CN101582884B - System and method for 3G data packet reorganization based on FPGA - Google Patents

Abstract

The invention discloses an FPGA-based 3G data packet recombination system and method. The system of the present invention includes an EMAC core module and a user interface module, wherein the user interface module includes: a message type processing module, a HASH module, an IMSI storage module, a read-write control module, an IMSI insertion module, and an IMSI non-null judgment module. The method of the present invention extracts the user identity information IMSI according to the control signaling protocol GTP-C between the SGSN and the GGSN, then stores the IMSI information according to the TEID-CP and TEID-DII, and combines the user's online and offline state information with the user identity information Bind and transmit to the back-end processing; and search the IMSI for the data packets in the user data protocol GTP-U according to the TEID-DII of the header, bind the user data and the IMSI to reassemble the data packets, and combine different user data packets according to the application layer Different protocol types are sent to the backend for processing. The invention improves the efficiency of the overall supervision system, and the speed is fast.

Description

3G data packet reassembly system and method based on FPGA

technical field

The invention relates to an FPGA-based 3G data packet recombination system and method, and belongs to the data recombination system and method in the field of TD-SCDMA network security.

Background technique

3G mobile communication technology mainly includes three standard systems: TD-SCDMA standard in China, WCDMA standard in Europe and Japan and CDMA2000 standard in the United States. The TD-SCDMA standard and WCDMA standard have inherited the original core network structure of GSM, and their data packets are uniformly encapsulated in the GTP protocol. Therefore, if all the GTP protocols are obtained, the core network data information of all mobile users can be monitored. The GTP protocol is divided into GTP-C and GTP-U. Among them, GTP-C is a user signaling protocol, and some signaling protocols include the International Mobile Subscriber Identity (IMSI). GTP-U encapsulates user data information, does not contain the IMSI that marks the user identity, and cannot unify user data and user information. However, in the monitoring system, the unity of user identity, user status and user data is required. Therefore, during the data collection process, the 3G core network data packets need to be reassembled through the connection hub TEID (tunnel identification number) between GTP-C and GTP-U.

At present, the binding and reorganization of user identity information, user status, and user data are usually implemented on a software platform. However, due to the supervision of a large number of users, it is necessary to dynamically access a large number of user identity information (IMSI). The software often uses a tree table in the data structure to implement. According to the test, the software realizes the binding of user data and user identity, and the processing speed It can only reach 150Mbps. However, the communication rate of 3G mobile communication is often as high as 1Gbps, and the use of software to process the binding of data user identity and user data cannot achieve the real-time purpose.

Contents of the invention

The technical problem to be solved by the present invention is to provide an FPGA-based 3G data packet recombination system and method for the defects in the prior art.

In order to achieve the above object, the present invention adopts the following technical solutions:

The FPGA-based 3G data packet reassembly system of the present invention is characterized in that it includes an EMAC core module and a user interface module, wherein the user interface module includes: a message type processing module, a HASH module, an IMSI storage module, a read-write control module, an IMSI insertion module, The IMSI non-empty judging module, the output of the message type processing module is connected in series with the HASH module, the read-write control module, the IMSI plug-in module, and the IMSI non-empty judging module, the output of the message type processing module is connected to the input of the IMSI plug-in module, HASH The output terminal of the module is connected to the input terminal of the IMSI storage module, the IMSI storage module is bidirectionally connected to the read-write control module, the input terminal of the message type processing module is connected to the output terminal of the EMAC core module, and the output terminal of the IMSI non-empty judgment module is connected to the EMAC core module input terminal.

The recombination method of the described 3G packet recombination system based on FPGA is characterized in that comprising the steps:

Step (1): adopt the receiving client interface of the EMAC soft core module to receive all 3G packets on the link of the gateway node GGSN and the support node SGSN;

Step (2): the 3G data packet described in the step (1) is judged to obtain the protocol type of the gateway node GGSN and the support node SGSN through the message type processing module:

When the protocol type between the gateway node GGSN and the support node SGSN is the control signaling protocol GTP-C, the flag bit 0 is inserted;

When the protocol type between the gateway node GGSN and the support node SGSN is the user data protocol GTP-U, insert flag 1;

Step (3): the data packet of the control signaling protocol GTP-C and the user data protocol GTP-U described in the step (2) is obtained through the HASH module to access the address of the IMSI;

Step (4): The address of accessing the IMSI described in step (3) is read or written to the IMSI information through the read-write control module:

a) When it is a data packet of the control signaling protocol GTP-C type, then judge the message type of the control signaling protocol GTP-C header: 1. when the message type of the control signaling protocol GTP-C header is establishment request information, Then store the IMSI into the address of the described access IMSI in step (3); 2. when the message type of the control signaling protocol GTP-C header is to set up request response information, then the data packet header of the control signaling protocol GTP-C type The internal TEID-CP obtains the IMSI new address through the HASH module to obtain the IMSI, and sends the control signaling protocol GTP-C type data packet to the upstream TEID-DII through the HASH module to obtain the IMSI new address, and stores the IMSI into the IMSI new address. ③ When the message type of the control signaling protocol GTP-C header is offline response information, the TEID-CP in the header of the data packet of the control signaling protocol GTP-C type is obtained through the HASH module to obtain the new address of the IMSI get IMSI;

b) When it is a data packet of the user data protocol GTP-U type, the TEID-DII of the data packet header of the user data protocol GTP-U type is obtained through the HASH module to obtain the IMSI new address to obtain the IMSI;

Step (5): Insert the IMSI information read out in step (4) into the user data packet and the user log-off and offline response information through the IMSI insertion module to obtain the reassembled data packet;

Step (6): pass the reorganized data described in step (5) through the IMSI non-null judgment module: when the IMSI part in the reassembled data packet is zero, the reassembled data packet is sent to the designated host as an abnormal packet for processing; If the IMSI part in the packet is not all zero, the reassembled data packet is input into the TCP/IP protocol stack as a new data load, and finally output through the sending client of the EMAC core module.

The invention provides an FPGA-based TD-SCDMA data packet recombination system and method. Since the core network of TD-SCDMA aggregates packet data from multiple base stations, a large amount of traffic data will greatly increase the difficulty of data packet reassembly. The FPGA-based TD-SCDMA data packet reassembly method utilizes the fast processing capability of the FPGA, extracts the user identity information IMSI according to the control signaling protocol GTP-C between the SGSN and the GGSN, and then stores it according to the TEID-CP and TEID-DII IMSI information, and the user's online and offline status information and user identity information are bound and transmitted to the backend for processing; and the data packet in the user data protocol GTP-U is searched for the IMSI according to the TEID-DII in the header, and the user data is bound to the IMSI Customize and reassemble data packets, and send different user data packets to the backend for processing according to different protocol types at the application layer. This reorganization method effectively improves the efficiency of the overall supervision system and is beneficial to the load balancing of the backend.

The invention adopts FPGA hardware programming to realize, and due to the high speed of hardware processing, the highest speed can reach 1.6Gbps, which can meet the demand for 3G supervision data processing.

Description of drawings

Fig. 1 is a schematic diagram of the packet domain structure of the TD-SCDMA core network;

Fig. 2 is the Gn interface protocol stack model;

Figure 3 is a schematic diagram of the working principle of TEID;

Figure 4 is a schematic diagram of the Virtex5 EMAC core module,

Fig. 5 is a schematic diagram of a data packet reorganization structure based on FPGA;

Figure 6 is a flow chart of FPGA-based packet reassembly

Fig. 7 is a schematic structural diagram of the user interface module.

Detailed ways

Below in conjunction with accompanying drawing, the technical scheme of invention is described in detail:

The position of the system used in the present invention in the TD-SCDMA packet domain network is shown in FIG. 1 .

As far as this system is concerned, the devices and communication links we consider are the SGSN and GGSN devices and the communication links between them.

The main role of the GPRS Serving Support Node (SGSN) is to record the current location information of the mobile station, and complete the sending and receiving of mobile packet data between the mobile station and the GGSN. At the same time, as an important part of the GPRS/WCDMA core network packet domain equipment, SGSN completes the routing and forwarding of packet data packets, mobility management, session management, logical link management, authentication and encryption, bill generation and output and other functions. The GRPS gateway node (GGSN) mainly acts as a gateway, which can convert the GPRS packet data packets in the core network, so that these packet data packets can be transmitted to the remote TCP/IP or X.25 network. It can be connected to many different data networks.

In addition, the interface between SGSN and GGSN is Gn/Gp interface, where Gn is used to describe the interface between SGSN and GGSN of the same PLMN, and Gp is used to describe the interface between SGSN and GGSN of different PLMNs. The Gn/Gp interface protocol stack is shown in Figure 2. The GTP protocol is based on the Gn/Gp interface of the 3G core network and is responsible for the transmission of data and signaling between the SGSN and the GGSN.

The GTP protocol is divided into control signaling protocol (GTP-C), user data protocol (GTP-U), and billing protocol (GTP’). The GTP protocol analysis here mainly refers to GTP-C and GTP-U. If network supervision is to be implemented, user data and user identity information are two essential aspects, but not all information in the GTP protocol contains user identity IMSI information. Among them, the user's first online request information (Create PDP Request) includes user identity IMSI (International Mobile Subscriber Identity) information. In order to achieve the binding of user data, user log-off and offline information, and user identity, it is necessary to reassemble the 3G core network data packets by analyzing the GTP protocol. The data reorganization mentioned here is very different from the reorganization of IP fragments in the ordinary sense. The reorganization here is to extract and store the IMSI information that marks the user identity from the online request signaling, and then insert the IMSI information into the Into the user's online and offline response information and user data packet, so as to obtain a data packet containing user identity information, and send it to the background for processing.

The only element in the GTP protocol that associates user control signaling with user data is the TEID. The uplink (SGSN to GGSN direction) link and downlink (GGSN to SGSN direction) link in the core network use different TEIDs, and user data information and control signaling use different TEIDs, so a user uses TEIDs during the entire session. The four TEIDs are defined as follows: TEID_UP_C (used for uplink control signaling), TEID_UP_U (used for uplink user data information), TEID_DOWN_C (used for downlink control signaling), and TEID_DOWN_U (used for downlink user data information). The specific working principle of TEID is shown in Fig. 3 . During the process of acquiring data, three TEID addresses, TEID_DOWN_C, TEID_DOWN_U, and TEID_UP_U, need to be used to calculate the IMSI information.

Each module is described below.

1. EMAC core module

The hardware platform used for improving the invention method is a v5lxtPCI development board. There are two tri-state Ethernet ports and two Gigabit electrical ports on the platform. The FPGA chip is V5LX50T, which contains 4 built-in tri-state Ethernet MAC modules (TEMAC). The Virtex5 EMAC core module is shown in Figure 4. The EMAC core is mainly divided into the following interfaces: receiving client (RX Client), sending client (TX Client), flow control interface (Flow Control), generic host bus interface (Generic Host Bus), DCR bus interface (DCR Bus ), physical layer interface (Physical Interface), GTP transceiver (GTPTransceiver), management data input/output interface (Management Data I/O). The following is a brief introduction to each interface of the Ethernet core:

(1) The sending/receiving client is mainly to connect the user transceiver end with the Ethernet MAC transceiver engine;

(2) The design of the flow control interface complies with Clause 31 of IEEE 802.3;

(3) The universal host bus interface and the DCR bus interface are two control optional bus interfaces with the Ethernet MAC host interface, and any one of them can be selected through the signal line of the Ethernet MAC. In the case of MAC cooperation, it is ideal to choose the DCR bus interface, and the host bus interface is more suitable for the situation where the FPGA logic directly controls the Ethernet MAC;

(4) The physical layer interface can be connected to any physical layer device that conforms to the Ethernet physical layer standard BASE-T, BASE-X; when the physical layer interface is configured as 1000BASE-X or SGMII mode, it needs to use the Ethernet MAC internal The PCS/PMA sublayer module is connected with the GTP transceiver interface of the Ethernet MAC. This GTP transceiver interface connects directly to the GTP transceiver outside the Ethernet MAC to implement the 1000BASE-X physical layer.

2. User interface module

The FPGA-based data packet reassembly structure is shown in Figure 5. Among them, the FPGA module is connected in series between SGSN and GGSN, and can capture all data packets passing through the 3G core network.

The entire data packet reassembly process first judges the type of GTP data packet obtained from the core network according to the UDP port number (the GTP-U port number is 2152, and the GTP-C port number is 2123), and then retrieves the user IMSI according to the TEID in the data packet header. The IMSI information is inserted into the user data to realize data packet reassembly. The packet reassembly process is shown in Figure 6:

Due to the large number of supervised users, during the data reorganization process, the binding of user data and user characteristic information requires continuous dynamic access to IMSI information. Therefore, to ensure real-time processing, the bottleneck part in the entire data packet processing process - The dynamic access of IMSI requires finding a way to achieve line speed processing.

The data packet reassembly module is shown in Figure 7, which mainly includes a message type processing module, a HASH module, an IMSI storage module, a read-write control module, an IMSI insertion module, and an IMSI non-null judgment module. The functions of each module are briefly described below.

(1) Message type processing module: the message type processing module is used to judge the type of the GTP protocol. And make different marks for GTP-C and GTP-U respectively, so that they can be distinguished during background processing.

(2) HASH module: HASH module is the most critical part in the whole module, it mainly realizes the calculation of IMSI access address. Since the Create PDP Request signaling containing IMSI information (signaling is information and does not need to be repeated) is associated with user online and offline response information and user data information through TEID, so in order to meet the dynamic access of a large number of users to IMSI, it is necessary Find the access method directly associated with TEID and IMSI. According to this idea, this paper proposes an FPGA-based Hash algorithm to realize address calculation. The algorithm process mainly uses the following Hash function: h(x, y)=ax+y (a is a power of 2, x, y ∈ Z ⁺ ) decomposes TEID by calling this Hash function multiple times to obtain different addressing signals. The specific data reorganization search algorithm process is: (assuming that the three TEID values of the user are A, B, and C respectively)

1. XOR the three TEIDs of the user with the corresponding base TEID (values are set to A ₁ , B ₁ , C ₁ ), and the obtained values are recorded as A ₂ , B ₂ , and C ₂ ;

2. Decompose A ₁ , B ₁ , and C ₁ respectively according to the HASH function: h(x, y)=2 ¹⁶ x+y (0≤x≤2 ¹⁷ -1, 0≤y≤2 ¹⁵ -1). Find the values of coefficients x and y, take the processing of _A1 as an example, set the coefficients obtained by _A1 as E and F respectively;

3. Decompose the value of E according to h(x, y)=2 ⁸ x+y (0≤x≤2 ⁸ -1, 0≤y≤2 ⁸ -1). Find the values of coefficients x and y, and record them as G and H respectively; set the value of F according to h(x, y)=2 ⁸ x+y (0≤x≤2 ⁸ -1, 0≤y≤2 ⁸ - 1) Decomposition. Find the values of the coefficients x and y, and record them as I and J respectively;

4. Exclusive OR the G and H, and record the obtained value as K, do 3 times of J for cyclic shift, and the obtained value is L.

5. The obtained I is used as the chip select signal of the RAM, L is used as the initial address value; the value of K is used as the storage and search of the IMSI of the out-of-range user.

The following is a brief comment on the algorithm. The base TEID in the first step is the value of the TEID of any user randomly selected, and the base TEID remains unchanged for T time. The reason for this is that in reality, the allocation of user TEID is similar to the allocation of user IP, and has an overall upward trend. If all users are XORed with the TEID of the same user at time T, the TEID of different users can be combined The difference of , from the original distribution in the low position of the TEID moving in different positions, where the selection of T has a great influence on the collision probability. In this way, a large number of users can be distinguished with a small number of bits. The XOR of this step can be realized with a simple hardware description language, and the operation of this step requires two time cycles.

The second step is to use the HASH function to decompose. Here is a brief explanation of the selection of the function coefficients. In the second step, the coefficient 2 ¹⁶ is selected to decompose the digits of E and F to 16 bits. The purpose of this choice is mainly to pave the way for the decomposition of E and F in the third step. The decomposition of this step is also very simple to implement with a hardware description language, and the operation of this step requires a time period.

For the decomposition of F in the third step, the coefficient is selected as 2 ⁸ , and the digits of I and J obtained from the decomposition are 8 bits. The purpose of doing this is based on the number of monitoring users. The number of online users is 10,000, and the IMSI of each user is 8Byte. Since a user needs 3 TEIDs to associate with its IMSI, the required storage space is 10 ⁴ *3*8*8bit≈1.5*2 ²¹ Mbit, the size of the BRAM we use to store IMSI is 2 ¹¹ * 2 ^3. We need 28 such RAMs. The I obtained in this way is used as a chip select signal, and J is shifted to the left by 3 bits to obtain an 11-bit address signal. The capacity is 8 Byte. to store a user's IMSI. The hardware language implementation of the operation is the same as the second step. This operation takes a period of time

The fourth step operation is simple and easy to understand without much explanation. This operation takes a period of time

The out-of-range in the fifth step means that within the time T, the distribution trend of the total TEID of users is increasing, and then the difference can be transferred to a low position by the XOR of the base TEID in the first step, but because the TEID distribution has In some special cases, the variation range may exceed the selected number of digits. This special case needs to be considered, so the TEID in special cases is called an out-of-range user, and the IMSI of these users is stored in a RAM separately. In practice, such out-of-range users are rare. The storage or reading of the final IMSI takes eight time cycles.

(3) IMSI storage module: The memory used by the IMSI storage module is BRAM.

(4) Read-write control module: The read-write control module takes action according to the sign made by the message type processing module. If it is Create PDP Request signaling, it writes RAM according to the address calculated by the Hash module. If it is a user data packet or user The online and offline response information is read from the RAM according to the address calculated by the Hash module.

(5) IMSI insertion module: The IMSI insertion module mainly completes the insertion of the read IMSI information into the user log-off response information and user data information. For user log-off and offline response information, insert the IMSI into the first 8Byte of the GTP protocol header, and if it is user data information, insert the IMSI into the first 8Byte of the data payload.

(6) IMSI non-empty module: The IMSI non-empty module is used to determine whether the inserted IMSI part is empty. If the IMSI information of a certain user is not stored due to the delay in processing, or network packet loss, etc., the IMSI insertion part in the user's log-off and offline response information and user data information will all be zero. If the IMSI non-empty module judges that this part is all zero, the user data packet will be sent to the designated host as an abnormal packet; if not all zero, the reassembled data packet will be input to the TCP/IP protocol stack as a new data load In the process, generate a TCP/IP packet and transmit it to the background for processing.

Claims (3)

1. the 3G data packet reorganization based on FPGA is united; It is characterized in that comprising ethernet mac EMAC core module and Subscriber Interface Module SIM; Wherein Subscriber Interface Module SIM comprises: type of message processing module, HASH module, IMSI memory module, read-write control module, IMSI insert module, IMSI non-NULL judge module; The output of type of message processing module is connected in series HASH module, read-write control module, IMSI insert module, IMSI non-NULL judge module successively; The input of the output termination IMSI insert module of type of message processing module, the input of the output termination IMSI memory module of HASH module, control module is two-way is connected with read-write for the IMSI memory module; The output of the input termination EMAC core module of type of message processing module, the input of the output termination EMAC core module of IMSI non-NULL judge module.

2. a recombination method of uniting based on the 3G data packet reorganization of FPGA as claimed in claim 1 is characterized in that comprising the steps:

Step (1): all the 3G packets on the reception client-side interface reception gateway node GGSN of employing EMAC core module and the link of support node SGSN;

Step (2): the described 3G packet of step (1) is judged the protocol type that obtains gateway node GGSN and support node SGSN through the type of message processing module:

When the protocol type of gateway node GGSN and support node SGSN for control signaling protocol GTP-C, then insert flag bit 0;

When the protocol type of gateway node GGSN and support node SGSN is User Data Protocol GTP-U, then insert flag bit 1;

Step (3): the address that the packet of step (2) described control signaling protocol GTP-C and User Data Protocol GTP-U is obtained access IMSI through the HASH module;

Step (4): the address of the said access IMSI of step (3) is read IMSI information through the read-write control module or write:

A) when packet for control signaling protocol GTP-C type; Then judge the type of message of control signaling protocol GTP-C head: 1. the type of message when control signaling protocol GTP-C head is to set up solicited message, then IMSI is stored the address of progressive rapid (3) said access IMSI; 2. the type of message when control signaling protocol GTP-C head is to set up the request response message; The tunnel mark number TEID-CP that then will control the packet head of signaling protocol GTP-C type obtains getting the new address of IMSI through the HASH module and obtains IMSI; And the up TEID-DII of the packet that will control signaling protocol GTP-C type obtains depositing the new address of IMSI through the HASH module, IMSI stored into deposit in the new address of IMSI; 3. the type of message when control signaling protocol GTP-C head is the response message that rolls off the production line, and the TEID-CP that then will control the packet head of signaling protocol GTP-C type obtains getting the new address of IMSI through the HASH module and obtains IMSI;

B), then the TEID-DII of the packet head of User Data Protocol GTP-U type is obtained getting the new address of IMSI through the HASH module and obtain IMSI when the packet that is User Data Protocol GTP-U type;

Step (5): the IMSI information via IMSI insert module of reading in the step (4) is inserted in user data package and the user's going on line or off line response message removes to obtain the recombination data bag;

Step (6): with the described recombination data of step (5) through IMSI non-NULL judge module: the IMSI part is zero entirely in the recombination data bag, then this recombination data bag is mail to given host as unusual bag processing; The IMSI part is not zero entirely in the recombination data bag, and then the packet of reorganization is input in the ICP/IP protocol stack as new data payload and goes, and exports through the transmission client of EMAC core module at last.

3. the recombination method of the 3G data packet reorganization system based on FPGA according to claim 2, it is characterized in that comprising in the HASH module HASH function: h (x, y)=ax+y, wherein a is 2 power, x, y are that positive integer is the coefficient of HASH function.

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