CN105743787B

CN105743787B - Control method and system for label request information and up-down cursor label exchange router

Info

Publication number: CN105743787B
Application number: CN201410758978.4A
Authority: CN
Inventors: 陈尔严; 刘闯; 郭纯宝
Original assignee: ZTE Corp
Current assignee: ZTE Corp
Priority date: 2014-12-11
Filing date: 2014-12-11
Publication date: 2020-09-25
Anticipated expiration: 2034-12-11
Also published as: WO2016090950A1; CN105743787A

Abstract

The invention provides a method and a system for controlling label request information and an upstream label switching router and a downstream label switching router, belonging to the field of communication. And in a downstream on-demand label publishing mode, firstly sending a label request message to a downstream label switching router, then receiving a first notification message fed back by the downstream label switching router when the downstream label switching router does not meet the label request message of the upstream label switching router, wherein the first notification message comprises a first control message of the label request message, the first notification message is used for controlling the sending of the label request message, analyzing the first notification message, and controlling the sending of the label request message according to the analyzed first control message. Compared with the prior art, the label request message is stopped from being sent to the downstream label switching router according to the fed-back first notification message, so that the situation that the upstream label repeatedly sends the label request message can be avoided, the resource consumption of the system in processing the messages is reduced, the resources are saved, and the processing performance of the system is improved.

Description

Control method and system for label request information and up-down cursor label exchange router

Technical Field

The present invention relates to the field of communications, and in particular, to a method and a system for controlling label request information, and an upstream label switching router and a downstream label switching router.

Background

MPLS (Multiprotocol Label Switching) originated from IPv4(Internet Protocol version 4), and was originally proposed to increase forwarding speed, and its core technology can be extended to a variety of network protocols, including IPv6(Internet Protocol version 6), IPX (Internet Packet Exchange), Appletalk, and CLNP (connectionless network Protocol), etc. The "M" in MPLS refers to support for multiple network protocols.

MPLS provides a way to map IP addresses to simple labels of fixed length for different packet forwarding and packet switching techniques. Compared with the traditional IP routing mode, the method has the advantages that when data are forwarded, the IP message header is only analyzed at the network edge, and the IP message header is not needed to be analyzed at each hop; fixed length tags are inserted at the beginning of each packet or cell and can be used by hardware to quickly switch packets between two links, thereby saving processing time. MPLS has the following advantages: 1) MPLS encapsulates network layer packets by using labels of fixed length, and routers in the MPLS network do not search for routes according to destination IP addresses, but forward packets according to the labels, thereby speeding up forwarding. 2) Each node on the packet forwarding path establishes a virtual channel for packet forwarding by allocating a label, thereby providing a connection-oriented service for the network layer. 3) Various link layer protocols and network layer protocols are supported. MPLS is located between the link layer and the network layer and may be built on top of various link layer protocols (e.g., PPP, ATM, frame relay, ethernet, etc.) to provide connection-oriented services for various network layers (IPv4, IPv6, IPX, etc.). 4) Not only supports various routing protocols, but also supports constraint routing based on strategies, and can meet the requirements of various new applications on the network. 5) Although MPLS was originally proposed as a protocol for increasing the forwarding speed of a router, its use is not limited to this, and MPLS can be used to construct a VPN network, implement traffic engineering, provide QoS guarantee, and the like, and is favored by a large-scale IP network.

The specification and processing of the label request message in the DOD mode means that in the DOD mode, for a particular FEC, the upstream LSR explicitly sends a label request message to the LSR next to the FEC to notify the downstream LSR to allocate a label to the FEC. When the downstream LSR meets the protocol requirements, a label is assigned for the FEC and a label mapping message is sent to advertise the binding of the label to the FEC. When the downstream LSR does not meet the protocol requirements (e.g., there is no entry in the routing table of the downstream LSR that matches the FEC address prefix, or there is other reason for insufficient non-label resources), the downstream LSR may reply with a notification message with a status code of "no route" to the upstream LSR. The upstream LSR will later resend the label request message for this FEC to the downstream LSR, as required by RFC 3031. When there are a large number of such FECs that need to send the request label message in the upstream LSR, and the downstream LSR cannot always satisfy the condition to send the label mapping message to the upstream LSR, the same process goes around, and the system always consumes more resources to process these messages, thereby affecting the device performance.

Disclosure of Invention

The invention provides a method and a system for controlling label request information and an upstream label switching router and a downstream label switching router, and solves the problem that resources are wasted when label request information is repeatedly sent in the prior art.

In order to solve the above problem, the present invention provides a method for controlling a tag request message, including:

sending a label request message to a downstream label switching router in a downstream on-demand label publishing manner, wherein the label request message comprises an identifier of a forwarding equivalence class, and the label request message is used for the downstream label switching router to allocate a label to the forwarding equivalence class;

when a downstream label switching router does not meet a label request message of an upstream label switching router, receiving a first notification message fed back by the downstream label switching router, wherein the first notification message comprises a first control message of the label request message, and the first notification message is used for controlling the sending of label request information;

and analyzing the first notification message, and controlling the sending of the tag request message after the analysis according to the first control message obtained by the analysis.

In an embodiment of the present invention, the first control message includes a message to stop the forwarding equivalence class, and/or a message to stop all forwarding equivalence classes; the sending of the tag request message after being controlled according to the parsed control message includes: if the message for stopping the forwarding equivalence class is obtained by analysis, stopping sending the label request message to the forwarding equivalence class; and if the message for stopping all forwarding equivalence classes is obtained by analysis, stopping sending the label request message to all forwarding equivalence classes.

In an embodiment of the present invention, after controlling sending of a subsequent label request message according to the parsed first control message, when a next label switching router satisfies a label request message of an upstream label switching router, receiving a second notification message sent by the downstream label switching router, where the second notification message includes a second control message of the label request message, and the second control message includes a message for recovering the forwarding equivalence class and/or a message for recovering all forwarding equivalence classes; analyzing the second notification message, and if the analyzed message is the message for recovering the forwarding equivalence class, re-sending a label request message to the forwarding equivalence class; and if the message for recovering all the forwarding equivalence classes is obtained by analyzing, the label request message is sent to all the forwarding equivalence classes again.

In one embodiment of the invention, the first control message is a message extended into an extended status value of the first notification message and/or the second control message is a message extended into an extended status value of the second notification message.

In order to solve the above problem, the present invention further provides a method for controlling a tag request message, including:

receiving a label request message sent by an upstream label switching router in a downstream on-demand label publishing mode, wherein the label request message comprises an identifier of a forwarding equivalence class and is used for distributing labels for the forwarding equivalence class;

when the label request message of the upstream label switching router is not satisfied, feeding back a first notification message to the upstream label switching router, wherein the first notification message comprises a first control message of the label request message, and the first notification message is used for controlling the sending of the label request message.

In an embodiment of the present invention, the label request message that does not satisfy the upstream label switching router includes that a label cannot be allocated to all forwarding equivalence classes of the upstream label switching router, and/or a label cannot be allocated to the forwarding equivalence classes of the upstream label switching router; the first notification message fed back to the upstream label switching router comprises: when the label cannot be distributed to all the forwarding equivalence classes of the upstream label switching router, feeding back a first control message comprising a message of stopping all the forwarding equivalence classes to the upstream label switching router; feeding back a first control message including a message to stop forwarding the equivalence class to the upstream label switching router when a label cannot be assigned to the forwarding equivalence class of the upstream label switching router.

In an embodiment of the present invention, after sending a label request message after controlling according to a first control message obtained by parsing, when a next label switching router satisfies a label request message of an upstream label switching router, sending a second notification message to the upstream label switching router, where the second notification message includes a second control message of the label request message, and determining whether to feed back a first control message including a message of stopping forwarding all forwarding equivalence classes before, and if so, sending a second control message including a message of restoring all forwarding equivalence classes; if not, judging whether a first control message comprising the message of stopping the forwarding equivalence class is fed back before, if so, sending second control information comprising the message of recovering the forwarding equivalence class.

In an embodiment of the present invention, the first notification message is extended, the first control message is extended into an extended status value of the first notification message, and/or the second notification message is extended, and the second control message is extended into an extended status value of the second notification message.

in a downstream on-demand label publishing mode, an upstream label switching router sends a label request message to a downstream label switching router, wherein the label request message comprises an identifier of a forwarding equivalence class, and the label request message is used for the downstream label switching router to distribute labels for the forwarding equivalence class;

the downstream label switching router receives a label request message sent by the upstream label switching router;

when the label request message of the upstream label switching router is not satisfied, the downstream label switching router feeds back a first notification message to the upstream label switching router, wherein the first notification message comprises a first control message of the label request message, and the first notification message is used for controlling the sending of the label request message;

and the upstream label switching router receives the first notification message fed back by the downstream label switching router, analyzes the first notification message, and controls the sending of the label request message after the analysis according to the first control message obtained by the analysis.

In order to solve the above problem, the present invention further provides an upstream label switching router, which includes a label request sending module and a notification message receiving module:

the label request sending module is used for sending a label request message to a downstream label switching router in a downstream label publishing mode according to needs, wherein the label request message comprises an identifier of a forwarding equivalence class, and the label request message is used for the downstream label switching router to distribute labels for the forwarding equivalence class;

when a downstream label switching router does not satisfy a label request message of an upstream label switching router, the notification message receiving module is configured to receive a first notification message fed back by the downstream label switching router, where the first notification message includes a first control message of the label request message, and the first notification message is used to control sending of label request information;

the notification message receiving module is further configured to parse the first notification message, and notify the tag request sending module of sending of the tag request message after being controlled according to the parsed first control message.

In an embodiment of the present invention, the first control message includes a message to stop the forwarding equivalence class, and/or a message to stop all forwarding equivalence classes; the notification message receiving module is further configured to: if the message analyzed by the notification message receiving module is the message for stopping the forwarding equivalence class, notifying the label request sending module to stop sending the label request message to the forwarding equivalence class; and if the message for stopping all forwarding equivalence classes is obtained by analysis, informing the label request sending module to stop sending the label request message to all forwarding equivalence classes.

In an embodiment of the present invention, after the notification message receiving module notifies the label request sending module to control sending of a subsequent label request message according to the parsed first control message, when the next label switching router satisfies the label request message of the upstream label switching router, the notification message receiving module is further configured to receive a second notification message sent by the downstream label switching router, where the second notification message includes a second control message of the label request message, and the second control message includes a message for recovering the forwarding equivalence class and/or a message for recovering all forwarding equivalence classes; the notification information receiving module is further configured to analyze the second notification message, and notify the tag request sending module to send a tag request message to the forwarding equivalence class again if the second notification message is obtained by analyzing and the forwarding equivalence class is recovered; and if the message for recovering all the forwarding equivalence classes is obtained by analysis, the label request sending module is informed to send the label request message to all the forwarding equivalence classes again.

In order to solve the above problem, the present invention further provides a downstream label switching router, which includes a label request receiving module and a notification message sending module:

the label request receiving module is used for receiving a label request message sent by an upstream label switching router in a downstream on-demand label publishing mode, wherein the label request message comprises an identification of a forwarding equivalence class, and the label request message is used for distributing labels for the forwarding equivalence class;

when the label request message of the upstream label switching router is not satisfied, the notification message sending module is configured to send a first notification message to the upstream label switching router, where the first notification message includes a first control message of the label request message, and the first notification message is used to control sending of the label request message.

In an embodiment of the present invention, the label request message that does not satisfy the upstream label switching router includes that a label cannot be allocated to all forwarding equivalence classes of the upstream label switching router, and/or a label cannot be allocated to the forwarding equivalence classes of the upstream label switching router; the notification message sending module is further configured to: when the label cannot be distributed to all the forwarding equivalence classes of the upstream label switching router, feeding back a first control message comprising a message of stopping all the forwarding equivalence classes to the upstream label switching router; feeding back a first control message including a message to stop forwarding the equivalence class to the upstream label switching router when a label cannot be assigned to the forwarding equivalence class of the upstream label switching router.

In an embodiment of the present invention, after controlling sending of a label request message after controlling according to a first control message obtained through parsing, when a next label switching router satisfies a label request message of an upstream label switching router, the notification message sending module is further configured to send a second notification message to the upstream label switching router, where the second notification message includes a second control message of the label request message, determine whether to feed back a first control message including a message that stops forwarding all forwarding equivalence classes before, and if so, send second control information including a message that resumes all forwarding equivalence classes; if not, judging whether a first control message comprising the message of stopping the forwarding equivalence class is fed back before, if so, sending second control information comprising the message of recovering the forwarding equivalence class.

In order to solve the above problem, the present invention further provides a system for controlling a label request message, including an upstream label switching router and a downstream label switching router:

the upstream label switching router is used for sending a label request message to a downstream label switching router in a downstream on-demand label publishing mode, wherein the label request message comprises an identifier of a forwarding equivalence class, and the label request message is used for the downstream label switching router to distribute labels for the forwarding equivalence class;

the downstream label switching router is used for receiving a label request message sent by the upstream label switching router;

when the label request message of the upstream label switching router is not satisfied, the downstream label switching router is further configured to send a first notification message to the upstream label switching router, where the first notification message includes a first control message of the label request message, and the first notification message is used to control sending of the label request message;

the upstream label switching router is further configured to receive a first notification message fed back by the downstream label switching router, analyze the first notification message, and control sending of the subsequent label request message according to the first control message obtained through analysis.

the notification message receiving module is further configured to parse the first notification message, and control sending of the tag request message after the parsing according to the parsed first control message.

In an embodiment of the present invention, the first control message includes a message to stop the forwarding equivalence class, and/or a message to stop all forwarding equivalence classes; the tag request sending module is further configured to: if the message for stopping the forwarding equivalence class is obtained by analysis, stopping sending the label request message to the forwarding equivalence class; and if the message for stopping all forwarding equivalence classes is obtained by analysis, stopping sending the label request message to all forwarding equivalence classes.

In an embodiment of the present invention, after the label request sending module controls sending of a label request message after being controlled according to the parsed first control message, when the next label switching router satisfies a label request message of an upstream label switching router, the notification information receiving module is further configured to receive a second notification message sent by the downstream label switching router, where the second notification message includes a second control message of the label request message, and the second control message includes a message for recovering the forwarding equivalence class and/or a message for recovering all the forwarding equivalence classes; the notification message receiving module is further configured to analyze the second notification message, and if the second notification message is obtained by analyzing that the forwarding equivalence class is recovered, send a label request message to the forwarding equivalence class again; and if the message for recovering all the forwarding equivalence classes is obtained by analyzing, the label request message is sent to all the forwarding equivalence classes again.

when the label request message of the upstream label switching router is not satisfied, the notification message sending module is configured to send a first notification message to the upstream label switching router, where the first notification message includes a first control message of the label request message, and the first notification message is used to control sending of the label request message;

when the label request message of the upstream label switching router is satisfied, the notification message sending module is configured to allocate a label to the forwarding equivalence class and feed back a label mapping message of the forwarding equivalence class to the upstream label switching router.

The invention has the beneficial effects that:

the invention provides a control method and a system of label request information and an upstream label switching router and a downstream label switching router, and the control method of the label request information specifically comprises the following steps: firstly sending a label request message to a downstream label switching router in a downstream on-demand label publishing mode, wherein the label request message comprises an identifier of a forwarding equivalence class, the label request message is used for the downstream label switching router to distribute labels for the forwarding equivalence class, then when the downstream label switching router does not meet the label request message of the upstream label switching router, receiving a first notification message fed back by the downstream label switching router, the first notification message comprises a first control message of the label request message, the first notification message is used for controlling the sending of the label request message, analyzing the first notification message, and controlling the sending of the label request message according to the analyzed first control message; and when the downstream label switching router meets the label request message of the upstream label switching router, receiving the label mapping message of the downstream label switching router feedback forwarding equivalence class. Compared with the prior art, when the next label switching router cannot meet the label request message of the upstream label switching router, the sending of the label request message to the downstream label switching router is stopped according to the fed-back first notification message, so that the situation that the upstream label repeatedly sends the label request message can be avoided, the resource consumption of a system for processing the messages is reduced, the resources are saved, and the processing performance of the system is improved.

Drawings

Fig. 1 is a schematic flowchart of a method for controlling tag request information according to an embodiment of the present invention;

fig. 2 is a flowchart illustrating a first method for controlling tag request information according to a second embodiment of the present invention;

fig. 3 is a flowchart illustrating a second method for controlling tag request information according to a second embodiment of the present invention;

fig. 4 is a schematic diagram of a topology structure of an upstream label switching router and a downstream label switching router in a flow of a control method for label request information according to a third embodiment of the present invention;

fig. 5 is a first flowchart illustrating a control method for tag request information according to a third embodiment of the present invention;

fig. 6 is a schematic flow chart illustrating a control method for tag request information according to a third embodiment of the present invention;

fig. 7 is a third schematic flowchart of a control method for tag request information according to a third embodiment of the present invention;

fig. 8 is a schematic flow chart of a control method of tag request information according to a third embodiment of the present invention;

fig. 9 is a schematic flowchart of a control method for tag request information according to a third embodiment of the present invention;

fig. 10 is a flowchart illustrating a sixth method for controlling tag request information according to a third embodiment of the present invention;

fig. 11 is a schematic structural diagram of an upstream label switching router according to a fourth embodiment of the present invention;

fig. 12 is a schematic structural diagram of a downstream label switching router according to a fourth embodiment of the present invention;

fig. 13 is a schematic structural diagram of a control system for requesting information by a tag according to a fourth embodiment of the present invention.

Detailed Description

Example one

The concept related to the related MPLS (Multiprotocol Label Switching) technology in this embodiment is as follows: 1) FEC (Forwarding Equivalence Class) is an important concept in MPLS. MPLS is actually a sort-forwarding technique that classifies packets having the same forwarding treatment (same destination, same forwarding path used, or same class of service, etc.) into one class, called forwarding equivalence class. Packets belonging to the same forwarding equivalence class will get exactly the same processing in the same MPLS network. 2) A label is a fixed-length, only locally meaningful identifier that uniquely identifies an FEC to which a packet belongs. One label can represent only one FEC. The tag length is 4 bytes. 3) An LSP (Label Switched Path) refers to a Path formed by LSRs that a forwarding equivalence class passes through in an MPLS network, i.e., a unidirectional Path from an ingress LSR to an egress LSR, and is called an LSP. 4) An LSR (label switching Router) is a device with label publishing capability and label switching capability, and is an essential element in an MPLS network. All LSRs have MPLS capability. The network of LSRs is called an MPLS domain. On the packet forwarding path, the sender router of a data packet is the upstream LSR of an LSP and the receiver router is the downstream LSR. 5) And (3) a label issuing mode: label distribution is to advertise the label allocated for FEC to other LSRs. There are two label distribution methods used in MPLS: downstream autonomic mode DU (Downstream autonomic): for a particular FEC, the downstream LSR assigns a label to the FEC and proactively advertises the label to the upstream LSR. Downstream on demand DOD (Downstream on demand): for a particular FEC, the upstream LSR requests the downstream LSR to assign a label to the FEC, and the downstream LSR, upon receiving the request, assigns the label to the FEC and advertises the label to the upstream LSR. 6) The label assignment control scheme is a scheme for establishing an LSP for FEC. The label distribution control mode is divided into two types: independent tag control mode (Independent): an LSR may advertise a label mapping at any time to the LSR to which it is connected. Ordered tag control mode (Ordered): an LSR may advertise a label mapping for a FEC to its upstream LSR only if it receives the label assigned by its downstream LSR for that FEC or if the LSR is the egress node for that FEC. 7) And (3) label issuing protocol: the label distribution protocol is a signaling protocol of MPLS and is responsible for dividing FEC, distributing labels, establishing and maintaining LSPs, and the like. The Label issuing protocols are of various types, and there are protocols specifically set for Label issuing, such as LDP (Label Distribution Protocol), and also protocols supporting Label issuing after expansion, such as BGP and RSVP-TE. The technology of the invention is realized based on the LDP specified in RFC 5036.

The method for controlling tag request information in this embodiment, as shown in fig. 1, includes the following steps:

step S101: sending a label request message to a downstream label switching router in a downstream label publishing mode according to needs;

in this step, the label request message includes an identifier of the forwarding equivalence class, and the label request message is used by the downstream label switching router to allocate a label for the forwarding equivalence class; the upstream LSR may send a label request to the downstream LSR for a certain FEC to which no label has been assigned. Specifically, in the DOD mode, for an equivalent FEC such as a certain forwarding class that has not obtained a label from a downstream LSR yet, the upstream LSR sends a label request message to the downstream LSR; and records the related content of the label request message so that the corresponding FEC can be identified when the first notification message of the feedback is received later.

Step S102: when the downstream label switching router does not meet the label request message of the upstream label switching router, receiving a first notification message fed back by the downstream label switching router;

in this step, the first notification message includes a first control message of the tag request message, and the first notification message is used to control the sending of the tag request message; when receiving a label request message of an upstream LSR for a certain FEC and judging that the label request message of the upstream LSR cannot be met, a downstream LSR feeds back a first notification message to the upstream LSR, wherein the first notification message is used for controlling the sending of the label request message; it should be understood that the first notification message is a message that can tell the upstream LSR that the downstream LSR cannot satisfy the label request message and let it stop sending subsequent label request messages. The judgment result that the downstream LSR cannot satisfy the label request message of the upstream LSR includes two conditions: first, it is not possible to allocate labels to the FECs in the label request message and advertise the binding of labels and FECs. For example: the downstream LSR learns route incompletion without an entry in its routing table matching the FEC address prefix. Secondly, labels cannot be allocated to the FEC of the upstream LSR for all the next hops of the upstream LSR, and the binding between the labels and the FEC cannot be announced. For example: the downstream LSR has configured a policy to prohibit advertising a label to the upstream LSR; or the downstream LSR uses an ordered label control scheme and has not received a label mapping message from its downstream LSR. Further, when receiving a label request message from an upstream LSR for a certain FEC, the downstream LSR needs to record the relevant content of the label request message, so that when subsequently sending a "no route" notification message, the downstream LSR can correctly fill the relevant fields required by the protocol.

Step S103: analyzing the first notification message, and controlling the sending of the label request message according to the analyzed first control message; .

In this step, it should be understood that, after receiving the first notification message fed back by the downstream LSR, the upstream LSR parses a specific content of the first notification message, that is, parses a specific first control message, and controls the sending of the label request information according to the specific content of the first control message, where the sending of the control label request information includes stopping sending the FEC label request information for a certain request and also includes stopping sending all the FEC label request information that is not allocated.

Preferably, the first control message includes a message for stopping forwarding the equivalence class, and/or a message for stopping forwarding all the equivalence classes; the step S103 of controlling the transmission of the tag request message according to the parsed control message includes: if the message of stopping forwarding the equivalence class is obtained by analysis, stopping sending the label request message to the forwarding equivalence class; and if the message for stopping all forwarding equivalence classes is obtained by analysis, stopping sending the label request message to all forwarding equivalence classes. Preferably, the first notification message includes an extended status value, parsing the first notification message includes parsing the extended status value of the first notification message, and sending of the tag request information is controlled according to the parsed extended status value. For example, the first notification message may be an extended "no route" notification message. Specifically, the first control message may be set to a first preset extension state value correspondingly to the message of the forwarding equivalence class, and the first control message may be set to a third preset extension state value correspondingly to the message of all the forwarding equivalence classes. The sending of the tag request information is controlled according to the analyzed extended state value, and the sending comprises the following steps: if the expansion state value obtained by analysis is the first preset expansion state value, stopping sending the label request message to the forwarding equivalence class, and continuing sending the label request message to other forwarding equivalence classes; and if the expansion state value obtained by analysis is the third preset expansion state value, stopping sending the label request message to all the forwarding equivalence classes. Specifically, when the first notification message is an extended "no route" notification message, the extended "no route" notification message is parsed to control the sending of the tag request information. For example, when the downstream LSR receives a label request message of an upstream LSR for a certain FEC, and determines that the label request message of the upstream LSR cannot be satisfied, the downstream LSR informs the upstream LSR that the label request message does not need to be repeatedly sent by sending an extended "no route" notification message; the upstream stops sending the label request information when receiving the extended 'no route' notification message, and controls the sending of the label request message according to the analysis of the extended state value in the extended 'no route' notification message. Therefore, the situation that the upstream LSR repeatedly sends the label request message can be avoided, the resource consumption of the system in processing the message is reduced, and the processing performance of the system is improved. Of course, when the next label switching router satisfies the label request message of the upstream label switching router, the downstream label switching router feeds back the label mapping message of the forwarding equivalence class. For example, when the downstream LSR meets the protocol requirements, a label may be assigned to the FEC and a label mapping message may be sent to advertise the binding of the label to the FEC.

Further, after step S103, that is, after the sending of the label request message after being controlled according to the parsed first control message, when the lower label switching router satisfies the label request message of the upstream label switching router, receiving a second notification message sent by the downstream label switching router, where the second notification message includes a second control message of the label request message, and the second control message includes a message of recovering the forwarding equivalence class and/or a message of recovering all the forwarding equivalence classes; analyzing the second notification message, and if the message for recovering the forwarding equivalence class is obtained by analyzing, sending the label request message to the forwarding equivalence class again; and if the message for recovering all the forwarding equivalence classes is obtained by analyzing, the label request message is sent to all the forwarding equivalence classes again. Preferably, the second notification message includes an extended status value, the parsing of the second notification message includes parsing of the extended status value of the second notification message, and the sending of the tag request information is controlled according to the parsed extended status value. For example, the second notification message may be an extended "no route" notification message. Specifically, the second control message may include that the message for restoring the forwarding equivalence class may be set to a second preset extended state value, and the message for restoring all the forwarding equivalence classes may be set to a fourth preset extended state value. The sending of the tag request information is controlled according to the analyzed extended state value, and the sending comprises the following steps: if the expansion state value obtained by analysis is the second preset expansion state value, the label request message sent to the forwarding equivalence class is recovered; and if the expansion state value obtained by analysis is the fourth preset expansion state value, the label request message is sent to all the forwarding equivalence classes. Specifically, when the second notification message is an extended "no route" notification message, the extended "no route" notification message is parsed to control the sending of the tag request information. For example, when the downstream LSR learns again or recovers from a failure, and determines that the label request message of the upstream LSR is satisfied, the upstream LSR is informed of retransmitting the label request message by sending an extended "no route" notification message; the upstream resumes sending the label request information upon receiving the extended "no route" notification message, and controls the sending of the label request message according to parsing the extended state value in the extended "no route" notification message. Therefore, the upstream LSR can know the specific condition of the downstream LSR, and control the sending of the label request information according to the specific condition, thereby improving the processing performance of the system.

Example two

The method for controlling tag request information in this embodiment, as shown in fig. 2, includes the following steps:

step S201: receiving a label request message sent by an upstream label switching router in a downstream on-demand label publishing mode;

in this step, the label request message includes an identification of the forwarding equivalence class, and the label request message is used by the downstream label switching router to assign a label to the forwarding equivalence class.

Step S202: when the label request message of the upstream label switching router is not satisfied, feeding back a first notification message to the upstream label switching router;

in this step, the first notification message includes a first control message of the tag request message, and the first notification message is used to control transmission of the tag request information. Of course, when the label request message of the upstream label switching router is satisfied, the label is allocated to the forwarding equivalence class, and the label mapping message of the forwarding equivalence class is fed back to the upstream label switching router.

Specifically, in step S202, the label request message that does not satisfy the upstream label switching router includes that a label cannot be allocated to all forwarding equivalence classes of the upstream label switching router, and/or a label cannot be allocated to a forwarding equivalence class of the upstream label switching router; the first notification message fed back to the upstream label switching router includes: when the labels cannot be distributed to all the forwarding equivalence classes of the upstream label switching router, feeding back a first control message comprising a message for stopping all the forwarding equivalence classes to the upstream label switching router; when the label cannot be allocated to the forwarding equivalence class of the upstream label switching router, feeding back a first control message including a message for stopping forwarding the equivalence class to the upstream label switching router.

Further, after step S202, that is, after the sending of the label request message after being controlled according to the parsed first control message, when the next label switching router satisfies the label request message of the upstream label switching router, sending a second notification message to the upstream label switching router, where the second notification message includes the second control message of the label request message, and determining whether to feed back the first control message including the message of stopping forwarding all forwarding equivalence classes before, and if so, sending the second control message including the message of restoring all forwarding equivalence classes; if not, judging whether a first control message comprising the message of stopping forwarding the equivalence class is fed back before, if so, sending second control information comprising the message of recovering the forwarding the equivalence class.

Further, the first notification message is expanded, the first control message is expanded into the expanded state value of the first notification message, and/or the second notification message is expanded, and the second control message is expanded into the expanded state value of the second notification message.

The embodiment also provides a method for controlling another tag request message, as shown in fig. 3, including the following steps:

step S301: in a downstream on-demand label publishing mode, an upstream label switching router sends a label request message to a downstream label switching router;

step S302: a downstream label switching router receives a label request message sent by an upstream label switching router;

Step S303: when the label request message of the upstream label switching router is not satisfied, the downstream label switching router feeds back a first notification message to the upstream label switching router;

in this step, the first notification message includes a first control message of the tag request message, and the first notification message is used to control the sending of the tag request message;

step S304: the upstream label switching router receives a first notification message fed back by the downstream label switching router, analyzes the first notification message, and controls the sending of a label request message after the first notification message is analyzed according to a first control message obtained by the analysis; certainly, when the label request message of the upstream label switching router is satisfied, the downstream label switching router distributes labels for the forwarding equivalence class and feeds back the label mapping message of the forwarding equivalence class to the upstream label switching router; the upstream label switching router receives the label mapping message of the downstream label switching router feedback forwarding equivalence class.

EXAMPLE III

The method for reducing tag request messages in DOD mode according to the present invention is described in an embodiment. In this embodiment, the first notification message and the second notification message are specifically "no route" notification messages carrying the extended status TLV, but the first notification message and the second notification message are not limited to this, and other messages that can be used to control the tag request may be used, where the first control message and the second control message are an extended status value in the first notification message and an extended status value in the second notification message, respectively. The specific first notification message and the second notification message may be defined as "no route" notification messages containing an extended status value. For example, an extended status TLV structure carried in an optional parameter of the LDP notify message defined in RFC5036 is adopted to indicate whether the upstream LSR continues to send the label request message with a different extended status value. The U-bit of the extended state TLV structure needs to be set to 1; the F-bit needs to be set to 0. The extended state value is a 4-byte length value. For convenience of description, the extended state value herein uses a specific value, which can be defined as follows: 0x3F 000001: indicating that no label request messages need to be sent for this FEC; 0x3F 000002: indicating that a label request message needs to be sent for the FEC; 0x3F 000003: all FECs that indicate that the next hop is not required to be the downstream LSR and from which the label has not been received continue to send label request messages; 0x3F 000004: indicating that the label request message needs to be sent for all FECs from which the next hop is the downstream LSR again and from which labels have not been received. Of course, the value is not limited to the definition of the extended status value, and the value may be specifically defined according to specific situations. After an upstream LSR sends a label request message for a certain FEC, when receiving a "no route" notification message replied by the downstream LSR, it determines whether an extended state TLV structure exists, and if so, it continues to determine an extended state value. If the value is 0x3F000001, then the label request message of the FEC is not retransmitted to the downstream LSR; if the value is 0x3F000003, then all FECs that are subsequently no longer the downstream LSR for the next hop and from which labels have not been received continue to send label request messages. When the configuration or route learning of the downstream LSR changes and can satisfy the label request message sent by the upstream LSR before, the downstream LSR retransmits the "no route" notification message with only different extended state values once according to the "no route" notification message sent before. If the "no route" notification message with the extended state value of 0x3F000003 occurs before, the "no route" notification message with the extended state value changed to 0x3F000004 is retransmitted once. Whereas if the "no route" notification message with the extended status value of 0x3F000003 was not previously transmitted, the condition has been satisfied, and all FECs that have previously transmitted the "no route" notification message with the extended status value of 0x3F000001 retransmit the "no route" notification message with the extended status value of 0x3F000002 once. Wherein, when the upstream LSR receives the "no route" notification message retransmitted by the downstream LSR, if the extended status value is 0x3F000004, the upstream LSR starts to retransmit the label request message for all FECs from which labels have not been received for the next hop as the downstream LSR. If the value is 0x3F000002, the upstream LSR sends a label request message only for the FEC corresponding to the message.

The method for reducing the label request message in the DOD mode of the MPLS network of the invention needs the cooperative processing of the upstream LSR and the downstream LSR.

The processing steps of the upstream LSR are shown in fig. 4, and include:

step S401: in the DOD mode, for a particular FEC that has not yet obtained a label from a downstream LSR, the upstream LSR sends a label request message to the downstream LSR; and recording the related content of the tag request message;

step S402: when receiving a 'no route' notification message replied by a downstream LSR, judging whether an extended state TLV structure exists; if the TLV structure exists, the step S403 is carried out, otherwise, the original flow process specified by the LDP protocol is processed;

step S403: continuing to determine the extended state value in the TLV structure. If the value is 0x3F000003, continuing to send label request messages for all FECs that are subsequently no longer the next hop to the downstream LSR and from which labels have not been received; if the value is 0x3F000001, then the label request message of the FEC is not retransmitted to the downstream LSR any more, and the processing of other FECs is continued; if the value is 0x3F000004, the process of step S404 is performed; if the value is 0x3F000002, the process of step S405 is performed; if the value is a value other than 0x3F000001 to 0x3F000004 defined in the present invention, the label request message of the FEC needs to be continuously sent to the downstream LSR.

Step S404: the upstream LSR starts to send label request messages for all the FECs from which labels have not been received for which the next hop is the downstream LSR again;

step S405: the upstream LSR sends a label request message only for the FEC corresponding to the message.

The processing of the downstream LSR is shown in fig. 5, and includes:

step S501: when receiving a label request message of an upstream LSR aiming at a certain FEC, a downstream LSR records the relevant content of the label request message;

step S502: judging whether the label request message of the upstream LSR is satisfied and distributing labels for the FEC; if the label resource is not insufficient and the label cannot be allocated to the FEC corresponding to the label requesting message, continuously judging whether the current LDP connection is in a DOD mode; if the DOD mode is adopted, the step S503 is carried out, otherwise, the original flow process specified by the LDP protocol is carried out;

step S503: judging whether the downstream LSR can not distribute labels for the FEC of the upstream LSR for all the next hops of the upstream LSR and advertise the binding of the labels and the FEC; if yes, processing in step S504 is carried out; otherwise, processing in step S505;

step S504: sending a 'no route' notification message carrying an extended status TLV to an upstream LSR; wherein, the U-bit of the expansion state TLV is set to 1, the F-bit is set to 0, and the expansion state value is set to 0x3F 000003; then, the step S506 is carried out;

step S505: sending a 'no route' notification message carrying an extended status TLV to an upstream LSR; wherein, the U-bit of the expansion state TLV is set to 1, the F-bit is set to 0, and the expansion state value is set to 0x3F 000001;

further, when the configuration of the downstream LSR or the route learning changes and can satisfy the label request message sent by the upstream LSR before, the "no route" notification message with different extension state values is retransmitted once; if the notification message of "no route" with the extended status value of 0x3F000003 is transmitted, the notification message of "no route" with the extended status value changed to 0x3F000004 is retransmitted once. If the downstream LSR has not previously sent the "no route" notification message with the extended status value of 0x3F000003, then the condition has been met, and all FECs that have previously sent the "no route" notification message with the extended status value of 0x3F000001 retransmit the "no route" notification message with the extended status value of 0x3F000002 once.

The following detailed description is made with reference to fig. 6-9:

as shown in fig. 6, the arrows indicate the next hop direction of all FECs on the respective LSRs. For a certain FEC, 2 LSPs are formed between two LSRs R1 and R6, LSP1: R1- > R2- > R4- > R6 and LSP 2: r1- > R3- > R5- > R6. The label issuing mode between R1 and R2 and R3 is a DOD mode, and R2 and R3 are downstream equipment of R1 equipment. Normally, the data traffic corresponding to the FEC is forwarded on LSP1 and LSP 2. When the R4 node fails, R2 may be allowed to de-label all FECs assigned to R1 to prevent traffic from being forwarded on the failed LSP1 path. Before the R4 node fails over, R1 needs to send a label request message to R2 for all FEC from which a label has not been obtained, as specified by the current protocol, that is R2 for the next hop.

The implementation of the technical scheme on R1 and R2 is further described in detail in the following steps in combination with the attached drawings:

as shown in fig. 7, the processing of replying a "no route" notification message by a downstream LSR after an upstream LSR sends a label request message specifically includes the following steps:

in step S701, R1, which is an upstream LSR, transmits a label request message for a certain FEC to R2 downstream thereof. And waits for the reply message of R2 before proceeding to the processing of step S702.

Specifically, as shown in fig. 8, in step S801, after receiving the tag request message sent by R1, R2 records the related content of the message; in step S802, it is determined that the tag request message of R1 cannot be satisfied; further, in step S803, it is determined that the current LDP connection is the DOD mode; and in step S804, it is determined that R2 has been unable to allocate labels for all next hops on R1 as FEC of this LSR; then, in step S805, a "no route" notification message carrying an extended status TLV, the extended status value of which is 0x3F000003, is sent to R1.

Step S702, the R1 receives the R2 reply notification message of 'no route', and after judging that the received notification message of 'no route' contains the extended status TLV, the step S703 is entered;

step S703, after R1 judges that the extended status value in the extended status TLV belongs to the range defined by the present invention, step S704 is entered;

step S704, after determining that the extended state value is 0x3F000003, proceed to step S705;

in step S705, R1 no longer sends the label request message for all FECs whose next hop is R2.

As shown in fig. 9, when the R4 node is cleared, R2 finds that the LSP corresponding to R1- > R2- > R4- > R6 can be recovered for these FECs, and retransmits the "no route" notification message with different extended state values, which specifically includes the following steps:

step S901, after R2 confirms that R4 is recovered, it can satisfy the previous label request message sent by the upstream LSR, and then step S902 is entered;

in step S902, R2 determines that the "no route" notification message with the extended status value of 0x3F000003 was sent before, and proceeds to step S903;

step S903, R2 retransmits a "no route" notification message to R1 with the extended state value changed to 0x3F000004 once;

as shown in fig. 10, after re-receiving the "no route" notification message containing the extended status TLV sent by R2, R1 restarts sending the tag request message to R2, which specifically includes the following steps:

in step S1001, the R1 receives the notification message of "no route" containing the extended status TLV sent by the R2 again, and proceeds to step S1002

In step S1002, R1 determines that the extended state value is 0x3F000004, and proceeds to step S1003;

in step S1003, R1 starts sending label request messages for all FECs whose next hop is R2 and from which label bindings have not been received, and the process ends.

Example four

The present embodiment provides an upstream label switching router 1101, as shown in fig. 11, including a label request sending module 1111 and a notification message receiving module 1112: the label request sending module 1111 is configured to send a label request message to the downstream label switching router 1201, where the label request message includes an identifier of a forwarding equivalence class, and the label request message is used by the downstream label switching router 1201 to allocate a label to the forwarding equivalence class; when the downstream label switching router 1201 does not satisfy the label request message of the upstream label switching router 1101, the notification message receiving module 1112 is configured to receive a first notification message fed back by the downstream label switching router 1201, where the first notification message includes a first control message of the label request message, and the first notification message is used to control sending of the label request message; the notification message receiving module 1112 is further configured to parse the first notification message, and notify the tag request sending module 1111 to control sending of the subsequent tag request message according to the parsed first control message.

Further, the first control message comprises a message for stopping forwarding the equivalence class and/or a message for stopping all forwarding the equivalence classes; the notification message receiving module 1112 is further configured to: if the message for stopping forwarding the equivalence class is obtained through analysis, the tag request sending module 1111 is notified to stop sending the tag request message to the forwarding equivalence class; if the message for stopping all forwarding equivalence classes is obtained through the analysis, the tag request sending module 1111 is notified to stop sending the tag request message to all forwarding equivalence classes.

Further, after the notification message receiving module 1112 notifies the label request sending module 1111 of sending the controlled label request message according to the parsed first control message, when the next label switching router 1201 satisfies the label request message of the upstream label switching router 1101, the notification message receiving module is further configured to receive a second notification message sent by the downstream label switching router 1201, where the second notification message includes a second control message of the label request message, and the second control message includes a message of recovering the forwarding equivalence class and/or a message of recovering all the forwarding equivalence classes; the notification message receiving module 1112 is further configured to analyze the second notification message, and if the second notification message is the message for recovering the forwarding equivalence class obtained through analysis, notify the tag request sending module 1111 to send the tag request message to the forwarding equivalence class again; if the message for recovering all forwarding equivalence classes is obtained by parsing, the tag request sending module 1111 is notified to send the tag request message to all forwarding equivalence classes again.

Further, the first control message is a message extended into the extended status value of the first notification message and/or the second control message is a message extended into the extended status value of the second notification message.

The present embodiment provides a downstream label switching router 1201, as shown in fig. 12, including a label request receiving module 1211 and a notification message sending and receiving module 1212: the label request receiving module 1211 is configured to receive a label request message sent by the upstream label switching router 1101, where the label request message includes an identifier of a forwarding equivalence class, and the label request message is used to allocate a label to the forwarding equivalence class; when the label request message of the upstream label switching router 1101 is not satisfied, the notification message sending and receiving module 1212 is configured to send a first notification message including a first control message of the label request message, to the upstream label switching router 1101, where the first notification message is used to control sending of the label request information.

Further, the label request message that does not satisfy the upstream label switching router 1101 includes a label that cannot be assigned to all forwarding equivalence classes of the upstream label switching router 1101, and/or a label that cannot be assigned to a forwarding equivalence class of the upstream label switching router 1101; the notification message sending and receiving module 1212 is further configured to: when the label cannot be allocated to all the forwarding equivalence classes of the upstream label switching router 1101, feeding back a first control message including a message for stopping all the forwarding equivalence classes to the upstream label switching router 1101; when a label cannot be assigned to the forwarding equivalence class of the upstream label switching router 1101, a first control message including a message to stop forwarding the equivalence class is fed back to the upstream label switching router 1101.

Further, after controlling the sending of the label request message after the control according to the parsed first control message, when the next label switching router 1201 satisfies the label request message of the upstream label switching router 1101, the notification message sending and receiving module 1212 is further configured to send a second notification message to the upstream label switching router 1101, where the second notification message includes a second control message of the label request message, determine whether to feed back the first control message including the message of stopping forwarding all forwarding equivalence classes before, and if so, send second control information including the message of restoring all forwarding equivalence classes; if not, judging whether a first control message comprising the message of stopping forwarding the equivalence class is fed back before, if so, sending second control information comprising the message of recovering the forwarding the equivalence class.

The present embodiment provides a control system of a label request message, as shown in fig. 13, including an upstream label switching router 1101 and a downstream label switching router 1201: the upstream label switching router 1101 is configured to send a label request message to the downstream label switching router 1201, where the label request message includes an identifier of a forwarding equivalence class, and the label request message is used by the downstream label switching router 1201 to allocate a label to the forwarding equivalence class; the downstream label switching router 1201 is configured to receive a label request message sent by the upstream label switching router 1101; when the label request message of the upstream label switching router 1101 is not satisfied, the downstream label switching router 1201 is further configured to send a first notification message including a first control message of the label request message to the upstream label switching router 1101; the upstream label switching router 1101 is further configured to receive a first notification message fed back by the downstream label switching router 1201, analyze the first notification message, and control sending of a subsequent label request message according to the first control message obtained through analysis.

It will be understood by those skilled in the art that all or part of the steps of the above methods may be implemented by instructing the relevant hardware through a program, and the program may be stored in a computer readable storage medium, such as a read-only memory, a magnetic or optical disk, and the like. Alternatively, all or part of the steps of the above embodiments may be implemented using one or more integrated circuits. Accordingly, each module/unit in the above embodiments may be implemented in the form of hardware, and may also be implemented in the form of a software functional module. The present invention is not limited to any specific form of combination of hardware and software.

The above embodiments are merely to illustrate the technical solutions of the present invention and not to limit the present invention, and the present invention has been described in detail with reference to the preferred embodiments. It will be understood by those skilled in the art that various modifications and equivalent arrangements may be made without departing from the spirit and scope of the present invention and it should be understood that the present invention is to be covered by the appended claims.

Claims

1. A method for controlling a tag request message, comprising:

2. The method for controlling a tag request message according to claim 1, wherein the first control message comprises a message to stop the forwarding equivalence class and/or a message to stop all forwarding equivalence classes; the sending of the tag request message after being controlled according to the parsed control message includes: if the message for stopping the forwarding equivalence class is obtained by analysis, stopping sending the label request message to the forwarding equivalence class; and if the message for stopping all forwarding equivalence classes is obtained by analysis, stopping sending the label request message to all forwarding equivalence classes.

3. The method according to claim 2, wherein after controlling the sending of the subsequent label request message according to the parsed first control message, when the next label switching router satisfies the label request message of the upstream label switching router, receiving a second notification message sent by the downstream label switching router, where the second notification message includes a second control message of the label request message, and the second control message includes a message for recovering the forwarding equivalence class and/or a message for recovering all forwarding equivalence classes; analyzing the second notification message, and if the analyzed message is the message for recovering the forwarding equivalence class, re-sending a label request message to the forwarding equivalence class; and if the message for recovering all the forwarding equivalence classes is obtained by analyzing, the label request message is sent to all the forwarding equivalence classes again.

4. The method of controlling a tag request message according to claim 3, wherein the first control message is a message extended into an extended status value of the first notification message, and/or the second control message is a message extended into an extended status value of the second notification message.

5. A method for controlling a tag request message, comprising:

6. The method for controlling label request message according to claim 5, wherein the label request message not satisfying the upstream label switching router includes that a label cannot be allocated to all forwarding equivalence classes of the upstream label switching router, and/or a label cannot be allocated to the forwarding equivalence classes of the upstream label switching router; the first notification message fed back to the upstream label switching router comprises: when the label cannot be distributed to all the forwarding equivalence classes of the upstream label switching router, feeding back a first control message comprising a message of stopping all the forwarding equivalence classes to the upstream label switching router; feeding back a first control message including a message to stop forwarding the equivalence class to the upstream label switching router when a label cannot be assigned to the forwarding equivalence class of the upstream label switching router.

7. The method according to claim 6, wherein after controlling the sending of the label request message after the first control message obtained by parsing, when the next label switching router satisfies the label request message of the upstream label switching router, sending a second notification message to the upstream label switching router, the second notification message including a second control message of the label request message, determining whether to feed back the first control message including the message of stopping all forwarding equivalence classes before, and if so, sending the second control message including the message of resuming all forwarding equivalence classes; if not, judging whether a first control message comprising the message of stopping the forwarding equivalence class is fed back before, if so, sending second control information comprising the message of recovering the forwarding equivalence class.

8. The tag request message control method of claim 7, wherein the first notification message is extended to extend the first control message into an extended status value of the first notification message, and/or the second notification message is extended to extend the second control message into an extended status value of the second notification message.

9. A method for controlling a tag request message, comprising:

10. An upstream label switching router, comprising a label request sending module and a notification message receiving module:

11. The upstream label switching router of claim 10, wherein the first control message comprises a stop message for the forwarding equivalence class, and/or a stop message for all forwarding equivalence classes; the notification message receiving module is further configured to: if the message analyzed by the notification message receiving module is the message for stopping the forwarding equivalence class, notifying the label request sending module to stop sending the label request message to the forwarding equivalence class; and if the message for stopping all forwarding equivalence classes is obtained by analysis, informing the label request sending module to stop sending the label request message to all forwarding equivalence classes.

12. The upstream label switching router according to claim 11, wherein after the notification message receiving module notifies the label request sending module of sending the label request message after being controlled according to the parsed first control message, when the next label switching router satisfies the label request message of the upstream label switching router, the notification message receiving module is further configured to receive a second notification message sent by the downstream label switching router, where the second notification message includes a second control message of the label request message, and the second control message includes a message for recovering the forwarding equivalence class and/or a message for recovering all forwarding equivalence classes; the notification message receiving module is further configured to analyze the second notification message, and if the second notification message is obtained by analyzing that the forwarding equivalence class is recovered, notify the tag request sending module to send a tag request message to the forwarding equivalence class again; and if the message for recovering all the forwarding equivalence classes is obtained by analysis, the label request sending module is informed to send the label request message to all the forwarding equivalence classes again.

13. A downstream label switching router is characterized by comprising a label request receiving module and a notification message sending module:

14. The downstream label switching router of claim 13, wherein the not-satisfied label request message for the upstream label switching router comprises a failure to assign a label to all forwarding equivalence classes of the upstream label switching router and/or a failure to assign a label to the forwarding equivalence classes of the upstream label switching router; the notification message sending module is further configured to: when the label cannot be distributed to all the forwarding equivalence classes of the upstream label switching router, feeding back a first control message comprising a message of stopping all the forwarding equivalence classes to the upstream label switching router; feeding back a first control message including a message to stop forwarding the equivalence class to the upstream label switching router when a label cannot be assigned to the forwarding equivalence class of the upstream label switching router.

15. The downstream label switching router of claim 14, wherein after controlling the sending of the subsequent label request message according to the parsed first control message, when the next label switching router satisfies the label request message of the upstream label switching router, the notification message sending module is further configured to send a second notification message to the upstream label switching router, where the second notification message includes a second control message of the label request message, determine whether to feed back the first control message including the message of stopping all forwarding equivalence classes before, and if so, send second control information including the message of restoring all forwarding equivalence classes; if not, judging whether a first control message comprising the message of stopping the forwarding equivalence class is fed back before, if so, sending second control information comprising the message of recovering the forwarding equivalence class.

16. A control system for a label request message, comprising an upstream label switching router and a downstream label switching router: