WO2008031291A1

WO2008031291A1 - A method for recovering synchronization of the signaling transport layer-two peer to peer adaptation layer sequence numbers

Info

Publication number: WO2008031291A1
Application number: PCT/CN2006/003230
Authority: WO
Inventors: Qingyong Liang
Original assignee: Zte Corporation
Priority date: 2006-09-07
Filing date: 2006-11-30
Publication date: 2008-03-20
Also published as: CN101127763A; CN101127763B

Abstract

A method for recovering synchronization of the Signaling Transport Layer-two Peer to Peer Adaptation Layer sequence numbers that especially deals with MTP2 Peer to Peer Adaptation Protocol, aims to resolve the question that the M2PA protocol unity transmitter can't synchronize the sequence numbers with the M2PA protocol unity receiver when the M2PA protocol unity receives the out-of-sequence MSU in the current M2PA protocol. The M2PA protocol unity according to the invention that receives the out-of-sequence message signaling unit constructs at least one new type of message unit, in which the at least one new type of message unit carries the sequence number information of the discarded message signaling unit. The M2PA protocol unity that receives the out-of-sequence message signaling unit then transmits one of the at least one new type of message unit to the M2PA protocol unity that transmits the out-of-sequence message signaling unit. The invention realizes recovering MSU sequence numbers transmitted between the M2PA protocol unities, and avoids the M2PA signaling link interruption possibility owing to message unit packet losing and out of sequence.

Description

Transmission signaling layer two peering

TECHNICAL FIELD The present invention relates to an IP network signaling transmission protocol (SIGTRAN protocol), and in particular, to an abnormal situation such as a packet loss misordering of an MTP2 peer-to-peer adaptation protocol (M2PA protocol), correspondingly The serial number restores the solution to the synchronization mechanism. BACKGROUND With the gradual maturity of IP network technologies, IP networks can be used to carry services such as voice, data, and multimedia. Traditional circuit-switched networks and IP networks are in a phase of convergence. In order to realize the interconnection and interconnection between traditional circuit-switched networks and IP networks, The need to transmit circuit-switched signaling protocols such as SS7 over IP networks. In order to meet the requirements of transmitting signaling protocols over IP networks, the IETF Network Working Group has established a dedicated signaling transport group, and their IP network signaling transport protocol (SIGTRAN protocol) supports the transmission of traditional circuit-switched signaling over IP networks. . In 2005, the IETF working group officially released the MTP2 Peer to Peer Adaption Layer (MTP) protocol. The M2PA protocol is used to implement reliable messages between two MTP3 peer-to-peer protocol entities carried on an IP network. Order delivery. In 2002, China's Ministry of Information Industry also officially released the M2PA communications industry standard. The specific protocol structure of M2PA is shown in Figure 1 and Figure 2.

As the transmission signaling layer 2 in the IP network, M2PA is directly carried on the SCTP protocol (RFC2960) entity, and the SCTP protocol entity has the characteristics of reliable and orderly transmission. Therefore, there is no further description of the reliable and orderly transmission mechanism of M2PA in the RFC protocol standard and China's communication industry standards. However, M2PA acts as the transport signaling link layer under the MTP3 protocol entity and passes the SCTP. The protocol entity and the M2PA protocol entity work together to perform reliable and orderly transmission of messages between MTP3 protocol entities. When an error condition such as packet loss or out-of-order occurs in the IP network transmission process between the two peer-to-peer protocol entities of the SCTP, the SCTP protocol entity can ensure the synchronization of the sequence number recovery through retransmission and other mechanisms. However, when an abnormality such as a message loss occurs between the M2PA protocol entity and the SCTP protocol entity, the message receiver M2PA protocol entity will always discard the data packet of the discontinuous sequence number sent by the sender M2PA protocol entity, and the message sender M2PA protocol entity The message is continuously sent to the M2PA receiver protocol entity because it is not clear about the message loss that occurred before. This abnormality continues until the sender M2PA protocol entity detects that the packet loss message has not been answered for a long time, causing the Out of Service to be sent to the receiver M2PA protocol entity. The MTP3 data retrieval and the switching of the signaling link are performed, and in severe cases, the abnormal situation such as the unreachable signaling office may be caused. See Figure 3 for this anomaly. SUMMARY OF THE INVENTION In order to overcome the above drawbacks, an object of the present invention is to provide a method for recovering synchronization of a transmission layer two-layer peer-to-peer adaptation layer sequence number, which solves a message signaling unit (MSU) that receives an out-of-sequence in an M2PA protocol entity. The sender M2PA protocol entity and the method for recovering the synchronization of the transmission signaling layer 2 peer-to-peer adaptation layer sequence includes the following steps:

(1) The M2PA protocol entity that receives the out-of-order message signaling unit constructs a new at least one type of message unit, and the new at least one type of message unit carries the sequence number information of the discarded message signaling unit; (2) The M2PA protocol entity that receives the out-of-order message signaling unit sends a message unit of one type of the new at least one type of message unit to the M2PA protocol entity that sends the out-of-order message signaling unit;

(3) If no transmission of the out-of-order message signaling unit occurs between the M2PA protocol entity receiving the message signaling unit and the M2PA protocol entity transmitting the message signaling unit, the process of transferring the out-of-order message signaling unit does not occur. Wherein, step (1) is specifically:

(11) The M2PA protocol entity that receives the out-of-order message signaling unit constructs a new link state signaling unit, and the new link state signaling unit carries the sequence number information of the discarded message signaling unit; step (2) is specifically :

(21) The M2PA protocol entity that has received the out-of-order message signaling unit sends the new link state signaling unit to the M2PA protocol entity that sent the out-of-order message signaling unit. Wherein, step (11) is specifically:

(111) when the M2PA protocol entity receiving the out-of-order message signaling unit receives the out-of-order message signaling unit, the buffer subsequently receives the message signaling unit sent by the M2PA protocol entity that sends the out-of-order message signaling unit;

(112) The M2PA protocol entity receiving the out-of-order message signaling unit constructs a new link state signaling unit carrying the sequence number information of the discarded message unit or the new link state letter Let the unit value be restored. Wherein, step (21) is specifically:

(211) The M2PA protocol entity that receives the out-of-order message signaling unit sends a new link state signaling unit to the M2PA protocol entity that sends the out-of-order message signaling unit;

(212) After receiving the new link state signaling unit sent by the M2PA protocol entity of the out-of-order message signaling unit, the M2PA protocol entity that sends the out-of-order message signaling unit performs the legality of the new link state signaling unit. Checking, if legal, the M2PA protocol entity sending the out-of-order message signaling unit waits for the data response timer to restart; if not, sending the M2PA protocol entity of the out-of-order message signaling unit to the new link state signaling unit message Carry out the disposal process;

(213) The M2PA protocol entity that sends the out-of-order message signaling unit decodes the sequence number information of the discarded message unit or the new sequence number recovery link state signaling unit in the received new link state signaling unit, and is to be decoded. The discarded message signaling unit is resent to the M2PA protocol entity that receives the out-of-order message signaling unit. In step (212), the retransmission queue of the M2PA protocol entity that sends the out-of-order message signaling unit is used to check whether the new link state signaling unit is merged. The process of transmitting the out-of-order message signaling unit in step (3) is specifically: if the out-of-order message signaling unit does not occur between the M2PA protocol entity that receives the message signaling unit and the M2PA protocol entity that sends the message signaling unit Transmitting, then receiving the M2PA protocol entity of the message signaling unit to send the message signaling unit The sequence number information of the discarded message unit in the new link state signaling unit sent by the M2PA protocol entity is empty. The process of transmitting the out-of-order message signaling unit in step (3) is specifically: if the out-of-order message signaling unit does not occur between the M2PA protocol entity that receives the message signaling unit and the M2PA protocol entity that sends the message signaling unit In the case of transmission, the M2PA protocol entity receiving the message signaling unit does not send a new link state signaling unit whose value is recovered to the M2PA protocol entity transmitting the message signaling unit. The present invention further provides an apparatus for transporting signaling Layer 2 peer-to-peer adaptation layer sequence number synchronization synchronization, comprising: creating means for constructing a new at least one M2PA protocol entity that receives the out-of-order message signaling unit a type of message unit, the new at least one type of message unit carries the sequence number information of the discarded message signaling unit; and the sending device is configured to enable the M2PA protocol entity that receives the out-of-order message signaling unit to re-new at least one One type of message unit of the type of message unit is sent to the M2PA protocol entity that sends the out-of-order message signaling unit; and the processing device, the M2PA protocol entity that receives the message signaling unit and the M2PA protocol entity that sends the message signaling unit In the case where no transmission of the out-of-order message signaling unit occurs, the flow of the transmission of the out-of-order message signaling unit does not occur. The new at least one type of message unit includes a new link state signaling unit. The processing device sends the M2PA protocol entity that receives the message signaling unit to the case that no transmission of the out-of-order message signaling unit occurs between the M2PA protocol entity that receives the message signaling unit and the M2PA protocol entity that sends the message signaling unit. New link status sent by the M2PA protocol entity that sent the message signaling unit The sequence number information of the discarded message unit in the signaling unit is empty, or the M2PA protocol entity that receives the message signaling unit does not send a new link state signaling with the value of the serial number recovery to the M2PA protocol entity that sends the message signaling unit. unit. Compared with the existing protocol technology, the present invention solves the problem that the M2PA protocol entity receives the out-of-order message unit, which inevitably causes the M2PA signaling link to be interrupted, and can prevent the loss of the upper layer user data of the M2PA protocol entity to the greatest extent. At the same time, it is proposed to add the message unit recovery synchronization mechanism in the M2PA protocol, and avoid the possibility that the M2PA signaling link is interrupted due to the M2PA protocol entity message unit packet loss disorder. Other features and advantages of the invention will be set forth in the description which follows, The objectives and other advantages of the invention will be realized and attained by the <RTI The drawings are intended to provide a further understanding of the invention, and are intended to be a part of the description of the invention. In the drawing: Figure 1 is the protocol stack of M2PA applied in IPSP; Figure 2 is the protocol stack of M2PA applied in SG; Figure 3 is the current M2PA RFC protocol and M2PA postal protocol standard about M2PA out-of-order error processing flow FIG. 4 is a flowchart of an implementation method for implementing sequence number synchronization by modifying an existing LSSU (Link State Signaling Unit): In Service message; 5 is a diagram showing an implementation method of the serial number synchronization by adding a LSSU (Link State Signaling Unit): Recovery message; and FIG. 6 is a structural diagram showing a sequence number recovery synchronization apparatus according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The preferred embodiments of the present invention are described with reference to the accompanying drawings. In the Layer 2 protocol of the transport signaling, the sequence number recovery synchronization is a message unit between two peer-to-peer protocol entities due to abnormal conditions such as packet loss between two peer-to-peer signaling layer 2 protocol entities. The serial number has an inconsistent and asynchronous recovery method. In the transmission signaling, the operation of message unit retransmission and sequence number synchronization between two peer protocol entities is often implemented by means of sequence number indication flag inversion and link state message signaling unit interaction. The invention mainly improves the accompanying parameters and functions of one or several types of message units of the existing M2PA protocol, and completes the serial number recovery synchronization between the M2PA ten-party entities. Or, one or several types of message units not currently in the M2PA protocol are added, and the M2PA protocol is improved to implement sequence number recovery synchronization between the M2PA protocol entities. The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings: FIG. 3 is a diagram showing the processing of the M2PA RFC protocol and the M2PA postal protocol standard regarding the M2PA ^L sequence packet loss; FIG. 3 can be seen from FIG. In the current M2PA protocol, the M2PA protocol entity-B sends an MSU (Message Signaling Unit) to the M2PA protocol entity, ie, the M2PA protocol entity does not receive the M2PA protocol entity--the MSU: FSN -7 BSN=6; (wherein FSN is: Forward Sequence Number, forward sequence number, representing the message signaling unit sent by the current sender M2PA protocol entity) The BSN is: Backward Sequence Number, the backward sequence number, which represents the number of the message signaling unit currently received from the peer M2PA protocol entity:); therefore, the M2PA protocol entity that is subsequently received—the MSU sent by B is always discarded. . This condition continues until the M2PA protocol entity-B corresponding to the MSU: FSN=7, BSN=6 packet waiting for the response timer Timer T7 timeout (the specific processing flow is related to the related M2PA protocol), and sends the LSSU to the M2PA protocol entity-A: Out Of Service begins to release the signaling link. As can be seen from the description of the protocol flow, once the packet loss occurs between the M2PA protocol entities, the M2PA signaling link will be released. The interval of the link detection must be within the Timer T7 interval. If the traffic of the upper layer user message unit of the M2PA protocol entity is relatively large, a large number of data packets are discarded between the M2PA peer protocol entities. As shown in FIG. 4, the present invention implements serial number synchronization between M2PA protocol entities by improving the LSSU: In Service message in the existing M2PA communication industry standard protocol specification. The principle of this embodiment is to minimize the loss of the signaling link and to perform sequence number recovery of the data message as much as possible. The specific processing procedure is as follows: This solution is implemented by tampering with the LSSU message structure. At the end of the LSSU: In Service message structure of the existing protocol, a message interval list is added. The LSSU: In Service message structure before modification is:

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

1 State I + - +- ₊ - +-+-+- +-+-+-+- +- +-+-+- +-+-+-+ +-+ +-+-+-+-+ —+_+—+—+-+—+—+—+ The present invention ^ The modified LSSU: In Service message structure is:

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

+一+—+—+—+—+—+—+—+—+—+—+—+—+—+—+—+—+—+—+—+—+—+—+—+— +—+—+—+—+—+—+—+

1 State I +— ₊ — +—+—+—+— +—+_+— +一+一+_+—+—+—+—+—+—+—+—+—+—+—+ —+— +- +—+—+—+—+—+— +

I FSN List Element Begin 1 (FLEB1) |

+—+— +一+—+—+—+一+一+—+—+—+—+—+—+—+—+—11+-+一+—+—+—+—+— +-+-+-+-+-+-+-+ I FSN List Element End 1 (FLEE1)

+—+—+—+—+—+—+—+—+—+—+—+—+—+—+—+—+—+—+—+—+—+—+, +—+— +— +— +—+—+—+—+—+

I FSN List Element Begin 2 (FLEB2)

I FSN List Element End 2 (FLEE2)

+—+—+—+—+—+—+—+—+—+—+—+—+—+—+—+—+—+—+—+—+—+—+—+—+— +—+■ I FSN List Element Begin 3 (PLEB3 )

+—+—+—+—+—+—+—+—+—+—+—+—+—+—+—+—÷—+—+—+—+—+_—+—+—+ _+—·

I FSN List Element End 3 (FLEE 3)

+— _ (·—H 1 1 1 1 i 1 1 h~ -\ hTM H 1 h— H 1 1 1 1- -

·—+_+—+—+—+—+—+—+—+—+—+—+—+—+—+—+—+—+—+_+—+—+—+—+— +—+-

■ -} 1 1 1 1 1 1 1 (*— +— H h~ -+—+—+—+—+—+

+—+—+—+—+—+—+—+—+—+—+—+—+—+—+—+—+—+—+—+—+—+-

FSN List element Begin n-1 (FLEB n-1) —+—+—+—+—+—+—+—+—+—+—+—+—+—+—+—+—+—+— +—+—+

FSN List Element End n-1 (FLEE n-1)

+—+—+—+ .+—+—+—+—+—+—+—+—+—+—+—+—+—+—+_+—+—+—+—+—+— +—+—+—+—+-

FSN List Element Begin n (FLEB n)

.+- + - + -+- + _+- + - + -4·- FSN List Element End n(FLEE n)

Where: FSN List Element Begin (FLEB) represents the first missing packet sequence number of a lost sequence interval FSN

FSN List Element End (FLEE) represents the last lost packet number FSN of a lost sequence interval The sequence number is: n represents the number of lost sequence intervals, and the value range of the value of n can be different according to the specific implementation of the software. When n is a value of 1, it is a special case of a packet that only loses one interval. The improved LSSU: In Service message processing steps are as follows: Step 101: Under normal circumstances, when no packet loss occurs, both parties of the M2PA protocol entity send a LSSU: In Service to reply the message. The FSSU: In Service FSN List Element list is empty. That is, the number n of lost sequence intervals is zero. At this time, the M2PA protocol entity processing mechanism is handled by the current Chinese communication industry standard M2PA protocol. Step 102: A packet loss occurs between two peer-to-peer protocol entities of the M2PA due to various abnormal conditions. Step 103: The M2PA protocol entity-A receives the out-of-order message unit MSU when there is a packet loss condition. Step 104: The M2PA protocol entity_A cache receives the out-of-order MSU into the receiving buffer of the M2PA protocol entity A. Step 105: The M2PA protocol entity A constructs a specific LSSU according to the out-of-order packet loss condition: the In Service message is sent to the message sender M2PA protocol entity-B. In the specific implementation, the LSSU: In Service can be sent regardless of whether the user data is sent by the MSU, and the sender and the receiver can be quickly synchronized. Step 106: The M2PA protocol entity B receives the LSSU: In Service message from the M2PA protocol entity A, and checks the validity of the message. If the message is illegal, the process is discarded (recommended to use the M2PA protocol entity-B retransmission queue) Check to see if there is a missing sequence contained in the LSSU: In Service message The FSN sequence number is separated, but the present invention does not limit the specific implementation method. If the message is legal, the M2PA protocol entity-B will wait for the data response timer Timer T7 to restart. Prevents the M2PA protocol entity_B from releasing the signaling link due to Timer T7 timeout. Step 107: The M2PA protocol entity “B” decodes the FSN List element Begin and the FSN List element End according to the received LSSU: In Service to determine which data messages are specifically lost during the data transmission process. M2PA Protocol Entity—B chooses to retransmit the corresponding lost data message to the M2PA protocol entity—A. Step 108: When receiving the retransmission data message sent by the M2PA protocol entity_B, the M2PA protocol entity A determines whether it is cached or handed over to the upper layer user according to the data sequence number in the receiving buffer (the specific principle is: if the data message is And the cached data message can ensure the order of the upper layer user data, and the data message and the corresponding cached data are handed over to the upper layer user. Otherwise, the data message is also cached in the receive buffer for processing). The foregoing only provides an implementation method for implementing the technical solution of the present invention. The specific implementation method is not limited to the method flow described in this embodiment. FIG. 5 shows another embodiment of implementing the technical solution of the present invention. This embodiment adds a new signaling link state signaling unit LSSU by using the existing M2PA RFC protocol specification: Recovery (Serial Number Recovery) The message is used to implement the M2PA i "sequence synchronization process between the entities. The present invention has some differences between the processing of the new message LSSU: Recovery and the implementation of the LSSU: In Service message unit shown in Figure 4. YES: The LSSU: Recovery message unit does not have the operation associated with step 101 in the embodiment shown in Figure 4 above, ie in the absence of packet loss. Under normal circumstances, LSSU: Recovery is not actively sent. However, when a packet loss occurs, the LSSU:Recovery message is sent actively. In step 102 and subsequent processing, the processing of the LSSU: Recovery message is consistent with the LSSU: In Service processing.

The LSSU: Recovery message unit will only be sent and processed after the M2PA signaling link is put into service. In other cases, it should be discarded as an undesired message. For the example of FIG. 4 and FIG. 5, only one implementation method of the present invention is given, but the specific implementation method, the newly added message name and the like are not limited to the description of the embodiment. Figure 6 is a block diagram showing the structure of the serial number recovery synchronizing apparatus according to the present invention. In FIG. 6, the apparatus 600 for transmitting signaling layer 2 peer-to-peer adaptation layer sequence number synchronization includes: a creating apparatus 602, configured to construct a new type of at least one type of M2PA protocol entity that receives the out-of-order message signaling unit Message unit, the new at least one type of message unit carries the sequence number information of the discarded message signaling unit; and the sending device 604 is configured to enable the M2PA protocol entity that receives the out-of-order message signaling unit to re-new at least one new type One type of message unit of the type of message unit is sent to the M2PA protocol entity that sends the out-of-order message signaling unit; and the processing device 606, the M2PA protocol entity that receives the message signaling unit and the M2PA protocol entity that sends the message signaling unit In the case where no transmission of the out-of-order message signaling unit occurs, the flow of the transmission of the out-of-order message signaling unit does not occur. In the apparatus, the new at least one type of message unit includes a new link state signaling unit. Further, in the apparatus, the processing apparatus 600 enables the reception of the message signaling in the case where the transmission of the out-of-order message signaling unit does not occur between the M2PA protocol entity that receives the message signaling unit and the M2PA protocol entity that transmits the message signaling unit. The M2PA protocol entity of the unit sends the sequence number information of the discarded message unit in the new link state signaling unit sent by the M2PA protocol entity that sends the message signaling unit to null, or makes the M2PA protocol entity that receives the message signaling unit not The M2PA protocol entity transmitting the message signaling unit transmits a new link state signaling unit whose value is recovered. The present invention mainly proposes a message unit sequence number synchronization synchronization mechanism in the M2PA protocol, which is a remedy for the defects of the current M2PA protocol. The above two embodiments are only two specific methods for implementing the technical solution of the present invention, and are not limited to the existing M2PA. Modification/add/delete mode of the protocol message unit, modification/addition/deletion of the existing M2PA protocol message unit function, modification/addition/deletion of the parameter field attached to the existing M2PA protocol message unit, or may be any of the above methods combination. Compared with the existing protocol technology, the present invention solves the problem that the M2PA protocol entity receives the out-of-order message unit, which inevitably causes the M2PA signaling link to be interrupted. The loss of upper user data of the M2PA protocol entity can be prevented to the greatest extent. At the same time, the synchronization mechanism of the booster port message unit in the M2PA protocol is proposed. The possibility of the M2PA signaling link interruption caused by the M2PA protocol entity message unit packet loss sequence is avoided from the message flow. The above is only the preferred embodiment of the present invention, and is not intended to limit the present invention, and various modifications and changes can be made to the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and scope of the present invention are intended to be included within the scope of the present invention.

Claims

Claim

A method for transmitting and signaling a layer 2 peer-to-peer adaptation layer sequence to restore synchronization, characterized in that the method includes the following steps: silver:

(1) The M2PA protocol entity that has received the out-of-order message signaling unit constructs a new at least one type of message unit, the new at least one type of message unit carrying the sequence number information of the discarded message signaling unit;

(2) the M2PA protocol entity that has received the out-of-order message signaling unit transmits another one of the new at least one type of message unit to the M2PA protocol entity that sent the out-of-order message signaling unit;

(3) If no transmission of the out-of-order message signaling unit occurs between the M2PA protocol entity receiving the message signaling unit and the M2PA protocol entity transmitting the message signaling unit, the process of transmitting the out-of-order message signaling unit does not occur.

The method of claim 1, wherein the step (1) is specifically:

(11) The M2PA protocol entity that has received the out-of-order message signaling unit constructs a new link state signaling unit, and the new link state signaling unit carries the sequence number information of the discarded message signaling unit;

The step (2) is specifically:

(21) The M2PA protocol entity that has received the out-of-order message signaling unit sends the new link state signaling unit to the M2PA server that sent the out-of-order message signaling unit. The method for recovering synchronization of the transmission signaling layer 2 peer-to-peer adaptation layer sequence number according to claim 2, wherein the step (11) is specifically:

(111) when the M2PA protocol entity receiving the out-of-order message signaling unit receives the out-of-order message signaling unit, the buffer subsequently receives the message signaling unit sent by the M2PA protocol entity that sent the out-of-order message signaling unit;

(112) The M2PA protocol entity receiving the out-of-order message signaling unit constructs a new link state signaling unit carrying the sequence number information of the discarded message unit or the new link state letter Let the unit value be restored. The method for recovering synchronization of the transmission signaling layer 2 peer-to-peer adaptation layer sequence according to claim 3, wherein the step (21) is specifically:

(211) The M2PA protocol entity that receives the out-of-order message signaling unit sends the new link state signaling unit to the M2PA 1⁄4, the negotiation entity that sends the out-of-order message signaling unit;

(212) After the M2PA protocol entity that sends the out-of-order message signaling unit receives the new link state signaling unit sent by the M2PA protocol entity that receives the out-of-order message signaling unit, the new link state signaling unit is legal. Checking, if it is legal, the M2PA protocol entity sending the out-of-order message signaling unit waits for the data response timer to restart; if not, sending the M2PA protocol entity of the out-of-order message signaling unit to the new link state signaling Unit message is discarded; and

(213) transmitting, by the M2PA protocol entity of the out-of-order message signaling unit, sequence number information of the discarded message unit in the received new link state signaling unit or the new sequence number recovery link state signaling unit Decoding is performed, and the discarded message signaling unit is resent to the M2PA protocol entity that receives the out-of-order message signaling unit. The method for recovering synchronization of the transmission signaling layer 2 peer-to-peer adaptation layer sequence number according to claim 4, wherein in the step (212), retransmission of the M2PA protocol entity that sends the out-of-order message signaling unit is adopted. The queue checks if the new link state signaling unit is legal. The method for recovering synchronization of the transmission signaling layer 2 peer-to-peer adaptation layer sequence number according to claim 4 or 5, wherein the process of transmitting the out-of-order message signaling unit in the step (3) is specifically as follows: The M2PA protocol entity that receives the message signaling unit does not transmit the out-of-order message signaling unit between the M2PA protocol entity that sends the message signaling unit, and the M2PA protocol entity that receives the message signaling unit sends the message signaling unit The sequence number information of the discarded message unit in the new link state signaling unit sent by the M2PA protocol entity is empty. The method for recovering synchronization of the transmission signaling layer 2 peer-to-peer adaptation layer sequence number according to claim 4 or 5, wherein the process of transmitting the out-of-order message signaling unit in the step (3) is specifically as follows: The M2PA protocol entity receiving the message signaling unit does not send the message signaling unit when the M2PA protocol entity receiving the message signaling unit does not transmit the out-of-order message signaling unit between the M2PA protocol entity that sends the message signaling unit. The M2PA protocol entity sends a new link state signaling unit with a value of sequence number recovery. An apparatus for transmitting and signaling a layer 2 peer-to-peer adaptation layer sequence number synchronization synchronization, comprising: a creating device, configured to configure a M2PA protocol entity that receives an out-of-order message signaling unit to construct a new at least one type of message a unit, the new at least one type of message unit carrying sequence number information of the discarded message signaling unit; a sending device, configured to: send, by the M2PA protocol entity that receives the out-of-order message signaling unit, one type of the message unit of the new at least one type of message unit to the M2PA protocol entity that sends the out-of-order message signaling unit And processing means, in the case that no transmission of the out-of-order message signaling unit occurs between the M2PA protocol entity receiving the message signaling unit and the M2PA protocol entity transmitting the message signaling unit, the transfer does not occur in the out-of-order message signaling unit transmission Process. The device for recovering synchronization of the transmission signaling layer 2 peer-to-peer adaptation layer sequence number according to claim 8, wherein the new at least one type of message unit comprises a new link state signaling unit. The apparatus for transmitting and signaling a layer 2 peer-to-peer adaptation layer sequence number synchronization according to claim 9, wherein the processing apparatus receives an M2PA protocol entity of a message signaling unit and an M2PA protocol for transmitting a message signaling unit. In the case that no transmission of the out-of-order message signaling unit occurs between the entities, the M2PA protocol entity of the received message signaling unit is caused to be sent to the M2PA protocol entity transmitting the message signaling unit in a new link state signaling unit. The sequence number information of the discarded message unit is empty, or the M2PA protocol entity of the received message signaling unit does not send a new link state signaling unit whose value is restored to the M2PA protocol entity that sends the message signaling unit.