WO2012041250A1 - Method and device for handling congestion in machine type communications - Google Patents

Abstract

Disclosed are a method and a device for handling congestion in machine type communications (MTC). The method comprises: upon receiving a tracking area update (TAU) request message initiated by a user equipment (UE), a mobility management entity (MME) confirming a subscribed access point name (APN) of the UE; the MME confirming among the subscribed APNs an APN being congested; the MME indicating in a TAU accept message being returned to the UE the congested APN among the subscribed APNs, and indicating a session management back-off timer being allocated for the congested APN. The present invention provides an improvement over the illogicality in the prior art, reduces signaling resource consumption to the greatest possible extent, and ensures the running of normal operations.

Description

 Congestion processing method and device in machine type communication This application claims to be submitted to the Chinese Patent Office on September 30, 2010, the application number is 201010504058.1, and the invention name is "a method and device for congestion processing in machine type communication". Priority of Chinese Patent Application, the entire contents of which is incorporated herein by reference. Technical field

 The present invention relates to a machine type communication technology, and in particular to a congestion processing method and apparatus in machine type communication. Background technique

 In the existing MTC (Machine Type Communications) technology, due to MTC Device

The number of (machine-type communication devices) is large, and it is necessary to take into account the network congestion caused by the large amount of signaling and data transmission generated. Therefore, in 3GPP (3rd Generation Partnership Project), research is proposed. Congestion Control feature of MTC communication.

 At this meeting of SA2#80, NTT DoCoMo proposed a congestion control method based on APN (Access Point Name) to avoid and resolve congestion associated with a specific APN. The network starts a back-off timer according to whether the PGW (PDN Gateway, PDN Gateway, PDN: Packet Data Network) of a certain APN is congested, including the Mobility Management back-off timer. The STP management backoff timer and the Session Management back-off timer indicate that the MTC Device cannot initiate a request to access the network or request a connection before the back-off timer expires. The steps are as follows:

 1. The MME (Mobility Management Entity) detects the congestion based on APN according to certain criteria. The standards include:

 a. Per APN (per APN) The maximum number of active EPS Bearers (EPS bearers, EPS: Evolved Packet System, Evolved Packet System);

 b. Per APN's EPS Bearer activation rate;

c MME is unreachable to one or more PDN GWs, or receives a congestion indication from these PDN GWs; when a congestion for an APN occurs, the MME stores a Mobility Management back-off Timer (for EPS Mobility Management processes, such as Attach, TAU

(Traking Area Update) process and a Session Management back-off timer (such as the PDN Connectivity Request process), if UE (User) Equipment, user equipment) Before these timers expire, initiate an access or connection request to this APN, and the network should reject it. Detailed breakdown:

 a. When the APN requested in the Attach or TAU process is in a congested state, the MME shall reject the process and start the Mobility Management back-off timer, and indicate that the UE cannot initiate any Mobility Management process until the timer expires.

 b. The PDN Connectivity Request process initiated by the UE carries the APN. If the APN is not carried, the default APN (default APN) in the subscription data is used. If it is determined that the used APN is in a congested state, the MME should

The macro PDN Connectivity Request message, and ^ ^: indicates that the UE starts the Session Management back-off timer. Before the timer expires, the UE cannot initiate the PDN Connectivity Request process corresponding to the APN.

 The TAU process is divided into the process of carrying the active flag and the process without the active flag. If the TAU Request message carries the active flag, the network activates all active bearers of the UE after the TAU process is completed. (Activate the bearer), the procedure is the same as the Service Request, but starts with the MME starting the bearer.

 The disadvantages of the prior art are: when the UE has multiple PDN connections, and multiple PDN connections may use different APNs, the APN-based congestion control scheme causes congestion when the PGW corresponding to the APN of one of the PDNs is congested. All PDNs cannot be used. Summary of the invention

 The technical problem to be solved by the present invention is to provide a method and a device for processing congestion in a machine type communication, which are used to solve the problem in the prior art when multiple PDN connections exist in a UE, and multiple PDN connections use different APNs. The problem that one PDN corresponding to the PPN connected to the PDN is congested causes all PDNs to be unusable.

 An embodiment of the present invention provides a congestion processing method in an MTC, including the following steps:

 After receiving the TAU Request message initiated by the UE, the MME determines the subscription APN of the UE;

 The MME determines that the APN in the contracted APN is congested;

 The MME indicates, in the TAU Accept message of the returning UE, the APN that is congested in the subscribed APN, and the Session Management back-off timer that is allocated to the APN that is congested.

 An embodiment of the present invention provides a congestion processing method in an MTC, including the following steps:

Receiving, by the UE, a TAU Accept message returned by the MME to the UE, where the TAU Accept message indicates the signing of the UE A congested APN in the APN and a Session Management back-off timer allocated to the congested APN; the UE sets a Session Management back-off timer to the congested APN.

 The embodiment of the present invention provides a mobility management entity device, including:

 An APN determining module, configured to: after receiving a TAU Request message initiated by the UE, determine a contracted APN of the UE; a congestion determining module, configured to determine a congested APN in the subscribed APN;

 The indication module is configured to indicate, in the TAU Accept message of the returning UE, the APN that is congested in the subscribed APN, and the Session Management back-off timer that is indicated to be in the congested APN.

 A user equipment is provided in the embodiment of the present invention, including:

 a receiving module, configured to receive a TAU Accept message sent by the MME to the UE, where the TAU Accept message indicates a CPN that is congested in the APN of the UE and a Session Management back-off timer allocated to the APN that is congested;

 A setting module is configured to set a Session Management back-off timer for the APN that is congested.

 In the technical solution provided by the embodiment of the present invention, after receiving the TAU Request message initiated by the UE, the MME determines the APN that is congested in the subscribed APN; and indicates to the UE that the APN in the subscribed APN is congested, and indicates that the pair is in congestion. The APN sets the Session Management back-off timer. Instead of allocating a Session Management back-off timer to all APNs. The UE can enable the APN to initiate a service request, or initiate a service request after the session management back-off timer of the APN is timed out. Therefore, when there are multiple PDN connections in the UE, and multiple PDN connections use different APNs, all PDNs will not be used due to congestion of the PGW corresponding to one of the PDNs connected to the PDN.

 It can be seen that the technical solution provided by the embodiment of the present invention can improve the irrationality of the prior art, minimize the signaling resource consumption in the network, and ensure the normal service operation. DRAWINGS

 1 is a schematic flowchart of a method for implementing congestion processing in an MTC on an MME side according to an embodiment of the present invention; FIG. 2 is a schematic flowchart of a method for implementing congestion processing in an MTC at a UE side according to an embodiment of the present invention;

 3 is a schematic diagram of a TAU process in which a SGW changes in an embodiment of the present invention;

 4 is a schematic structural diagram of a mobility management entity device according to an embodiment of the present invention;

FIG. 5 is a schematic structural diagram of a user equipment according to an embodiment of the present invention. detailed description The inventor noticed during the invention:

 In the MTC technology, due to the large number of MTC devices, if a large number of MTC devices simultaneously perform signaling interaction or data transmission with the network, network congestion may occur. Congestion of the network can be divided into user plane congestion and signaling plane congestion. Once network congestion occurs, the network should reject the corresponding signaling connection request or data transmission request. In the existing protocol, there is a method for congestion control based on APN. It is proposed that in the TAU process, if there is congestion of the PGW corresponding to the APN, the TAU Request is rejected, and a Mobility Management back-off timer is started. The MTC Device cannot initiate any Mobility Management requests until the device times out.

 However, in the existing TAU procedure, the TAU Request message is a per UE. When there are multiple PDN connections in the UE, and multiple PDN connections may use different APNs, the APN-based congestion control method cannot be good. Work, for example, at least the following two inappropriate scenarios:

 1. It is assumed that the UE initiates the TAU Request procedure of the intra MME intra SGW without active flag (SGW: Serving Gateway, Serving Gateway), and the PGW corresponding to all APNs related to the UE is congested. , MME does not need to refuse.

 2. Assume that there are three PDN connections in the UE, and that APN1, APN2, and APN3 are used respectively. The network determines that APN1 is in a congested state. According to the APN Based congestion control method of NTT Docomo, the network needs to be in a congested state because the requested APN1 is in congestion. The TAU Reject message is sent to the UE, and the Mobility Management back-off timer is started. The UE cannot initiate any Mobility Management request before the α3⁄4 timer expires. However, the PGW corresponding to the APN2 and APN3 is not congested and can accept the service request. At this time, the UE should not be rejected by the network.

 It can be seen that the TAU process is per UE, and one UE can have multiple PDN connections, if only one of them

If the PGW corresponding to the APN of the PDN is congested, the network should not reject the entire TAU Request. Therefore, in the embodiment of the present invention, a NAS (Non Access Stratum) back-off timer is set in the TAU process. The solution enables the APN that is not in a congested state to obtain services. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described with reference to the accompanying drawings.

 In the description process, the implementation of the MME side and the UE side will be described first, and finally, the implementation of the two will be described. However, this does not mean that the two must be implemented together. In fact, when the MME is implemented separately from the UE, At the same time, the problems existing on the MME side and the UE side are also solved, but when the two are used in combination, a better technical effect is obtained.

 FIG. 1 is a schematic flowchart of a method for implementing congestion processing in an MTC on the MME side. As shown in the figure, the following steps may be included:

Step 101: After receiving the TAU Request message initiated by the UE, the MME determines the contracted APN of the UE. Step 102: The MME determines that the APN in the contracted APN is congested;

 Step 103: The MME indicates, in the TAU Accept message of the returning UE, the APN that is congested in the subscribed APN, and the Session Management back-off timer that is indicated to be in the congested APN.

 In an implementation, the MME may determine that the APN in the APN in the bearer contexts of the UE's bearer context in the UE's subscription APN is congested.

 Specifically, after receiving the TAU Request, the MME can simultaneously determine whether the APN in the bearer contexts of the UE is in a congested state.

 Correspondingly, the congestion processing scheme in the MTC on the UE side is also provided in the embodiment of the present invention.

 2 is a schematic flowchart of a method for implementing congestion processing in an MTC on the UE side. As shown in the figure, the following steps may be included:

 Step 201: The UE receives a TAU Accept message that the MME returns to the UE, where the TAU Accept message indicates that the APN of the subscribed APN of the UE is congested and the session management back-off timer allocated for the congested APN.

 Step 202: The UE sets a Session Management back-off timer to the APN that is congested.

 In the implementation, it may further include:

 The UE determines the APN that is congested and not congested;

 The UE selects a non-congested APN to initiate a service request, or initiates a service request after the timeout of the Congested APN Session Management back-off timer expires.

 It can be seen that the MME receives the TAU Request and determines whether the APN in the bearer contexts of the UE is in a congested state. Then the MME indicates in the TAU Accept message, which APNs in the UE subscription information are in a congested state, and notify the UE that The Session Management back-off timer allocated by each congested APN; after receiving the back-off timer in the TAU Accept message, the UE starts the corresponding timer, and does not initiate a service request or connection request for these APNs before the timer expires. .

 Further, if the MME finds that the APN is in a congested state, and the SGW changes in the process, the session management process to the corresponding PGW of the APN may be deferred, that is, the PDN connection needs to be subsequently initiated to the Session Management process of the corresponding PGW; Or, in the TAU process, although the SGW does not change, the MME needs to trigger a signaling procedure to the PGW, for example, there is no SGW change in the TAU process of the Intra MME intra SGW.

In this case, when the UE initiates a Mobility Management process after the timeout of the ASN's Session Management back-off timer expires, the network should first perform the previously delayed Session Management process for the APN, or cancel the trigger to the PGW. Signaling process. Therefore, performing congestion processing on the MME side may further include:

 The MME determines that if there is a congested APN in the TAU process, and the SGW changes; or, the MME delays initiating a Session Management process to the PGW, the PGW is a PGW corresponding to the APN being congested; or, the MME determines that in the TAU process When the MME needs to trigger the signaling process to the packet data network gateway PGW, the MME cancels the signaling process that triggers the PGW.

 In a specific implementation, the MME delays initiating the session management process to the PGW, and the method includes: the MME does not send a Create Session Request to the SGW, and marks that the process is delayed.

 Performing congestion processing on the MME side may further include:

 The MME determines that when the UE initiates a Mobility Management process after the Session Management back-off timer timeout of an APN, if the APN is no longer in congestion, the previously delayed Session Management process for the APN is performed.

 In the specific implementation, the MME determines that the UE is in the next Mobility Management process, and there is a delay flag in the Bearer Contexts corresponding to the PDN connection in the UE, the MME may determine that the UE initiates a Session Management back-off timer timeout of an APN. Mobility Management process.

 The Session Management process referred to in the application refers to the MME sending a Create Session Request to the new SGW, then the new SGW generates a Modify Bearer Request to the PGW, and then the PGW returns a Response (Response). ) to new SGW, new SGW returns response to MMEo

 For a better understanding of the specific embodiments of the present invention, an implementation of a functional device including an MME, a UE, and the like will be described below by way of example.

 Example 1

 3 is a schematic diagram of a TAU process in which the SGW changes. In the figure, the new MME, the new SGW is the MME and the SGW after the TAU is updated, the old MME, the old SGW is the MME and the SGW before the TAU update; as shown in the figure, in the Tracking Area Update In the procedure with Serving GW change, the following process can be included in the process:

 Step 301: Triggering a TAU process begins;

 Step 302: The UE sends a TAU request message to the eNB.

 Step 303: The eNB sends a TAU request message to the new MME.

 Step 304: The new MME sends a context request message to the old MME.

 Step 305: The old MME sends a context response message to the new MME.

Step 306, authentication, security authentication, and the like; Step 307: The new MME sends a context confirmation message to the old MME.

 Step 308: The new MME initiates a session establishment request message to the new SGW.

 Step 309: The new SGW initiates a bearer modification request message to the PDN GW.

 Step 310: The PDN GW returns a tampering response message to the new SGW.

 Step 311: The new SGW returns a session establishment response message to the new MME.

 Step 312: The new MME initiates a location update message to the HSS (Home Subscriber Server).

 Step 313: The HSS sends a location cancellation message to the old MME.

 Step 314: The old MME returns a location cancellation acknowledgement message to the HSS.

 Step 315: The old MME sends an Iu interface release command message to the RNC (Radio Network Controller):

 Step 316: The RNC returns an Iu interface release completion message to the old MME.

 Step 317: The HSS sends a location update confirmation message to the new MME.

 Step 318: The old MME sends a delete session request message to the old SGW.

 Step 319: The old SGW sends a delete session response message to the old MME.

 Step 320: The new MME returns a TAU accept message to the UE.

 Step 321: The UE sends a TAU complete message to the new MME.

 In the above process, the behavior of the MME and the UE can be implemented as follows:

 1. The New MME detects which PGWs corresponding to the APNs that the UE subscribes to are in a congested state;

 2. The UE sends a TAU Request to the new MME, new MME to view the Bearer Contexts of the UE, and detects which APNs corresponding to the PDN connection are in a congested state;

 3. For this PDN connection, the new MME does not send the Create Session Request to the new SGW, but the process is delayed, and the delay can be marked in the PDN connection. In the specific implementation, the Delay can be added in TS23.401 5.7.2. Flag (delay flag) is as follows:

 For each active PDN connection:

This flag indicates that the SGW of this PDN connection has been changed but the related ESM procedure hasn't been executed. (The o3⁄4 flag indicates that the connection SGW of the o3⁄4 PDN has changed, but the related ESM process has not been executed. ESM: EPS Session Management , session management of the EPS system) APN in The APN currently used. This APN shall be composed of the APN Network Use Identifier and the default APN Operator Identifier, as specified in TS 23.003 [4], clause 9.1.2. Any received value in the APN OI Replacement field is not Applied here.

4. The New MME carries the Session Management back-off timer of all APNs in the congested state to the UE in the TAU Accept message. In the implementation, the message format can be bolded in the following message format:

 This message is sent by the network to the UE to provide the UE with EPS mobility management related data in response to a tracking area update request message. See table 8.2.26.1.

 Message type: TRACKING AREA UPDATE ACCEPT

 Significance: dual

 Direction: network to UE

Table 8.2.26.1 : TRACKING AREA UPDATE ACCEPT message content

其中， Session backoff Timer List表示会话退避定时器列表， Backoff Timer List x. 示退避定时器列表， O表示可选， TLV表示类型 -长度 -值， X表示信元长度。

The session backoff Timer List indicates a session backoff timer list, the Backoff Timer List x. indicates a backoff timer list, O indicates optional, TLV indicates type-length-value, and X indicates cell length.

In the implementation, the definition of Backoff Timer List can be as follows: 8 6 4 3 2

 Backoff Timer list IE (backoff timer list information element) octet 1

Length of Backoff Timer List octet 2-3

Access point name 1 (access point name 1 ) octet 4 octet i

 Backoff Timer 1 (backoff timer 1) octet i+1

 Octet i+2 octet i+3 octet j

 Access point name n (access point name n ) octet j+1 octet k

 Backoff Timer n (access point name n ) octet k+1

 In the octet k+2 implementation, the Backoff Timer can use the definition of GPRS Timer in 10.4.7.3 of TS 24.008 (see Figure 10.5.146/3GPP TS 24.008: GPRS Timer information element for details):

 8 7 6 5 4 3 2 1

 GPRS Timer IEI octet 1

 In the implementation of Unit Timer value octet 2, Access point name can use the definition of 10.5.6.1 in TS24.008 (see Figure 10.5.152/3GPP TS 24.008: Access point name information element for details).

 8 7 6 5 4 3 2 1

 Access point name IEI octet 1

 Length of access point name contents octet 2

Access point name value octet 3 octet n ^:

5. After receiving the TAU Accept message, the UE starts the Session Management back-off timer corresponding to each APN in the congested state, indicating that the service request or connection request for the APN will not receive a response from the network.

 6. In the next Mobility Management process, for example, the TAU, Service Request process, if the network finds that there is a delay flag in the Bearer Contexts corresponding to the PDN connection in the UE, but the APN is no longer in the congestion state, the MME first initiates The EPS Session Mobility process sends a Create Session Request to the new SGW, and then the new SGW sends a Modify Bearer Request to the PGW.

 Example 2

 This embodiment is for an intra MME intra SGW without active flag TAU scenario.

In this process, during the TAU process, the SGW does not change, but the MME needs to trigger the signaling process to the packet data network gateway PGW, and the MME is in congestion even if the MME detects the APN corresponding to the PDN connection in the UE. In the state, the MME still accepts the TAU Request, and sets the session management back-off timer of the APN in the congestion state, and transmits the message to the UE through the TAU Accept message. For the message format, refer to the implementation manner in Embodiment 1.

 After receiving the timer, the UE starts the Session Management back-off timer corresponding to the APNs. When the UE wants to initiate a service request corresponding to an APN, it first checks whether the APN has a Session Management back-off timer, and whether the timer expires. If not, the UE should not initiate a request, otherwise it can.

 Based on the same inventive concept, an embodiment of the present invention further provides a mobility management entity device and a user device. Since the principle of solving the problem of these devices is similar to the congestion processing method in the MTC, the implementation of the devices may refer to the implementation of the method. , the repetition will not be repeated.

 4 is a schematic structural diagram of a mobility management entity device. As shown in the figure, the MME may include:

 The APN determining module 401 is configured to: after receiving the TAU Request message initiated by the UE, determine the subscription APN of the UE; the congestion determining module 402 is configured to determine the APN that is congested in the subscription APN;

 The indicating module 403 is configured to indicate, in the TAU Accept message of the returning UE, the APN that is congested in the subscribed APN, and the Session Management back-off timer that is allocated to the APN that is in congestion.

 In the implementation, the APN determining module may be further used to determine the implementation in the bearer contexts of the UE in the subscribed APN, and the MME may further include:

 The deferring module 404 is configured to determine that if there is a congested APN in the TAU process, and the SGW changes, the session management process to the PGW is postponed, the PGW is a PGW corresponding to the APN in the congestion; or, if in the TAU process The signaling process that the MME triggers to the PGW is required to cancel the signaling process that triggers the PGW.

 In the implementation, the deferred module may be further used to not send a Create Session Request to the SGW during the postponement of the Session Management process initiated to the PGW, and mark that the process is postponed.

 In the implementation, the MME may further include:

 The mobility management module 405 is configured to: when determining that the UE is in a certain Mobility Management process after initiating a session management back-off timer timeout of an APN, if the APN is no longer in congestion, perform 40 pairs that were previously deferred. The α3⁄4 APN Session Management process.

 In an implementation, the mobility management module may be further configured to: when determining that the UE has a delay flag in the Bearer Contexts corresponding to the PDN connection in the UE in the next Mobility Management process, determine that the UE is initiating a Session Management back of an APN. A Mobility Management process after the off timer expires.

FIG. 5 is a schematic structural diagram of a user equipment. As shown in the figure, the UE may include: The receiving module 501 is configured to receive a TAU Accept message that is returned to the UE, where the TAU Accept message indicates a congested APN in the UE's subscription APN and a Session Management back-off timer allocated to the congested APN.

 The setting module 502 is configured to set a Session Management back-off timer for the APN that is congested.

 In the implementation, the UE may further include:

 The service request module 503 is configured to determine an APN that is congested and not congested; select an APN that does not congest to initiate a service request, or initiate a service request after a Session Management back-off timer of the APN is timed out.

 For convenience of description, the various parts of the above described devices are described in terms of functions divided into various modules or units. Of course, the functions of the various modules or units may be implemented in one or more software or hardware in the practice of the invention.

 It can be seen from the above that the technical solution provided by the embodiment of the present invention can improve the irrationality of the prior art, and can reduce the signaling resource consumption in the network and ensure the normal service operation.

 Those skilled in the art will appreciate that embodiments of the present invention can be provided as a method, system, or computer program product. Accordingly, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment, or a combination of software and hardware. Moreover, the present invention can be embodied in the form of a computer program product embodied on one or more computer-usable storage interfaces (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer usable program code.

 The present invention has been described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (system), and computer program products according to embodiments of the invention. It will be understood that each process and/or block of the flowchart illustrations and/or FIG. These computer program instructions can be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing device to produce a machine for the execution of instructions for execution by a processor of a computer or other programmable data processing device. Means for implementing the functions specified in one or more of the flow or in a block or blocks of the flow chart.

 The computer program instructions can also be stored in a computer readable memory that can direct a computer or other programmable data processing device to operate in a particular manner, such that the instructions stored in the computer readable memory produce an article of manufacture comprising the instruction device. The apparatus implements the functions specified in one or more blocks of a flow or a flow and/or block diagram of the flowchart.

These computer program instructions can also be loaded onto a computer or other programmable data processing device such that a series of operational steps are performed on a computer or other programmable device to produce computer-implemented processing for execution on a computer or other programmable device. The instructions provide steps for implementing the functions specified in one or more of the flow or in a block or blocks of a flow diagram. Although the preferred embodiment of the invention has been described, it will be apparent to those skilled in the art that, Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and the modifications and

 It is apparent that those skilled in the art can make various modifications and variations to the invention without departing from the spirit and scope of the invention. Thus, it is intended that the present invention cover the modifications and modifications of the invention

Claims

Rights request  A congestion processing method in a machine type communication MTC, comprising the following steps: after receiving a tracking area update request TAU Request message initiated by a user equipment UE, the mobility management entity MME determines a subscription access point of the UE. Name APN;  The MME determines that the APN is congested in the subscribed APN;  The MME indicates in the TAU Accept message of the returning UE that the APN in the subscribed APN is congested, and the session management backoff timer that is indicated to be in the congested APN.  2. The method according to claim 1, wherein the MME determines that the APN in the APN in the bearer contexts of the UE in the subscribed APN of the UE is congested.  3. The method of claim 1, further comprising:  The MME determines that if there is a congested APN in the TAU process and the serving gateway SGW changes, the MME marks the session management process initiated to the PGW as being delayed, and the PGW is the corresponding PGW of the APN that is congested;  Or, the MME determines that, in the TAU process, when the MME is required to trigger the signaling process to the packet data network gateway PGW, the MME marks the signaling process triggered to the PGW as cancelled.  4. The method of claim 3, further comprising:  The MME determines that the UE is in a mobility management Mobility Management process after the timeout of the Session Management back-off timer of the APN is initiated, and the Bearer Contexts corresponding to the PDN connection in the UE is deferred, if the APN is no longer in congestion. , the MME restores the Session Management process for this APN.  5. A method for processing congestion in an MTC, comprising the steps of:  Receiving, by the UE, a TAU Accept message sent by the MME to the UE, where the TAU Accept message indicates a CPN that is congested in the APN of the UE and a session management backoff timer allocated for the congested APN;  The UE sets a Session Management back-off timer for the congested APN.  6. The method of claim 5, further comprising:  The UE determines the APN that is congested and not congested; The UE selects a non-congested APN to initiate a service request, or initiates a service request after the timeout of the congested APN's Session Management back-off timer expires. 7. A mobility management entity device, comprising:  An APN determining module, configured to: after receiving a TAU Request message initiated by the UE, determine a contracted APN of the UE; a congestion determining module, configured to determine a congested APN in the subscribed APN;  The indication module is configured to indicate, in the TAU Accept message of the returning UE, the APN that is congested in the subscribed APN, and the Session Management back-off timer that is indicated to be in the congested APN.  8. The apparatus according to claim 7, wherein the APN determining module is further configured to determine an APN in a bearer contexts of the UE in the subscribed APN.  9. The device according to claim 7, further comprising:  a delaying module, configured to determine that if there is a congested APN in the TAU process, and the SGW changes, the Session Management process initiated to the PGW is marked as being deferred, and the PGW is a PGW corresponding to the APN in the congestion; or, if In the TAU process, the MME is required to trigger a signaling process to the PGW, and the signaling process triggered to the PGW is marked as cancelled.  The device according to claim 9, further comprising:  The Mobility Management module is configured to determine that the UE is in a Mobility Management process after the timeout of the Session Management back-off timer of the APN is initiated, and the Bearer Contexts corresponding to the PDN connection in the UE is deferred. If it is no longer in congestion, the MME resumes the Session Management process for this APN.  11. A user equipment, comprising:  a receiving module, configured to receive a TAU Accept message returned by the MME to the UE, where the TAU Accept message indicates that the APN in the subscribed APN of the UE is congested and the session management back-off timer allocated for the congested APN ;  A setting module is configured to set a Session Management back-off timer for the APN that is congested.  The user equipment of claim 11, further comprising:  The service request module is configured to determine the APN that is congested and not congested; select the APN that is not congested to initiate a service request, or initiate a service request after the Session Management back-off timer of the APN is timed out.