1-Manthri SS7

Today ‘s Topic

SS7 - So Simple --- If not

Make it Simple

Means

Overview On SS7

Signaling

What is Signaling in Telecom networks?

User A: Tells the network he wants to talk to User B.Network signaling: Sets up the call and Charges the right amount.

User

User

User User B User

User

User A Telephone Network

Access Signaling

ON/Off hook Tones Dial pulses/DTMF tones

Telephone Exchange

Trunk Signaling

Telephone Exchange

Telephone Exchange

Seizing

Seizing acknowledged

B number

Conversation

Release

Release complete

Signaling System 7

Q.700 Introduction to CCITT Signaling No.7 Q.701- Q.709Message transfer part MTP Q.710 Simplified message transfer part Q.711-Q.716 Signaling connection control part SCCP Q.721-Q.725 Telephone user part TUP Q.730 ISDN supplementary services Q.741 Data user part DUP Q.761-Q766 Integrated services digital network ISUP Q.771-Q.775 Transaction Capabilities Application Part TCAP Q.780-Q.783 Test specification Q.791 Monitoring and measurements Q.795 Operation,Maintenance and Administration part

OMAP

Signaling System no. 7 recommendations

SS7 History

1980: CCITT Yellow Book MTP - TUP1984: SS7 in operation in Denmark1984: CCITT Red Book SCCP - ISUP1984: Bellcore: Intelligent Network1985: SS7 in operation in Sweden and UK1986: SS7 in operation in Australia and France1988: CCITT Blue Book TCAP - ISUP1989: SS7 in operation in Italy1992: CCITT White Book Q.767 - test & surveillance - performance

Reduced call set-up time

Enhanced call control

Less signaling equipment ~ cost effective

Requirement for ISDN (call setup time < 100 ms)

Requirement for GSM Mobile Telephone

(register updates)

Why SS7 ??

CAS SS7max 2 kbit/s max 64 kbit/s

Telephone

Integrated Services Digital Network (ISDN)

Mobile Cellular Radio (GSM, NADC)

Billing Services (ABS)

Custom Local Area Switching Service (CLASS)

Private Virtual Network (PVN)

Services to be provided by SS7

SS7 Network

Typical SS7 Network

Traffic circuits

STP STP

STP STP

SCP

PC = 248-132-1

PC = 248-132-2

PC = 248-132-3

PC = 248-43-0

PC = 248-43-1

PC = 248-43-2

PC = 248-43-3

Endoffice

Endoffice

SSP SSP

Data base

Signaling Points - types

Service Switching Point (SSP) :

provides the functionality of communicating with the voice switch and creating the messages or signal units needed for transmission in SS7 network.

Signal Transfer Point (STP) :

serves as router in the SS7 network. It switches the SS7 messages as received from various SSPs through the network to their appropriate destinations.

Service Control Point.(SCP) :

serves as an interface to telephone company databases. These databases store information about subscribers services, calling card validation and fraud protection.

Linksets and Loadsharing

Linkset

Link

1

2

3

n

STP

max = 16

SSP

signaling System No 7 (SS7)

Flag

Flag

SS7 Message

essage

SS7 M

SS7 Protocol Stack

Physical

Signaling Link

Network

SCCP

TCAP

ISUP

TUP

MTP

Level 1

Level 2

Level 3

Level 4

Layer 1

Layer 2

Layer 3

Layer 4,5,6

Layer 7

OSI Model SS7 LevelMAP

OMAPINAP

Signaling System Number 7

Physical Level

Standard Interfaces: 2.048 Mb/s (CCITT G.703/704)1.544 Mb/s (DS-1)V.35, DS-0, DS-0ADatacom RS-232, RS-449

Data Rate: usually 56 or 64 kb/s but down to 4.8 kb/s for some interfaces.

Error Performance : 1 x 10-6

MTP Level 1 (Physical Layer)


The Signaling Link

SS#7 Signaling Link Functions

LINK STATE CONTROL

TRANSMITFUNCTIONS

RECEIVEFUNCTIONS

FLOWCONTROL

DELIMITING, ALIGNMENT AND ERROR DETECTION

FRAMES

MESSAGES MESSAGES

LINKSTATUS

BITS

FRAMES

LEVEL 1

LEVEL 3

FLAG CK FLAG Information

01111110 0111111016bit N x 8 bit

Basic Frame

DELIMITING, ALIGNMENT AND ERROR DETECTION

From frames to bits and back

CK INF

INF

INFCK

F INFCK F

CHECKSUMCOMPUTATION

ZEROINSERTION

FLAGADDING

CHECKSUMVERIFICATION

ZEROREMOVAL

FLAGREMOVAL

Zero Bit Insertion Technique

FLAG = 01111110

DATA TO BE SENT:0011111110101111000011111010INSERTED ZEROS AFTER FIVE ONES

TRANSMITTED DATA:001111101101011110000111110010INSERTED ZEROS REMOVED

DATA AS DELIVIRED:0011111110101111000011111010

Transmission direction

Basic Signal Unit (Frame)

FBSNBIB

FSNFIB

INFORMATIONF CK

8717162N x 8168

Span of frame check and zero insertion

First bit transmitted

FSN - Forward Sequence Number

7 bit field

Modulus 127

FSN is a tag on each frame

Used to detect discarded frames

Incremented for each new frame

BSN - Backward Sequence Number

7 bit field

Modulus 127

Used to acknowledge frames

Used to request retransmissions

Acknowledge

FSN = 1

FSN = 0

FSN = 2

BSN = 2

FSN = 3

FSN = 4

BSN = 4

Retransmit

FSN = 81

FSN = 80

FSN = 82

BSN = 81

FSN = 82

FSN = 83

FSN = 83

One bit field

Used to detect requests for retransmissions

Toggled for every request for retransmission

BIB -Backward Indicator Bit

One bit field Used to detect new frames from retransmitted frames Toggles for every retransmitted frame

FIB -Forward Indicator Bit

Flag

SP SP

Error correction and re-transmission

Inform Fib=0 Fsn=1CK Bib=0 Bsn=0 Flag

Flag

Flag

Flag

Flag

Flag

Flag

Flag

Flag

Flag

CK

CK

CK

CK

CK

CK

CK

CK

CK

Inform

Inform

Inform

Inform

Inform

Inform

Inform

Inform

Inform

Fib=1

Fib=0

Fib=0

Fib=0

Fib=0

Fib=0

Fib=0

Fib=0

Fib=0

Fsn=7

Fsn=2

Fsn=7

Fsn=6

Fsn=5

Fsn=1

Fsn=4

Fsn=3

Fsn=2 Bib=0

Bib=0

Bib=1

Bib=0

Bib=0

Bib=0

Bib=0

Bib=0

Bib=0

Bsn=2

Bsn=6

Bsn=1

Bsn=1

Bsn=1

Bsn=4

Bsn=0

Bsn=0

Bsn=0

Flag

Flag

Flag

Flag

Flag

Flag

Flag

Flag

Flag

Error Monitoring

ERROR

DOWNGOOD

UP

COUNTER

ALARM

/ 256

Signalining Units

Signal Unit TYPES

F CK SIF SIO LI FSNBIB

BSN FMSU

LSSU

FISU

F CK SF LI FSNBIB

BSN F

F CK LI FSNBIB

BSN F

FIB

FIB

FIB

Length Indicator

F CK SIF SIO LI FSNBIB

BSN FFIB

6 bit field

Tell about number of bytes remaining in message

Message length less than 62 bytes field value is valid.

Message length more than 63 bytes field value is always 63.

LI = 0 Then it is a FISU

LI = 1 OR 2 it is LSSU

LI = MORE THAN 2 it is MSUThe Next Field is 2 bits which is Spare

LI - Length Indicator

Fill In Signal Unit

Fill In Signal Unit

FISU F CK LI FSNBIB

BSN FFIB

Short message (only 7 bytes including flags)

FSN & BSN not incremented as a rule

Transmitted when nothing else to transmit

Link Status Signal Unit

Message with 8 or 9 Bytes including flags

Transmitted when Alignment is required between the Links

and to pass the information About Status of the Link.

LSSU -Link Status Signal Unit

F CK SF LI FSNBIB

BSN FFIB

SF Carries Status of Link

LSSU -- LINK STATUS SIGNAL UNIT

F CK SF LI FSNBIB

BSN FFIB

ABCSPARE

C B A Indication0 0 0 Status "O" - Out of Alignment ---- SIO0 0 1 Status "N" - Normal Alignment --- SIN0 1 0 Status "E" - Emergency Alignment -- SIE0 1 1 Status "OS" - Out of Service -- SOS1 0 0 Status "PO" - Processor Outage -- SPO1 0 1 Status "B" - Busy ----------------- SIB

Alignment of a NEW Signaling Link

LSSU SIO

SP SP

LSSU SIO or SIN

LSSU SIN

LSSU SIN

LSSU SIN

LSSU SIN

Start

Aligned

Proving

8.2 sec

Aligned andready

Alignment

Message Signal Unit

F SIO FIB FSN BIB BSN CK FSIF LI>2Label

Management information SLC OPC DPCMTP L3messages

Signaling informationCircuit ID Code

OPC DPCTUPmessages SLS

Signaling information CIC OPC DPCISUPmessages SLS

SCCP User Data OPC DPCSCCPmessages SLS

MSU -- Message Signal UnitTypes

Transmit Priorities

LSSU - Line Status Signal Unit MSU - Message Signal Unit FISU - Fill In Signal Unit

! Line is always active.


Network Level

MTP Level 3 (Network Layer Functions)Message Handling

distribution

discrimination

routing

Network Management

–traffic management–route management–link management

Level 4

Level 2


Management information SLC OPC DPCMTP L3messages

MSU -- Message Signal Unit MTP Layer 3

• Signaling NW Management Messages ---- SNM

• Signaling NW Testing Messages --- SNT

TYPES


D C B A D C B ASub-service

FieldService

indicator

Indication D C B A

Signaling NW management messages - SNM

Signaling NW testing messages - SNT

0 0 0 0

0 0 0 1

Service Information Octet

Service indicator :

Sub Service FieldCD AB

SpareInternational Network Spare

National Network

Reserved For National Use

00

01

10

11

Signaling Network Management --SNM

Signaling Network Management -- Functions

Link Management

Traffic Management

Route Management

F SIO FIB FSN BIB BSN CK FSIF LI>2

NW Management information H1 H0 Routing Label

4 4

SNM Message Format

SIO

SSXX0000

LABEL

DPC

14

OPC

14

SLC

4

HEADINGCODE

8

Signaling Network Management Message

N X 8

Message group and type

Signaling link code

Standard routing point codes

Network id

Signaling Network Management

Heading Codes(8 -bits)

Heading Code Formatting

4-BITMESSAGEGROUP

INDICATOR

4-BITMESSAGE

TYPEINDICATOR

D C B AD C B A

H1 H0

• Changeover and changeback messages (CHM)

• Emergency-changeover message (ECM)

• Signaling-traffic-flow-control messages (FCM)

• Transfer-prohibited / allowed / restricted messages (TFM)

• Signaling-route-set-test messages (RSM)

• Management inhibit messages (MIM)

• Traffic-restart-allowed message (TRM)

• Signaling-data-link-connection-order message (DLM)

• User part flow control messages (UFC)

Signaling Network Management - messages Group Indicators --- (H0)

•Changeover-order signal (COO)

•Changeover-acknowledgement signal (COA)

•Changeback-declaration signal (CBD)

•Changeback acknowledgement signal (CBA)

1. Changeover and changeback messages H00001

Message Type Indicator H1

•Emergency changeover order signal (ECO)

•Emergency changeover acknowledgement signal (ECA)

2. Emergency-changeover message (ECM):


H00010

•Transfer controlled message (TFC)

•signaling-route-set-congestion-test signal (RCT)

3. Signaling-traffic-flow-control Messages (FCM):


H00011

•Transfer prohibited signal (TFP)

•Transfer restricted signal (TFR)

•Transfer allowed signal (TFA)

4. Transfer-prohibited / allowed / restricted messages:


H00100

•Signaling route set test signal for prohibited destination (RST)

•Signaling route set test signal for restricted destination (RSR)

5. Signaling-route-set-test messages (RSM)

H00101


•Link inhibit signal (LIN) •Link uninhibited signal (LUN) •Link inhibit acknowledgement signal (LIA) •Link uninhibited acknowledgement signal (LUA) •Link inhibit denied signal (LID) •Link forced uninhibited signal (LFU) •Link local inhibit test signal (LLT) •Link remote inhibit test signal (LRT)

6. Management inhibit messages (MIM):H00110


•Traffic-restart-allowed message (TRM):

•Transfer restart allowed signal (TRA)

7. Traffic-restart-allowed message


H00111

•Signaling-data-link-connection-order signal (DLC)

•Connection-successful signal (CSS)

•Connection-not-successful signal (CNS)

•Connection-not-possible signal (CNP)

8. Signaling-data-link-connection-order message (DLM)


H01000

•User part unavailable (UPU)

9. User part flow control messages (UFC):


H01010

Signaling Network Testing ---- SNT

SNT Message Format

SIO

SSXX0001

LABEL

DPC

14

OPC

14

SLC

4

HEADINGCODE

8

Message group and type

Signallng link code

Standard routing point codes

Network id

Signaling Network Testing

Spare

4

Length indicator

4

Test pattern

n x 8

D C B A Meaning

0 0 0 1 (SLTM) signaling link test message 0 0 1 0 (SLTA) signaling link test acknowledgement

message

Signaling Network Testing ----- H0

H1

Test sequence

A B

A5A5A5A5A5A5A5 SLTM

SLTA A5A5A5A5A5A5A5

Network Layer -Examples

Change over

BA

A

COOTFP

COO

Concerned SP Affected SP

B

COO

TFP

TFP

A

B

C

D

E

F

CBD

CBD

TFA

TFA

A

B

C

D

E

F

CBA

Change back

TFA

Application Layer

ISDN User Part (ISUP)

CCITT Recommendations

Q.761 Functional description of the ISDN user part

Q.762 General function of messages and signals

Q.763 Formats and codes

Q.764 Signaling procedures

Q.766 Performance objectives in the ISDN application

Telephone signaling

Calling party identification

Called party identification

Call redirection

Connect when free

Complete when busy

Malicious call identification

Closed user groups

ISDN User Part - Services

F SIO FIB FSN BSN CK FSIF LI>2Label

Signaling information CIC OPC DPCISUPmessages SLS

Format of ISUP message

BIB

Signaling information H1 HO

ISDN UP Messages

Groups -- H0 Messages- H1

Forward set-up

General set-up

Backward set-up

Call supervision

Circuit group supervision

Circuit supervision

In-call modification

End-to-end

IAM, SAM

INR, INF, COT

ACM, CON CPG

ANM, FOT, REL

DRS, RLC, CCR, RSC, LPA, BLO, UBL, UCIC,

BLA, UBA, OLM, SUS, RES, CFN

CGB, CGU, CGBA, CGUA, GRS, GRA, COR

CMR, CMC, CMPJ, FAA, FAR, FJR

PAM, USR

ISUP Message Types

ACM Address complete ANM Answer BLO BlockingBLA Blocking acknowledgementCMC Call modification completedCMRJ Call modification rejectCPG Call progressCRG Circuit group blockingCCB Circuit group blocking ack.CGBA Circuit group queryGRS Circuit group query responseGRA Circuit group resetCGUA Circuit group reset ack.CGU Circuit group unblockingCQM Circuit group unblocking ack.CQR Charge information

Message type Code

0000 01100000 10010001 00110001 01010001 11010001 11000001 11100010 11000001 10000001 10100010 10100001 01110010 10010001 10010001 10110011 0001

ISUP Message Types cont.

CFN Confusion CON Connect COT ContinuityCCR Continuity check requestDRS Delayed releaseFAA Facility acceptedFRJ Facility rejectFAR Facility requestFOT Forward transfer.INF InformationINR Informatin requestIAM Initial addressLPA Loop back acknowledgementOLM OverloadPAM Pass-along.

Message type Code

0010 11110000 01110000 01010001 00010010 01110010 00000010 00010001 11110000 10000000 01000000 00110000 00010010 01000011 00000010 1000

ISUP Message Types cont.

REL Release RLC Release completeRSC Reset circuitRES ResumeSAM Subsequent addressSUS SuspendUBL UnblockingUBA Unblocking acknowledgementUCIC Unequipped CIC.USR User to user information

Message type Code

0000 11000001 00000001 00100000 11100000 00100000 11010001 01000001 01100010 11100010 1101

ISDN successful call

C

STP

B

SP

A

SP

Set-up IAM IAM

ACM ACM

Alerting

ANMANM

ConnectConnect

Alertin

g

Set-up

ISDN call release

C

STP

B

SP

A

SP

Disconnect

RELREL

RLC RLCRelease

Disconnect

SS7 Protocol Stack

Physical

Signaling Link

Network

SCCP

TCAP

ISUP

TUP

MTP

Level 1

Level 2

Level 3

Level 4

Layer 1

Layer 2

Layer 3

Layer 4,5,6

Layer 7

OSI Model SS7 LevelMAP

OMAPINAP

SCCP

Provides setup of logical signaling

connections

Provides release of logical signaling

connections

Provides transfer of data

TCAP

Purpose:

Support of real-time sensitive information transfer in a distributed environment.

Intelligent Networks ----- SS7

LX

IP

SSPLX

SSPTX

SCP SDP

SMSSCESCE - Service Creation EnvironmentSMS - Service Management SystemSCP - Service Control PointSDP - Service Data Point (Database)IP - Intelligent PeripheralSSP - Service Switching PointSTP - Signaling Transfer PointTX - Transit ExchangeLX - Local Exchange

SpeechSignalingProprietary

STP

IN Protocols ----- 800 Service ------ SS7

MTPMTP

SSP STP

SCCP

TCAP

INAP

SCCP

TCAP

INAP

MTP

800

800+TCAP

800+TCAP+SCCP

SCCP FRAME SCCP FRAME SCCP FRAME

SCP

800 Call Setup

LX

STP STP

LX

SCP

BobBob

Jim’s Jim’s AutoAuto parts parts 800-800-555555-1234-1234

Voice Path

TCAP

Quer

y

TCAP

Quer

y

Res

pons

e

Res

pons

e

Res

pons

e

Res

pons

eIAM

IAM IAM

THANK YOU

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1-Manthri SS7