sccp slide

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1 Nokia Siemens Networks Presentation / Author / Date / Document Number

For public use IPR applies

Signalling Connection Control Part (SCCP)Switching Core Network Signalling

M14/U4


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Nokia Siemens Networks Academy

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Document change history

Date Version Name Change comment

20 January 2008 Version 01 Noppamat Ponyarat


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SCCP: Signalling Connection Control Part

Provides additional function to MTP to cater for both connectionless and

connection-oriented network service to transfer non-circuit related signalling information between exchanges in

telecommunication network

Provide the means for

Control logical signalling connection (setup/release) within SS7 network A transfer capability for network service data units with or without the use of

logical signalling connection

Provides routing function which allows signalling message to be routed to a

signalling point based on e.g. dialled digits (GT translation)

Combination of MTP and SCCP is called Network Service Part (NSP)


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MTP

RANAP/

BSSAP

SCCP

TUP/

ISUP

TCAP

MAP/CAP

Connection-oriented Service

SCCP services

Connectionless Service


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SCCP services

Basic

Connectionless

Service

Sequenced

Connectionless

Service

Basic

Connection-

oriented

Service

Flow Control

Connection-

oriented

Service

Connectionless

Services

Connection-oriented

Services

0 1 2 3

Services provided by the SCCP

Protocol

Class

(not used in GSM)


7/407 Nokia Siemens Networks Presentation / Author / Date / Document Number


SCCP Connectionless

UDT

...UDT




SCCP connectionless messages

Message Service

type

Description

UDT 0,1 Unitdata

UDTS 0,1 Unitdata Service. Used to indicate to the originating SCCP that a UDT cannot be delivered to its

destination.

XUDT 0,1 Extended Unitdata. Used to send data along with optional parameters.

XUDTS 0,1 Extended Unitdata Service. Used to indicate to the originating SCCP that an XUDT cannot be

delivered to its destination.

LUDT 0,1 Long Unitdata. Used to send data along with optional parameters over MTP3b (Q.2210). Up to 3952

octets without segmentation are allowed.

LUDTS 0,1 Long Unitdata Service. Used to indicate to the originating SCCP that an LUDT cannot be delivered to

its destination.





Positive cases

UDT(Sender,Receiver,

Protocol class,

User message)

XUDT(Sender,Receiver,

Protocol class, Hop Counter,

Segmentation,User message)





Negative cases

XUDTS(Sender,Receiver,

Cause,

User message)

UDT(Sender,Receiver,

Protocol class,

User message)

XUDT(Sender,Receiver,

Protocol class, Hop Counter,

Segmentation,User message)

XUDTS(Sender,Receiver,

Cause, Hop Counter,

Segmentation, User message) X




SCCP connection-oriented messages

Message Service type Description

CC 2,3 Connection Confirm

CR 2,3 Connection Request

CREF 2,3 Connection Refused

AK 3 Data acknowledgement. Used to control the window flow control mechanism selected for the data

transfer phase.

DT1 2 Data Form 1

DT2 3 Data Form 2 (not used in GSM-protocol class 3)

ED 3 Expedited Data. Similar to DT2 but it can bypass the flow control mechanism.

EA 3 Expedited Data acknowledgement. Every ED message must be acknowledged with EA message before

another ED is sent.

IT 2,3 Inactivity Test. Sent periodically to check if the connection is still active at both ands and to audit the

consistency of data.

ERR 2,3 Protocol Data Unit Error. Sent on detection of the SCCP protocol error.

RLSD 2,3 Released

RLC 2,3 Release Complete

RSC 3 Reset Confirm.

RSR 3 Reset Request. Indicates that the SCCP needs to reset the sequence numbers.




SCCP Connection-oriented

Connection Request (CR)

Connection Confirm (CC)

DT1

...DT1

Released (RLSD)

Released Complete (RLC)

One sig. Connection :same Local Ref. No + SLS


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A BSel

LRA

Sel

LRB

LRBLRA

CR

(Protocol class, LRA,

Receiver,

poss. User message)

CC

(LRB, Protocol class, LRA,

poss. User message)

Successful SCCP connection establishment

ABSel

LRA

LRA

CR

(Protocol class, LRA,

Receiver,

poss. User message)

CREF

(LRA, Cause)

Unsuccessful SCCP connection establishment

X


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* If the massage is longer than 255 bytes

A B

LRBLRA

DT1

(LRB, Segmenting/Reassembling *),

User message)

DT1

(LRA, Segmenting/Reassembling *),

User message)

LRB LRA

A B

LRBLRA

RLSD

(LRA,LRB, Cause,

poss. User message)

LRB LRA

RLC

(LRA,LRB)

SCCP data transfer

SCCP connection release


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SCCP message structure: General Layout

D P C

O P C

S L S

Message type code

Mandatory fixed part

Optional part

Mandatory variable part

MTP

Routing

Label

SCCP

Message

SIF


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SCCP message structure

Massage type code

Mandatory parameter A

Mandatory parameter F

Pointer to parameter M

Pointer to parameter PPointer to start of optional part

Length indicator to parameter MMandatory parameter M

Length indicator parameter P

Mandatory parameter P

Identifier parameter XLength indicator parameter X

Optional parameter X

Identifier parameter Z

Length indicator parameter Z

Optional parameter Z

End of tue optional parameters

Mandatory fixed part...

.

.

.

.

.

.

.

.

.

Mandatory variable part

Optional part

8 | 7 | 6 | 5 | 4 | 3 | 2 | 1


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SCCP message example - UDT

Parameter Type Length(octets)

Value

Message type Mandatory fixed part 1 09

Protocol class Mandatory fixed part 1 0 or 1

Called party address Mandatory variable

part

2 minimum

Calling party address Mandatory variable

part

2 minimum

Data Mandatory variable

part

2-Xa)

a) Due to the ongoing studies on the SCCP called and calling party address, the maximum length of

this parameter needs further study. Note that the transfer of up to 255 octets of user data is allowed

when the SCCP called and calling party address do not include global title.


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SCCP message structure: example of UDT

F CK SIF SIO LIF

I

BFSN

B

I

BBSN FMTP

messageFirst bit

transmitted

8n 8 8 32 4 4 [bit]

User DataPointer

to data

Protocol

class

Messagetype

H09 UDT

RoutingLabel

(SLS,OPC,DPC)

SSF1000

NA0

SI0011

SCCP

User data

Le

n

g

t

h

Calling

party

address

Le

n

g

t

h

Called

party

address

Le

n

g

t

h

Data

Ptr.

CgPA

Ptr.

CdPA

Ptr

SCCP

message


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SCCP Addressing

Addressing within SCCP makes use of 3 separate elements

i.e. DPC, GT, SSN

DPC is the address that requires no translation Determine if the message is destined for that in SP or required to be

routed over SS7 via MTP

GT may comprise of dialed digits or another form of addressthat will not be recognized in SS7 network

If the message required to be routed over SS7 network, translation isrequired

SSN will identify a subsystem accessed via the SCCP within anode


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SCCP Addressing for Called/Calling party addressReserved

for

national

use

Routing

indicatorGlobal title indicator

SSN

indicator

Point code

indicator

S P C

Subsystem Number

Translation Type (TT)

Numbering Plan (NP) Encoding Scheme

Nature of Address (NA)Spare

O/E*

* With Typ 1 : Odd-Even-IndicatorWith Typ 4: Spare (0)

2. GT-Digit

4. GT-Digit

1. GT-Digit

3. GT-Digit

0 0

12345678

MSB

LSB

Address IndicatorOctet 1

Octet 2

Octet 3

.

.

.

Octet n


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Address indicator

Bit 1: 1 indicates that the address contains a Signalling Point Code (SPC)

Bit 2:1

indicates that the address contains a Subsystem Number (SSN)Bit 3-6: contain the Global Tible Indicator (GTI), which is encoded as follows:Bits 6 5 4 3

0 0 0 0 No global title includes

0 0 0 1 Global title includes nature of address indicator only

0 0 1 0 Global title includes translation type only

0 0 1 1 Global title includes translation type, numbering plan and encoding scheme

0 1 0 0 Global title includes translation type, numbering plan, encoding schemeand nature of address indicator

0 1 0 1 Spare international

0 1 1 1

1 0 0 0 Spare national

1 1 1 0

1 1 1 1 Reserved for extension

Bit 7: contains Routing Indicator (RI) 1 indicates routing on SSN 0 indicates routing on GT

Bit 8: reserved for national use and is always set to zero on an international network


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Subsystem number (SSN)

Bits 8 7 6 5 4 3 2 10 0 0 0 0 0 0 0 SSN not known/not used

0 0 0 0 0 0 0 1 SCCP management (SCMG)0 0 0 0 0 0 1 0 Reserved for ITU-T allocation

0 0 0 0 0 0 1 1 ISDN user part

0 0 0 0 0 1 0 0 OMAP (Operation, Maintenance and Administration Part)

0 0 0 0 0 1 0 1 MAP (Mobile Application Part )

0 0 0 0 0 1 1 0 HLR (Home Location Register)

0 0 0 0 0 1 1 1 VLR (Visitor Location Register)

0 0 0 0 1 0 0 0 MSC (Mobile Switching Centre)0 0 0 0 1 0 0 1 EIC (Equipment Identifier Centre)

0 0 0 0 1 0 1 0 AUC (Authentication Centre)

0 0 0 0 1 0 1 1 ISDN supplementary services

0 0 0 0 1 1 0 0 Reserved for international use

0 0 0 0 1 1 0 1 Broadband ISDN

0 0 0 0 1 1 1 0 TC test responder

0 0 0 0 1 1 1 1 Reserved for international use

0 0 0 1 1 1 1 10 0 1 0 0 0 0 0 Reserved for national networks

1 1 1 1 1 1 1 0

1 1 1 1 1 1 1 1 Reserved for expansion of national and international SSN


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Translation type

Bits 87654321 Decimal value Translation type

00000000 0 Unknown

00000001 1

00111111 63

International services

01000000 64

01111111 127

Spare

10000000 128

11111110 254

National network specific

11111111 255 Reserved for expansion


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Encoding scheme

Bits 4321 Encoding scheme

0000 Unknown

0001 BCD, Odd number of digits

0010 BCD, Even number of digits

0011 National specific

0100

1110

Spare

1111 Reserved


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Numbering plan

Bits 8765 Numbering plan

0000 Unknown

0001 ISDN/telephony numbering plan

(Recommendations E.163 and E.164)

0010 Generic numbering plan

0011 Data numbering plan (Recommendation X.121)

0100 Telex numbering plan (Recommendation F.69)

0101 Maritime mobile numbering plan (Recommendations E.210, E.211)

0110 Land mobile numbering plan (Recommendation E.212)

0111 ISDN/mobile numbering plan (Recommendation E.214)

1000

1101

Spare

1110 Private network or network-specific numbering plan

1111 Reserved


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Nature of address

Bits 7654321 Nature of address

0000000 Unknown

0000001 Subscriber number

0000010 Reserved for national use

0000011 National significant number

0000100 International number

0000101

1111111

Spare


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SCCP Global Title

E.164 Mobile Station ISDN Number, MSISDN

Used both in subscriber and network element numbering

MSISDN = Country Code + National Destination Code + SubscriberNumber

E.212 International Mobile SubscriberIdentity, IMSI

Used in identifying subscribers and subscribers HLRs

IMSI = Mobile Country Code + Mobile Network Code + Mobile Station Identification Number

E.214 Land Mobile Global Title

Used in identifying subscribers HLRs

Country Code + National Destination Code + Mobile Station Identification Number


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Two types of routing by SCCP

Routing on MTP3 routing label

Routing on GT (Global Title)


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Routing by DPC vs GT

To be able to route out signalling message by MTP

Upper layer has to know DPC (Destination Point Code)

What will happen ifDPC is unknown from upper layer?


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Routing on Label and on GT

BSSAP/ RANAP MAP INAP

Is DPC contained

in the message?

Yes No (there is a GT)

Routing on label(do nothing)

Routing on GT(GT analysis)

Message handling

Applicationparts

SCCP

MTP


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SCCP message routing

BSSAP MAP INAP

RI = GT

Application parts

SCCP

MTPSIO = SCCP

GT Analysis

Other DPC

Discrimination

DPC = own SPC

Routing

Distribution

DPC is not own SPC

RI RI = SSN

DPC Own SPCSSN


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Global Title Analysis

GT analysis is used to analyze a GT to find out the destination

of the signalling message

When the DPC receives the messageRI = SSN, there is no need for GT analysis

RI = GT, the GT analysis has to be performed

GT

analysis

NumberingPlan

Digits

DPC

RI


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Example of SCCP routing on GT

International Roaming, the first location update

MS sends IMSI to the VLR in VPLMN

VLR will send update location message to HLR

Does the VLR know the SPC of the HLR?Does the VLR know the HLR address?

How can the VLR send the LU message to the HLR?


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IMSI analysis: result is GT

IMSI analysis is used to analyze IMSI to find out where the

subscribers HLR is

IMSI

analysis

IMSI

(E.212)

Hybrid no.

(E.214)

MCC MNC MSIN Operator No. MSIN

I t ti l R i Th fi t l ti d t


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International Roaming: The first location updateIMSI or E.212

Hybrid no. or E.214

Message handling

SCCP routing on GT

MTP

IMSI

analysis

GT

analysis

E l f SCCP i l b l


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Example of SCCP routing on label

Home subscriber, the first location update

MS sends IMSI to the VLR in HPLMN

VLR will send update location message to HLR

Does the VLR know SPC of the HLR?

How can the VLR send LU message to the HLR?

IMSI l i lt i DPC


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IMSI analysis: result is DPCIMSI analysis is used to analyze IMSI to find out where the

subscribers HLR is

IMSI

analysis

IMSI

(E.212)DPC of HLR

MCC MNC MSIN

H b ib th fi t l ti d t


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Home subscriber: the first location update

IMSI or E.212

DPC of HLR

Message handling

SCCP routing onlabel

MTP

IMSI

analysis

O t t f GTT f ti


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39 Nokia Siemens Networks Presentation / Author / Date / Document NumberFor public use IPR applies

Output of GTT function

Successful

Output contains required parameter to route the messageforward in the network or to distribute the message

Unsuccessful where no translation exist

Failure cause: no translation for an address of such nature,no translation for this specific address

Unsuccessful where translation exist but no availabledestination can be found

Failure cause: MTP failure, SCCP failure, Subsystem failure

SCCP t (SCMG)


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F bli IPR li

SCCP management messages (SCMG)

Message Description

SSA Subsystem Allowed

SOG Subsystem Out Of Service Grant

SOR Subsystem Out Of ServiceRequest

SSP Subsystem Prohibited

SST Subsystem Status Test

SSC Subsystem Congested

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