87641318 omf001005 gsm signalling system sccp bss training 20060531 a 2 0

8/18/2019 87641318 OMF001005 GSM Signalling System SCCP BSS Training 20060531 a 2 0

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Internal

OMF001005

GSM Signaling System-

SCCP(BSS)

ISSUE 2.0




Upon completion this course, you are

supposed to be able to:

Understand the necessity of SCCP.

Know the services provided by SCCP.

Know the SCCP message format.




Chapter 1 General

Chapter 2 Features & Functions of SCCP

Chapter 3 Addressing & Routing Functions

of SCCP

Chapter 4 SCCP Message Format




Limitation of MTP Transmission

The signaling point code is not the standard international code,

it is only effective within a certain network.

The limited capacity of the signaling point code (14-bit is

specified by CCITT) also limits the number of the signaling

point to be marked.

The 4-bit SI can not satisfy the increased requirements of the

modern communication as well, since it can only be assigned

to sixteen different user parts.

MTP can only provide the connectionless transmission.




When SCCP and MTP are combined together, they are called

as NSP (Network Service Part).

SCCP and MTP-3 both locate in the network layer of the OSI

model.

The Location of SCCP in CCS7





1.1 Application Features of SCCP

1.2 Service Functions of SCCP Network


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Application Features of SCCP

Enable to transfer both circuit-related and non-circuit-related

signaling messages in telecommunication networks.

Provide enhanced addressing and routing functions, and

enable to achieve the direct transmission between different

CCS7 networks.

Enable to provide both connectionless service and connection-

oriented service.




There are two kinds of service provided by the SCCP protocol:

Connectionless Service

0. Basic connectionless class

1. In-sequence delivery connectionless class

Connection-oriented Service

2. Basic connection-oriented class

3. Flow control connection-oriented class

Service Functions of SCCP Network




In the connectionless service, the routing information

must be contained in each data packet.

No logical connection is established between the end

nodes.





The connectionless SCCP offers two services:

The class 0 service allows the SCCP to insert SLS values randomly,

or with the aim to achieve an appropriate load sharing within the

underlying MTP network.

The class 1 service requires the SCCP to insert the same SLS for all

the SCCP-SDUs (service data unit) associated with given

parameters "sequence control" and "called address" .





UDT----unit data

UDTS----unit data service

XUDT----extended unit data

XUDTS---extended unit data service

Message type UDT UDTS XUDT XUDTS

Message type code 0x09 0x0A 0x11 0x12





SCCP procedure of connectionless service





Connection-oriented service is a way to realize the exchange of

signaling information by establishing a logical signaling connection

between the network service users.

The logical signaling connection is achieved by distributing a local

reference number to the signaling messages belonging together.





SCCP procedure of connection-oriented service





Chapter 1 General



of SCCP





Address in SCCP comprises three elements:

DPC

Global Title (GT)

Sub-System Number (SSN)

Addressing and Routing Functions of SCCP




0000 0000 SSN not known/not used

0000 0001 SCCP management

0000 0010 Reserved for ITU-T allocation

0000 0011 ISDN user part£ ISUP£ ©

0000 0100Operation, maintenance and

administration part (OMAP)0000 0101 Mobile application part£ MAP£ ©

0000 0110 Home location register£ HLR£ ©

0000 0111 Visitor location register£ VLR£ ©

0000 1000 Mobile switching centre£ ¨MSC£ ©

0000 1001 ... ... 1111 1101 Idle1111 1110 BSS Application Part (BSC)

1111 1111Reserved for expansion of nationaland international SSN

SSN




There are two basic categories of SCCP routing

GT

DPC+SSN






From SPA to SPD,

If DPC+SSN routing is adopted by SCCP, in the Called Party Address of SCCP

message, DPC is point code of SPD, while SSN depends on the different requirements.

The message is sent to STPB or STPC, the Called Party Address is not necessary to be

translated by STP.

If GT routing is adopted by SCCP, in the Called Party Address of SCCP message, GT is

the information of SPD. Because GT can’t be identified by MTP, actually, DPC should

be included in the SCCP message, in this case, DPC is point code of STP. The

message is sent to STPB or STPC, the Called Party Address is necessary to be

translated to the relevant point code and/or SSN by STP.

An example




Chapter 1 General



of SCCP





F CK SIF SIO LI FIB FSN BIB BSN FMandatory parameter A

…………

Mandatory parameter I

Pointer to parameter M

…………

Pointer to parameter P

Pointer to start of optional part

Length indicator of parameter M

Parameter M

…………

Length indicator of parameter P

Parameter P

Parameter name=X

Length indicator of parameter X

Parameter X

…………

Parameter name=Z

Length indicator of parameter Z

Parameter Z

End of optional parameters

8 16 8n,n>2 8 2 6 171 7 8

Routing label

Message type

Mandatory fixed part (F)

Mandatory variable part (V)

Optional part (O)

SCCP Message Format




F CK SIF SIO LI FIB FSN BIB BSN F

8 16 8n,n>2 8 2 6 171 7 8

Label

Message type (UDT)

Protocol class

Called party address pointer

Calling party address party

Data pointer

Called party address length

Called party address

Calling party address length

Calling party address

Data length

Data (TCAP)

MF

MV

MV

MV

Message Example




General

Features & Functions of SCCP

Addressing & Routing Functions of SCCP

SCCP Message Format

Summary



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87641318 omf001005 gsm signalling system sccp bss training 20060531 a 2 0

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