CN1710967A - Retransmission method of protocol data unit - Google Patents

Abstract

The invention discloses a forwarding method of a protocol data unit. After a general packet radio service (GPRS) service support node (SGSN) receives a service request from a user equipment (UE), it allocates a packet data protocol (PDP) with a direction identification bit. ) context index bit of the GPRS Tunneling Protocol (GTP) Tunnel Endpoint Identifier (TEID) value to establish the GTP tunnel required for the service; when the SGSN receives a protocol data unit (G-PDU) from the GTP tunnel, it The value determines the forwarding direction of the G-PDU, determines the target network node for message forwarding, and then finds the address of the forwarding target network node in the PDP context according to the PDP context index value, and forwards the G-PDU to the target network node according to the address. The application of the invention can reduce the overhead of the system and improve the forwarding efficiency of the G-PDU in the SGSN.

Description

A forwarding method of a protocol data unit

technical field

The invention relates to the technical field of General Radio Packet Service (GPRS) tunnel bearing in a Wideband Code Division Multiple Access (WCDMA) communication system, in particular to a protocol data unit forwarding method in a GTP tunnel.

Background technique

In the WCDMA core network (CN), the GPRS tunneling protocol (GTP) technology is applied to the data and signaling transmission of the GTP control plane and the GTP user plane between the Universal Mobile Telecommunications System (UMTS)/GPRS core network GPRS support node (GSN), Among them, GSN includes GPRS Serving Support Node (SGSN) and GPRS Gateway Support Node (GGSN). At the same time, the charging protocol GTP' also uses the GTP technology. In the user plane Iu interface between the radio network controller (RNC) and the SGSN, the GTP user (GTP-U) protocol is used as the data transmission bearer technology.

GPRS system logical structure is shown in Fig. 1 with reference to, and SGSN132 in CN130 is connected with RNC122 in Universal Mobile Communication System Terrestrial Radio Access Network (UTRAN) 120 by Iu interface, and then RNC122 is connected with base station (Node B) 121 by Iub interface The Node B121 connects with the UE110 through the Uu plane, establishes the connection between the SGSN132 and the UE110 through the logic control protocol (LLC), and realizes the transmission and bearing of user data by establishing the GTP tunnel between the SGSN132 and the RNC122.

In CN130, the interconnection between SGSN132 and SGSN132 is realized through the Gn/Gp interface, and user data exchange is realized by establishing a GTP tunnel; A channel is established between the Internet (INTERNET) 142 to provide the interconnection between the UE 110 and the Internet 142; the SGSN 132 can communicate with the public switched telephone network (PSTN) and the integrated services digital network ( ISDN) and other 141 to establish connections; through the Gs interface, SGSN132 sends address information to Mobile Switching Center/Visitor Location Register (MSC/VLR) 131, and receives paging requests from MSC/VLR131, realizing packet-type services and non-packet-type services associated.

The home location register (HLR) 134 stores GPRS user data and routing information, and the SGSN132 can access the HLR134 via the Gn interface or the GGSN135 via the Gc interface.

Through the above network structure, the communication between UE110 and external network 140 is established, and the main function of SGSN in the network is to record the current location information of UE, and realize the message receiving and sending between RNC, SGSN and GGSN. When the UE initiates a service request to the SGSN, the SGSN will assign the Tunnel Endpoint Identifier (TEID) value to the communication network node RNC, GGSN or SGSN required for the service according to the service type, and establish the GTP tunnel required for GTP packet forwarding. As a tunnel identifier, TEID is used to identify the data bearing tunnel between GSNs. At the same time when the service is established, a packet data protocol (PDP) context will be created for the service in RNC, SGSN, and GGSN, and the PDP context will be recorded in the local PDP context list. The PDP context records a series of related parameters such as the user access point name (APN), serial number, GGSN/SGSN/RNC network protocol (IP) address, service quality (Qos) and other related parameters of the user service, providing for GTP message forwarding information.

After the SGSN receives the GTP message, it judges whether the received GTP message is a GTP protocol data unit (G-PDU) by checking the message type (Message Type) in the message, if not, the message is a locally received message The text does not need to be forwarded. If it is a G-PDU, it needs to be forwarded. Determine the forwarding direction of the G-PDU by checking the TEID value in the G-PDU, and forward the G-PDU to the target address according to the target address required for G-PDU forwarding recorded in the PDP context.

For the TEID allocation algorithm, the general practice is to start from 0 and allocate one by one. When all 1s are reached, the allocation starts from 0. If there is a PDP release during the period, the released TEID value is recycled for the next allocation. Since the RNC only has an uplink GTP tunnel with the SGSN, and the GGSN only has a downlink GTP tunnel with the SGSN, corresponding to the same PDP context, they have only one direction of the GTP tunnel. For SGSN, there is GTP message exchange with GGSN, RNC, and SGSN, that is, at the same time, there may be corresponding to the same PDP context, and SGSN needs to establish GTP tunnels with GGSN, RNC, and SGSN respectively. If the GTP tunnels between the SGSN and the GGSN, RNC, and SGSN are simply assigned the same value, when the SGSN receives the G-PDU message, it can judge whether the message is an uplink message or an uplink message according to the source IP address of the input GTP message. The downlink message determines the forwarding target network node of the message.

With this method, each time the SGSN receives a G-PDU message, it not only needs to find the PDP context according to the TEID value, but also needs to judge whether the message is an uplink message or an uplink message according to the IP address of the RNC/GGSN saved in the PDP context. Downlink packets affect forwarding efficiency. Moreover, the GGSN IP address in the PDP context is only the destination IP address of the message sent by the SGSN to the GGSN, and does not indicate that this address is the source address of the message sent by the GGSN to the SGSN. When the source address of the message does not match the GGSN address stored in the PDP context, the SGSN cannot determine whether the message is an uplink message or a downlink message. If the UE performs radio network subsystem service redistribution (SRNSRelocation) between SGSNs, the Forward Relocation Request (Forward Relocation Request) message sent by the originally accessed SGSN of the UE to the newly accessed SGSN does not contain the original connection information. In this way, when the newly accessed SGSN receives the message sent by the originally accessed SGSN, it cannot determine the direction of the message.

In the prior art, in order to determine the direction of the message received by the SGSN, the GTP tunnel between the SGSN and the GGSN, RNC, and SGSN is simply assigned to different TEID values, and an index table is established for the TEID, and each TEID is recorded in the table. GTP packet direction and PDP context index corresponding to the TEID value. When a G-PDU is received, look up the direction of the GTP message and the PDP context index recorded in the index table according to the TEID value, then find the PDP context according to the PDP context index, take out the G-PDU forwarding target address, and forward the G-PDU to target address. The specific G-PDU forwarding process is shown in Figure 2:

Step 201: The SGSN assigns TEID values to the GTP tunnels between the RNC and the SGSN, between the GGSN and the SGSN, and between the SGSN and the SGSN, respectively, establishes an index table for the TEID values, and records the GTP message direction and direction corresponding to each TEID value. PDP context index.

For example, the index of the PDP context created in GGSN, SGSN, and RNC is PDP context 2, and the TEID value of the GTP tunnel between RNC and SGSN is allocated as 1000; the TEID value of the GTP tunnel between GGSN and SGSN is allocated as 1001; The GTP tunnel TEID allocation between the GTP tunnels is 1002, then the corresponding relationship between the TEID value recorded in the index table and the message direction and PDP context index is shown in Figure 3: the message direction from RNC to SGSN is uplink, corresponding to RNC and The TEID value of the GTP tunnel between SGSNs is 1000, which records the direction of GTP packets as uplink, and the PDP context index is PDP context 2; The direction of the message is downlink, and the PDP context index is PDP context 2; the direction of the message from SGSN to SGSN is handover, corresponding to the GTP tunnel TEID value 1002 between SGSN and SGSN, and the direction of the GTP message is handover, and the PDP context index is PDP context 2.

When a G-PDU is received, after finding the corresponding PDP context index in the index table as PDP context 2 according to the TEID value, you can directly go to the PDP context list to search for the G-PDU forwarding record recorded in the PDP context whose index is PDP context 2 Parameters are required.

After allocating TEID values, the index table records the GTP message direction and PDP context index corresponding to each TEID value, establishes a GTP tunnel, and starts receiving and forwarding GTP messages.

Steps 202-203: SGSN receives the GTP message, checks the message type in the message, and judges whether the GTP message is a G-PDU, if not, receives the message locally, does not need to forward the message, and exits the forwarding process ; If it is a G-PDU, the message needs to be forwarded, go to step 204.

Steps 204-205: Check the index table according to the TEID value in the G-PDU, and determine whether the TEID value is an uplink TEID value, a downlink TEID value, or a switching TEID value. If the TEID value is the uplink TEID, then the forwarding target is GGSN, proceed to step 206; if the TEID value is the downlink TEID value, then the forwarding target is RNC, proceed to step 207; if the TEID value is the switch TEID value, then the forwarding target is RNC, proceed Step 208.

Step 206: Check the PDP context index corresponding to the uplink TEID value in the index table, and then go to step 209.

Step 207: Check the PDP context index corresponding to the downlink TEID value in the index table, and then go to step 210.

Step 208: Check the PDP context index corresponding to the switching TEID value in the index table, and then go to step 211.

Step 209: Find the target GGSN address in the PDP context according to the PDP context index corresponding to the uplink TEID value, and then go to step 212.

Step 210: Find the target RNC address in the PDP context according to the PDP context index corresponding to the downlink TEID value, and then go to step 213.

Step 211: Find the target RNC address in the PDP context according to the PDP context index corresponding to the handover TEID value, and then go to step 214.

Step 212: forward the uplink G-PDU to the target GGSN address, and complete the forwarding process of an uplink G-PDU message.

Step 213: forward the downlink G-PDU to the address of the target RNC, and complete the forwarding process of a downlink G-PDU message.

Step 214: forward the handover G-PDU to the target RNC address, and complete a handover G-PDU message forwarding process.

According to the above method, when establishing a GTP tunnel, it is necessary to establish an index table for the TEID of the GTP tunnel, and record the message direction and PDP context index corresponding to each TEID in the index table. When the SGSN receives the G-PDU message, it needs to check the message direction and PDP context index corresponding to the TEID of the received G-PDU in the index table to determine the forwarding target network node of the G-PDU, and then according to the PDP The context index finds the address of the forwarding target network node in the PDP context, which increases the system overhead and reduces the forwarding efficiency of the G-PDU in the SGSN.

Contents of the invention

In view of this, the main purpose of the present invention is to provide a protocol data unit forwarding method, reduce system overhead, and improve G-PDU forwarding efficiency in SGSN.

According to above-mentioned object, the present invention provides a kind of forwarding method of protocol data unit, and this method comprises the following steps:

A, when setting up the GTP tunnel, assign the TEID value with the direction identification bit and the packet data protocol PDP context index bit to the GTP tunnel;

B. After receiving the G-PDU, determine the message forwarding direction according to the direction identification bit in the TEID value of the G-PDU, and determine the target network node for message forwarding;

C. Find the address of the target network node in the PDP context determined in step B according to the PDP context index value in the TEID, and forward the G-PDU to the target network node according to the address.

In the method, the step A is specifically: the general packet radio service GPRS service support node SGSN provides the GTP tunnel between the SGSN and the GPRS gateway support node GGSN, between the SGSN and the radio network controller RNC, between the SGSN and the SGSN, Assign the TEID value with the direction identification bit and the PDP context index bit respectively, and establish the GTP tunnel;

In step B, after receiving the G-PDU, the SGSN determines the forwarding direction of the G-PDU according to the direction identification bit of the TEID in the G-PDU, and determines the forwarding target network node.

The direction identification bit of the TEID value in the step A may be two bits; in step B, the forwarding direction of the G-PDU is determined according to the two direction identification bits of the TEID value.

Further, the direction identification bit of the TEID value in the step A is 20 to 21 bits; in step B, the forwarding direction of the G-PDU is determined according to the 20 to 21 direction identification bits of the TEID value.

The PDP context identification bit of the TEID value in the step A is 0 to 19 bits; in step C, the PDP context is searched according to the PDP context index value of the TEID value 0 to 19 bits.

It can be seen from the above scheme that when GTP tunnels are established, different GTP tunnels are assigned TEID values with direction identification bits and PDP context index bits, so that when a G-PDU is received, the TEID value in the TEID value of the G-PDU The direction identification bit determines the message forwarding direction, judges whether the target network node for message forwarding is RNC or SGSN, and then directly finds the target network node address for G-PDU forwarding in the PDP context according to the PDP context index value in the TEID, according to the address, Forward the G-PDU to the target network node. In this way, there is no need to establish index tables for different TEIDs in order to determine the direction of the GTP message, which reduces the steps of checking the index table after receiving the G-PDU message to find the message forwarding direction and PDP context index corresponding to the TEID , reducing system overhead and improving the forwarding efficiency of G-PDU in SGSN.

Description of drawings

Fig. 1 is a logical structural diagram of the GPRS system;

Fig. 2 is the forwarding flowchart of G-PDU in the prior art;

Fig. 3 is a schematic diagram of the corresponding relationship between the TEID value and the message direction and the PDP context index in the index table;

FIG. 4 is a flowchart of G-PDU forwarding according to an embodiment of the present invention;

FIG. 5 is a schematic diagram of a method for assigning TEID values according to an embodiment of the present invention.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the following examples are given and the present invention is further described in detail with reference to the accompanying drawings.

The core idea of the present invention is: when establishing a GTP tunnel, assign a TEID value having a direction identification bit and a PDP context index bit to different GTP tunnels, so that after receiving a G-PDU, the message is determined according to the direction identification bit in the TEID value The forwarding direction determines the target network node for message forwarding, and then finds the address of the target network node for message forwarding in the PDP context according to the PDP context index value in the TEID, and forwards the G-PDU to the target network node according to the address.

Give a preferred embodiment of the present invention. When the UE redistributes radio network subsystem services between SGSNs, the newly accessed SGSN needs to establish a GTP tunnel with the original SGSN accessed by the UE to obtain management information for the UE and create a new PDP context. At the same time, in order to serve the UE, the new SGSN also needs to establish GTP tunnels with the GGSN and the RNC to receive and send GTP messages. The new SGSN performs TEID value distribution and GTP packet forwarding process for each established GTP tunnel as shown in Figure 4:

Step 401: The SGSN assigns a TEID value to each GTP tunnel. The distribution method of TEID value is shown in Figure 5. First, use the 0 to 19 bits of the TEID value as the PDP context index bits, fill in the PDP context index value created by the SGSN for the service, and then use the 20 to 21 bits of the TEID value as the PDP context index bits. The direction identification bit of the GTP packet, fill in the direction identification value. Fill in the direction identification bit of the GTP tunnel between the RNC and the SGSN with 00, indicating that the direction of the GTP message received by the SGSN from the RNC is uplink; fill in the direction identification bit of the GTP tunnel between the GGSN and the SGSN with 01, indicating that the direction of the GTP message received by the SGSN is uplink; The direction of the GTP message from the GGSN is downlink; the direction identifier bit of the GTP tunnel between the SGSN originally accessed by the UE and the SGSN is filled with 10, indicating that the direction of the GTP message received by the SGSN from the SGSN originally accessed by the UE is downlink handover. After the TEID value is allocated, the GTP tunnel required for GTP packet forwarding is established.

Steps 402-403: The SGSN receives the GTP message, checks the message type in the GTP message, and judges whether the received GTP message is a G-PDU. If it is not a G-PDU, the GTP message is a locally received message and does not need to be forwarded, and the forwarding process is exited; if it is a G-PDU, the message needs to be forwarded, and step 404 is performed.

Step 404: Determine whether the 20 to 21 two-digit direction identification value of the TEID in the G-PDU is 00, 01, or 10. If it is 00, the received G-PDU is an uplink message, and the forwarding target is GGSN, then proceed to step 405; if it is 01, the received G-PDU is a downlink message, and the forwarding target is RNC, then perform step 406; If it is 10, the received G-PDU is a downlink handover message, and the forwarding target is RNC, then go to step 407.

Step 405: Find the PDP context in the PDP context list according to the 0 to 19 PDP context index value of the TEID in the G-PDU, take out the GGSN address of the uplink G-PDU forwarding target in the PDP context, and then proceed to step 408.

Step 406: Find the PDP context in the PDP context list according to the PDP context index value of 0 to 19 bits of the TEID, take out the RNC address of the downlink G-PDU forwarding target in the PDP context, and then proceed to step 409.

Step 406: Find the PDP context in the PDP context list according to the PDP context index value of 0 to 19 bits of the TEID, take out the RNC address of the downlink switching G-PDU forwarding target in the PDP context, and then proceed to step 410.

Step 417: forward the uplink G-PDU to the target GGSN, and complete an uplink G-PDU forwarding process.

Step 416: forward the downlink G-PDU to the target RNC, and complete a downlink G-PDU forwarding process.

Step 417: Forward the downlink handover G-PDU to the target RNC, and complete a forwarding process of the downlink handover G-PDU.

In the above-mentioned embodiment, when setting up the required GTP tunnel for receiving and sending the GTP message, the SGSN assigns 20 to 21 bits as the direction identification bit and 0 to 19 bits as the TEID value of the PDP context index bit to different GTP tunnels. After receiving the G-PDU, the SGSN determines the forwarding direction of the G-PDU according to the value of the 20 to 21 bits in the TEID, determines the target network node for message forwarding, and then according to the PDP context index of the 0 to 19 bits in the TEID value to find the target network node address in the PDP context, and forward the G-PDU to the target network node according to the address. In this way, there is no need to build an index table for the TEID, which reduces the need to check the TEID index table to determine the direction of the message and find The step of PDP context index reduces system overhead and improves the forwarding efficiency of G-PDU.

The preferred embodiments cited above have further described the purpose, technical solutions and advantages of the present invention in detail. It should be understood that the above descriptions are only examples of the present invention and are not intended to limit the present invention. Any modification, equivalent replacement, etc. within the spirit and principle of the present invention shall be included within the scope of the present invention.

Claims (5)

1, a kind of retransmission method of protocol Data Unit is characterized in that comprising following steps:

A, when setting up GPRS tunnel protocol GTP tunnel, distribute termination point of a tunnel sign TEID value to GTP tunnel with direction signs position and packet data protocol PDP Context index bit;

B, receive GTP user data cell G-PDU after, determine the message routing direction according to the direction signs position in the TEID value of G-PDU, judge the target network node that message is transmitted;

C, find the address of the target network node of judging by step B in the PDP Context, G-PDU is forwarded to target network node according to this address according to the PDP Context index value among the TEID.

2, the method for claim 1, it is characterized in that, described steps A is: general packet radio service gprs serving GPRS support node SGSN gives between SGSN and the GGSN GGSN, the GTP tunnel between SGSN and the radio network controller (RNC), between SGSN and the SGSN, distribute respectively to have the TEID value of direction signs position and PDP Context index bit, set up GTP tunnel;

Among the step B, after SGSN receives G-PDU, determine the routing direction of G-PDU, judge the target network node of forwarding according to the direction signs position of TEID among the G-PDU.

3, the method for claim 1 is characterized in that, the direction signs position of the value of TEID described in the steps A is two;

Determine the routing direction of G-PDU among the step B according to two direction signs positions of TEID value.

4, the method for claim 1 is characterized in that, the direction signs position of the value of TEID described in the steps A is 20 to 21 two;

Determine the routing direction of G-PDU among the step B according to 20 to 21 two direction signs positions of TEID value.

As claim 1,3 or 4 described methods, it is characterized in that 5, the PDP Context sign position of the value of TEID described in the steps A is 0 to 19;

0 to 19 PDP Context index value according to the TEID value among the step C is searched PDP Context.

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