Before introducing the protocols of the A interface, let us first review the model of the GSM signaling system:
Figure4-1 Signaling model of the GSM system
The A interface can be used to transfer two kinds of messages: BSSMAP message and DTAP message. Where, the BSSMAP message is responsible for the service flow control, which needs the processing of the corresponding interface functional module of the A interface. For the DTAP message, the A interface is equivalent to a transmission channel. From the NSS to the BSS, the DTAP message is directly transferred to the radio channels; while from the BSS to the NSS, the DTAP message is transferred to the corresponding function processing unit. For the A interface, the DTAP message is transparent.
The A interface is based upon the MTP and SCCP of SS7. The structure model is shown in Figure 4-2:
Figure4-2 Protocol structure of A interface
On the A interface, the point-to-point connection is used and various kinds of service and control information are transferred between the MSC and the BSS. For the implementation mode, please first set the signaling point codes at the two ends of the interface, and the direct addressing mode (DPC + SSN) is used between them so that the addressing mode is simplified at most and the network architecture is simpler.
2. BSSAP
The Base Station Subsystem Application Part (BSSAP) is located on the upper layer of the SCCP. The BSSAP of the GSM system includes the DTAP and the BSSMAP, with additional the allocation function. Its architecture is shown in Figure 4-3:
Figure4-3 BSSAP architecture
1) Allocation function
The allocation sublayer between the SCCP and the L3 implements the following functions:
(a) Differentiating the DTAP and BSSMAP messages.
(b) Allocating the DTAP messages from the MSC to the L2 access point of each radio link.
(c) Converging the DTAP messages received from the L2 access point of each radio link to the signaling link of the A interface.
The protocol of this sublayer only simply includes 1-octet or 2-octet data unit. Each SCCP subscriber data field should include an allocation data unit to serve as the initial tag, then include the length indication and the BSSMAP and DTAP messages of L3. The differences between the DTAP and the BSSMAP are shown in Figure 4-4:
Figure4-4 BSSMAP and DTAP message structure
2) Transmission of DTAP messages
The DTAP is responsible for transparent transmission of L3 messages from an MS to the MSC or from the MSC to the MS. The BSS will not make any analysis of the contents. The Class-2 service (basic connection-oriented class) of the SCCP is used for transmission between the BSS and the MSC.
The subscriber data field includes the allocation data unit, length indication and actual L3 message. Where, the allocation data unit includes two parameters: Discrimination parameter and Data Link Connection Identifier (DLCI) parameter.
In this case, the discrimination parameter is set as transparent transmission code as follows:
Figure4-5 Discrimination parameter code of DTAP message
In the messages sent from the MSC to the BSS, the parameter DLCI is used to indicate the data link type applied to the radio interface; while in the messages sent from the BSS to the MSC, it is used to indicate the data link type of generating the data on the radio interface.
3) Transmission of BSSMAP messages
The transmission of the BSSMAP messages in the SCCP is to implement the information exchange between the BSSMAP functional entities of the MSC and BSS. The allocation data unit of the BSSMAP messages only includes the discrimination parameter. Where the discrimination parameter D is configured as 0, indicating non-transparent transmission.
Figure4-6 Discrimination parameter code of BSSMAP message
In actual operations, many SCCP messages can be seen in the link tracing between the MSC and the BSC, where the BSSMAP DTAP messages are included to serve as the subscriber data. The analysis of the SCCP message has been described in detail in the elementary signaling course and Chapter 3 in this document. Here, based upon the above descriptions, a BSSMAP message and a DTAP message are used for the brief explanation of SCCP message analysis.
A complete SCCP CR message from the BSS to the MSC is described as follows:
01 03 00 41 02 02 06 04 43 02 13 FE 04 04 43 BA 13 FE 0F 1E
00 1C 57 05 08 00 64 F0 13 13 09 00 01 17 0F 05 08 71 64 F0 13 13 09 23 05 F4 32 D3 07 00
The analysis is as follows:
The first line: 01 (Message type: CR) 03 00 41(Source local reference) 02 (Protocol type: Class 2) 02 (Pointer of the called address) 06 (Start pointer of optional part) 04(Length of the called address) 43 02 13 FE 04(Optional parameter name: Calling address ) 04 (Length of the calling address) 43 BA 13 FE 0F(Optional parameter name: Subscriber data)1E(Subscriber data length)
From the second line to the last 00 is the BSSMAP message (the last 00 indicates the end of the subscriber data). The meaning of each 8-bit decimal number is as follows:
00: Discrimination parameter, here indicating the BSSMAP message
1C: Length of the BSSMAP message
57: Message type, L3 message
05: Message unit identification, it is the cell identification message unit
08: Length of the message unit
00: Cell identification discriminator, here it indicates the GCI code
64 F0 13 13 09 00 01 : Cell and GCI code, it ends when the cell identification message unit reaches 8 bytes.
17: Message unit identification, it is the complete L3 message unit.
0F: Length of the message unit
05: The higher four bits indicate the jumping indication and the lower four bits indicate the protocol discrimination: This is the mobility management message.
08: MM message type: Location updating request message
71: Higher 4BITS location updating type and lower 4BITS key sequence number
64 F0 13 13 09: Location area identification, five octets in total
23: Type of mobile type: Providing information on high priority of MS equipment
05: Length of MS identification unit
F4 32 D3 07 00: MS identification and the 3 bits after F4 indicate TMSI.
Set a DTAP message example once again, in the following, the DT1 message of the SCCP is sued to transfer TMSI re-allocation completion message from the BSS to the MSC:
06 00 00 40 00 01 05
01 00 02 05 5B
The first line 06(SCCP Message type DT1)00 00 40(Destination local reference) 00 (Segmentation/reassembly: Segmentation/reassembly is needed) 01 (Pointer of subscriber data) 05 (Subscriber data length)
The second line indicates the DTAP message
01: Discrimination parameter, indicating the DTAP message
00: DLCI
02: Message length
05: The front four bits indicate the jumping indication and the last four bits indicate the protocol discriminator: This is the mobility management message.
5B: Message type: Indicating the TMSI re-allocation is completed.
3. A Interface Flow
The A interface can use the two forms of the SCCP (connection-oriented class and connectionless class) to implement its functions. When an MS and the network need to switch communication-related information in radio resources, but there is no MS-related SCCP connection between the MSC and the BSS, a new connection should be set up. Furthermore, a new connection is also needed for external handover.
There are two connection setup cases:
1) Setting up a new processing connection in the radio channel: when the MS sends the ?access request? message in the RACH, the BSS will allocate a dedicated radio resource (DCCH or TCH) to the MS. After the L2 connection is set up in the SDCCH (or FACCH) channel of the allocated resource, the BSS will start the connection setup.
2) If the MSC wants to conduct an external handover (the destination BSS is possibly the original BSS), then a new DCCH or TCH should be reserved for the destination BSS. In this case, the MSC starts the connection setup.
With the connection or connectionless messages, the A interface mainly implements the following functional flow:
? Assignment
The purpose of the assignment is to guarantee the correct radio resource allocation or reallocate it to the MS needing the resource. Thus, the initial MS will immediately access and ?immediately be assigned? to a DCCH, which is processed by the BSS itself and is not under the control of the MSC.
? Block and unblock
In the assignment program, the MSC should select appropriate ground circuits. Therefore, if the BSS thinks that some ground circuits not be used continuously, it should inform the MSC. The block/unblock flow can implement this function.
? Resource indication
The purpose of the resource indication is to inform the MSC of the following information:
(a) The quantity of the free radio resources which can serve as the service channels in the BSS
(b) The quantity of all available radio resources (i.e., the quantity of the radio resources which can provide services or have already been assigned).
These quantities cannot be easily exported by the MSC from the service conditions. These information can be considered when the MSC wants to initiate the external handover.
? Reset
The purpose of the rest is to initialize the faulty BSS or MSC, for example, if the BSS fails and loses all reference information on processing, then the BSS will send the ?reset? message to the MSC to request the MSC to release the influenced calls, delete the influenced reference information and set all circuits related to the BSS as Free state.
If it is only a local MSC or BSS fault, the clear program can be used to clear the influenced part.
? Handover requirement
For the following reasons, the BSS can send the ?Handover requirement? to the MSC to require the handover for an MS already allocated with dedicated resources:
(a) The BSS detects a radio reason for the handover.
(b) The MSC starts the handover candidate query program and the MS is waiting the handover.
(c) Due to congestion, the service cell needs to be changed during the call setup stage, for example, directional retry.
The ?handover requirement? requires the message to be retransmitted every a period of time until one of the following phenomena occurs:
(a) Receiving the ?handover command? message from the MSC
(b) Receiving the ?reset? message
(c) All communications with the MS are interrupted and the processing is aborted.
(d) The processing ends, for example, call clear.
? Handover resource allocation
With the handover resource allocation, the MSC can request resource from the destination BSS and the BSS will reserve the resource and wait the next MS to access this channel.
? Handover execution
The handover execution is a process in which the MSC indicates the MS to access the dedicated radio resources of another cell. During the handover execution, the original dedicated radio resources and ground resources will be held until the MSC sends the ?clear command? message or resets.
? Handover candidate query
With the handover candidate query program, the MSC can determine whether some MSs in a special cell can be handed over to other designated cells. Only one ?Handover candidate query? message can be sent to a cell once.
? Release of radio resources and ground resources
When a certain processing is completed, the MSC sends a ?clear command? to instruct the BSS to release the radio resources. When receiving the command, the BSS will start the clear program on the radio interface, and then set the dominated ground circuits as free state and then return a clear completion message to the MSC. Then, the MSC will release the local ground resources.
If the resource release is needed due to BSS reasons, the BSS will send a ?clear request? to request the MSC to release the response resources.
? Paging
The connectionless service of the SCCP is used to transfer the MS paging through the BSSMAP. If the BSS receives the ?paging response? message on the radio channel interface, it will set up a connection from the MSC to the SCCP. The paging response message is loaded in the ?Complete L3 message? of the BSSMAP and is transferred to the MSC through this signaling connection.
? Trace request
The purpose of the trace request is to notify the entity receiving this message to conduct trace record of the service processing this time. On the A interface, this message should be transferred in the connection-oriented service traced and recorded, but does not require confirmation.
? Flow control
The flow control can prevent the entities from entering instable state due to receiving excessive services. The A interface implements the flow control by notifying the service source to reduce the traffic.
? Level processing
The purpose of the level updating is to inform the receiving entity of the level information received by the MS. Generally, the BSS either informs the MSC after receiving the level information from the MS or after the handover is completed. The MSC sends the level information of the corresponding MS to the new BSS through the A interface.
? Encryption mode control
The encryption mode control flow permits the MSC to transfer the encryption mode control information to the BSS and start the user equipment and signaling encryption equipment with correct keys.
? Queue indication
The purpose of this program is to notify the MSC and BSS to delay the allocation of the necessary radio resources. This program takes effect only when the queue function is used for the service channel assignment and handover in the BSS.
? Load indication
The purpose of the load indication is inform all the neighboring BSSs of the service conditions of a cell so that the handover service in an MSC can receive overall control.
4 Analysis of A Interface Messaged
4.1 Brief Introduction to A interface Messages
After learning the A interface flow and protocols, we will focus on the analysis of the A interface messages in this section. First, we will take a look at the main messages of the A interface:
1) Connection setup messages:
? Location updating Request
? CM Service Request message
? Connect Confirm message
2) Normal connection messages:
? AUTHENTICATION REQUEST message
? AUTHENTICATION RESPONSE message
? CIPHER MODE COMMAND message
? CIPHER MODE COMPLETE message
? LOCATION UPDATING ACCEPT message
? CM SERVICE ACCEPT message
? SETUP message
? CALL PROCEEDING message
? ASSIGNMENT REQUEST message
? ASSIGNMENT COMPLETE message
? ALERTING message
? CONNECT message
? CONNECT ACKNOWLEDGE connection}
? DISCONNECT message
? RELEASE message
? RELEASE COMPLETE message
? CLEAR COMMANG
? CLEAR COMPLETE
3) Connectionless message:
? RESET CIRCUIT
? BLOCK CIRCUIT
? UNBLOCK CIRCUIT
? RESET message
? Unequipped circuit
5 Message Analysis
5.1. Location updating message
In the following, we will make a detailed analysis of the location updating message traced on an A interface:
FB 0B 3B C3 B2 40 30 E0 01 01 00 41 02 02 06 04 43 B2 00 FE 04 04 43 C1 00 FE 0F 21 00 1F 57 05 08 00 64 F0 20 25 00 00 01 17 12 05 08 20 64 F0 00 25 00 01 08 49 06 20 72 90 00 00 60 00
first, we will analyze the MTP and SCCP messages (note: ?X? indicates the BIT to be analyzed and ??? indicates BIT not analyzed for the time being):
Then, let us look at the resolution of the BSSMAP message:
0x00: BSSMAP indicator
0x1f: BSSMAP message length = 31
0x57: Complete L3 information
0x05: Cell ID IEI
0x08: Cell ID length
0x00: Cell ID discriminator
0x64 0xf0: MCC dig.
0x20: MNC dig.
0x25 0x00: LAC
0x00 0x01: CI
0x17: L3 information IEI
0x12: L3 information length = 18
0x05: SI = 0 ( 4 bit ) , PD = B_0101 ( Mobile Manager )
0x08: message type : Locate Update request
0x20: The lower four bits indicate the location updating type, LocUpdate type = 0/1 ( 4 bit ) : Normal Location Updating/Periodic Updating, 0 indicates the normal location updating. The higher four bits indicate CKSN, Ciphering key sequence = 2
0x64 0xf0: MCC
0x20: MNC
0x25 0x00: LAC
0x01: Classmark1
0x08: Mobile ID length
0x49: Mobile ID type = 001 (lower three bits) : IMSI
The explanation of the eight bits is as follows:
H G F E D C B A
0 0 1 IMSI used for mobile station
0 1 0 IMEI used for mobile station
0 1 1 IMEISV used for mobile station
1 0 0 TMSI used for mobile station
0 0 0 No identity
The bit D indicates the odd/even of the identity: 0 indicates even bits and 1 indicates odd bits.
Bits HGFE: If the identity is odd number, then the higher four bits indicate the first bit of the identity; if the identity is even number, then they should be set as 1111.
Here, since the bit D is 1, the higher four bits indicate the first bit of the IMSI: 4
0x06 0x20 0x72 0x90 0x00 0x00 0x40 : IMSI number
In the above, we have made detailed explanation of an MTP message with location updating message. Thus, we know the common format of this message, and in the same way, we can know the specific meaning of the location updating messages with different information fields and contents.
5.2. CM Service Request message:
Message traced by the A interface:
91 9C 3B C3 B2 40 30 C0 01 3D 00 41 02 02 06 04 43 B2 00 FE 04 04 43 C1 00 FE 0F 21 00 1D 57 05 08 00 64 F0 20 25 00 00 01 17 12 05 24 21 02 02 04 08 49 06 20 72 90 00 00 60 00 00 00 00
Where, the resolution of the MTP and SCCP messages is basically the same as that of the location updating message. For details, please refer to the above analysis.
The resolution of the BSSMAP message is as follows:
0x00: BSSMAP indicator
0x1D: BSSMAP message length = 29
0x57: Complete L3 information
0x05: Cell ID IEI
0x08: Cell ID length
0x00: Cell ID discriminator
0x64 0xf0: MCC dig.
0x20: MNC dig.
0x25 0x00: LAC
0x00 0x01: CI
0x17 : L3 information IEI
0x10: L3 information length = 16
0x05: TI = 0 ( 4 bit ) , PD = B_0101 ( Mobile Manager )
0x24: message type : CM service request
0x21 CM type = 1 ( 4 bit ) : Mobile Originating Call
Ciphering key sequence = 2 ( 4 bit )
0x02: Classmark 2 information length
0x02 0x00: Classmark 2 information
0x08: Mobile ID length
0x49: Mobile ID type = 001 (lower three bits) : IMSI
0x06 0x20 0x72 0x90 0x00 0x00 0x60: IMSI number
In the above, we have made detailed explanation of an MTP message with the CM service request message. Thus, we know the common format of this message, and by analogy, we can know the specific meaning of the CM service request messages with different information fields and contents.
5.3. Connect Confirm message:
Message traced by the A interface:
0C FF 22 C3 C1 80 2C 30 02 03 00 41 00 00 41 02 00
Resolution of the MTP and SCCP messages: (note: ?X? indicates the BIT to be analyzed and ??? indicates the BIT not analyzed for the time being)
In the above, we have made detailed explanation of an MTP message with ?Connect Confirm" message. Here, the CC message does not have any parameter. However, by analogy, we can also know the specific meaning of the CC messages with different information fields and contents.
5.4. Normal connection message
1) AUTHENTICATION REQUEST message:
Message traced by the A interface:
0C FF 22 C3 C1 80 2C 30 06 03 00 41 00 01 16 01 00 13 05 12 03 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11
First, let us take a look at the resolution of the MTP and SCCP messages: (Note: ?X? indicates the BIT to be analyzed and ??? indicates the BIT not analyzed for the time being)
The resolution of the DTAP message is as follows:
0x01: DTAP message type
0x00: Spare, DLCI
0x13: DTAP message length
0x05: PD=5 TI=0
0x12: Authentication Request
0x03: CSKN
Authentication parameter rand IEI
0x01 0x01 0x01 0x01 0x01 0x01 0x01 0x01
0x01 0x01 0x01 0x01 0x01 0x01 0x01 0x01
In the above, we have made detailed explanation of an MTP message with the authorization request. Thus, we know the common format of this message, and by analogy, we can know the specific meaning of the authorization request messages with different information fields and contents..
2) AUTHENTICATION RESPONSE message:
Message traced by the A interface:
FE 0D 15 C3 B2 40 30 E0 06 00 00 41 00 01 09 01 00 06 05 14 02 02 02 02
The resolution of the MTP and SCCP message header of this message is basically the same as that of the authorization request message (except the direction). For details, please refer to the above analysis.
Resolution of the DTAP message:
0x01: DTAP message flag
0x00: Spare
0x06: Length of DTAP message
0x05: Protocol discriminator=5 (L4 bit);Transaction Identifier=0 (H4 bit)
0x14: Message type , Authentication Response
0x02 0x02 0x02 0x02 : Authentication parameter SRES
In the above, we have made detailed explanation of an MTP message with the authorization response message. Thus, we know the common format of this message, and by analogy, we can know the specific meaning of the authorization response messages with different information fields and contents..
3) LOCATION UPDATING ACCEPT message:
Message traced by the A interface:
18 8C 1D C3 C1 80 2C 50 06 07 00 41 00 01 11 01 00 0E 05 02 64 F0 00 25 00 17 05 F4 0A 0E 01 00
The resolution of the MTP and SCCP message header of this message is basically the same as that of the authorization request message. For details, please refer to the above analysis.
Please see the resolution of the DTAP message:
0x01: DTAP message type
0x00: Spare
0x0e: DTAP message length
0x05: PD=5 TI=0
0x02: Location upgrade accept
0x64: MCC digit
0xf0: MCC third code (L4 bit)
0x00: MCC=460, MNC=0
0x25 0x00: LAC
0x17: Mobile Identify type (O&V)
0x05: Length of mobile identify type
0xf4: L4 bit=0100b: TMSI
0x0A 0x0E 0x01 0x00: TMSI
In the above, we have made detailed explanation of an MTP message with the LOCATION UPDATING ACCEPT message. Thus, we know the common format of this message, and by analogy, we can know the specific meaning of the LOCATION UPDATING ACCEPT messages with different information fields and contents.
4) CM SERVICE ACCEPT message:
Message traced by the A interface:
18 8C 1D C3 C1 80 2C 50 06 07 00 41 00 01 11 01 00 02 05 21
The resolution of the MTP and SCCP message header of this message is basically the same as that of the authorization request message. For details, please refer to the above analysis.
The resolution of the DTAP message is as follows
0x01: DTAP message type
0x00 : Spare
0x02 : DTAP message length
0x05: PD_CC
0x21 CM service accept
In the above, we have made detailed explanation of an MTP message with the CM SERVICE ACCEPT message. Thus, we know the common format of this message, and by analogy, we can know the specific meaning of the CM SERVICE ACCEPT messages with different information fields and contents (Note: this message does not have any parameter).
5) SETUP message:
Message traced by the A interface:
A1 B0 1C C3 B2 40 30 C0 06 3C 00 41 00 01 10 01 00 0D 03 05 04 01 A0 5E 06 80 31 29 07 20 50
The resolution of the MTP and SCCP message header of this message is basically the same as that of the authorization request message (except the direction). For details, please refer to the above analysis.
Please see the resolution of the DTAP message in the following:
0x01: dtap_msg_type
0x00: DLCI
0x0d: Length
0x03 : pd_cc
0x05: msg_type
0x04: bear_ie
0x01: bear_len
0xa0: bear_val
0x5e : called_num_ie
0x06 : called_num_len
0xa1 0x31 0x29 0x07 0x00 0x40: called_num_val
In the above, we have made detailed explanation of an MTP message with the SETUP message. Thus, we know the common format of this message, and by analogy, we can know the specific meaning of the SETUP messages with different information fields and contents.
6) CALL PROCEEDING message:
Message traced by the A interface:
B3 A7 11 C3 C1 80 2C 00 06 3D 00 41 00 01 05 01 00 02 83 02
The resolution of the MTP and SCCP message header of this message is basically the same as that of the authorization request message. For details, please refer to the above analysis.
The resolution of the DTAP message is as follows
0x01: DTAP message type
0x00: Spare
0x02: DTAP message length
0x83: PD_CC
0x02: CALL PROCEEDING
In the above, we have made detailed explanation of an MTP message with the CALL PROCEEDING message. Thus, we know the common format of this message, and by analogy, we can know the specific meaning of the CALL PROCEEDING messages with different information fields and contents (Note: this message does not have any parameter).
7) ASSIGNMENT REQUEST message:
Message traced by the A interface:
B3 A8 20 C3 C1 80 2C 00 06 3D 00 41 00 01 14 00 12 01 0B 03 01 08 01 07 02 06 00 06 01 0C 01 00 64 19 01
The resolution of the MTP and SCCP message header of this message is basically the same as that of the authorization request message. For details, please refer to the above analysis.
The resolution of the BSSMAP message is as follows:
0x00 : BSSMAP indicator
0x12: BSSMAP message length
0x01: Assignment request information
0x0b: Channel type IEI
0x03: Channel type length
0x01: indicator = 1 : voice type
0x08: indicator = 8 : TCH/Bm
0x01: transparent service ( gsm voice algorithm 1st version )
0x07: L3 header information IEI
0x02: L3 header length
0x06: PD = B_0110 ( Radio Resource Manager )
0x00: TI = 0
0x06: Priority level IEI
0x01: Priority level length
0x03: Priority level
0x01: Circuit ID IEI
0x00 0x64;Circuit ID
0x19: Downlink DTX flag IEI
0x01: Downlink DTX flag : use DTX
In the above, we have made detailed explanation of an MTP message with the ASSIGNMENT REQUEST message. Thus, we know the common format of this message, and by analogy, we can know the specific meaning of the ASSIGNMENT REQUEST messages with different information fields and contents.
ASSIGNMENT COMPLETE message:
Message traced by the A interface:
A1 B0 1C C3 B2 40 30 C0 06 3C 00 41 00 01 15 00 13 02 15 01 05 08 00 64 F0 00 01 00 03 00 21 08 23 01 24 01
The resolution of the MTP and SCCP message header of this message is basically the same as that of the authorization request message (except the direction). For details, please refer to the above analysis.
The resolution of the BSSMAP message is as follows:
0x00: BSSMAP indicator
0x13: BSSMAP message length = 19
0x02: Assignment Ack. information
0x15: RR cause IEI
0x01: RR cause
0x05: Cell ID IEI
0x08: Cell ID length
0x00: Cell ID discriminator
0x64 0xf0: MCC dig.
0x00: MNC dig.
0x01 0x00: LAC
0x03 0x00: CI
0x21 chosen channel IEI( phase 2 )
0x08: channel
0x23: chosen Encryption algorithm IEI( phase 2 )
0x01: No Encryption
0x24: circuit pool IEI( phase 2 )
0x01: circuit pool number
In the above, we have made detailed explanation of an MTP message with the ASSIGNMENT COMPLETE message. Thus, we know the common format of this message, and by analogy, we can know the specific meaning of the ASSIGNMENT COMPLETE messages with different information fields and contents.
We have spent so much effort and time in the detailed analysis of multiple common connection-oriented messages. For other connection-oriented messages, we will not describe here. For the BSSMAP message, please refer to the specifications GSM08.08 and for the DTAP message, please refer to the specifications GSM04.08.
5. Connectionless messages
1) RESET CIRCUIT:
Message traced by the A interface:
FB 0B 3B C3 B2 40 30 E0 09 00 02 07 0B 04 43 B2 00 FE 04 04 43 C1 00 FE 09 00 07 34 01 00 03 04 01 20
In the following, let us look at the resolution of the MTP and SCCP messages:
The resolution of the BSSMAP message is as follows:
0x00: BSSMAP indicator
0x07: BSSMAP message length = 7
0x34: Reset Circuit information
0x01: Circuit ID IEI
0x00 0x03: Circuit ID 0
x04: Cause IEI
0x01: Cause length
0x20: Equipment error In the above, we have made detailed explanation of an MTP message with the RESET CIRCUIT message. Thus, we know the common format of this message, and by analogy, we can know the specific meaning of the RESET CIRCUIT messages with different information fields and contents.
2) BLOCK CIRCUIT:
Message traced by the A interface:
FB 0B 3B C3 B2 40 30 E0 09 00 02 07 0B 04 43 B2 00 FE 04 04 43 C1 00 FE 09 00 07 40 01 00 03 04 01 07
The resolution of MTP and SCCP message header of this message is basically the same as that of the RESET CIRCUIT message (note: the message transfer direction is different). For details, please refer to the above analysis. The resolution of the BSSMAP message is as follows:
0x00: BSSMAP indicator
0x07: BSSMAP message length = 7
0x40: Block Circuit information
0x01: Circuit ID IEI
0x00 0x03: Circuit ID
0x04: Cause IEI
0x01: Cause length
0x07: O&M In the above, we have made detailed explanation of an MTP message with the BLOCK CIRCUIT message. Thus, we know the common format of this message, and by analogy, we can know the specific meaning of the BLOCK CIRCUIT messages with different information fields and contents.
3) UNBLOCK CIRCUIT:
Message traced by the A interface:
FB 0B 3B C3 B2 40 30 E0 09 00 02 07 0B 04 43 B2 00 FE 04 04 43 C1 00 FE 09 00 07 42 01 00 03 04 01 07 The resolution of MTP and SCCP message header of this message is basically the same as that of the RESET CIRCUIT message (note: the message transfer direction is different). For details, please refer to the above analysis.
The resolution of the BSSMAP message is as follows:
0x00: BSSMAP indicator
0x07: BSSMAP message length = 7
0x42: UnBlock Circuit information
0x01: Circuit ID IEI
0x00 0x03 : Circuit ID
0x04;Cause IEI 0x01: Cause length
0x07: O&M In the above, we have made detailed explanation of an MTP message with the UNBLOCK CIRCUIT message. Thus, we know the common format of this message, and by analogy, we can know the specific meaning of the UNBLOCK CIRCUIT messages with different information fields and contents.
4) RESET message: Message traced by the A interface:
FB 0B 3B C3 B2 40 30 E0 09 00 02 07 0B 04 43 B2 00 FE 04 04 43 C1 00 FE 09 00 04 30 04 01 20
The resolution of MTP and SCCP message header of this message is basically the same as that of the RESET CIRCUIT message (note: the message transfer direction is different). For details, please refer to the above analysis.
The resolution of the BSSMAP message is as follows:
0x00: BSSMAP indicator
0x04: BSSMAP message length = 4
0x30: Reset information
0x04: Cause IEI
0x01: Cause length
0x20: Equipment error In the above, we have made detailed explanation of an MTP message with the RESET message. Thus, we know the common format of this message, and by analogy, we can know the specific meaning of the RESET messages with different information fields and contents.
5) Unequipped circuit:
Message traced by the A interface:
FB 0B 3B C3 B2 40 30 E0 09 00 02 07 0B 04 43 B2 00 FE 04 04 43 C1 00 FE 09 00 08 48 01 00 01 1E 02 00 01
The resolution of MTP and SCCP message header of this message is basically the same as that of the RESET CIRCUIT message (note: the message transfer direction is different). For details, please refer to the above analysis.
The resolution of the BSSMAP message is as follows:
0x00: BSSMAP indicator
0x08: BSSMAP message length = 8
0x48: Unequipped circuit information
0x01: Circuit ID IEI
0x00 0x01 : Circuit ID
0x1e: Circuit ID list IEI
0x02: length
0x00: circuit scope , range is 3
0x01: ;circuit state
In the above, we have made detailed explanation of an MTP message with the unequipped circuit message. Thus, we know the common format of this message, and by analogy, we can know the specific meaning of the unequipped messages with different information fields and contents.
In the following, we will set the location updating and call flow as example to describe the message analysis of the A interface:
1. Location updating message of the A interface
>SCCP INT 3983 000 00B8 00B1 01(Message type: CR) 01 00 41(Source local reference: Three bytes) 02(Protocol type: Class 2, basic connection-oriented service)02(Pointer 1 of mandatory variable length part : Called address) 06(Start pointer of optional part)04(Length of the called address, i.e., the last four bits indicate the called address)43 B1 00 FE 04(Optional parameter name: Calling address )04(Length of the calling address, i.e., the last four bits indicate the calling address)43 B8 00 FE 0F(Optional parameter name: Subscriber data) 21 (Subscriber data length) 00 (BSSMAP ID) 1F (BSSMAP MSG lEN) 57 (CMP L3 IND) 05(CELL IEI) 08(CELL LEN) 00(CELL TYPE:CGI) 64 F0 20 25 01 00 01 17 (L3 INF) 12 (L3 INF LEN) 05 (PD:MM) 08 (MSG:LOC_REQ) 20 (LOC_TYPE: 0NORMAL) 64 F0 20 25 01 01 08 49 06 20 72 80 00 10 47 00
SCCP INT 3984 00f 00B1 00B8 02(Message type: CC) 01 00 41(Destination local reference: Three bytes) 00 00 41(Source local reference: Three bytes) 02 (Protocol type: Class 2, basic connection-oriented service)00(without optional parameters)
SCCP INT 4053 00f 00B1 00B8 06(Message type:DT1) 01 00 41(Destination local reference: Three bytes) 00(Segmentation/reassembly: Without more data) 01(Pointer 1 of mandatory variable length part : Subscriber data)16(Subscriber data length) 01(DTAP ID)00(SPARE)13(DTAP MSG LEN) 05(PD:MM) 12(MSG:AUTH_REQ) 00 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11
SCCP INT 4187 000 00B8 00B1 06(Message type:DT1) 00 00 41(Destination local reference: Three bytes) 00(Segmentation/reassembly: Without more data) 01(Pointer 1 of mandatory variable length part : Subscriber data)09(Subscriber data length) 01(DTAP ID)00(SPARE)06(DTAP MSG LEN) 05(PD:MM) 14(MSG:AUTH_RSP) 02 02 02 02
SCCP INT 4324 00f 00B1 00B8 06(Message type:DT1) 01 00 41(Destination local reference: Three bytes) 00(Segmentation/reassembly: Without more data) 01(Pointer 1 of mandatory variable length part : Subscriber data)0A(Subscriber data length) 00(BSSMAP ID)08(BSSAP MSG LEN)53(MSG:CIPH_MOD_CMD) 07 02 06 00 0A 01 01
SCCP INT 4396 000 00B8 00B1 06(Message type:DT1) 00 00 41(Destination local reference: Three bytes) 00(Segmentation/reassembly: Without more data) 01(Pointer 1 of mandatory variable length part : Subscriber data)03(Subscriber data length) 00(BSSMAP ID)01(BSSAP MSG LEN)55(MSG:CIPH_MOD_CMP)
SCCP INT 4397 00f 00B1 00B8 06(Message type:DT1) 01 00 41(Destination local reference: Three bytes) 00(Segmentation/reassembly: Without more data) 01(Pointer 1 of mandatory variable length part : Subscriber data)11(Subscriber data length) 01(DTAP ID)00(SPARE) 0E(DTAP MSG LEN) 05(PD:MM) 02(MSG:LOC_ACP) 64 F0 20 25 01 17 05 F4 01 E9 00 00
SCCP INT 4600 000 00B8 00B1 06(Message type:DT1) 00 00 41(Destination local reference: Three bytes) 00(Segmentation/reassembly: Without more data) 01(Pointer 1 of mandatory variable length part : Subscriber data)05(Subscriber data length) 01(DTAP ID)00(SPARE) 02(DTAP MSG LEN) 05(PD:MM) 1B(MSG:TMSI_REAL_CMP)
SCCP INT 4601 00f 00B1 00B8 06(Message type:DT1) 01 00 41(Destination local reference: Three bytes) 00(Segmentation/reassembly: Without more data) 01(Pointer 1 of mandatory variable length part : Subscriber data)0A(Subscriber data length) 00(BSSMAP ID)08(BSSAP MSG LEN)20(MSG:CLEAR_CMD) 07 02 06 00 04 01 10
SCCP INT 4618 000 00B8 00B1 06(Message type:DT1) 00 00 41(Destination local reference: Three bytes) 00(Segmentation/reassembly: Without more data) 01(Pointer 1 of mandatory variable length part : Subscriber data)03(Subscriber data length) 00(BSSMAP ID)01(BSSAP MSG LEN)21(MSG:CLEAR_CMP)
SCCP INT 4619 00f 00B1 00B8 04(Message type: RLSD) 03 00 41(Destination local reference: Three bytes)02 00 41(Source local reference: Three bytes) 00(Release cause: endpoint user originates the release) 00(without optional parameters)
SCCP INT 4629 000 00B8 00B1 05(Message type: RLC) 02 00 41(Destination local reference: Three bytes)03 00 41(Source local reference: Three bytes)
2. SCCP message of the A interface when an MS calls an MS (in the same BSC)
SCCP INT 4756 000 00B8 00B1 01(Message type: CR) 01 00 41(Source local reference: Three bytes) 02(Protocol type: Class 2, basic connection-oriented service)02(Pointer 1 of mandatory variable length part : Called address) 06(Start pointer of optional part)04(Length of the called address, i.e., the last four bits indicate the called address)43 B1 00 FE 04(Optional parameter name: Calling address )04 (Length of the calling address) 43 B8 00 FE 0F(Optional parameter name: Subscriber data)1F(Subscriber data length) 00(BSSMAP ID)1D(BSSMAP MSG lEN) 57(CMP L3 IND) 05(CELL IEI) 08(CELL LEN) 00(CELL TYPE:CGI) 64 F0 20 25 01 00 01 17(L3 INFO) 10(L3 INF LEN) 05(PD:MM) 24(MSG:CM_SER_REQ) 21(CM_SER_TYPE:1MOC) 03 03 18 00 08 49 06 20 72 80 00 10 45 00 (Optional parameter end)
SCCP INT 4757 00b 00B1 00B8 02(Message type: CC) 01 00 41(Destination local reference: Three bytes)00 00 41(Source local reference: Three bytes)02(Protocol type: Class 2, basic connection-oriented service)00(without optional parameters)
SCCP INT 4829 00b 00B1 00B8 06(Message type:DT1) 01 00 41(Destination local reference: Three bytes)00(Segmentation/reassembly: Without more data) 01(Pointer 1 of mandatory variable length part : Subscriber data) 16(Subscriber data length) 01(DTAP ID)00(SPARE) 13(DTAP MSG LEN) 05(PD:MM) 12(MSG:AUTH_REQ) 00 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11
SCCP INT 4963 000 00B8 00B1 06(Message type: DT1) 00 00 41(Destination local reference: Three bytes)00(Segmentation/reassembly: Without more data) 01(Pointer 1 of mandatory variable length part : Subscriber data) 09(Subscriber data length) 01(DTAP ID)00(SPARE) 06(DTAP MSG LEN) 05(PD:MM) 14(MSG:AUTH_RSP) 02 02 02 02
SCCP INT 4964 00b 00B1 00B8 06(Message type: DT1) 01 00 41(Destination local reference: Three bytes)00(Segmentation/reassembly: Without more data) 01(Pointer 1 of mandatory variable length part : Subscriber data) 12(Subscriber data length) 00(BSSAP ID) 10(BSSAP MSG LEN)53(MSG:CIPH_MOD_CMD) 07 02 06 00 0A 09 02 03 03 03 03 03 03 03 03
SCCP INT 5178 000 00B8 00B1 06(Message type: DT1) 00 00 41(Destination local reference: Three bytes)00(Segmentation/reassembly:
Without more data) 01(Pointer 1 of mandatory variable length part : Subscriber data) 03(Subscriber data length) 00(BSSAP ID) 01(BSSAP MSG LEN)55(MSG:CIPH_MOD_CMP)
SCCP INT 5282 000 00B8 00B1 06(Message type: DT1) 00 00 41(Destination local reference: Three bytes)00(Segmentation/reassembly: Without more data) 01(Pointer 1 of mandatory variable length part : Subscriber data) 10(Subscriber data length) 01(DTAP ID)00(SPARE) 0D(DTAP MSG LEN) 03(PD:CC) 05(MSG:SETUP) 04 01 A0 5E 06 A1 31 28 07 10 55
SCCP INT 5302 00b 00B1 00B8 06(Message type:DT1) 01 00 41(Destination local reference: Three bytes)00(Segmentation/reassembly: Without more data) 01(Pointer 1 of mandatory variable length part : Subscriber data) 05(Subscriber data length) 01(DTAP ID)00(SPARE) 02(DTAP MSG LEN) 83(PD:CC) 02(MSG:CALL_PROCEEDING)
SCCP INT 5302 00b 00B1 00B8 06(Message type:DT1) 01 00 41(Destination local reference: Three bytes)00(Segmentation/reassembly: Without more data) 01(Pointer 1 of mandatory variable length part : Subscriber data) 14(Subscriber data length) 00(BSSAP ID) 12(BSSAP MSG LEN)01(MSG:ASS_REQ) 0B 03 01 08 01 07 02 06 00 06 01 0C 01 00 0A 19 01
SCCP INT 5339 000 00B8 00B1 06(Message type: DT1) 00 00 41(Destination local reference: Three bytes)00(Segmentation/reassembly: Without more data) 01(Pointer 1 of mandatory variable length part : Subscriber data) 05(Subscriber data length) 00(BSSAP ID) 03(BSSAP MSG LEN)02(MSG:ASS_CMP) 15 00
SCCP INT 5396 009 00B1 00B8 09(Message type: UDT) 00(Protocol type: Class 0 basic connectionless service without returned message) 03(Pointer 1 of mandatory variable length part : Called address) 07(Pointer 2 of mandatory variable length part : Calling address ) 0B(Start pointer of optional part) 04(Length of the called address, i.e., the last four bits indicate the called address) 43 B8 C0 FE 04(Length of the called address, i.e., the last four bits indicate the called address) 43 B1 00 FE 1B(Subscriber data length)00(BSSMAP ID)19(BSSMAP MSG lEN) 52(MSG:PAGING) 08 08 49 06 20 72 80 00 10 55 09 04 01 BE 00 00 1A 06 04 64 F0 20 25 01
SCCP INT 5850 001 00B8 00B1 01(Message type: CR) 03 00 41(Source local reference: Three bytes) 02(Protocol type: Class 2, basic connection-oriented service)02(Pointer 1 of mandatory variable length part : Called address) 06(Start pointer of optional part) 04(Length of the called address, i.e., the last four bits indicate the called address) 43 B1 00 FE 04(Length of the calling address, i.e., the last four bits indicate the called address) 04 43 B8 00 FE
0F(Optional parameter name: Subscriber data)1F(Subscriber data length)00(BSSMAP ID)1D(BSSMAP MSG lEN) 57(CMP L3 IND) 05(CELL IEI) 08(CELL LEN) 00(CELL TYPE:CGI) 64 F0 20 25 01 00 01 17(L3 INFO) 10(L3 INF LEN) 06(PD:RR) 27(MSG:PAGING_RSP) 02 03 02 00 00 08 49 06 20 72 80 00 10 55 00
SCCP INT 5851 00c 00B1 00B8 02(Message type: CC ) 03 00 41(Destination local reference: Three bytes)02 00 41(Source local reference: Three bytes) 02(Protocol type: Class 2, basic connection-oriented service) 00(without optional parameters)
SCCP INT 5869 00c 00B1 00B8 06(Message type:DT1) 03 00 41(Destination local reference: Three bytes)00(Segmentation/reassembly: Without more data) 01(Pointer 1 of mandatory variable length part : Subscriber data) 16(Subscriber data length) 01(DTAP ID)00(SPARE) 13(DTAP MSG LEN) 05(PD:MM) 12(MSG:AUTH_REQ) 00 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11
SCCP INT 6059 001 00B8 00B1 06(Message type:DT1) 02 00 41(Destination local reference: Three bytes)00(Segmentation/reassembly: Without more data) 01(Pointer 1 of mandatory variable length part : Subscriber data) 09(Subscriber data length) 01(DTAP ID)00(SPARE) 06(DTAP MSG LEN) 05(PD:MM) 14(MSG:AUTH_RSP) 02 02 02 02
SCCP INT 6060 00c 00B1 00B8 06(Message type:DT1) 03 00 41(Destination local reference: Three bytes)00(Segmentation/reassembly: Without more data) 01(Pointer 1 of mandatory variable length part : Subscriber data) 12(Subscriber data length) 00(BSSAP ID) 10(BSSAP MSG LEN)53(MSG:CIPH_MOD_CMD) 07 02 06 00 0A 09 02 03 03 03 03 03 03 03 03
SCCP INT 6269 001 00B8 00B1 06(Message type:DT1) 02 00 41(Destination local reference: Three bytes)00(Segmentation/reassembly: Without more data) 01(Pointer 1 of mandatory variable length part : Subscriber data) 03(Subscriber data length) 00(BSSAP ID) 01(BSSAP MSG LEN)55(MSG:CIPH_MOD_CMP)
SCCP INT 6271 00c 00B1 00B8 06(Message type:DT1) 03 00 41(Destination local reference: Three bytes)00(Segmentation/reassembly: Without more data) 01(Pointer 1 of mandatory variable length part : Subscriber data) 08(Subscriber data length) 01(DTAP ID)00(SPARE) 05(DTAP MSG LEN) 03(PD:CC) 05(MSG:SETUP) 04 01 A0
SCCP INT 6342 001 00B8 00B1 06(Message type:DT1) 02 00 41(Destination local reference: Three bytes)00(Segmentation/reassembly: Without more data) 01(Pointer 1 of mandatory variable length part : Subscriber data) 05(Subscriber data length) 01(DTAP ID)00(SPARE) 02(DTAP MSG LEN) 83(PD:CC) 08(MSG:CALL_CNF)
SCCP INT 6345 00c 00B1 00B8 06(Message type:DT1) 03 00 41(Destination local reference: Three bytes)00(Segmentation/reassembly: Without more data) 01(Pointer 1 of mandatory variable length part : Subscriber data) 14(Subscriber data length) 00(BSSAP ID) 12(BSSAP MSG LEN)01(MSG:ASS_REQ) 0B 03 01 08 01 07 02 06 00 06 01 0C 01 00 0B 19 01
SCCP INT 6639 001 00B8 00B1 06(Message type:DT1) 02 00 41(Destination local reference: Three bytes)00(Segmentation/reassembly: Without more data) 01(Pointer 1 of mandatory variable length part : Subscriber data) 05(Subscriber data length) 00(BSSAP ID) 03(BSSAP MSG LEN)02(MSG:ASS_CMP) 15 00
SCCP INT 6741 001 00B8 00B1 06(Message type:DT1) 02 00 41(Destination local reference: Three bytes)00(Segmentation/reassembly: Without more data) 01(Pointer 1 of mandatory variable length part : Subscriber data) 05(Subscriber data length) 01(DTAP ID)00(SPARE) 02(DTAP MSG LEN) 83(PD:CC) 01(MSG:ALERT)
SCCP INT 6742 00b 00B1 00B8 06(Message type:DT1) 01 00 41(Destination local reference: Three bytes)00(Segmentation/reassembly: Without more data) 01(Pointer 1 of mandatory variable length part : Subscriber data) 05(Subscriber data length) 01(DTAP ID)00(SPARE) 02(DTAP MSG LEN) 83(PD:CC) 01(MSG:ALERT)
SCCP INT 6849 001 00B8 00B1 06(Message type:DT1) 02 00 41(Destination local reference: Three bytes)00(Segmentation/reassembly: Without more data) 01(Pointer 1 of mandatory variable length part : Subscriber data) 05(Subscriber data length) 01(DTAP ID)00(SPARE) 02(DTAP MSG LEN) 83(PD:CC) 07(MSG:CONNECT)
SCCP INT 6850 00b 00B1 00B8 06(Message type:DT1) 01 00 41(Destination local reference: Three bytes)00(Segmentation/reassembly: Without more data) 01(Pointer 1 of mandatory variable length part : Subscriber data) 05(Subscriber data length) 01(DTAP ID)00(SPARE) 02(DTAP MSG LEN) 83(PD:CC) 07(MSG:CONNECT)
SCCP INT 7053 000 00B8 00B1 06(Message type: DT1) 00 00 41(Destination local reference: Three bytes)00(Segmentation/reassembly: Without more data) 01(Pointer 1 of mandatory variable length part : Subscriber data) 05(Subscriber data length) 01(DTAP ID)00(SPARE) 02(DTAP MSG LEN) 03(PD:CC) 0F(MSG:CONNECT_ACK)
SCCP INT 7055 00c 00B1 00B8 06(Message type: DT1) 03 00 41(Destination local reference: Three bytes)00(Segmentation/reassembly: Without more data) 01(Pointer 1 of mandatory variable length part : Subscriber data) 05(Subscriber data length) 01(DTAP ID)00(SPARE) 02(DTAP MSG LEN) 03(PD:CC) 0F(MSG:CONNECT_ACK)
SCCP INT 7770 000 00B8 00B1 06(Message type: DT1) 00 00 41(Destination local reference: Three bytes)00(Segmentation/reassembly: Without more data) 01(Pointer 1 of mandatory variable length part : Subscriber data) 09(Subscriber data length) 01(DTAP ID)00(SPARE) 06(DTAP MSG LEN) 03(PD:CC) 25(MSG:DISCONNECT) 03 60 81 90
SCCP INT 7772 00b 00B1 00B8 06(Message type:DT1) 01 00 41(Destination local reference: Three bytes)00(Segmentation/reassembly: Without more data) 01(Pointer 1 of mandatory variable length part : Subscriber data) 09(Subscriber data length) 01(DTAP ID)00(SPARE) 06(DTAP MSG LEN) 83(PD:CC) 2D(MSG:RELEASE) 08 02 E0 90
SCCP INT 7772 00c 00B1 00B8 06(Message type:DT1) 03 00 41(Destination local reference: Three bytes)00(Segmentation/reassembly: Without more data) 01(Pointer 1 of mandatory variable length part : Subscriber data) 08(Subscriber data length) 01(DTAP ID)00(SPARE) 05(DTAP MSG LEN) 03(PD:CC) 25(MSG:DISCONNECT) 02 E0 90
SCCP INT 7975 000 00B8 00B1 06(Message type:DT1) 00 00 41(Destination local reference: Three bytes)00(Segmentation/reassembly: Without more data) 01(Pointer 1 of mandatory variable length part : Subscriber data) 05(Subscriber data length) 01(DTAP ID)00(SPARE) 02(DTAP MSG LEN) 03(PD:CC) 2A(MSG:RELEASE_CMP)
SCCP INT 7976 00b 00B1 00B8 06(Message type:DT1) 01 00 41(Destination local reference: Three bytes)00(Segmentation/reassembly: Without more data) 01(Pointer 1 of mandatory variable length part : Subscriber data) 0A(Subscriber data length) 00(BSSAP ID) 08(BSSAP MSG LEN)20(MSG:CLR_CMD) 07 02 06 00 04 01 10
SCCP INT 7998 000 00B8 00B1 06(Message type:DT1) 00 00 41(Destination local reference: Three bytes)00(Segmentation/reassembly: Without more data) 01(Pointer 1 of mandatory variable length part : Subscriber data) 03(Subscriber data length) 00(BSSAP ID) 01(BSSAP MSG LEN)21(MSG:CLR_CMP)
SCCP INT 7999 00b 00B1 00B8 04(Message type: RLSD) 01 00 41(Destination local reference: Three bytes)00 00 41(Source local reference: Three bytes) 00(Release cause: endpoint user originates the release) 00(without optional parameters)
SCCP INT 8009 000 00B8 00B1 05(Message type: RLC) 00 00 41(Destination local reference: Three bytes)01 00 41(Source local reference: Three bytes)
SCCP INT 8093 001 00B8 00B1 06(Message type: DT1) 02 00 41(Destination local reference: Three bytes)00(Segmentation/reassembly: Without more data) 01(Pointer 1 of mandatory variable length part : Subscriber data) 05(Subscriber data length) 01(DTAP ID)00(SPARE) 02(DTAP MSG LEN) 83(PD:CC) 2D(MSG:RELEASE)
SCCP INT 8094 00c 00B1 00B8 06(Message type:DT1) 03 00 41(Destination local reference: Three bytes)00(Segmentation/reassembly: Without more data) 01(Pointer 1 of mandatory variable length part : Subscriber data) 09(Subscriber data length) 01(DTAP ID)00(SPARE) 06(DTAP MSG LEN) 03(PD:CC) 2A(MSG:RELEASE_CMP) 08 02 E0 90
SCCP INT 8094 00c 00B1 00B8 06(Message type:DT1) 03 00 41(Destination local reference: Three bytes)00(Segmentation/reassembly: Without more data) 01(Pointer 1 of mandatory variable length part : Subscriber data) 0A(Subscriber data length) 00(BSSAP ID) 08(BSSAP MSG LEN)20(MSG:CLR_CMD) 07 02 06 00 04 01 10
SCCP INT 8118 001 00B8 00B1 06(Message type:DT1) 02 00 41(Destination local reference: Three bytes)00(Segmentation/reassembly: Without more data) 01(Pointer 1 of mandatory variable length part : Subscriber data) 03(Subscriber data length) 00(BSSAP ID) 01(BSSAP MSG LEN)21(MSG:CLR_CMP)
SCCP INT 8119 00c 00B1 00B8 04(Message type: RLSD) 03 00 41(Destination local reference: Three bytes)02 00 41(Source local reference: Three bytes) 00(Release cause: endpoint user originates the release) 00(without optional parameters)
SCCP INT 8128 001 00B8 00B1 05(Message type: RLC) 02 00 41(Destination local reference: Three bytes)03 00 41(Source local reference: Three bytes)
6. Summary
This chapter mainly describes the protocols, procedures and message analysis method of the A interface. Through the learning of this chapter, we can master the message analysis method and considerations of the A interface.
7. Exercise
Please analyze the following two messages traced on the A interface:
18 8C 1D C3 C1 80 2C 50 06 07 00 41 00 01 11 01 00 02 83 01
2 B8 AD 16 C3 C1 80 2C F0 06 3B 00 41 00 01 0A 00 08 20 07 02 06 00 04 01 20
