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Owa330011 bssap protocol analysis issue 1.0

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Owa330011 bssap protocol analysis issue 1.0

  1. 1. www.huawei.com Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved. BSSAP Protocol Analysis
  2. 2. Page2Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved. References  GSM TS 0808
  3. 3. Page3Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved. Objectives  Upon completion of this course, you will be able to:  Outline the main function of BSSAP protocol  Describe the main procedure of BSSAP
  4. 4. Page4Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved. Contents 1. BSSAP Protocol Basic Principles 2. BSSAP Main Procedure Analysis
  5. 5. Page5Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved. Contents 1. BSSAPProtocol Basic Principles 2. BSSAP Main Procedure Analysis
  6. 6. Page6Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved. 1. BSSAP Protocol Basic Principles 1.1 Protocol Stacks 1.2 BSSAP Protocol Functions 1.3 BSSAP Message Structure Contents
  7. 7. Page7Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved. BSSAP Protocol of A Interface  Base Station Subsystem Application Part (BSSAP) is the application protocol used on the A interface to the GSM network. Information carried through this interface includes:  Mobile station management  Base station management  Mobility management  Connection management MSOFTX3000 内部接口 UMG8900 MSC/VLR A BSSAP BSS BSC MSOFTX3000 Internal interface UMG8900 MSC/VLR A BSSAP BSS BSC
  8. 8. Page8Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved. Protocol Stacks
  9. 9. Page9Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved. 1. BSSAP Protocol Basic Principles 1.1 Protocol Stacks 1.2 BSSAPProtocol Functions 1.3 BSSAP Message Structure Contents
  10. 10. Page10Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved. BSSAP Protocol DTAP BSSMAP Distribution Function To air interfaceTo air interface transmissiontransmission equipmentequipment To otherTo other processprocess within BSCwithin BSC BSSAPBSSAP SCCP MTP BSSMAP DTAP Distribution Function BSSAPBSSAP SCCP MTP To other applicationTo other application E.g. call controlE.g. call control A interfaceA interface MSC sideMSC sideBSC sideBSC side
  11. 11. Page11Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved. Components of BSSAP Protocol  BSSAP protocol is composed of:  BSSMAP: Base Station Subsystem Management Application Part;  BSSMAPmessagescontrolserviceprocess, andarehandled bytheinternalfunctionalmoduleofcorrespondingA interface.  DTAP: Direct Transfer Application Part  ForDTAPmessages, theAinterfaceonlyfunctionsasa transportchannel. AtBSSside, DTAPmessagesaredirectly conveyedtoaradiochannel; atNSSside, DTAPmessagesare carriedtothecorrespondingfunctionalprocessingunit.  Distribution Function: distribute the message to
  12. 12. Page12Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved. Classification of BSSMAP Procedures  There are two types of BSSMAP procedures:  Connectionless procedures  Itisaglobalprocedurewhichconcernsacompletecellor BSS, orspecificterrestrialcircuits.  ItusestheconnectionlessservicesoftheSCCP  Connection-oriented procedures  Itisadedicatedprocedurewhichconcernsasinglededicated radioresourceontheradiointerface, orinthecaseofa multi slotconfiguration, allradioresourcesallocatedtoone mobilestation.  ItusestheconnectionorientedservicesoftheSCCP, onthe connectionwhichhasbeensetuptosupportthatcallor transaction
  13. 13. Page13Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved. Connectionless Procedures of BSSMAP Procedure Messages Blocking BLOCK BLOCKING ACKNOWLEDGE UNBLOCK UNBLOCKING ACKNOWLEDGE Resource indication RESOURCE REQUEST RESOURCE INDICATION Reset RESET RESET ACK Handover candidate enquiry HANDOVER CANDIDATE ENQUIRE HANDOVER CANDIDATE RESPONSE Paging PAGING Flow control OVERLOAD Reset circuit RESET CIRCUIT RESET CIRCUIT ACKNOWLEDGE
  14. 14. Page14Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved. Connection-oriented Procedures of BSSMAP Procedures Messages Assignment ASSIGNMENT REQUEST ASSIGNMENT COMPLETE ASSIGNMENT FAILURE Handover required indication HANDOVER REQUIRED HANDOVER REQUIRED REJECT Handover resource allocation HANDOVER REQUEST HANDOVER REQUEST ACKNOWLEDGE HANDOVER FAILURE Handover execution HANDOVER COMMAND HANDOVER DETECT HANDOVER COMPLETE HANDOVER SUCCEEDED Release CLEAR REQUEST CLEAR COMMAND CLEAR COMPLETE Classmark update CLASSMARK UPDATE
  15. 15. Page15Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved. Connection-oriented Procedures of BSSMAP Procedures Messages Cipher mode control CIPHER MODE COMMAND CIPHER MODE COMPLETE Trace invocation MSC INVOKE TRACE BSS INVOKE TRACE Initial MS message COMPLETE LAYER 3 INFORMATION Queuing indication QUEUING INDICATION Data link control SAPI not equal to 0 DTAP message (in normal case) SAPI “N” REJECT (in case of failure) PDSS1 flow control SUSPEND RESUME Circuit re-selection CHANGE CIRCUIT CHANGE CIRCUIT ACKNOWLEDGE Location Aquisition LOCATION INFORMATION COMMAND LOCATION INFORMATION REPORT
  16. 16. Page16Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved. 1. BSSAP Protocol Basic Principles 1.1 Protocol Stacks 1.2 BSSAP Protocol Functions 1.3 BSSAPMessage Structure Contents
  17. 17. Page17Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved. BSSAP Message Structure Distribution data unit Length indicator Message body BSSAP messageBSSAP message  The distribution data unit of BSSMAP message and DTAP message are different.  The length indicator is 1 octet long.
  18. 18. Page18Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved. Distribution Data Unit of BSSMAP  The Distribution Data Unit only consists of the Discrimination parameter, which is set to the "Not Transparent" value. Bit 8 Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 0 0 0 0 0 0 0 D Discrimination ParameterDiscrimination Parameter  The discrimination bit D is set to “0”, means "Not Transparent" .
  19. 19. Page19Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved. Distribution Data Unit of DTAP  The Distribution Data Unit consists of two parameters:  Discrimination parameter  Data Link Connection Identification (DLCI) parameter. Discrimination ParameterDiscrimination Parameter  The discrimination bit D is set to “1”, means "Transparent" . Bit 8 Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 0 0 0 0 0 0 0 D
  20. 20. Page20Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved. Distribution Data Unit of DTAP  The DLCI parameter is 1 octet long.  In the direction of MSC to BSC: to indicate the type of data link connection to be used over the radio interface.  In the direction of BSS to MSC: to indicate the type of originating data link connection over the radio interface.
  21. 21. Page21Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved. Contents 1. BSSAP Protocol Basic Principles 2. BSSAPMain Procedure Analysis
  22. 22. Page22Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved. 2. BSSAP Main Procedure Analysis 2.1 Paging 2.2 Initial MS Message 2.3 Cipher Mode Control 2.4 Assignment 2.5 Handover 2.6 Release 2.7 DTAP Message Contents
  23. 23. Page23Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved. Paging BSSMS First SABM frame (PAGING RESPONSE) MSC RR: PAGING REQUEST TYPE 1, 2, 3 BSSMAP: COMPLETE LAYER 3 INFORMATION ( PAGING RESPONSE) BSSMAP: PAGING  SABM: Set asynchronous balanced mode command
  24. 24. Page24Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved. PAGING Message Information Element type Direction Description Message Type M MSC- >BSC IMSI M MSC- >BSC TMSI O MSC- >BSC Cell Identifier List M MSC- >BSC Channel Needed O MSC- >BSC  This message is sent from the MSC to the BSS and contains sufficient information to allow the paging message to be transmitted by the correct cells at the correct time.
  25. 25. Page25Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved. 2. BSSAP Main Procedure Analysis 2.1 Paging 2.2 Initial MS Message 2.3 Cipher Mode Control 2.4 Assignment 2.5 Handover 2.6 Release 2.7 DTAP Message Contents
  26. 26. Page26Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved. Initial MS Message Procedure  When BSC receive the radio interface initial L3 message from the MS (piggybacked on the SABM frame), BSC will setup the SCCP connection via CR/CC message, and passing the entire radio interface initial L3 message to the MSC using BSSMAP “COMPLETE LAYER 3 INFORMATION” message which encapsulated in SCCP CR message.
  27. 27. Page27Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved. Initial MS Message Procedure  The radio initial L3 message can be:  CM SERVICE REQUEST,  PAGING RESPONSE,  CM REESTABLISHMENT REQUEST,  LOCATION UPDATING REQUEST,  IMSI DETACH,  NOTIFICATION RESPONSE,  IMMEDIATE SETUP
  28. 28. Page28Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved. Initial MS Message Procedure BSSMS First SABM frame (initial L3 message: CM SERVICE REQUEST, LOCATION UPDATING REQUEST, PAGING RESPONSE, IMSI DETACH etc. ) MSC SCCP: CR ( BSSMAP: COMPLETE LAYER 3 INFORMATION (CM SERVICE REQUEST, LOCATION UPDATING REQUEST, PAGING RESPONSE, IMSI DETACH etc. ) ) SCCP: CC
  29. 29. Page29Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved. COMPLETE LAYER 3 INFORMATION Information Element type Direction Description Message Type M BSC- >MSC Cell Identifier M BSC- >MSC Layer 3 Information M BSC- >MSC “paging response” etc. Choose Channel O BSC- >MSC the channel rate/type on which the initial layer 3 message was received Location Information O BSC- >MSC to provide Location Services related information
  30. 30. Page30Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved. 2. BSSAP Main Procedure Analysis 2.1 Paging 2.2 Initial MS Message 2.3 CipherMode Control 2.4 Assignment 2.5 Handover 2.6 Release 2.7 DTAP Message Contents
  31. 31. Page31Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved. Cipher Mode Control Procedure  The cipher mode control procedure allows the MSC to pass cipher mode information to the BSS to select and load the user data and signalling encryption device with the appropriate key.  If the BSS is unable to support the ciphering algorithm specified in the CIPHER MODE COMMAND message then it shall return a CIPHER MODE REJECT message with Cause value "Ciphering algorithm not supported".
  32. 32. Page32Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved. Cipher Mode Control BSSMS RR: CIPHER MODE COMPLETE MSC RR: CIPHER MODE COMMAND BSSMAP: CIPHER MODE COMPLETE BSSMAP: CIPHER MODE COMMAND BSSMAP: CIPHER MODE REJECT
  33. 33. Page33Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved. CIPHER MODE COMMAND Information Element type Direction Description Message Type M MSC- >BSC Encryption Information M MSC- >BSC Cipher Response Mode O MSC- >BSC This information element is used by the MSC to indicate whether the IMEI is to be included in the CIPHERING MODE COMPLETE message to be sent by the Mobile Station.
  34. 34. Page34Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved. Encryption Information IE 8 7 6 5 4 3 2 1 Element identifier octet 1 Length octet 2 Permitted algorithms octet 3 Key octet 4-N
  35. 35. Page35Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved. Encryption Information IE Bit 8 Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 0 or 1 0 or 1 0 or 1 0 or 1 0 or 1 0 or 1 0 or 1 0 or 1 GSM A5/7 GSM A5/6 GSM A5/5 GSM A5/4 GSM A5/3 GSM A5/2 GSM A5/1 No encry ption  Permitted algorithms:  if the bit set to 1, the BSC will use the algorithm.  If the bit set to 0, the BSC won’t use the algorithm.  Key:  It shall be present if at least one of the A5 encryption algorithms is permitted. When present, the key shall be 8 octets long.
  36. 36. Page36Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved. CIPHER MODE COMPLETE Information Element type Direction Description Message Type M BSC- >MSC Layer 3 Message Contents O BSC- >MSC To pass the contents of radio interface messages from MS to MSC. Chosen Encryption Algorithm O BSC- >MSC A specific algorithm
  37. 37. Page37Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved. CIPHER MODE REJECT Information Element type Direction Description Message Type M BSC- >MSC Cause M BSC- >MSC  Typical Cause values are:  Ciphering algorithm not supported,  Invalid message contents
  38. 38. Page38Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved. 2. BSSAP Main Procedure Analysis 2.1 Paging 2.2 Initial MS Message 2.3 Cipher Mode Control 2.4 Assignment 2.5 Handover 2.6 Release 2.7 DTAP Message Contents
  39. 39. Page39Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved. Assignment Procedure  The purpose of the assignment procedure is to ensure that the correct dedicated radio resource(s) can be allocated or reallocated to a MS that requires it.
  40. 40. Page40Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved. Assignment BSSMS RR: ASSIGNMENT COMPLETE MSC RR: ASSIGNMENT COMMAND BSSMAP: ASSIGNMENT COMPLETE BSSMAP: ASSIGNMENT REQUEST BSSMAP: ASSIGNMENT FAILURE RR: ASSIGNMENT FAILURE
  41. 41. Page41Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved. ASSIGNMENT REQUEST Information Element type Direction Description Message Type M MSC- >BSC Channel Type M MSC- >BSC Speech, data or signalling; Speech: Full rate or half rate; Data: full rate or half rate and maximum channel numbers, data rates; Signalling: SDCCH channel or full rate, half rate channel Priority O MSC- >BSC The priority of the request. Circuit Identity Code O MSC- >BSC
  42. 42. Page42Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved. ASSIGNMENT COMPLETE Information Element type Direction Description Message Type M BSC- >MSC RR Cause O BSC- >MSC Circuit Identity Code O BSC- >MSC Cell Identifier O BSC- >MSC Chosen Channel O BSC- >MSC Chosen Encryption Algorithm O BSC- >MSC
  43. 43. Page43Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved. ASSIGNMENT FAILURE Information Element type Direction Description Message Type M BSC- >MSC Cause M RR Cause O BSC- >MSC Circuit Pool O BSC- >MSC Circuit Pool List O BSC- >MSC
  44. 44. Page44Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved. Typical Cause Values  radio interface message failure,  O and M intervention,  equipment failure,  no radio resource available,  requested terrestrial resource unavailable,  requested transcoding/rate adaption unavailable,  terrestrial resource already allocated,  invalid message contents,  radio interface failure - reversion to old channel,  directed retry,  circuit pool mismatch,  switch circuit pool.  requested speech version unavailable.
  45. 45. Page45Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved. 2. BSSAP Main Procedure Analysis 2.1 Paging 2.2 Initial MS Message 2.3 Cipher Mode Control 2.4 Assignment 2.5 Handover 2.6 Release 2.7 DTAP Message Contents
  46. 46. Page46Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved. Handover Procedure  Handover procedure include:  Handover required indication  HANDOVERREQUIRED  HANDOVERREQUIREDREJECT  Handover resource allocation  HANDOVERREQUEST  HANDOVERREQUESTACKNOWLEDGE  HANDOVERFAILURE  Handover execution  HANDOVERCOMMAND  HANDOVERDETECT  HANDOVERCOMPLETE  HANDOVERSUCCEEDED
  47. 47. Page47Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved. Handover BSSMS MSC BSSMAP: HANDOVER REQUIRED BSS MS BSSMAP: HANDOVER REQUEST ACK BSSMAP: HANDOVER REQUEST BSSMAP: HANDOVER COMMANDHANDOVER COMMAND HANDOVER ACCESSBSSMAP: HANDOVER DETECT HANDOVER COMPLETEBSSMAP: HANDOVER COMPLETE BSSMAP: CLEAR COMMAND BSSMAP: CLEAR COMPLETE Measurement report form MS BSSMAP: HANDOVER SUCCEEDED
  48. 48. Page48Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved. HANDOVER REQUIRED Information Element type Direction Description Message Type M BSC- >MSC Cause M BSC- >MSC Cell Identifier List M BSC- >MSC Circuit Pool List O BSC- >MSC Current Channel Type 1 O BSC- >MSC Signalling, data or speech Speech Version (Used) O BSC- >MSC
  49. 49. Page49Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved. HANDOVER REQUIRED  Typical Cause values are:  uplink quality,  uplink strength,  downlink quality,  downlink strength,  distance,  better cell,  response to MSC invocation,  O&M intervention,  directed retry,  switch circuit pool,  traffic,  preemption.
  50. 50. Page50Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved. HANDOVER REQUIRED REJECT Information Element type Direction Description Message Type M MSC- >BSC Cause M MSC- >BSC  Typical Cause values are:  Equipment failure,  No radio resource available,  Requested terrestrial resource unavailable,  Invalid message contents,  Requested transcoding/rate adaptation unavailable,  O and M intervention.
  51. 51. Page51Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved. HANDOVER REQUEST (1) Information Element type Direction Description Message Type M MSC- >BSC Channel Type M MSC- >BSC Encryption Information M MSC- >BSC Classmark Information 1/2 M MSC- >BSC Cell Identifier (serving) M MSC- >BSC Circuit Identity Code O MSC- >BSC
  52. 52. Page52Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved. HANDOVER REQUEST (2) Information Element type Direction Description Cause O MSC- >BSC Classmark Information 3 O MSC- >BSC Current Channel Type 1 O MSC- >BSC Speech Version (Used) O MSC- >BSC Chosen Encryption Algorithm (serving) O MSC- >BSC Old BSC to New BSC Information O MSC- >BSC
  53. 53. Page53Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved. HANDOVER REQUEST (3)  Typical Cause values are:  uplink quality,  uplink strength,  downlink quality,  downlink strength,  distance,  better cell,  response to MSC invocation,  O and M intervention,  directed retry,  switch circuit pool,  traffic,  preemption.
  54. 54. Page54Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved. HANDOVER REQUEST ACK Information Element type Direction Description Message Type M BSC- >MSC L3 Information M BSC- >MSC Carrying a radio interface HANDOVER COMMAND message Chosen Channel O BSC- >MSC channel rate/type Chosen Encryption Information O BSC- >MSC Circuit Pool O BSC- >MSC Speech Version (chosen) O BSC- >MSC
  55. 55. Page55Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved. HANDOVER COMMAND Information Element type Direction Description Message Type M MSC- >BSC L3 Information M MSC- >BSC Carrying a radio interface HANDOVER COMMAND message Cell Identifier O MSC- >BSC channel rate/type
  56. 56. Page56Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved. HANDOVER DETECT Information Element type Direction Description Message Type M BSC- >MSC  This message is sent from the BSS to the MSC via the relevant SCCP connection.  It indicates that the correct MS has successfully accessed the target cell.
  57. 57. Page57Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved. HANDOVER COMPLETE Information Element type Direction Description Message Type M BSC- >MSC RR Cause O BSC- >MSC This element is passed from the radio interface to the MSC transparently  This message is sent from the BSS to the MSC via the relevant SCCP connection.  It indicates that the correct MS has successfully accessed the target cell.
  58. 58. Page58Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved. HANDOVER SUCCEEDED Information Element type Direction Description Message Type M MSC- >BSC  This message is sent from the MSC to the old BSS via the relevant SCCP connection.  It indicates that the correct MS has successfully accessed the target cell.
  59. 59. Page59Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved. HANDOVER FAILURE Information Element type Direction Description Message Type M BSC- >MSC Cause M BSC- >MSC RR Cause O BSC- >MSC This element is passed from the radio interface to the MSC transparently Circuit Pool O BSC- >MSC Circuit Pool List O BSC- >MSC
  60. 60. Page60Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved. HANDOVER FAILURE  Typical Cause values are:  radio interface message failure;  O and M intervention;  Equipment failure;  no radio resource available;  requested terrestrial resource unavailable;  requested transcoding/rate adaption unavailable;  terrestrial resource already allocated;  invalid message contents;  radio interface failure - reversion to old channel;  ciphering algorithm not supported;  circuit pool mismatch;  switch circuit pool;  requested speech version unavailable.
  61. 61. Page61Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved. 2. BSSAP Main Procedure Analysis 2.1 Paging 2.2 Initial MS Message 2.3 Cipher Mode Control 2.4 Assignment 2.5 Handover 2.6 Release 2.7 DTAP Message Contents
  62. 62. Page62Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved. Release Procedure  There are 3 types of release reason:  Release Due To Transaction Completion  Release due to BSS generated reason  Release due to successful handover
  63. 63. Page63Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved. Release BSSMS L2 Message: DISC MSC RR: CHANNEL RELEASE BSSMAP: CLEAR COMPLETE BSSMAP: CLEAR COMMAND BSSMAP: CLEAR REQUEST L2 Message: UA
  64. 64. Page64Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved. CLEAR REQUEST Information Element type Direction Description Message Type M BSC- >MSC Cause M BSC- >MSC  Typical Cause values are:  Radio interface message failure,  O and M intervention,  Equipment failure,  Joined group call channel,  Protocol error between BSS and MSC,  Preemption.
  65. 65. Page65Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved. CLEAR COMMAND Information Element type Direction Description Message Type M MSC- >BSC Cause M MSC- >BSC  Typical Cause values are:  Call control,  O and M intervention,  Equipment failure,  Handover successful  protocol error between BSS and MSC,
  66. 66. Page66Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved. CLEAR COMPLETE Information Element type Direction Description Message Type M BSC- >MSC  This message is sent from the BSS to the MSC to inform the MSC that the associated dedicated resource(s) has been successfully cleared.  The message is sent via the BSSAP SCCP connection associated with the dedicated resource(s).
  67. 67. Page67Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved. 2. BSSAP Main Procedure Analysis 2.1 Paging 2.2 Initial MS Message 2.3 Cipher Mode Control 2.4 Assignment 2.5 Handover 2.6 Release 2.7 DTAPMessage Contents
  68. 68. Page68Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved. DTAP Message  DTAP message is used to transfer the L3 message between MS and MSC/MSC Server, using connection-oriented SCCP service.  The L3 message is encapsulated into DTAP message besides the following message which is transfer by BSSMAP COMPLETE LAYER 3 INFORMATION:  CM SERVICE REQUEST,  PAGING RESPONSE,  CM REESTABLISHMENT REQUEST,  LOCATION UPDATING REQUEST,  IMSI DETACH,  NOTIFICATION RESPONSE,  IMMEDIATE SETUP
  69. 69. Page69Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved. DTAP BSSMS L3 Message: CALL CONFIRM MSC L3 message: SETUP DTAP: CALL CONFIRMATION DTAP: SETUP
  70. 70. Page70Copyright © 2008 Huawei Technologies Co., Ltd. All rights reserved. Summary  BSSAP protocol is composed of BSSMAP and DTAP part  BSSMAP message will be interpreted and processed by BSC.  The DTAP information is not interpreted by the BSS.
  71. 71. Thank you www.huawei.com

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