interface of each node, the type of link cascading supported by the link, the link delay, the differential delay constraint of the interface, the interface number, and the connection with the remote end are flooded between nodes. Connected interface number and other information. For the convenience of description, the embodiments of the present invention include the time slot status of the links corresponding to the interfaces of the nodes in the network, the link delay, the type of link cascading support, the differential delay constraints of the interface, the interface number, and the connection with the remote end. The interface number is called the cascading capability of the interface. For example, node N1 can flood the interface cascading capabilities of interfaces I12, I14 and I1 to nodes N2, N3, N4, N5 and PCE in the network, and node N2 can flood the network to nodes N1, N3, N4, N5 and PCE Interface cascading capability of universal interface I21 and I23. In a network divided into network domains, each node in the network sends the cascading capability of its interface to the PCE, and the path computation unit PCE receives the cascading capability of each interface of the node in the network. In general, all PCEs in the network have path calculation capabilities, including the ability to calculate single paths, continuous cascaded paths, and virtual cascaded paths; however, due to different network conditions, PCEs in some networks do not have path computing capabilities. ability, or only have the ability to calculate one of the continuous cascade path and the virtual cascade path, or only have the ability to calculate a single path; in order to meet the needs of different networks, the path calculation method provided by the embodiment of the present invention , the ability of PCE to send its own path calculation to all nodes in the network.

The nodes in the network of the embodiment of the present invention send the level of each interface of themselves through the Open Shortest Path First (OSPF-TE, Open the Shortest Path First with TE) protocol message of Generalized Multi-Protocol Label Switching (GMPLS, Generalized MPLS) with traffic engineering PCE also uses GMPLS OSPF-TE to send its own path calculation capability.

In order to meet the needs of the node's own capabilities in the network, the embodiment of the present invention expands the GMPLS OSPF-TE protocol message, and increases the node interface cascading capability object. The node interface cascading capability object is as follows:

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

| Reserved | Flags |c|v| Delay Diff. | TS number |

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

|

|

//Time Slots Info.//

|

|

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

Among them, when the flag bit v is 1, it means that the link supports virtual concatenation, and Delay Diff indicates the differential delay constraint condition of the interface; when the flag bit c is 1, it means that the link supports continuous concatenation; TSnumber indicates the time slot Number; Time slots info indicates the occupancy of each time slot in the link in a bitmap manner.

In order to meet the needs of the PCE to send its own path calculation capability to the nodes in the network, the embodiment of the present invention expands the GMPLS OSPF-TE protocol message and increases the PCE path calculation capability object, as follows:

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

| Reserved |Flags |c|v| Reserved |

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

Wherein, the c flag bit is 1, indicating that the PCE has the continuous cascading path computing capability; the v flag bit is 1, indicating that the PCE has the virtual cascading path computing capability.

Finally, the nodes in the network store the cascading capability of the interface of each node in the network and the capability of PCE path calculation. In a network divided into network domains, nodes in the network store the cascading capability of the interface of the node in the network domain and the PCE path calculation capability in the network. The PCE stores the cascading capability of each interface of the nodes in the network.

When the node N1 connected to the client-side network receives the client-side transmission service request, it determines the number of cascades to be provided and the cascade unit according to the bandwidth required by the request, the destination node of the requested signal transmission, and the signal type of the client-side transmission service And the cascading type cascading constraints, and send a path calculation request to the PCE.

As shown in FIG. 2 , it is a flow chart of the path calculation method provided by the first embodiment of the present invention.

Step 101, the path computation client sends a path computation request message to the path computation unit, and the path computation request message carries the source node and the destination node for accessing the client-side service, and cascade constraint conditions of the path.

It can be seen from FIG. 1 that the node N1, acting as the PCC, sends a path calculation request message to the PCE.

Assuming that node N1 receives a request from the client side to transmit services, node N1 acts as the head node of the path, and node N3 acts as the exit node of the path. Node N1, as PCC, sends a path calculation request message to PCE, and sends a path calculation request through PCReq message in the PCEP protocol; node N1, as PCC, judges whether the path to be established is a continuous cascading path or a virtual level according to the bandwidth required by the client-side transmission service The PCReq message carries the source node and destination node for accessing the client-side service, and the cascading constraints of the path. Taking a path established by the service-side network as an example, the source node of the path is connected to the client-side network that transmits the service, and the destination node of the path is connected to the client-side network that receives the service. When the path to be established is a continuous cascading path, the cascading constraint conditions include: cascading unit, cascading quantity, and cascading type. When the path to be established is a virtual cascading path, the cascading constraint conditions include: cascading unit, cascading quantity, and cascading type.

The embodiment of the present invention extends the PCEP protocol, so that the PCReq message carries the concatenation unit, the concatenation quantity, the concatenation type and the concatenation constraint condition. Add a cascading constraint object in the PCReq message, and the format of the object is as follows:

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

|LSP Enc.Type|Switching Type|Src Delay Diff.|Dst Delay Diff.|

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

| Signal Type |Concat.Type | Reserved | LSP number |

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

Among them, "LSP Enc.Type", "Switching Type" and "Signal Type" determine the cascade unit. For example, when the cascading unit is ODU2, LSP Enc.Type＝12(G.709ODUk), Switching Type＝100(TDM), Signal Type＝2(ODU2); when the cascading unit is VC4, LSP Enc.Type＝5( SDH ITU-T G.707/SONET ANSI T1.105), SwitchingType=100(TDM), SignalType=6(VC4).

Concat.Type indicates the type of concat, currently defined: 1 means continuous concatenation, 2 means virtual concat.

LSP number indicates the number of cascades. When the path requested to be calculated is a continuous cascade path or a virtual cascade path, this value is any value greater than 1.

Src Delay Diff. Indicates the source node differential delay constraint; Dst Delay Diff. Indicates the destination node differential delay constraint.

It should be noted that if the PCE does not store the differential delay constraints of the destination nodes of the cascade path to be calculated, the node N1 sending the path calculation request sends a message to obtain the destination node differential delay constraints to the destination node N3. In the embodiment of the present invention, the constraint condition of the differential time delay of the destination node is acquired through the GMPLS call message.

The embodiment of the present invention extends the LINK_CAPABILITY object in the GMPLS CALL call message (Notify) to carry the differential time delay constraint condition information of the interface:

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

| Reserved | Flags |v| Max Delay Difference |

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

| | | |

//(Subobjects)//

| | | |

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

The V flag bit indicates the virtual concatenation capability of the link; the Max Delay Difference field indicates the differential delay constraint condition of the interface of the recording destination node.

The path computation request message sent by the path computation client also carries the differential delay constraints between the source node and the destination node accessing the client-side service.

Step 102, the path computation unit receives a path computation request message, and the path computation request message carries the source node and destination node for accessing the client-side service, and cascade constraint conditions of the path.

The PCReq message received by the PCE carries the source node and destination node for accessing the client-side service, and the cascading constraints of the path. The cascading constraints include the cascading unit, the cascading quantity, and the cascading type. When the request is a continuous cascading path, the PCReq message indicates that the source node of the client-side service is N1 and the destination node is N3, the cascading unit and the number of cascading, and indicates that the cascading type is continuous cascading; when the request is a virtual cascading path , the PCReq message indicates that the source node of the client-side service is N1 and the destination node is N3, the concatenation unit and the concatenation quantity, and indicates that the concatenation type is virtual concatenation.

Step 103, the path calculation unit calculates the path according to the source node and destination node accessing the client side service, the cascading constraints of the path, and the cascading capability of each interface of the nodes in the network.

The cascading capabilities of each interface in the network stored on the PCE are shown in Table 1:

interface number Link slot status Remote interface number I12 000111... I21 I14 110111... I41 I21 000111... I12 I23 000000... I32 I32 000000... I23 I41 110111... I14

When establishing a virtual cascading path, the cascading capabilities of each interface of the nodes in the network are shown in Table 2:

It should be noted that the items in the above Tables 1 and 2 that represent the interface cascading capabilities, such as link time slot status, link delay, and interface differential delay constraints, will be related to the interface number and remote interface number. corresponding storage. In this embodiment, in order to more clearly describe the path calculation method provided by the embodiment of the present invention, Table 1 and Table 2 that respectively satisfy the calculation of continuous concatenation and virtual concatenation are extracted from the information stored corresponding to the interface concatenation capabilities.

PCE is based on the source node and destination node accessing the client-side service, the cascading unit of the path, the number of cascading paths, the cascading type, the differential delay constraints of the source node and the destination node, and the cascading of each interface of the nodes in the network Ability to exclude links that do not meet the constraints, and use algorithms to calculate cascading paths. Assuming that the bandwidth required by the client side to transmit services is 155M/S, it is judged that a cascade path needs to be established, and the path requested for calculation is a continuous cascade path. According to the bandwidth calculation, two cascade paths are required to transmit the client side service, that is, an interface link is required. There are two consecutive free time slots on the road, and the PCE is calculated based on the concatenation constraints carried in the PCReq message and the concatenation capabilities of each interface of the node in Table 1 (such as the state of the link time slot, the corresponding interface and the number of the remote interface) Path I12-I21-I23-I32 that meets the requirements. Assuming that the bandwidth required by the client side to transmit services is 155M/S, it is judged that a cascading path needs to be established, and the path requested for calculation is a virtual cascading path. The path I1-I12-I21-I23-I32-I3 that meets the requirements is calculated based on the connection capability (such as link time slot status, link delay, interface differential delay constraints and other information and the corresponding interface and remote interface number) And I1-I14-I41-I45-I54-I53-I35-I3.

In step 104, the path computation unit sends a path computation response message to the path computation client, where the path computation response message carries the computed path.

The PCE sends the calculated path information to the PCC through the PCReq message. The path is a cascade path that satisfies the cascade constraint conditions. The cascade constraint conditions include: cascade unit, cascade quantity, and cascade type. For the cascade path For example, the number of cascades is any value greater than 1.

Step 105, the path calculation client receives the path calculation response message returned by the path calculation unit, which carries the path. The cascading capability of the interface is calculated.

The path calculation client establishes a connection according to the cascading path and the cascading constraints of the path.

So far, a path that satisfies client-side signal transmission has been established on the service-side network.

Under the network framework provided by the embodiment of the present invention, the path calculation method provided by this embodiment is also applicable to the calculation of a single path. The calculation of a single path differs from the embodiments described above mainly in that: in step 101, the path calculation client sends the path calculation request message to the path calculation unit. Quantity is 1, wherein the LSP number value of indicating cascading quantity in the PCReq message is 1, and the Concat.Type value of indicating the cascading type is 0; What PCReq message carried in the step 102 is that the source node of access client side business is N1 and The destination node is N3, the cascading unit and the number of cascading; in step 103, assuming that the bandwidth required by the client side to transmit services is 100M/S, node N1 judges that the path to be established is a single path, and the path to be calculated is a single path, then The PCE calculates the path I12-I21-I23-I32 that meets the requirements according to the cascading constraints carried in the PCReq message and the cascading capabilities of each interface of the node in Table 1. The calculation of a single path uses the cascading capabilities of each interface mainly through the interface The time slot status of the link; the path carried in the path calculation response message in step 104 is a single path that meets the requirements of the cascading unit; after step 105, when a single path establishes a connection, it does not need to rely on cascading constraints.

Embodiment two

In the embodiment of the present invention, a Synchronous Digital Hierarchy (SDH, Synchronous Digital Hierarchy) network is taken as an example to illustrate a path calculation method, a node device, and a path calculation unit. However, the path calculation method, node device, and path calculation unit provided by the embodiments of the present invention can also be applied to other TDM networks, such as an Optical Transport Network (OTN, Optical Transport Network).

In the embodiment of the present invention, a Path Computation Element (PCE, Path ComputationElement) is built in the service side network. PCE is a functional entity responsible for path computation in the network. Create a cascading path that satisfies the constraints. The PCE can be located anywhere in the network, can be integrated inside the network equipment, or can be an independent equipment. The Path Computation Client (PCC, Path Computation Client) requests the PCE to calculate the path and receives the path returned by the PCE. PCC and PCE and between PCE and PCE communicate through path computation protocol (PCEP, PCE Protocol). PCEP messages are used to submit path computation requests and obtain path computation results.

This embodiment illustrates the path calculation method provided by the embodiment of the present invention by using the calculation of the continuous concatenation path and the virtual concatenation path. This embodiment receives the path calculation request message sent to the PCE by the node that transmits the service request on the client side. After calculating the request message, directly calculate the path that satisfies the requirements according to the cascading constraints.

The path calculation method provided by the embodiment of the present invention is described by taking the network structure in FIG. 1 as an example.

Taking the SDH network as an example, the service side network is composed of 5 nodes. Each interface of the node has a corresponding interface number I1, I14, I12, I21, I23, I3, I32, I35, I53, I54, I45 and I41 ( I represents Interface), and the nodes N1 and N3 are respectively connected to the client-side network. In the network without dividing the network domain, the time slot status of the link corresponding to the interface of each node, the link delay, the type of link support cascading, the differential delay constraint of the interface, the interface number and the connection with the remote end are flooded between nodes. Connected interface number and other information. For the convenience of description, the embodiment of the present invention uses the time slot status of the link corresponding to each interface of the node in the network, the link delay, the type of link support cascading, the differential delay constraint condition of the interface, the interface number, and the connection with the remote The number of the connected interface is called the cascading capability of the interface. For example, node N1 can flood the interface cascading capabilities of interfaces I12, I14 and I1 to nodes N2, N3, N4, N5 and PCE in the network, and node N2 can flood nodes N2, N3, N4, N5 and PCE in the network Interface cascading capability of universal interface I21 and I23. In a network divided into network domains, each node in the network sends the cascading capability of its interface to the PCE, and the path computation unit PCE receives the cascading capability of each interface of the node in the network. In general, all PCEs in the network have path calculation capabilities, including the ability to calculate single paths, continuous cascaded paths, and virtual cascaded paths; however, due to different network conditions, PCEs in some networks do not have path computing capabilities. ability, or only have the ability to calculate one of the continuous cascading paths or virtual cascading paths, or only have the ability to calculate a single path; in order to meet the needs of different networks, the path calculation method provided by the embodiment of the present invention , PCE sends its own path calculation capability to all nodes in the network.

The nodes in the network of the embodiment of the present invention send the cascading capabilities of their own interfaces through the GMPLS OSPF-TE protocol message, and the PCE also uses the GMPLS OSPF-TE to send its own path calculation capabilities.

In order to meet the needs of the node's own capabilities in the network, the embodiment of the present invention expands the GMPLS OSPF-TE protocol message, and increases the node interface cascading capability object. The node interface cascading capability object is as follows:

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

| Reserved | Flags |c|v| Delay Diff. | TS number |

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

|

|

//Time Slots Info.//

|

|

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

Among them, when the flag bit v is 1, it means that the link supports virtual concatenation, and Delay Diff indicates the differential delay constraint condition of the interface; when the flag bit c is 1, it means that the link supports continuous concatenation; TSnumber indicates the time slot Number; Time slots info indicates the occupancy of each time slot in the link in a bitmap manner.

In order to meet the needs of the PCE to send its own path calculation capability to the nodes in the network, the embodiment of the present invention expands the GMPLS OSPF-TE protocol message and increases the PCE path calculation capability object, as follows:

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

| Reserved | Flags |c|v| Reserved |

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

Wherein, the c flag bit is 1, indicating that the PCE has the continuous cascading path computing capability; the v flag bit is 1, indicating that the PCE has the virtual cascading path computing capability.

Finally, the nodes in the network store the cascading capability of the interface of each node in the network, and the capability of PCE path calculation. In a network divided into network domains, nodes in the network store the cascading capability of the interface of the node in the network domain and the PCE path calculation capability in the network. The PCE stores the cascading capability of each interface of each node in the network.

When the node N1 connected to the client-side network receives the client-side transmission service request, according to the bandwidth required by the request, the destination node of the requested transmission service, and the signal type of the client-side transmission service, it needs to provide information including the number of cascades and the cascade unit. And the cascading type cascading constraints, and send a path calculation request to the PCE.

As shown in FIG. 3 , it is a flow chart of the path calculation method provided by the second embodiment of the present invention.

Step 201, the path computation client sends a path computation request message to the path computation unit, and the path computation request message carries the source node and destination node for accessing the client-side service, and the signal type of the client-side transmission service.

It can be seen from FIG. 1 that the node N1, acting as the PCC, sends a path calculation request message to the PCE.

Assuming that node N1 receives a request from the client side to transmit services, node N1 acts as the head node of the path, and node N3 acts as the exit node of the path. Node N1 sends a path calculation request message to PCE as a PCC, and sends a path calculation request through a PCReq message in the PCEP protocol; the PCReq message (path calculation request message) carries the source node and destination node for accessing the client-side service, and the client-side transmission service signal type information. The signal type information of the transmission service at the client side includes information such as bandwidth required by the transmission service at the client side.

Step 202, the path computation unit receives a path computation request message, and the path computation request message carries a source node and a destination node for accessing a service on the client side, and a signal type of a service transmitted by the client side.

Step 203, the path calculation unit determines the cascading constraints of the path according to the signal type of the service transmitted by the client side.

When requesting the calculation of a continuous cascading path, the cascading constraints include: cascading unit, cascading quantity, and cascading type, where the cascading type specifies continuous cascading; when requesting the calculation of a virtual cascading path, the cascading constraints Yes: cascade unit, cascade quantity, and cascade type, where the cascade type specifies virtual cascade.

Step 204, the path calculation unit calculates the path according to the source node and destination node accessing the client-side service, the cascading constraints, and the cascading capability of each interface of the nodes in the network.

According to the stored cascading capabilities and cascading constraints of the interfaces of the nodes shown in Table 1 and Table 2, the PCE excludes links that do not meet the constraints, and uses an algorithm to calculate the cascading path.

Step 205, the path calculation unit sends a path calculation response message carrying the path to the path calculation client side, and the path calculation response message carries the calculated path and the cascading constraint conditions of the path.

Step 206, the path calculation client receives the path calculation response message returned by the path calculation unit, which carries the path, the path is determined by the path calculation unit according to the signal type of the client-side transmission service. The source node and destination node, and the cascading capabilities of each interface of the nodes in the network are calculated.

The embodiment of the present invention extends the PCEP protocol so that the PCReq response message carries the cascading constraint conditions including the concatenation unit, the concatenation quantity, and the concatenation type. Add a cascading constraint object in the PCReq response message, the format of which is as follows:

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

|LSP Enc.Type |Switching Type |Src Delay Diff.|Dst Delay Diff.|

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

| Signal Type |Concat.Type | Reserved | LSP number |

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

Among them, "LSP Enc.Type", "Switching Type" and "Signal Type" determine the cascade unit. For example, when the cascading unit is ODU2, LSP Enc.Type＝12(G.709 ODUk), Switching Type＝100(TDM), Signal Type＝2(ODU2); when the cascading unit is VC4, LSP Enc.Type＝5 (SDH ITU-T G.707/SONET ANSI T1.105), SwitchingType=100(TDM), SignalType=6(VC4).

Concat.Type indicates the type of concat, currently defined: 1 means continuous concatenation, 2 means virtual concat.

LSP number indicates the number of cascades. When the path requested to be calculated is a continuous cascade path or a virtual cascade path, this value is any value greater than 1.

Src Delay Diff. Indicates the source node differential delay constraint; Dst Delay Diff. Indicates the destination node differential delay constraint.

The path calculation client establishes a connection according to the cascading path and cascading constraints.

So far, a path that satisfies client-side signal transmission has been established on the service-side network.

Under the network framework provided by the embodiment of the present invention, the path calculation method provided by this embodiment is also applicable to the calculation of a single path. The difference from the above-described embodiment mainly includes: when the PCE determines in step 203 that the path requested to be established is a single path, the determined cascading constraints include: the cascading unit and the cascading number, and the cascading number is 1; step 204 The concatenation capability of each interface used in the calculation of a single path is mainly the time slot state of the interface link; in the PCReq response message in step 205, the Concat.Type indicating the concatenation type is 0, and the LSP number value indicating the concatenation quantity is 1 , the path carried in the path calculation response message is a single path required by the cascade unit. After step 206, a single path does not need to rely on cascading constraints when establishing a connection.

Embodiment Three

Embodiments of the present invention also provide a node device and a path calculation unit using the above method.

As shown in FIG. 4 , it is a schematic structural diagram of a node device provided by the third embodiment of the present invention.

A node device, comprising:

The request message sending module 110 is configured to send a path computation request message to the path computation unit after receiving a request from the client side to transmit a service, the path computation request message carrying the source node and the destination node for accessing the client side service, and the concatenation of paths Restrictions;

The response message receiving module 120 is configured to receive the path calculation response message carrying the path returned by the path calculation unit after the request message sending module sends the path calculation request message to the path calculation unit; The source node and destination node of the access client-side service, the cascading constraints, and the cascading capabilities of the interfaces of the nodes in the network are calculated and obtained.

Further, the node device also includes:

The differential delay acquisition module 130 is used to obtain the differential delay constraint condition of the destination node accessing the client side service after receiving the request for transmitting the service from the client side and before sending the path calculation request message to the path calculation unit; wherein, The cascading constraints in the path computation request message include: a cascading unit, a cascading type, and a cascading quantity, and the cascading quantity is greater than 1;

The path calculation request message sent by the request message sending module also carries the differential delay constraint condition of the source node accessing the client-side service and the differential delay constraint condition of the destination node accessing the client-side service.

Further, the node device also includes:

The computing capability acquiring module 140 is used to acquire the path computing capability of the path computing unit before the request message sending module sends the path computing request message to the path computing unit; the path computing capability includes at least one of the following: single path computing capability, continuous Computing capabilities for cascading paths and computing capabilities for virtual cascading paths.

In another node device provided by the embodiment of the present invention, the path calculation request message sent by the node request message sending module in this embodiment only carries the source node and the destination node, and the type of the signal transmitted by the client side, and does not carry the level of the path. Link constraints.

A node device, comprising:

The request message sending module is used to send a path calculation request message to the path calculation unit after receiving a request for transmitting services from the client side. The path calculation request message carries the source node and destination node for accessing the client side service, and the client side transmits the service the signal type;

A response message receiving module, configured to receive a path computation response message carrying a path returned by the path computation unit; the path is a cascading constraint condition determined by the path computation unit according to the signal type of the client-side transmission service, the access client It is obtained by calculating the cascading capability of the source node and destination node of the side service, and each interface of the node in the network.

Further, the node device also includes:

A differential delay acquisition module, configured to acquire the differential delay of the destination node accessing the client-side service after the request message sending module receives the request for transmitting the service from the client side and before sending the path calculation request message to the path calculation unit A constraint condition; wherein, the cascading constraint condition in the path computation request message includes: a cascading unit, a cascading type, and a cascading quantity, and the cascading quantity is greater than 1;

The path calculation request message sent by the request message sending module also carries the differential delay constraint condition of the source node accessing the client-side service and the differential delay constraint condition of the destination node accessing the client-side service.

Further, the node device further includes: a computing capability acquiring module, configured to acquire the path computing capability of the path computing unit before the request message sending module sends the path computing request message to the path computing unit; the path computing unit capability includes the following At least one of: single path computing capability, continuous cascading path computing capability and virtual cascading path computing capability.

Fourth embodiment

An embodiment of the present invention also provides a path calculation unit using the above method.

As shown in FIG. 5 , it is a schematic structural diagram of the path calculation unit provided by the fourth embodiment of the present invention.

A routing computing unit, comprising:

A node capability receiving module 210, configured to receive the cascading capability of each interface sent by a node in the network;

The request message receiving module 220 is configured to receive a path computation request message, the path computation request message carrying a source node and a destination node accessing the client-side service, and cascading constraint conditions of the path;

The path calculation module 230 is used to calculate the path according to the source node and destination node accessing the client-side service, the cascading constraints of the path, and the cascading capabilities of the interfaces of the nodes in the network;

The response message sending module 240 is configured to send a path calculation response message, where the path calculation response message carries the path.

Further, the path calculation unit also includes:

The computing capability sending module 250, before the request message receiving module receives the path computing request message, sends its own path computing capability; the path computing capability includes at least one of the following: single path computing capability, continuous cascading path computing capability and virtual level Link path computing capability.

fifth embodiment

The embodiment of the present invention also provides another path calculation unit. The path calculation unit in this embodiment calculates the cascade constraint condition of the path according to the type of the client-side signal.

As shown in FIG. 6 , it is a schematic structural diagram of a routing calculation unit provided by the fifth embodiment of the present invention.

In this embodiment, the routing calculation unit calculates the cascading constraint condition of the path according to the signal type of the client-side service, and then calculates the path according to the cascading constraint condition of the path.

A routing computing unit, comprising:

A node capability receiving module 210, configured to receive the cascading capability of each interface sent by a node in the network;

The request message receiving module 220 is configured to receive a path computation request message, the path computation request message carrying the source node and destination node for accessing the client-side service, and the signal type of the client-side transmission service;

A determination module 260, configured to determine the cascading constraints of the path according to the type of the client-side transmission signal;

The path calculation module 230 is used to calculate the path according to the source node and destination node accessing the client-side service, the cascading constraints, and the cascading capabilities of each interface of the nodes in the network;

The response message sending module 240 is configured to send a path calculation response message, where the path calculation response message carries the path.

Further, the path calculation unit also includes:

The computing capability sending module 250, before the request message receiving module receives the path computing request message, sends its own path computing capability; the path computing capability includes at least one of the following: single path computing capability, continuous cascading path computing capability and Virtual cascading path computing capability.

For the specific signal processing and execution process between the modules in the above-mentioned node device and the path calculation unit, since it is based on the same concept as the method embodiment of the present invention, please refer to the descriptions in Embodiments 1 and 2 of the present invention. Let me repeat.

Through the description of the above embodiments, those skilled in the art can clearly understand that the present invention can be realized by means of software plus a necessary hardware platform, and of course all can be implemented by hardware, but in many cases the former is better implementation. Based on this understanding, all or part of the contribution made by the technical solution of the present invention to the background technology can be embodied in the form of software products, and the computer software products can be stored in storage media, such as ROM/RAM, magnetic disks, optical disks, etc. , including several instructions to make a computer device (which may be a personal computer, a server, or a network device, etc.) execute the methods described in various embodiments or some parts of the embodiments of the present invention.

A path calculation method, comprising: after receiving a client-side service transmission request, sending a path calculation request message to a path calculation unit, the path calculation request message carrying a source node and a destination node accessing the client-side service, and a path level connection constraints; receive the path calculation response message carrying the path returned by the path calculation unit, the path is determined by the path calculation unit according to the source node and destination node of the access client side service, the cascade constraint Conditions and the cascading capability of each interface of the nodes in the network are calculated.

The cascading constraints include: a cascading unit and a cascading quantity, and the cascading quantity is 1; the path carried in the path computation response message is a single path that meets the requirements of the cascading unit.

The cascading constraints include: a cascading unit, a cascading number, and a cascading type, and the cascading number is greater than 1; the path carried in the path calculation response message is a cascading path that meets the cascading constraints .

After receiving the client-side service transmission request, before sending the path computation request message to the path computation unit, obtain the differential delay constraint condition of the destination node accessing the client-side service; the path computation request message also carries the The source node differential delay constraint condition for accessing the client-side service and the differential delay constraint condition for the destination node accessing the client-side service are described.

Before sending the path computation request message to the path computation unit, obtain the path computation capability of the path computation unit; the path computation capability includes at least one of the following: a single path computation capability, a continuous cascading path computation capability, and a virtual path computation capability Cascading path computing capabilities.

A path calculation method, comprising: receiving the cascading capability of each interface sent by a node in the network; receiving a path calculation request message, the path calculation request message carrying a source node and a destination node for accessing a client-side service, and a cascading path Constraints; calculate paths according to the source node and destination node accessing the client-side service, the cascading constraints, and the cascading capabilities of each interface of the nodes in the network; send a path calculation response message, and the path calculation response The message carries the path.

Before receiving the path computation request message, send its own path computation capability; the path computation capability includes at least one of the following: single path computation capability, continuous cascade path computation capability, and virtual concatenation path computation capability.

The cascading constraint conditions include: a cascading unit and a cascading quantity, and the cascading quantity is 1; the path carried in the path computation response message is a single path conforming to the cascading unit.

The cascading constraints include: a cascading unit, a cascading number, and a cascading type, and the cascading number is greater than 1; the path carried in the path calculation response message is a cascading path that meets the cascading constraints .

A path calculation method, comprising: after receiving a request from a client side to transmit a service, sending a path calculation request message to a path calculation unit, the path calculation request message carrying a source node and a destination node accessing the client side service, and the client side transmitting The signal type of the service; receiving the path calculation response message carrying the path returned by the path calculation unit, the path is a concatenation constraint determined by the path calculation unit according to the signal type of the service transmitted by the client side, the It is obtained by calculating the cascading capabilities of the source nodes and destination nodes accessing client-side services, and the interfaces of nodes in the network.

A path calculation method, comprising: receiving the cascading capability of each interface sent by a node in the network;

Receive a path calculation request message, the path calculation request message carries the source node and destination node for accessing the client-side service, and the signal type of the client-side transmission service; determine the cascade constraint condition of the path according to the signal type of the client-side transmission service ; Calculate a path according to the source node and destination node accessing the client-side service, the cascading constraints, and the cascading capability of each interface of the node in the network; send a path calculation response message, and the path calculation response message carries the path.

A node device, comprising: a request message sending module, configured to send a path computation request message to a path computation unit after receiving a client-side service transmission request, the path computation request message carrying a source node accessing client-side services Concatenated constraints with the destination node and the path; a response message receiving module, configured to receive the path carrying the path returned by the path computing unit after the request message sending module sends the path computing request message to the path computing unit Computing a response message; the path is calculated by the path calculation unit according to the source node and destination node accessing the client-side service, the cascading constraints and the cascading capabilities of the interfaces of the nodes in the network.

The node device further includes: a differential time delay acquiring module, configured to acquire the received time delay after the request message sending module receives a request for service transmission from the client side and before sending a path calculation request message to the path calculation unit. The differential delay constraint condition of the destination node of the client-side service; wherein, the cascading constraint condition in the path calculation request message includes: cascading unit, cascading type and cascading quantity, and the cascading quantity is greater than 1 ; The path calculation request message also carries the differential delay constraint condition of the source node accessing the client-side service and the differential delay constraint condition of the destination node accessing the client-side service.

The node device further includes: a computing capability acquiring module, configured to acquire the path computing capability of the path computing unit before the request message sending module sends a path computing request message to the path computing unit; the path computing capability Including at least one of the following: single path computing capability, continuous cascading path computing capability and virtual cascading path computing capability.

A path computation unit, comprising: a node capability receiving module, configured to receive cascading capabilities of interfaces sent by nodes in the network; a request message receiving module, configured to receive a path computation request message, the path computation request message carrying an access The source node and destination node of the client-side service, the cascading constraint conditions of the path; the path calculation module, used to access the source node and the destination node of the client-side service, the cascading constraint condition and the nodes in the network A cascading capability calculation path of each interface; a response message sending module, configured to send a path calculation response message, where the path calculation response message carries the path.

The path computing unit further includes: a computing capability sending module, which sends its own path computing capability before the request message receiving module receives the path computing request message; the path computing capability includes at least one of the following: a single path computing capability , continuous cascading path computing capability and virtual cascading path computing capability.

A node device, comprising: a request message sending module, configured to send a path computation request message to a path computation unit after receiving a client-side service transmission request, the path computation request message carrying a source node accessing client-side services and the destination node, as well as the signal type of the service transmitted by the client side; the response message receiving module is used to receive the path computation response message carrying the path returned by the path computation unit; the path is determined by the path computation unit according to the client It is obtained by calculating the concatenation constraints determined by the signal type of the service transmitted on the client side, the source node and the destination node for accessing the service on the client side, and the concatenation capability of each interface of the nodes in the network.

A path computation unit, comprising: a node capability receiving module, configured to receive cascading capabilities of interfaces sent by nodes in the network; a request message receiving module, configured to receive a path computation request message, the path computation request message carrying an access The source node and destination node of the client-side business, the signal type of the client-side transmission service; the determination module is used to determine the cascading constraints of the path according to the client-side transmission signal type; the path calculation module is used to determine the path according to the access The source node and destination node of the client-side business, the cascading constraints and the cascading capability calculation path of each interface of the nodes in the network; a response message sending module, configured to send a path calculation response message, and the path calculation response message carry the path.

The path calculation method, node device, and path calculation unit provided by the embodiments of the present invention are described above in detail. In this paper, specific examples are used to illustrate the principle and implementation of the present invention. The descriptions of the above embodiments are only for help Understand the technical scheme of the present invention; At the same time, for those of ordinary skill in the art, according to the principles of the present invention, there will be changes in the specific implementation and application scope. In summary, the content of this specification should not be understood as Limitations on the Invention.

Claims (17)

1. A path calculation method, characterized in that, comprising: The path calculation client sends a path calculation request message to the path calculation unit, and the path calculation request message carries the source node and destination node for accessing the client-side service, and the cascading constraints of the path; the cascading constraints include: Unit, number of cascades and type of cascades, where the number of cascades is greater than 1; The path computation client receives the path computation response message carrying the path returned by the path computation unit, the path is determined by the path computation unit according to the source node and the destination node, the It is obtained by calculating the cascading capability of each interface of the node. 2. The path calculation method according to claim 1, wherein: The cascading type is continuous cascading, and the path carried in the path computation response message is a continuous cascading path that meets the cascading constraint condition. 3. The path computation method according to claim 1, wherein before the path computation client sends the path computation request message to the path computation unit, the method further comprises: When the path calculation client connected to the client-side network receives the client-side transmission service request, the cascading constraints are determined according to the bandwidth required by the request, the destination node of the requested signal transmission, and the signal type of the client-side transmission service. 4. The path calculation method according to claim 1, 2 or 3, wherein before the path calculation client sends the path calculation request message to the path calculation unit, the method further comprises: Acquiring the differential delay constraint condition of the destination node; the path computation request message also carries the differential delay constraint condition of the source node and the differential delay constraint condition of the destination node. 5. A path calculation method, characterized in that, comprising: The path computation unit receives a path computation request message, and the path computation request message carries a source node and a destination node for accessing the client-side service, and cascade constraint conditions of the path; The path calculation unit calculates a path according to the source node and the destination node, the cascading constraints, and the cascading capabilities of the interfaces of the nodes in the network; wherein, the cascading capabilities of the interfaces of the nodes in the network are stored in the in the path calculation unit; The path computation unit sends a path computation response message, where the path computation response message carries the path. 6. The path computation method according to claim 5, wherein the path computation unit sends its own path computation capability before receiving the path computation request message; the path computation capability includes at least one of the following: a single path Computing capabilities, computing capabilities for continuous cascading paths, and computing capabilities for virtual cascading paths. 7. The path calculation method according to claim 5 or 6, wherein the cascading constraints include: a cascading unit and a cascading number, and the cascading number is 1; The path carried in the path computation response message is a single path conforming to the cascade unit. 8. The path calculation method according to claim 5 or 6, wherein the cascading constraints include: a cascading unit, a cascading quantity, and a cascading type, and the cascading quantity is greater than 1; The path carried in the path computation response message is a cascading path that meets the cascading constraint condition. 9. A path calculation client, comprising: A module for sending a path computation request message to a path computation unit, the path computation request message carrying a source node and a destination node for accessing client-side services, and cascading constraint conditions of the path; the cascade constraint conditions include: cascading Unit, number of cascades and type of cascades, and the number of cascades is greater than 1; A module for receiving a path computation response message carrying a path returned by the path computation unit, where the path is determined by the path computation unit according to the source node and the destination node, the cascading constraints, and the network It is obtained by calculating the cascading capability of each interface of the node. 10. The path calculation client according to claim 9, characterized in that, The cascading type is continuous cascading, and the path carried in the path computation response message is a continuous cascading path that meets the cascading constraint condition. 11. The path computation client according to claim 9, wherein the path computation client is connected to the client-side network, and the path computation client further comprises: Before sending the path computation request message to the path computation unit, after receiving the client-side transmission service request, determine the level according to the bandwidth required by the request, the destination node of the request transmission signal, and the signal type of the client-side transmission service Modules with associated constraints. 12. The path calculation client according to claim 9, 10 or 11, wherein the path calculation client further comprises: A module for obtaining the differential delay constraint condition of the destination node before sending the path calculation request message to the path calculation unit; the path calculation request message also carries the differential delay constraint condition of the source node and the The differential delay constraints of the destination node. 13. A path calculation unit, comprising: A module for receiving a path computation request message, where the path computation request message carries a source node and a destination node for accessing client-side services, and cascading constraints of paths; A module for calculating a path according to the source node and the destination node, the cascading constraints, and the cascading capabilities of interfaces of nodes in the network; A module for storing the cascading capability of each interface of a node in the network; A module for sending a path computation response message, where the path computation response message carries the path. 14. The path calculation unit according to claim 13, wherein the path calculation unit further comprises: A module for sending its own path computing capability before receiving the path computation request message; the path computing capability includes at least one of the following: single path computing capability, continuous cascading path computing capability, and virtual cascading path computing capability . 15. The path calculation unit according to claim 13 or 14, wherein the cascading constraints include: a cascading unit and a cascading quantity, and the cascading quantity is 1; The path carried in the path computation response message is a single path conforming to the cascade unit. 16. The path computation unit according to claim 13 or 14, wherein the cascading constraints include: a cascading unit, a cascading quantity, and a cascading type, and the cascading quantity is greater than 1; The path carried in the path computation response message is a cascading path that meets the cascading constraint condition. 17. A communication system, characterized in that the communication system includes a path computation client and a path computation unit, wherein the path computation client is connected to the path computation unit, and the path computation client is as claimed in the right The path computation client according to claims 9-11, the path computation unit is the path computation unit according to claims 13-14.

Images