Owa330011 bssap protocol analysis issue 1.0

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BSSAP Protocol Analys is


References

GSM TS 0808


Objectives

Upon completion of this course, you will be able to: Outline the main function of BSSAP protocol

Describe the main procedure of BSSAP


Contents

1. BSSAP Protocol Basic Principles

2. BSSAP Main Procedure Analysis



1.1 Protocol Stacks

1.2 BSSAP Protocol Functions

1.3 BSSAP Message Structure

Contents


BSSAP Protocol of A Inte rface

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

Internalinterface

UMG8900

MSC/VLR

A

BSSAP

BSS

BSC


Protocol S tacks



1.1 Protocol Stacks



Contents


BSSAP Protocol

DTAP BSSMAP

Distribution Function

To air interface To air interface transmission transmission equipmentequipment

To other To other process process within BSCwithin BSC

BSSAPBSSAP

SCCP

MTP

BSSMAP DTAP

Distribution Function

BSSAPBSSAP

SCCP

MTP

To other applicationTo other applicationE.g. call controlE.g. call control

A interfaceA interface MSC sideMSC sideBSC sideBSC side


Components of BSSAP Protocol

BSSAP protocol is composed of: BSSMAP: Base Station Subsystem Management Application

Part; BSSMAP messages control service process, and are handled by the internal functional module of corresponding A interface.

DTAP: Direct Transfer Application Part For DTAP messages, the A interface only functions as a transport channel. At BSS side, DTAP messages are directly conveyed to a radio channel; at NSS side, DTAP messages are carried to the corresponding functional processing unit.

Distribution Function: distribute the message to

BSSMAP/DTAP


Class ifica tion of BSSMAP Procedures There are two types of BSSMAP procedures:

Connectionless procedures It is a global procedure which concerns a complete cell or BSS, or specific terrestrial circuits.

It uses the connectionless services of the SCCP

Connection-oriented procedures It is a dedicated procedure which concerns a single dedicated radio resource on the radio interface, or in the case of a multi slot configuration, all radio resources allocated to one mobile station.

It uses the connection oriented services of the SCCP, on the connection which has been set up to support that call or transaction


Connectionless Procedures of BSSMAP

Procedure Messages

Blocking BLOCK BLOCKING ACKNOWLEDGE UNBLOCKUNBLOCKING 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


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 DETECTHANDOVER COMPLETE HANDOVER SUCCEEDED

Release CLEAR REQUEST CLEAR COMMAND CLEAR COMPLETE

Classmark update CLASSMARK UPDATE


Connection-oriented Procedures of BSSMAP

Procedures Messages

Cipher mode control CIPHER MODE COMMANDCIPHER MODE COMPLETE

Trace invocation MSC INVOKE TRACEBSS 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 SUSPENDRESUME

Circuit re-selection CHANGE CIRCUITCHANGE CIRCUIT ACKNOWLEDGE

Location Aquisition LOCATION INFORMATION COMMANDLOCATION INFORMATION REPORT



1.1 Protocol Stacks



Contents


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.


Dis tribution 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" .


Dis tribution 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" .


0 0 0 0 0 0 0 D


Dis tribution 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.


Contents





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


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


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.



2.1 Paging



2.4 Assignment

2.5 Handover

2.6 Release

2.7 DTAP Message

Contents


Initia l 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.



The radio initial L3 message can be: CM SERVICE REQUEST,

PAGING RESPONSE,

CM REESTABLISHMENT REQUEST,

LOCATION UPDATING REQUEST,

IMSI DETACH,

NOTIFICATION RESPONSE,

IMMEDIATE SETUP



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


COMPLETE LAYER 3 INFORMATION


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



2.1 Paging



2.4 Assignment

2.5 Handover

2.6 Release

2.7 DTAP Message

Contents


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".


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


CIPHER MODE COMMAND



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.


Encryption Information IE

8 7 6 5 4 3 2 1

Element identifier octet 1

Length octet 2

Permitted algorithms octet 3Key octet 4-N


Encryption Information IE


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 encryption

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.


CIPHER MODE COMPLETE



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


CIPHER MODE REJECT



Cause M BSC->MSC

Typical Cause values are: Ciphering algorithm not supported,

Invalid message contents



2.1 Paging



2.4 Assignment

2.5 Handover

2.6 Release

2.7 DTAP Message

Contents


Ass ignment 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.


Ass ignment

BSSMS

RR: ASSIGNMENT COMPLETE

MSC

RR: ASSIGNMENT COMMAND

BSSMAP: ASSIGNMENT COMPLETE

BSSMAP: ASSIGNMENT REQUEST

BSSMAP: ASSIGNMENT FAILURE

RR: ASSIGNMENT FAILURE


ASSIGNMENT REQUEST



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


ASSIGNMENT COMPLETE



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

Circuit Pool O BSC->MSC

Speech Version (chosen) O BSC->MSC

Can be Full rate version 1/2/3, half rate version 1/2/3,


ASSIGNMENT FAILURE



Cause M

RR Cause O BSC->MSC


Circuit Pool List O BSC->MSC


Typica l 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.



2.1 Paging



2.4 Assignment

2.5 Handover

2.6 Release

2.7 DTAP Message

Contents


Handover Procedure

Handover procedure include: 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


Handover

BSSMS MSC

BSSMAP: HANDOVER REQUIRED

BSS MS

BSSMAP: HANDOVER REQUEST ACK

BSSMAP: HANDOVER REQUEST

BSSMAP: HANDOVER COMMANDHANDOVER

COMMAND HANDOVER ACCESSBSSMAP: HANDOVER

DETECTHANDOVER COMPLETEBSSMAP: HANDOVER

COMPLETE

BSSMAP: CLEAR COMMAND

BSSMAP: CLEAR COMPLETE

Measurement report form MS

BSSMAP: HANDOVER SUCCEEDED


HANDOVER REQUIRED



Cause M BSC->MSC

Cell Identifier List M BSC->MSC


Current Channel Type 1 O BSC->MSC

Signalling, data or speech

Speech Version (Used) O BSC->MSC

Old BSC to New BSC Information

O BSC->MSC


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.


HANDOVER REQUIRED REJECT



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.


HANDOVER REQUEST (1)



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

Cell Identifier (target) M MSC->BSC




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



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.


HANDOVER REQUEST ACK



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


Speech Version (chosen) O BSC->MSC

Circuit Identity Code O BSC->MSC


HANDOVER COMMAND



L3 Information M MSC->BSC

Carrying a radio interface HANDOVER COMMAND

message

Cell Identifier O MSC->BSC

channel rate/type


HANDOVER DETECT



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.


HANDOVER COMPLETE



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.



HANDOVER SUCCEEDED



This message is sent from the MSC to the old BSS via the relevant SCCP connection.



HANDOVER FAILURE



Cause M BSC->MSC

RR Cause O BSC->MSC

This element is passed from the radio interface to

the MSC transparently




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.



2.1 Paging



2.4 Assignment

2.5 Handover

2.6 Release

2.7 DTAP Message

Contents


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


Release

BSSMS

L2 Message: DISC

MSC

RR: CHANNEL RELEASE

BSSMAP: CLEAR COMPLETE

BSSMAP: CLEAR COMMAND

BSSMAP: CLEAR REQUEST

L2 Message: UA


CLEAR REQUEST



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.


CLEAR COMMAND



Cause M MSC->BSC Typical Cause values are:

Call control, O and M intervention, Equipment failure, Handover successful protocol error between BSS and MSC,


CLEAR COMPLETE



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).



2.1 Paging



2.4 Assignment

2.5 Handover

2.6 Release

2.7 DTAP Message

Contents


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


DTAP

BSSMS

L3 Message: CALL CONFIRM

MSC

L3 message: SETUP

DTAP: CALL CONFIRMATION

DTAP: SETUP


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.

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Owa330011 bssap protocol analysis issue 1.0

Mobile

Transcript of Owa330011 bssap protocol analysis issue 1.0