telecom ss7 basic.pdf
TRANSCRIPT
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CCS Associated
CCS Quasi associated
CCS Non associated.
TELECOM BASICS
E1a) 256 bytes per frameb) 8 bits Each TS in E1 Framec) 0.125uS time taken by one framed) Total 8000 frames in One Second
Voice Theorma) Voice Frequency ~ 300 to 3300 Hz , bandwidth = 4000 Hzb) Nyquist theorm = Min 8000 sampling rate reqd ( 4000*2 )c) One Sample = 8 bits ( Reprsntation of 256 Voice Levels , 2 pow 8 =256)
Erlanga) Unit of Traffic descibes total traffic volume in one hour b) Erlang = Busy time for ckts / Avl Time for measurment , Ex : 20/60 = 3Er 15ckt - 8.1 Er 31ckt - 21.5 Er 3 E1 - 77 Er 10 E1 - 286 Er 20 - 59230ckt - 20.3 Er 02 E1 - 48 Er 5 E1 - 136 15 E1 - 439 Er 30 - 901
E1 Physical Interfacea) 0th TS used for synchronization ( 0011011)b) Modes of Operation
1. Unframed - No TS at all2. Framed - All 32 TS used for data3.Multiframe - 0 TS for sync, rest 31 for data
c) Bit '1' - 3V , Bit '0' - 0~0.3 V
CAS ( Channel Associated Signalling )a) Uses INBAND Signalling ( Voice frequencies )b) Signaliing Associated in that E1 only - TS = 16 Line Sig. And TS=All RegisteredSignalling
CAS Line Signallinga) Uses TS = 16 for indication of ck t. Status only ( I.e.FREE , SIEZ , FREE BY A/B , BUSY etc….)
ABCD Fwd ABCD Bckwd STATUS
10XX 10XX IDLE
00XX 10XX SIEZ
00XX 11XX SIEZ ACK
00XX 01XX ANS
00XX 11XX B PARTY REL
10XX 0/10XX A PARTY REL
Ist Frame : TS-1 & TS-17 (4+4 bits)
IInd Frame : TS-2 & TS-18
....
....15th Frame : TS-15 & TS-31
CAS Registered Signallinga) Uses voice TS for Registered Signalling .b) Types : DECADIC , DTMF , R2 Semi C , R2FullyCc) R2MF - R2 Multi Freq Fully Compled (Ack Reqd)
d) MF - Combination of 2 Freq to represent one info
CAS Registered Signalling
Grp A Bwd Sig. Grp B Bwd Sig.
1 Send Next Dig. 2 Changed No.
2 Restart 3 Called Line Busy
3 Change over grp B 4 Congestion
4 CLI 5 Unallocated No.
5 Send Cat of A Party 6 Normal subs free
6 Switch to speech
7 Send last but 2 digits8 Send last but 3 digits
9 Send last but 1 digitGrp 1 Fwd Sig. Grp II Fwd Sig.
1 Digit '1' 1 Ordinary Subs
2 Digit '2' 2 Priority Subs
3 Digit '3' 5 Operator
4 Digit '4' 6 STD Coin Box
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CCS STRUCTURE
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8 7 1 7 1 6 2 8
Layer#2
FLAG BSN BIB FSN FIB LI SPARE DATA CRC
Layer#
3
SubService Field Service Indicator
Priority - 1,2,3
( Low to High )
Network
Indicator
NAT0/1,
INAT0/1
SIOSIF
CCS 7 Layers
0 FISU1-2 LSSU3-63 MSU
Layer-2 : CRC , Retransmission ( PCR ) , Error Correction and detection Etc
Layer-3 :b. Signalling Route Management - Traffic / Sharing / Overloading Routingc. Signalling Link Management - Control / Monitor / Status of Linkse Signalling Traffic Management - Change over/ Back in case of Faile. Alignment - SIO , SIN , SIE , SIOSf. Message Distribution - Distributing the MSG to ISUP , SCCPg. Message Discrimination - Mine or Other DPC / NW
Service Indicator 0 - SNM ( Signalling NW Management Message )1 - MTN ( Mtc Regular Msg )2 - MTNs ( Mtc Special Message )3 - SCCP ( Carry Non-Voice Traffic Ex: SMS )4 - TUP5 - ISUP ( Voice related traffic )6 - Data User Part ( Call & ckt Related )7 - Data User part ( Facility Regn & Cancellation )
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DPC OPC
CIC
(only
ISUP)
ISUPMessage
Type
Optional
FIX
IAM
Optional VariableMandatory Variable
SLS ( 4
Bits ,
Max 16
Selection
Mandatory FIX
A Party Category , Forward Call
Indicator B Party No , User service Info
USER PART
CLI , Carrier , NW , HOPs
ISUP Message Type : IAM ( Initial Address Message )INR ( Information Request )
ACM ( Address Complete ) ANM ( Answer Message )REL ( Release Message )RLC ( Release Complete )BLO ( Blocking )UBL ( Uublocking )BLA ( Blocking Acknowledment )CPG ( Call Progress )
Layer-3 TimersT1 Delay to avoid message mis-sequencing on changeover .5 to 1.2 sec.T2 Wait for changeover Ack .7 to 2. 0 secT3 Delay to avoid message mis-sequencing on changeback .5 to 1.2 sec.T4 Wait for changeback Ack (1st attempt) 5 to 1.2 sec.T5 Wait for changeback Ack (2nd attempt) 5 to 1.2 sec.
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SCCPMessage
Type
Optional
FIX
UDT
XUDT
UDTs
XUDTs
Used to transport user data
and SCCP management
messages in the connection-
less mode. It can Segment /
DeSegment data as per itssize
Used to indicate to the
originating SCCP user that a
UDT message cannot be
delivered to the specified
destination. The data field of
the UDT message and the
reason for the return are
Used for Mandatory FIX
1. Called Party
2. Calling Party
3. User Data
Mandatory Variable
1. Called Party
2. Calling Party
3. User Data
1. Return Cause
2. Hop Counter
1. Called Party
2. Calling Party
3. User Data
1. Segmentation data
Optional Variable
1. Called Party
2. Calling Party
3. User Data
1. Return Cause
2. Hop Counter 1. Segmentation data
Protocol Class : Class -0 : Basic Connectionless ( Non Critical,TCAP )Class -1 : Sequenced Connectionless (Critical, TCAP )Class -2 : Basic Connection Oriented (BSSAP )
Class -3 : Flow Control Connection Oriented(BSSAP )Class -4 : Flow Control + Err Recovery
Calling / Called party :1. Address Indicator :
a. Routing Indicator : GT based or ( DPC + SSN )b. GTT Indicator : No GT or GT - 1 or 2 or 3 or 4c. SSN Indicator : Present / Not Presentd. Point Code Indicator : Present / Not Present
2. Address : a. Point Codeb. SSN
c. GT - 1 :i. Nature of Address Ind : Subscriber Number / National Sig. No. / International No.ii. Odd / Even Indicator ( Spr) iii. Address Information ( 919839212499 )
d. GT - 2 :i. Translation Type ii. Address Information ( 919839212499 )
e. GT - 3 :i. Translation Type ii. Encoing Scheme - Unknown / BCD Odd / BCD Eveniv. Address Information iii Numbering Plan - ISDN / Telephony / Data / Telex / Land Mobile / Mobile
e. GT - 4 :i. Translation Type ii. Encoing Scheme - Unknown / BCD Odd / BCD Eveniii. Numbering Plan iv. Nature of Address Indicator v. Address Information ( Contains Address for Example : 919839212499 )
User Data :1. Length Indicator 2. User Data Ex: TCAP etc
Connection Oriented
- Only used in BSSAP where heavy data transfer is required for ex. Between MSC/VLR to BSC to BTS
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SCCP - Routing Protocol
SSN1 SCCP Management3 ISDN user part4 OMAP (Operation, Maintenance and Administration Part)5 MAP (Mobile Application Part)6 HLR (Home Location Register)7 VLR (Visitor Location Register)8 MSC (Mobile Switching center)9 EIR (Equipment Identifier register)10 AUC (Authentication Centre)11 ISDN Supplementary Services (SSAP)13 Broadband ISDN edge-to-edge applications254 Base Station System Application Part (BSSAP)
SCMG Functions- Signaling point status management : Failure, recovery, and congestion information of signaling
points, provided by MTP
- Subsystem status management : Subsystem failure and recovery information, and SCCP(SSN 1)
congestion received in SCCP management messages.
- Subsystem status test : SSP , SSA , SST , SOR , SOG
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Hop Counter ( 15 to 1 ) : Counter is decremented upon GTTSegmentation : Max 16 Segments , each carries 246 bytes
GTT CASES1. SPC + SSN2. SPC + SSN + GT3. SSN + GT4. SPC + GT5. GT only
GT is performed on given SPC + SSN on the basis of GT info , to find outthe final A/B Party Address
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GTT> Method of hiding the SS7 point code and sub-system number from the originator of a message
a) GT Consists of – Translation type (TT) – Numbering plan (NP) – Nature of address (NA) – Global title digits (GTDIG)
b) GT Benefits – Central administration of routing information makes it easier to restructure the network – It is possible to set up alternative routing schemes and load sharing – More compact and dyanmic routing tables – The function is required for the introduction of certain new services (such as call completion to busy subscriber, CCBS and 800 free phone)
a) The result of a global title translation can be: – the point code for a signaling destination – a subsystem service group ( this is used in the intelligent network to guarantee a fail-safe service control point (SCP). Two SCPs can be combined to form a subsystem service group that is accessed frothe relevant service switching point (SSP) via globa l title translation. )
– a translator service group ( this consists of up to four signaling points, each of which can perform the necessary translation ) – a further translation in the same network node
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TRANSACTION DIALOG TAG COMPONENT TAG
TCAP :
1. Transaction Part : ( Deals with SCCP Message ) a. TCAP Message Type : BEGIN / UNI / END / CONTINUE / ABORTb. Length Indicatior of Transaction Tag ( Max 2048 , SCCP takes Care of Segmenting / Breaking )c. Transaction Info ( Not Valid for UNI )
i. Origination Transaction Id ( Mandatory for BEGIN , CONTINUE )- Length Indicator & Value
i. Destination Transaction Id ( Mandatory for END , ABORT , CONTINUE )- Length Indicator & Value
i. P_Abort Cause ( Mandatory for TC_P_Abort Request )- Reason for Abort
2. Dialog Part :a. Dialog Indicator Tagb. Length Indicatior of Dialog Tagc. Dialog Information - Depend on USER For Ex : MAP , INAP
3. Message Component Part : ( Deals with USERs such as MAP , INAP ...) a. Component Indicator Tagb. Length Indicatior of Component Tagc.Component Type : ( Invoke / Return Result Last / Return Result Not Last / Return Error / Reject )d. Component lengthe. Component User Information by MAP , INAP , CAMEL , OMAP , SSAP Etc..........
Functions of TCAP are to control:· The transaction between both endpoints in the network· The communication to the users of TCAP.
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Message type Function
Abort
Used to terminate the structured dialogue in a normal way
Used to terminate the structured dialogue in an off normal way.
Indicates that one of the Invoke, Return Result, or Return Error components received from the remote user/CSL could not be und
or was not expected.
Used to transport data in an unstructured dialogue
First message, to start a structured dialogue, sent once
Used to sustain the structured dialogue, more continue messages can be sent
Initiates/invokes a desired operation at the remote peer application entity.nvoke
Return result not last
Return result last
Return error
Begin
Continue
Used to carry a segment of the result of a successfully completed operation. It is used when a success reply is physically too lar
into a single message.
Represents the final success reply to an operation invocation. If the success reply was segmented, this component would repre
final segment of the reply
Indicates an operation invoked previously has failed due to some processing error. Error codes are supplied by TCAP users, and
passed transparently by TCAP.
Unidirectional
End
Reject
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SMSC1. SMS are stored in SMSC before they can be sent to MS ( 140 bytes each SMS )2. MAP USED is
> Forward Short Message Submit> Send Routing Info for SM> Forward Short Message Deliver
3. MO Forward SM : A party MS to SMSC ( Forward Short Message Submit )4. MT Forward SM : SMSC to B Party MS ( Forward Short Message Deliver )
HLR
GMS MSC/VLR
TCAP Begin/Invoke - SRI for SMTCAP End / Retrun Res - SRI Ack
SM_DELIVERBTS
TCAP Begin/Invoke - Forward SM
TCAP End / Retrun Res - Forward SM Ack
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SCP
SCP
STP
STP
STP
STP
A-
A-Access
A-
E-Extended
C-Cross D- B-Bridge Other STP NWService Control Pt C-Cross
VLR V
BTS
GMSCHLR
AUC-SIM
M
SMSC EIR
EC
G
B
H
F
D D
A
HLR
GM MSC/VLR
TCAP Begin/Invoke - Provide MSRNTCAP End / Retrun Res - MSRN Ack
TCAP Begin/Invoke - SRITCAP End / Retrun Res - SRI
IAM -
IAM - MSISDN
BTS
IMSI
IMEI
Mobile Terminating Call ( MTC )
GSM
C7 Network
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SSP (Service Switching Pt )
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GPRS ( General Packet Radio Services )a) Key Features
Speed immediacyNew applicationsBetter applicationsService access
b) Key Network Features of GPRSPacket switchingSpectrum efficiencyInternet awareSupports tdma and gsm
c) Limitations of GPRSLimited cell capacity for all usersSpeeds much lower in realitySupport of gprs mobile terminate by terminals is not ensuredSuboptimal modulationTransit delaysNo store and forward
d) SGSN - Serving GPRS Support Nodehandles session management, mobility management, billing and traffic measurementsbit level encryption of data which is to be sent over the air interface.Put GPRS data received from the BSC in IP format for sending to the GGSN and vice-versa.Provide GPRS routing to BSC’s
d) GGSN - GPRS Gateway Support NodeThe GGSN is the gateway in and out of the GPRS system.It routes packets from an external network ( "the Internet" ) to the SGSN which is currently serving the MS,and routes packets from the SGSNs to which it is connected to the external network. Th is concept is called tunnelling.
d) Similar TechniquesEnhanced Data rates for GSM Evolution (EDGE)Universal Mobile Telephone System (UMTS)
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FLAG
BSN
BIB
FIB
FSN
LI
SIO
SIF
SPARE USER DATA
CRC SLS
A PARTY - GT(N) /
SSN / SUB NO
USER DATA
DIALOG ID
COMPONENT TYPE = INVOKE
COMPONENT USER DATA , MT Forward
SM , MSIN DIGIT
DPC
OPC
TRANSACTION ID , BEGIN
UDT MESSAGE
PROTOCOL CLASS
= 0 / 1
B PARTY - GT(N) /
SSN / SUB NO
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MTP - 2 LAYER 3 SCCP TCAP
GSM Overview
IMSI : International Mobile Subs Identity [ SIM , MCC(3) + MNC(2) + MSISDN(<10) ]TMSI : Temporary Mobile Subs Identity [ VLR , MCC(3) + MNC(2) + MSISDN(<10) ]MSISDN : Mobile Stn Integrated Services Digital NW [ CC(1-3) + NDC(1-3) +MDN(10) ]
VLR VLR
BTS
GMHLR
AUC-
MSC
SMSC
EIR
EC
G
B
H
F
D D
A
IMSI
IMEIGSM Overview
IMSI Vs TMSIOne can't take hacking benefits with TMSI as it is dyanmically allocated by VLR, moreover TMSI is 4 octet shorter than IMSI .
MAP D ( HLR-VLR )Provide MSRN / MSRN Ack Update Location / Cancel Location / AckInsert / Delete Subs Data / AckSend Param / AckResetDeregister Mobile DataNote MS Present
MAP C ( HLR-MSC )Send Routing info SRI /
AckSend Routing info for SM / AckSet Message waitingdata
Alert Service CentreRegisster charging info
MAP E ( GMSC - MSC )Process access sigmnalling CCS 7Forward access Signalling CCS 7Send End Signal CCS 7Perform Handovers / Subsequent HOPerform Internal HandoversTrace subs activity
MAP I ( Subservices - MSC )Get Pwd / Register Pwd
Activate / Deactivate / Erase / Register SSInterrogate / Invoke SSForward SS Notification
MAP F ( EIR - MSC )Check IMEI
MAP H ( SMSC - MSC )Forward Short Message
MAP G ( VLR - VLR )Send Param
Intelligent Network ( IN )Requirement / Advantages
Rapid deployment of Vendor / SSP Free Services which are centrally administered
SSPCCF - Call Control Functions ( Takes Care of all call related processing in Switch )SSF - Service Switching functions ( Provides IN Triggering and IN Accessibility )SRF - Specialized resource function ( Provides interactioon bw Call processing SW
in SSP)
SCPSCF - Service Control Functions ( Executes IN service logic and interfaces witrh
SSP via SSF )SDF - Service data function ( Maintains all customer and nw data )SMP - Service Management Point ( Administration and Operation of IN )
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m
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erstood
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SC