1-Manthri SS7
-
Upload
chakravarthi-chittajallu -
Category
Documents
-
view
52 -
download
3
Transcript of 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)
Signaling System Number 7
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.
Signaling System Number 7
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
F SIO FIB FSN BIB BSN CK FSIF LI>2Label
Management information SLC OPC DPCMTP L3messages
MSU -- Message Signal Unit MTP Layer 3
• Signaling NW Management Messages ---- SNM
• Signaling NW Testing Messages --- SNT
TYPES
F SIO FIB FSN BIB BSN CK FSIF LI>2Label
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):
Message Type Indicator H1
H00010
•Transfer controlled message (TFC)
•signaling-route-set-congestion-test signal (RCT)
3. Signaling-traffic-flow-control Messages (FCM):
Message Type Indicator H1
H00011
•Transfer prohibited signal (TFP)
•Transfer restricted signal (TFR)
•Transfer allowed signal (TFA)
4. Transfer-prohibited / allowed / restricted messages:
Message Type Indicator H1
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
Message Type Indicator H1
•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
Message Type Indicator H1
•Traffic-restart-allowed message (TRM):
•Transfer restart allowed signal (TRA)
7. Traffic-restart-allowed message
Message Type Indicator H1
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)
Message Type Indicator H1
H01000
•User part unavailable (UPU)
9. User part flow control messages (UFC):
Message Type Indicator H1
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