4' day SS7

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1

Fundamentals of SS7and GSM protocol

architecture and proceduresGiuliano Paris

(TILS)email: giuliano.paris@ telecomitalia.it

Rio de Janeiro, September 2005

2

Outline

• Background on Signaling

• SS7 Characteristics and Protocol Architecture

• CCITT #7 Application Parts: TUP/ISUP and TCAP/ASEs

• GSM Protocol Architecture

GSM radio channels (signaling and Traffic channel)

GSM radio signaling channels (BCCH, RACH, etc)

Examples of procedures (location update, handover, call scenario,

roaming, SMS, etc.)

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3

Some background on Some background on SignalingSignaling

� Signaling is defined as the exchange of informationspecifically concerned with the establishment, releaseand other control of calls, and network management, in automatic telecommunication operation (ITU definition).

� Channel Associated Signaling (CAS) • A signaling method in which the signals necessary for the control of a

single user channel (e.g. speech channel) are transmitted in the channel itself or in a signaling channel permanently dedicated to it.

� Common Channel Signaling (CCS)• A signaling technique in which signaling information relating to a

multiplicity of circuits, and other information such as that used for the network management, is conveyed over a single channel by addressedmessages.

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CAS and CCSCAS and CCS

UI UI UI UI S S S S

1 2 3 ….. M

UI UI UI UI S

CommonChannel

UI = User Information

S= Signaling

1 2 3 ….. N 1 2 3 N

Channel Associated Signaling (CAS)

Common Channel Signaling (CCS)

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5

CAS and CCSCAS and CCS

� In telephony CAS traditionally consisted of strictly necessary signals(very poor vocabolary) to handle a call (off-hook/on hook, calledparty number, dial tones and busy signals). It was defined forelectromechanical switching systems (based on selectors and xpoints). The subscriber dials '958'

� CAS is relatively slow (long call setup time), it offers a poverty of signals (messages) and no error detection and recovery for signalinginformation and finally it has been subjected to frauds.

� The introduction of electronic processors in the switching systems(SPC switches) and the development of data communictiontechniques and protocols have given the possibility to implement the concept of CCS (named CCITT #7, or CCS #7, or SS7).

� CCS #7 enables all the network element (i.e. SPC switches, network databases, etc.) to exchange signaling information in a reliable, fast, secure (protections from fraud), flexible (in terms of number of signals) and standardised (worldwide use) manner.

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CAS CAS signalingsignaling CallCall

SEIZURE

CAS CAS

off-hook

first digits

last digitDIGITS

PROCEED TO SEND

SEIZURE

ringing

off-hook

DIGITS

PROCEED TO SEND

on-hook

ANSWER

CONVERSATION

on-hook CLEAR BACK CLEAR BACK

dial tone.

ADDRESS COMPLETEADDRESS COMPLETE

RINGING TONE

ANSWER

CLEAR FORWARD CLEAR FORWARDRELEASE GUARD RELEASE GUARD

post

dialling

delay

4

7

N

1

2

P. S.

N

1

2

P. S.

N

1

2

M. Transfer

N

1

2

M. TransferCCS link

signaling messages

speech + signaling

speech

From CHANNEL ASSOCIATED SIGNALING ....

... To COMMON CHANNEL SIGNALING

control

control control

control

8

Common Common ChannelChannel SignalingSignaling ModesModes

SP SP

SP SP

STP Speech TrunksSignaling link

Associated Mode

Non Associated Mode

SP= Signaling PointSTP= Signaling Transfer Point

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9

CCS #7 CCS #7 ProtocolProtocol ArchitectureArchitecture

� MTP 1: Equivalent to OSI layer 1 (generally 64Kb/s)

� MTP 2: Error detection and recovery, flow control (basedon HDLC, equivalent to OSI layer 2 )

� MTP 3: Provides message routing without lost or duplicated packets even in case of network failures or congestion (Equivalent to lower half of OSI layer 3)

MTP Level 1MTP Level 2MTP Level 3

USER PART USER PART

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ContentsContents of of RecommendationsRecommendations(Q.701(Q.701--Q.707) Q.707) relatingrelating toto the MTPthe MTP

Recommendation Q.701 contains a functional description and overview of the Message Transfer Part of SS No. 7.Recommendation Q.702 details the requirements of a signallingdata link to support SS No. 7.Recommendation Q.703 describes the signalling link functions.Recommendation Q.704 describes signalling network functionsand messages.Recommendation Q.706 defines and specifies values for MTP performance parameters.Recommendation Q.707 describes the testing and maintenancefunctions applicable to the MTP.

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CircuitCircuit RelatedRelated ApplicationsApplications� The signaling message coming from the USER Part

(i.e. TUP) includes the related Circuit IdentificationCode

��

��

��

�� !� �� !� ��" ��" �� !� �� !� �� !�!��#�#�

MTP Level 1

MTP Level 3

MTP Level 2

ISDN-UP/TUP

TransportSession

Presentation

Application

Physical

Data Link

Network

12

MTP-2

MTP-3

ISUPTUP/ISUP Message

MSU

ISUP

Switch A Switch B

The messages originated from a switch’s User Part (UP) are carried by the functional block MTP in a “Message Signalling Unit” (MSU) and delivered to the other switch’s UP.

MTP-3

MTP-2

MTP-1 MTP-1

callcontrol

callcontrol

CIC Signaling payloadDPC OPC

DPC: Destination Point Code

OPC: Originating Point Code

CIC: Circuit Identification Code

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13

A

B

T

(a)

(b)

Call Example with CCS (TUP/ISUP)

speech trunksSignaling circuit

(a) Calling party(b) Called party

switch with SP and STP function

switch with SP function

14

signaling regionA

SPSTP

signalinglink

QUAD

QUAD Model : non associated mode (stand-alone STP )

speech

signaling regionB

8

15

ConceptualConceptual modelsmodels: : transporttransport and control and control networksnetworks

switch

SP

SP

SP

SP

switch

switchswitch

SP

switch

STP

STP STP

STP

Signalling Network

Transport Network

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SignallingSignalling data linkdata link : : levellevel 1 (MTP1 (MTP--1)1)• Level 1 defines the physical, electrical and functional characteristics of a signalling data link and the means to access it. The level 1 elementprovides a bearer for a signalling link.• The standard channel time slot for the use of a signalling data link is time slot 16 (when available) in 2.048 Mbit/s digital path.• The access to the signalling data link can be realized by a semipermanent connection through the switching network

MTP-2

MTP-3Switch BMTP-3

MTP-2

2 Mb/s PCM path

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16

Switch A

Switch matrix

MTP-1Switch matrix

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SERVICE INDICATOR (SI)0000 Signalling network management messages0001 Signalling network testing and management messages0011 SCCP0100 Telephone User Part (TUP)0101 ISDN User Part (ISUP)0110 Data User Part (DUP).....

F CK SIF SIO LIFIB

FSNBIB

BSN F

8 16 8n (n>2) 4+4 2 6 1 7 1 7 8

MSU (Message Signal Unit)

Legenda:F = FlagCK = Check bits (CRC)SIF = Signalling Information FieldSIO = Service Indicator OctetLI = Length IndicatorFIB = Forward Indicator BitFSN = Forward Sequence NumberBIB = Backward Indicator BitBSN = Backward Sequence NumberSLS = Signaling Link Selection

UP Messagelabel

routingSINI

parts of interest to levels 3 and 4

SLS OPC DPC

SignallingSignalling link link functionsfunctions: : levellevel 2 (MTP2 (MTP--2)2)

NETWORK INDICATOR (NI)

00XX international network

01XX spare for international network

10XX national network

11XX spare for national network

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MTPMTP--2 2 signalsignal unitsunits: FISU, LSSU, MSU: FISU, LSSU, MSU

LI Value Signal Unit Type

0 Fill-In Signal Unit (FISU)

1..2 Link Status Signal Unit (LSSU)

3..63 Message Signal Unit (MSU)

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SignallingSignalling network network functionsfunctions: : levellevel 3 (MTP3 (MTP--3)3)

MESSAGE DISTRIBUTION

MESSAGEDISCRIMINATION

MESSAGEROUTING

MESSAGE HANDLING

SIGNALING NETWORK MANAGEMENT

SIGNALINGTRAFFIC

MANAGEMENT

SIGNALINGLINK

MANAGEMENT

MTP-3USER PARTS MTP-2

Message Flows

Control and Indication

SIGNALINGROUTE

MANAGEMENT

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SignallingSignalling network network functionsfunctions: : levellevel 3(MTP3):3(MTP3):SignallingSignalling TrafficTraffic Management Management ProceduresProcedures

•Changeover

•Changeback

•Forced Rerouting

•Controlled Rerouting

•Signalling Point Restart

•Signalling Traffic Flow Control

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21

SLS=XXX1

SLS=XXX0

A B

A BD E

F C

XXX0

XXX1

SIGNALING TRAFFIC LOAD SHARING (I) SIGNALING TRAFFIC LOAD SHARING (I)

Load sharing within a link set

Load sharing between link sets

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SIGNALING TRAFFIC MANAGEMENTSIGNALING TRAFFIC MANAGEMENT((ExampleExample of of changeoverchangeover))

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SIGNALING ROUTE MANAGEMENTSIGNALING ROUTE MANAGEMENT(EXAMPLE: Transfer (EXAMPLE: Transfer ProhibitedProhibited Procedure )Procedure )

6

13

19 89

STP sents a transfer prohibited message (TFP) to each of SPs.

the message has the following information:• Destination Point (DPC) = 6, 19, 13• Origin Point (OPC) = 9• Message Indication = TFP• TFP related Destination = 8

The 3 SPs (6,19,13), once received the TFP message, will execute a forcedrerouting procedure

STP

i

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MTP performance MTP performance requirementsrequirementsThe availability and dependability objectives for the transport of signalling messages by the MTP are:

• No more than one in 10E+7 (1 in 10,000,000) messages should be lost.

• No more than one in 10E+10 messages should be delivered out of sequence or duplicated.

• No more than one in 10E+9 message errors should remain undetected.

• The signalling route between an origination and destination SP should be available99.9998% of the times or better. This implies a maximum permissible downtime or unavailability of 10 minutes per year per route.

• Though there are no specific end-to-end delay objectives for SS7, they are specified forspecific services or uses of the SS7 protocol. Further there are delay objectives for some network components, and others can be calculated. Thus an estimate can be made forany given network configuration.

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Background: Background: ““WhatWhat isis ISDN?ISDN?””

“It represents the evolution of the IntegratedDigital Network (IDN), it offers an end-to-end 64 kbit/s digital connectivity in order to provide a very large set of voice and data services, through a limited number of standardisedaccess interfaces. ISDN provides the access toboth circuit and packet switched networks and services”.

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Background: Background: ISDN Network ISDN Network ArchitectureArchitecture

packet switchednetwork

circuit switchednetwork

...other networksISDNlocal

exchange

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Background: Background: ISDN Services ISDN Services CharacteristicsCharacteristics

� Bearer:

• end-to-end 64 kbit/s digital connectivity (circuit mode)

• speech and 3.1 KHz audio (circuit mode)

• packet connectivity

� Teleservices (examples):

• fax (G.3 and G.4), telephone, videoconference,etc.

� Supplementary services (examples):

• Call Completion Busy Subscriber (CCBS)

• Closed User Group (CUG)

• Calling Line Identity, etc.

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Background: ISDN Access Background: ISDN Access TypesTypes

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PABX

ISDN

NTBRA

BRA

PRA

NT

TA

15

29

� DSS1 (Digital Subscriber Signalling N. 1) is the ISDN standard access (user-network) protocol and ISUP-CCITT #7 is the network protocol (network-network).

� limitations of such an architecture for broadbandservices

NN--ISDN ISDN protocolprotocol architecturearchitecture

access protocol

(DSS1)

access protocol

(DSS1)

networkprotocol(ISUP/

CCITTn.7)

networkprotocol(ISUP/

CCITTn.7)

Network

ISDN Switch

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DSS1 DSS1 ProtocolProtocol

LAP-D (layer 2)

Q.931 (layer 3)(call handling)

Physical (layer 1)• 2 wires for BRA 2B1Q code• 4 wires for PRA HDB3 code

Q.931 provides the means to establish, mantain,and release network connections across anISDN between signaling entities. It alsoprovides procedures for the invocation and theoperation of supplementary services

LAP-D (Q.921) is the data link protocol usedover the D-channel. It provides frame error detection and error recovery, flow control, SAPI and TEI addressing (SAPI + TEI = DLCI)

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TUP and ISUPTUP and ISUP

ISUP comprehends, beyond all the capabilities provided by TUP, a set of capabilities needed to support ISDN services (i.e. beares services (speech,. 3.1 khz audio, 64 Kb/s unrestricted) and supplementary services (CLIP, CLIR, CUG, subaddressing, user to user signaling, etc.)

ISUP capabilitiesTUP capabilities

ISUP Reccomandations: Q.761 - Q.768

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Routing label

Circuit identification code

Message type code (es. IAM, ACM, etc.)

Mandatory fixed part

Mandatory variable part

Optional part

ISDN User Part (ISUP) : ISDN User Part (ISUP) : messagemessage formatformat12345678

T1148210-92/d14

Order of bit transmission

Order of octettransmission

Routine label

Circuit identification code

Message type code

Mandatory parameter A

Mandatory parameter F

Pointer to parameter P

Pointer to start of optional part

Length indicator of parameter M

Pointer to 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 parameter field

Mandatoryfixed part

Mandatoryvariable part

Optional part

(12 bits)

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M essage type: Initial address

Param eter Reference Type Length(octets)

M essage type

Nature of connection indicators

Forward call indicators

Calling party's category

Transm ission m edium requirem ent

Called party num ber

Calling party num ber

Optional forward call indicators

Closed user group interlock code

User-to-user inform ation

Access transport

User service inform ation

End of optional param eters

2.1

3.23

3.20

3.9

3.35

3.7

3.8

3.25

3.13

3.38

3.2

3.36

3.17

F

F

F

F

F

V

O

O

O

O

O

O

O

1

1

2

1

1

4-11

4-12

3

6

3-131

3-?

4-13

1

ISUP ISUP messagemessage: IAM (: IAM (InitialInitial AddressAddress MessageMessage))

34

64 Kbit/s call between ISDN users(en-bloc dialing and automatic answer)

IAM (# # # #) IAM(# # # #)

CONNECT CONNECT

DSS1 ISUP

SETUP(#...#)SETUP

CONNECTCONNECT

CONVERSATION (data transfer)

DISCONNECTRELEASE

RLCRELEASE

RLC

DISCONNECT RELEASE

REL. COMPLETERELEASE

REL. COMPLETE

ISUP DSS1

18

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ISUP: ISUP: CallCall betweenbetween POTS POTS subscriberssubscribers

IAM (# # # #) IAM(# # # #)

ISUP

CONVERSATIONSUS

ISUP

OFF-HOOK

First digits.

Last digit SAM

SAM

SAM

SAM

ringing

Off-hookANMANM

ACMACM

On-hookSUS

Off-hookRESRES

CONVERSATIONOn-hook REL REL

RLG RLG

36

LocalExchange

1) IAM 2) REL (*)

3) IAM

CONGESTION

REL(*) = the message has a parameter informing that cranck-back is possible (Crank-backindicator)

AutomaticAutomatic ReroutingRerouting ((CrankCrank--backback))

LocalExchange

TransitExchange

TransitExchange

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Example: outgoing trunk failure

IAM IAM IAM IAM

ACM ACM ACM ACM

REL (cause) REL (cause)REL (cause)REL (cause)

RLC RLC RLC RLC

CallCall failurefailure: : ISUP Cause and LocationISUP Cause and Location

• ISUP provides exact information on the failure cause of a call

• Cause value

• Cause indicators parameter

• Location

SGU SGTSGU

ISUP ISUP ISUP ISUP

38

0000001 (1) unallocated (unassigned) number0000011 (3) no route to destination0000100 (4) send special information tone0010000 (16) normal call clearing0010001 (17) user busy0010010 (18) no user responding0010011 (19) no answer from user (user alerted)0010101 (21) call rejected0010110 (22) number changed0011011 (27) destination out of order0011100 (28) address incomplete0011101 (29) facility rejected0011111 (31) normal unspecified0100010 (34) no circuit/channel available0100110 (38) network out of order0101001 (41) temporary failure0101010 (42) switching equipment congestion0101100 (44) requested channel not available0101111 (47) resource unavailable - unspecified0110111 (55) incoming calls barred within CUG0111001 (57) bearer capability not authorized0111010 (58) bearer capability not presently available0111111 (63) service/option not available - unspecified1000001 (65) bearer capability not implemented1001111 (79) service or option not implemented - unspecified1010111 (87) user not member of CUG1011000 (88) incompatible destination1011111 (95) invalid message - unspecified1100110 (102) recovery on timer expiry1101111 (111) protocol error - unspecified1111111 (127) interworking unspecified

Example: Cause value field (ISUP-S)

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Service Provisioning EvolutionCLASS

Services based on DB (SCP) queries

- I.N. Services- Personal Mobility Services- UPT services- .....

- Call forwarding- Call waiting- Itemised Billing- Three-way calling- Centralized Answering

Machine- ........

- Call Completion BusySubscriber (CCBS)

- ....

- Closed User Group (CUG)

- Calling Line IdentificationPresentation (CLIP) &CLIR

Supplementary Services

40

NonNon--CircuitCircuit RelatedRelated ApplicationsApplications� Transaction-oriented services

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SCCP

ASE

TCAP

MTP Level 1

MTP Level 3

MTP Level 2

ISDN-UP/TUP

Physical

Data Link

Network

TransportSession

Presentation

ApplicationASE

21

41

SignallingSignalling Connection Control Part (SCCP)Connection Control Part (SCCP)and and TransactionTransaction CapabilitiesCapabilities ApplicationApplication Part (TCAP) Part (TCAP)

• Enhance MTP for connection oriented and connectionlesscontrol• Identify subsytems in Signaling Points• Global Title Translation (GTT): translation of network address (eg Dialed Digits) to Point Code• Used for database access (eg 800) and Direct end-to-endinformation

• TCAP supports the exchange of non-circuit related data between applications across the SS7 network using the SCCP connectionless service. Queries and responses sentbetween SSPs and SCPs are carried in TCAP messages. Forexample, an SSP sends a TCAP query to determine the routing number associated with a dialed 800 number and tocheck the personal identification number (PIN) of a callingcard user.

42

ExamplesExamples implementingimplementing ASEsASEs

� GSM Networks

• MAPs (Mobile Application Parts): set of protocolsthat provides the information exchange betweenMSC, HLR, VLR, etc., necessary for mobile capabilities

� Intelligent Networks

• ASE-RI, INAP: protocol that supports the informationtransfer between Service Switching Points and specialized nodes (Service Control Points)

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WhyWhy SERVICES SERVICES providedprovided by the by the INTELLIGENT NETWORK ? INTELLIGENT NETWORK ?

� Simplicity, “time to market” introduction

� Customer Tailored

� Flexible Access (trasportability)

� Customer control

� Creation flexibility

� Manufacturer independency ??

44

IntelligentIntelligent Network (IN) ServicesNetwork (IN) Services

� Green Number (800 service-USA)

� Private Virtual Network

� Premium Charge (in Italy 144, 166)

� Split Charging

� Mass Calling

� Televoting

� Calling card

� Personal Number

� Universal Number

� . . . . .

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45

IntelligentIntelligent Network Network GoalsGoals

� Migration of service control software out of switchingnode (in the Service Control Points)

� Service Creation Environment (SCE) in order topersonalize the services

� Standardized Interfaces between the network elements

46

I.N. I.N. FunctionalFunctional ArchitectureArchitecture

SCF

CCF CCFCCF

SSF SSF

SDF

SRF

SMF

SMAF

SCEF

��

��

��

��

��

��

��

��

24

47

I.N. Network I.N. Network ArchitectureArchitecture

SCPSCP

SMSSMS

CustomerControl

SCEServiceManager

switchednetwork

PSTN

CCS n.7 network

SMS = Service Management System SCP = Service Control Point

SSP = Service Switching PointSCE=Service Creation Environment

SSPSSP

48

CCS#7 CCS#7 ProtocolProtocol ArchitectureArchitecture forforIntelligentIntelligent NetworkNetwork

SSP STP SCP

ASE

TCAP

SCCP

MTP MTP

SCCP

MTP

SCCP

TCAP

ASE

25

49

ExampleExample: Green : Green NumberNumber (800(800--service)service)

SDF

SSP

SCF

SSF

CCF CCF

SCP

SMFSMS

!!""""""

��

��

��

��

1

2

3

50

ISUP ISUP ApplicationsApplicationsInterconnection Interconnection betweenbetween operatorsoperators::

i.e. i.e. CarrierCarrier SelectionSelection

LELE

TETE

10xy-06-7654321

OLOOLOswitchswitch

OLO network

OLOOLOswitchswitchISUP with CLI

CLI check

Telecom Italia Network

LE: Local ExchangeTE: transit Exchange

TIM network

GMSCMSC

Subscriberdatabase

CLI: Calling Line Identity.OLO: Other Licensed Operator

26

51

HLR

GSM Network GSM Network ArchitectureArchitecture

MSC

BTS

BSC BSC

VLRVLR

BTSBTS

BTS

MSC

BSC BSC

PSTN/ISDN

AUC

LAi

LAj

access

coverage

switching

“intelligence”

52

GSM GSM ProtocolProtocol ArchitectureArchitecture

CM

MM

RR

LAPDm

TDMAFDMA

SCCP

Radio interfaceBSSMS MSC

LAPDm

RR

TDMAFDMA

BSSAP

MTP

CM

MM

SCCP

BSSAP

SCCP

TCAP

MAP

MTP MTP

A- interface

to the othernetwork elementsand PSTN

MAPTUP/ISUP

27

53

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GSM: GSM: interfacesinterfaces and and signalingsignaling protocolsprotocols

54

GSM GSM SignalingSignaling ProtocolsProtocols: : standard standard interfacesinterfaces

MSC MSC

HLREIR VLR VLR

BTSBSC

BSS

E

F C B

D G

A

Abis radio interface

PSTN

ISDN

ISUP /TUPMTP

MAPTCAPSCCPMTP

28

55

FixedFixed--MobileMobile CallCall(mobile (mobile terminatingterminating))

MSC

GMSC

HLR

PSTN

BTS

BSC

BTSBTS

BTS

BSC

LAi

LAj

VLR

VLR2

MSISDN3

1

IMSI

MSRN4 MSRN

5

6

ISUP /TUPMTP

MAPTCAPSCCPMTP

= 1,6

= 2,3,4,5

: Send Routing Information2

3 : Provide Roaming Number

56

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GSM GSM SignallingSignalling channels (I)channels (I)

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GSM GSM SignallingSignalling channels (II)channels (II)

58

GSM radio signaling channelsBroadcast channels (BCH)

� - Broadcast Control CHannel (BCCH) continually broadcasts, on the downlink (unidirectional) informationincluding Country and network identities, Location Area ID, Cell ID, etc. This channel is continuously active, with dummy bursts when there is no information to transmit, because its signal strengths are monitored by mobile stations for handover determination; BCCH is a low capacity channel(23 bytes each 0.235 sec. = 782 b/s). Each cell has one BCCH channel (or BTS) (time slot 0).

� - Frequency Correction CHannel (FCCH) and Synchronization CHannel (SCH): information sent from BSS for carrier and frame synchronization respectively;

30

59

Mobile Mobile initializationinitialization• Prior to establishing any communicationlinks to other parties, the MS must first acquire synchronization with the GSM system. This process begins after the MS isturned on in a PLMN. The first step of the process is for the MS to search for and acquire a frequency control channel(FCCH) burst on some common control frequency channel. The mobile will scan allor part of 124 RF channels and obtain the average signal strength of each channel

• After the frequency correction burst isdetected, the MS will try to synchronizewith the time synchronization burstsynchronization channel (SCH). The SCH always occurs in the next frame in the same time slot as the FCCH. This is eightburst periods later than the FCCH. The SCH contains precise timing information on the timeslot boundaries to permit refining the received slot timing. The SCH message alsocontains the current frame number to which the MS synchronizes

60

GSM radio signaling channelsCommon Control Channels (CCCH)

Common Control CHannels (CCCH) are used for transmitting signalinginformation between all mobiles and the BSS for call originating and call paging functions:

uplink

- Random Access CHannel (RACH): slotted aloha channel used by the mobile to request access to the network;

downlink

- Paging CHannel (PCH): used to alert the mobile station of incoming call;

- Access Grant CHannel (AGCH): used to allocate a dedicated control channel to a mobile following a request on the RACH.

31

61

GSM radio GSM radio channelschannels (bit rate)(bit rate)

62

ExampleExample: BCCH: BCCH

BCCH

By means of BCCH, one BTS continuously transmits, among others, the Location Area Identification (LAI), la cell identification, by whichMS can realize its position.

LAI = MCC + MNC + LACCGI = LAI + CI

MCC (*)= Mobile Country Code (3 digits)MNC= Mobile Network Code (2 digits)LAC= Location Area Code (2 digits)CGI= Cell Global IdentityCI = Cell Identity (2 bytes)

(*) MCC for Italy = 222

32

63

ExampleExample: RACH and AGCH: RACH and AGCH

AGCH (DCCH provided)

When a Mobile Station (MS) has to send, over the air, the phone numberdigits to make a call, prior the digits could be sent to the BTS, MS mustrequire, through RACH (common control channel), a dedicated control channel (SDCCH). The BSC assigns such a channel through the AGCH (common control channel). Over the SDCCH, all the signalling informationare exchanged for the call setup (authentication, dialing digits, TCH assignment, etc.)

+39335 …...

RACH(DCCH request)

64

DedicatedDedicated control control channelschannels� Stand Alone Dedicated Control CHannel (SDCCH): it is an eighth rate

traffic channel (TCH/8) used for the transfer of call control signaling to and

from the mobile during call setup, before the TCH is assigned (i.e. for

authentication, location update, ecc.); capacity of about 10 messages/sec.

� Slow Associated Control CHannel (SACCH): associated to a traffic

channel, it may carry about 2 messages/s and it used for non urgent

procedures (i.e. radio measurements concerning handover). It is

implemented on frame 12 and there is one dedicated signaling channel for

each of the 8 TCH channels.

� Fast Associated Control CHannel (FACCH): it is obtained on demand by

stealing from traffic channel (during call setup and release phases, no user

data are transmitted and therefore signaling may use the channel without

conflict). It carries information to indicate the call setup progress, or to

authenticate the subscriber, to command a handover, etc.

33

65

GSM radio GSM radio channelschannels

66

Control Control ChannelsChannels (i.e. 51 (i.e. 51 slotsslots framesframes))downlink uplink

34

67

Location Location updatingupdating

68

Location Location UpdatingUpdating (GSM 3.12)(GSM 3.12)

• Channel Request (RACH)• Channel Assignment (AGCH)• Request for Location Updating (SDCCH)• Authentication Request (SDCCH)• Authentication Response (SDCCH)• Ciphering Command (SDCCH)• Ciphering Complete (SDCCH)

•Location updating confirm, including new TMSI (optional) (SDCCH)

• new location andTMSI Ack (SDCCH)

• Channel release by the network (SDCCH)

MS Base Station

• Periodic location updating (6 min.-24 h)• Location updating on LA crossing

35

69

MobileMobile--OriginatedOriginated CallCall

70

Chiamata Chiamata MobileMobile--OriginatedOriginated (MOC)(MOC)

• Channel Request (RACH)• Channel Assignment (AGCH)• Call establishment Request (SDCCH)• Authentication Request (SDCCH)• Authentication Response (SDCCH)• Ciphering Command (SDCCH)• Ciphering Complete (SDCCH) • Setup message (includes called party number) (SDCCH)• Call Proceeding (SDCCH)• Traffic channel Assignment (SDCCH)• Assignment complete (FACCH)• Alerting (ringing on the called side) (FACCH)• Connect (called party answers) (FACCH)• Connect Ack (FACCH)• conversation phase (TCH)

MSBase

Station

14 signaling messages are exchanged before a conversation can begin

remark:

(*)

(*) optionallyTMSI reallocation

36

71

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GSM: GSM: interfacesinterfaces and and signalingsignaling protocolsprotocols

72

ReviewReview on DSS1 on DSS1 ProtocolProtocol (ISDN)(ISDN)

LAP-D (layer 2)

Q.931 (layer 3)(call handling)

Physical (layer 1)• 2 wires for BRA 2B1Q code• 4 wires for PRA HDB3 code

Q.931 provides the means to establish, mantain,and release network connections across anISDN between signaling entities. It alsoprovides procedures for the invocation and theoperation of supplementary services

LAP-D (Q.921) is the data link protocol usedover the D-channel. It provides frame error detection and error recovery, flow control, SAPI and TEI addressing (SAPI + TEI = DLCI)

37

73

GSM: radio GSM: radio protocolprotocol ArchitectureArchitectureThe signaling protocol in GSM is structured into 3 layers.

We have to be careful in not confusing layer 3 protocol functions defined by GSM with what is formally defined to be the layer 3 functions in the OSI model.The GSM layer 3 protocols are used for the communication of network resources, mobility, and call related management messages. Since, in the OSI model, some of these functions are actually provided by the higher layers, the term “message layer” may be more appropriate term for the layer 3 in the GSM.

• The message layer consists of 3 sublayers::

• Radio Resource (RR) implemented over the link between the MS and the BSS;• Mobility Management (MM) and• Connection Management (CM) sublayers providing the communication between the mobile station and the MSC .

74

GSM GSM ProtocolProtocol ArchitectureArchitectureRadio Interface (Radio Interface (UmUm -- betweenbetween MS and BSS) MS and BSS)

PhysicalPhysical and Data and Data LinkLink layerslayers• The physical layer, based on FDMA/TDMA, has been discussed in the radio interface channels section.• The data link layer is based on a LAPD- like protocol, called LAPDm, that has been modified for operation within the constraints set by the radio path. • LAPDm uses no flags for frame delimitation, since it is done by the physical layer. • LAPDm, uses no cyclic redundancy check bits for error detection. Error recovery and detection mechanisms are provided by a combination of block and convolutional coding used in the physical layer• Over the LAPDm two information flows coexist: signaling messages(SAPI=0) and Short Message Services (SAPI=3). The LAP-D layer, originally defined for the ISDN network, in the GSM network is used in the Abis (BTS- BSC interface).

38

75

The Radio Resource (RR) management performs the functions ofestablishing physical connections over the radio path for the purpose oftransmitting call related signaling information such as the establishment of signaling and traffic channels between a specific mobile user and the BSS. The RR management functions are basically implemented in the BSS. Moreover RR sublayer is also involved in handover procedures.Examples of signaling channels use at this layer are RACH, AGCH, PCH.

Some of the procedures involved in RR sublayer are:

• channels assignment and release• handover• frequencies change and hopping sequences• power control management

• ...

Radio Interface (Radio Interface (UUmm -- betweenbetween MS and BSS) MS and BSS) LayerLayer 3 3 -- Radio Radio ResourcesResources sublayersublayer

76

Radio Resource Management (RR)Mobility Management (MM)Connection Management (CM)Call Control (CC)Short Message Service (SMS)Supplementary Services (SS)Protocol Discriminator (PD)Service Access Point Identifier (SAPI)

CM

Legenda:

Radio Interface Radio Interface -- LayerLayer 3 (3 (messagemessage layerlayer) )

SDCCH e SACCH are the channels forthe transport of SMS messages

Note:Protocol Discriminator (PD) is used to addressRR sublayers (PD=06), MM (PD=05), CM(PD=03 for CC, SS e SMS)).

39

77

GSM: GSM: ProtocolProtocol ArchitectureArchitectureA Interface A Interface ((betweenbetween BSS and MSC)BSS and MSC) (GSM 8.0X)(GSM 8.0X)

• As mentioned earlier, over the radio interface an ISDN-like protocol is used (LAPDm), while at this interface the protocols used are based on Common Channel Signaling (CCS). The lower layers are based on MPT(1-3) and SCCP protocol (that is mainly involved in the Global Title Translation (GTT))..The A interface is used for messages between BSC and MSC as well for

messages to and from MS (using CC or MM protocol discriminator) therefore the BSSAP (BSS Application Part) layer must be able to detect messages addressed to the MS and to BSS:

- messages addressed to the MS are relayed transparently by the DTAP (Direct Transfer Application Part) sublayer;

- messages addressed to the BSS related to radio resources are handled by the BSSMAP (BSS management Application Part sublayer (for instance BSSMAP is involved in the handover when it occurs between different BSSs, and in the assignment/release of traffic channels over the A interface).

•

78

A InterfaceA Interface

At the physical layer the A interface is made of 2 Mb/s with traffic channelsof 64 K/s (transcoding 16->64 Kb/s in the TRAU).

TRAU= Transcodingand Adaption Unit

40

79

A Interface: DTAP and BSSMAPA Interface: DTAP and BSSMAP

MS B

SS

MSCBSSMAP

RadioResource

mngmt (RR)

DTAPCall Control (CC)

Mobility Mngmt (MM)

BSSMAP Message example : Assignmentthe request is sent during the connection setup phase (i.e.. Mobile terminating) in order to assing a channel over the A interface and over radio link; the message does not specify the radio channel “number”, while it identifies the (CIC) over the A interface;assign. complete is the positive answer to the TCH assignment

80

GSM: GSM: ProtocolProtocol ArchitectureArchitectureA InterfacceA Interfacce((betweenbetween BSS and MSC)BSS and MSC)

• The Mobility Management (MM) layer is built on top of RR layer (in the MS side) and it handles the functions that arise from the mobility of thesubscriber, as well as the authentication and security aspects. Locationmanagement is concerned with the procedures that enable the system to know the current location area of a powered-on mobile station so that incoming call routing can be completed.

• The Communication Management (CM) layer is responsible for call control, supplementary service management, and short message service. Each of these may be considered as a separate sublayer within the CM layer.The CM layer manages the call control in very similar way to Q.931 protocol of ISDN.

41

81

FunctionalFunctional DistinctionDistinction betweenbetweenBase Station Base Station SubsystemSubsystem(BSS) and MSC(BSS) and MSC

continued

82

GSM: GSM: ProtocolProtocol ArchitectureArchitectureInterfacesInterfaces betweenbetween MSC and MSC and otherother network network entitiesentities

• The MM and CM sublayers are both terminated within the MSC.

• The MSC performs the interrelaying functions between the CM, MM, and BBSMAP entities and the Application entities of SS7, such as ISUP, Mobile Application Part (MAP). In particular MAP requires the services provided by SCCP and TCAP in order to interrogate databases (HLR, VLR) in a similar way as the Intelligent Network services. MAP handles non call-related signaling among the different entities of the GSM network. • There are different protocols according the entities involved in the signaling exchange (MAP/A between BSS and MSC, MAP/B between MSC and VLR, etc..).

42

83

MAP MAP ProtocolsProtocols (TS (TS -- GSM 09.02)GSM 09.02)

MSC

HLRVLR

MSC

VLR GMSC

MAP/D

MAP/CMAP/E MAP/G

(B)

(B)

B (MSC-VLR)- Location registration- Incoming e outgoing call setup- Authentication- Management of security services- Operation of supplementary services

C (MSC-HLR)- Routing information

D (HLR-VLR)- Location registration and updating

E (MSC-MSC)- Handover inter-MSC

F (MSC-EIR)- Blacklist of MS equipment

G (VLR-VLR)- location updating using TMSI

Subscriber data (IMSI, authenticationparameters.)

EIRMAP/F

84

SCCP SCCP protocolprotocol

� In the SS7 two methods of addressing are possible

� The first one is based on the MTP3 addressing level using the so called Signaling Point Code (SPC) ed in particular Originating Point Code (OPC) and Destination Point Code (DPC). This scheme has a limited scope, such as one SS#7 national network. Within this scope, the networking function of the MTP3 are able to route messages with the DPC.

� The second method is based on the concept of global title. It is used in SCCP, where it provides in GSM (but also in other networks such as the Intelligent Network) the addressing capacity needed for the transport of MAP messages between network entities (MSC, HLR, VLR etc.).

� The global title may be a number with no direct relationship with SS#7, such as a PSTN number (E.164), a data number (X.121) or a GSM subscriber identity (an IMSI), etc. It does not contain explicit information on the way to route the message, and an SCCP translation function(called Global Title Translation, GTT) is required to know the MTP address from the global title, at least at each network border.

43

85

SS7: SCCP SS7: SCCP layerlayer

MAP/C

TCAP

SCCP

MTP

MSC STP

SCCP

MTP

MAP/C

TCAP

SCCP

MTP

HLR

= MSU, Message Segnaling Unit

86

MTP, SCCP and TCAP MTP, SCCP and TCAP MessagesMessagesF FCS SIF SIO LI FSN BSN F

Component Portion TransactionPortionComponent n Component 1. . .

MTP

SCCP

TCAP

User message/dataSCCPmessageheader

MessageType RL

C-ingPA+C-edPA+MFD

UD= User DataF= FlagFCS= Frame Check SequenceC-ingPA= Calling Party AddressC-edPA= Called Party AddressSIF= Signalling Information FieldMFD = Mandatory Fixed PartSIO = Service Information OctetMTC = Message Type CodeLI = Length IndicatorRL = Routing LabelFSN = Forward Sequence NumberBSN = Backward Sequence Number* = parte opzionale

Legenda:

44

87

SCCP SCCP layerlayer : : the the GlobalGlobal TitleTitle TranslationTranslation (GTT)(GTT)

MSC/ VLR

STP "B"

HLR

. . .

. . . .

“A”

“C”DPC + SSNGT

GTT

. . . . . OPC=ADPC=B

OPCSSN GT . .

RLC-edPA

C-ingPA

OPC=BDPC=C. . . . . . OPC

SSN SSN . . .

Strati MTP

Strato SCCP

UD= User Data F= FlagC-ingPA= Calling Party Address FCS= Frame Check SequenceC-edPA= Called Party Address SIF= Signalling Information FieldMFD= Mandatory Fixed Part SIO= Service Information OctetMTC= Message Type Code LI= Length IndicatorRL= Routing Label FSN= Forward Sequence Number*= parte opzionale BSN= Backward Sequence Number

Legenda:In the example MSC/VLR and HLR belong todifferent PLMNs.IMSI (Racc. E.212) è used to derive the MGT bythe Gateway entity.

IMSI = MCC + MNC + MSIN

88

A GW A

(MSC/VLR)

Signaling Point (SP)

Signaling Transfer Point (STP)

STP Gateway (GW) with SCCP Function (performs GTT)

BGW B

international SS7 NetNational SS7 network(country A)

National SS7 network(country B)

called SCCP = M. Global Title (derived from IMSI of MS)

OPC = A; DPC = GWA

SCCPlayer

OPC = GWA; DPC = GWB OPC=GWB; DPC=B

(HLR)

MTPlayer

GlobalGlobal TitleTitle TranslationTranslation (GTT)(GTT)

A B

GW A

45

89

HowHow toto obtainobtain the the Mobile Mobile GlobalGlobal TitleTitle (MGT) (MGT)

STRUCTURE:

MGT = CC + NDC + MSIN

E.164 E.212

MGT is obtained from IMSI:

IMSI = MCC + MNC + MSIN

MGT = CC + NDC + MSIN

CC: Country Code (39 for Italy);NDC: National Destination Code (339 for TIM);MSIN: Mobile Station Identification Number (10 digits).

• Example: a MS is roaming in a visiting PLMN, when it has to register in a such network, the only available information to VLR, to address the HLR of the MS is IMSI, from which the MGT is derived

90

Mobile Mobile terminatedterminated callcall (I)(I)

MSC

GMSC

HLR

PSTN

BTS

BSC

BTSBTS

BTS

BSC

LAi

LAj

VLR

VLR2

MSISDN3

1

MSRN Request (via IMSI)

MSRN4

MSRN

5

6

2

3

: Send Routing Information

: Provide Roaming Number

46

91

Mobile Mobile terminatedterminated callcall (II)(II)

92

PSTN (origin of the call)

GMSC

HLR

MSCVLR Speech Path

signaling

ISUPMAP/DISUP

COUNTRY VISITED BY THE COUNTRY VISITED BY THE CALLED PARTYCALLED PARTY

International routing for International routing for a roaming subscribera roaming subscriber

HOME COUNTRY OF HOME COUNTRY OF THE CALLED PARTYTHE CALLED PARTY

47

93

PSTN origin of the call

GMSC

HLR

MSC VLR

country B

country A

signaling

GSM: GSM: withoutwithout optimaloptimal routingrouting (2)(2)

ISUP

MAP/C

ISUP

MAP/D

Speech path



94

PSTN origin of the call

GMSC

HLR

signaling

MSC VLR

country B

country A

GSM: GSM: optimaloptimal routingrouting (3)(3)

ISUP

MAP/C

MAP/D Speech routing



(visited PLMN)

48

95

InterInter--system system RoamingRoaming

Source: http://www.ericsson.com/about/publications/review/1999_02/article52.shtml

• So far Cellular networks have handled (macro)mobility with a verticalapproach (radio access technology dependent: i.e. “direct” roaming is impossiblebetween GSM e TDMA/AMPS handsets) unless…..

96

CallCall delivery delivery toto a GSM a GSM subscribersubscriberroamingroaming in a TDMA/AMPS networkin a TDMA/AMPS network.

Source: http://www.ericsson.com/about/publications/review/1999_02/article52.shtml

3 = Send routing information invoke

4 = Provide roaming number invoke

5 = Routing request invoke

6 = Routing request return result

7 = Provide roaming number result

8 = Send routing information result

9 = Call delivery (voice trunk)

10 = Mobile terminal call setup

GAIT (GSM/ANSI136 Interoperability Team) is born in order to facilitate roaming between ANSI-136 and GSM

49

97

Location Location UpdatingUpdating (VLR (VLR changechange and and usingusing TMSI)TMSI)

If the subscriber identity is a TMSI, the VLR checks whether the previous location area identification (LAI) provided in the primitive received from MSC belongs to an area of thisVLR: - if so, the TMSI will be checked. In case of location area change within a VLR, the TMSI should be known and the processmay continue with the authentication check. - if the TMSI is not known or the subscriberdata stored are incomplete, e.g. because the new LA belongs to a different VLR or due toVLR restoration, the indicator "Confirmedby VLR" is set to "Not Confirmed" to initiateHLR updating later on.If the subscriber has not already beenregistered in the VLR, i.e. the previous LAI belongs to a different VLR, the indicators"Confirmed by HLR" and "Location Information Confirmed in HLR" are set to"Not Confirmed" and the VLR checkswhether the identity of the Previous VLR (PVLR) is derivable from the previous LAI:- if so, the IMSI and authenticationparameters are requested from that VLR

98

Location Location UpdatingUpdating (VLR (VLR changechange and and usingusing IMSI)IMSI)

/ AuC

VLR1= PVLR

50

99

MS BSS MSC VLR HLR GMSCPSTN

exchange

IAMSEND ROUTING INFO

ROUTING INFOIAM

PROVIDE R.N.

R.N. ACK

SEND INFO FOR I/CCALL SETUP

SEND PARAM. FROM HLR

CALL DATA ACK

PAGE MSPAGINGPAGING REQCHAN REQ

IMM ASSPAGE RESPONSE COMPLETE

LAYER 3 INFO

PROCESS ACCESS REQ.AUTHENTICATEAUTHENTIC. REQUEST

AUTHENTIC. RESPONSE AUTHENTIC. RESPONSE

START CIPHERINGCIPHER

TMSI TMSI ACKSETUPCALL CONF

ASSIGN REQASSIGN CMDASSIGN COM ASSIGN COMP

ALERT ADDRESS COMPLETE MESSAGE (ACM) ACMCONNECT ANSWER ANS

CONNECT ACK

FixedFixed toto Mobile Mobile callcall scenarioscenario

(*)

(*)= passi semplificati (alcuni messaggi non presenti)

100

MS BSS MSC VLR HLR CHIAMATO

PSTNexchange

CHAN REQIMM ASS

COMPLETE LAYER 3 INFO

PROCESS ACCESS REQ.

AUTHENTICATEAUTHENTIC. REQUESTAUTHENTIC. RESPONSE AUTHENTIC.

RESPONSESTART CIPHERINGCIPHER

TMSI REAL COMP TMSI ACK

SETUP

CALL PROC

ASSIGN REQASSIGN CMDASSIGN COM ASSIGN COMP

ALERT

INITIAL ADDRESS MESSAGE (IAM)

CONNECT ANSWER

CONNECT ACK

Mobile Mobile toto FixedFixed callcall scenarioscenario

SENDING INFO FOR O/G CALL

COMPLETE CALL

ADDRESS COMPLETE MESSAGE (ACM)

CM SERV REQ

(*)

(*)= semplified steps (some message are not present)

51

101

102

52

103

104

53

105

MS BSS_A MSC1

HND REQUIRED

interMSCinterMSC HandoverHandoverMSC2

PERFORM HANDOVER

HND REQ

HND CMD

HND CMD HND REQ ACK

PHYS INFO

HANDO ACCESS

CHAN REL CRL CMD

IAM

SEND END SIGNAL

BSS_B VLR

ALLOCATE HANDOVER NUMBER

SEND HANDOVER REPORT

RADIO CHAN ACK

ACMHND CMD

HND DETECT

HANDOVER COMHND CMPANS

CRL COM FORWD ACC. SIGNAL.CALL CONTROL OR MOBILITY MANAGEMENT MESSAGE

ACKNOWLEDGEMENT

CALL CONTROL OR MOBILITY MANAGEMENT MESSAGE

PROCESS ACC. SIGNAL

..END SIGNAL

HANDOVER REPORT

106

MS BSS 1 MSC

HND RQD

intraMSCintraMSC HandoverHandoverBSS 2

HND REQ

HND REQ ACKHND CMD

HND CMD

HANDO ACCESS

HND DETECT

PHYS INFO

HANDO COM

CHAN REL CRL CMD

CRL COM

HND CMP

54

107

radio channels used by SMS

Short Short MessageMessage ServiceService (SMS)(SMS)architecturearchitecture

SME

SMSC

SME

SME

SME

SMSGW-MSC MSC BSSCSS7

SMSC: Short Message Service CenterSMS-GW-MSC: SMS Gateway MSC

(usually integrated in the SMSC)SME: Short Message Entity (entity that

is able to Tx or Rx short messages; SME may be in the fixed network, maybe a MS, or other services center

HLR VLR

(Stand-by mode)

(Dedicated mode)

Outside the scope of GSM standard

108

Short Message Service (SMS)Short Message Service (SMS)

Mobile Originated

BSS

MSCMSC IWMSCIWMSC1 2 3 4SMSSMS--CC

BSSMSCMSCGMSCGMSC

14

78

2?

info3

5?

info6

HLR VLR

Mobile Terminated

55

109

Mobile Mobile OriginatedOriginated Short Short MessageMessage (MO (MO -- SM)SM)

110

Mobile Mobile TerminatedTerminated Short Short MessageMessage (MT (MT -- SM)SM)

56

111

QoSQoS requirements of traffic typesrequirements of traffic types

Jitter DelayConversational

Loss

Streaming

Interactive

Background

Voce

Video

Signaling

Internet

112

Network Network EvolutionEvolution: : simplifiedsimplified modelsmodels

STP

STP STP

STP

SS7 network(packet switching)

Telephone Network(Circuit switching)

VoiceServices

Signaling(+ SMS of GSM)

router

routerrouter

router

routerinternet (IP)(packet switching)

Data Services

57

113

RELIABLE

MAX DELAY

Current transport Protocols over IP

TCP

UDP

SIGNALINGREQUIREMENTS

NON REAL TIME

NON RELIABLE “FAST”

LIGHT

RELIABLE

“FAST” LIGHT

New Transport Protocol: SCTP(Stream Control Transmission Protocol) ;

Signaling over IP (Signaling over IP (SoIPSoIP))How to fulfill signaling requirements ?How to fulfill signaling requirements ?

ANSWER

114

ArchitecturalArchitectural ViewView of SCTP (RFC2960) of SCTP (RFC2960) •SCTP is viewed as a layer between the SCTP user application ("SCTP user" for short) and a connectionless packet network service such asIP. •The basic service offered by SCTP is the reliable transfer of usermessages between peer SCTP users.. It offers acknowledged error-freenon-duplicated transfer of datagrams (messages). Detection of data corruption, loss of data and duplication of data is achieved by usingchecksums and sequence numbers. A selective retransmissionmechanism is applied to correct loss or corruption of data• It performs this service within the context of an association betweentwo SCTP endpoints.•SCTP is connection-oriented in nature, but the SCTP association is a broader concept than the TCP connection.• SCTP provides the means for each SCTP endpoint to provide the other endpoint (during association startup) with a list of transportaddresses (i.e., multiple IP addresses in combination with an SCTP port) through which that endpoint can be reached and from which it willoriginate SCTP packets. The association spans transfers over all of the possible source/destination combinations which may be generated fromeach endpoint's lists.

58

115

MTP

1-3

M3UA/

SCTP/IP

SG MGC

ISUP

M3UA/

SCTP/

IP

PSTN/ISDN

DSS1MTP

1-3

ISUP

n:n

MGC

ISUP

M3UA/

SCTP/

IP/

IP network

n:n

MTP

1-3

M3UA/

SCTP/

IP

SGn:n

n:n

Signaling Transport over IP (I)Signaling Transport over IP (I)

MTP3 function resides in the

Signaling Gateway (SG)

116

MTP

1-2

M2UA/

SCTP/

IP/

SG

MGCPSTN/ISDN

1:nDSS1 MTP

1-2

ISUP

MTP3

ISUP

M2UA

SCTP/

IP/

MTP3

IP network

1:nASP

ASP

Signaling Transport over IP (I)Signaling Transport over IP (I)M2UA (RFC3331) provides an equivalent functionality to its users asMTP2 provides to MTP3. It is used between a SG and a MGC. UnlikeM2UA, M2PA (IETF draft) supports complete MTP3 messagehandling and network management between any two SS7 nodescommunicating over an IP network.

59

117

SignalingSignaling over IP over IP

IP Transfer Point (ITP), known in the industry as a Signaling Gateway (SG)

SEP: Signaling End Point

118

offload of SMS traffic from transit offload of SMS traffic from transit exchanges (TR/STP) exchanges (TR/STP) -- SMS over IPSMS over IP

Traffic from SMS procedures

Traffic from mobility procedures, Call handling and supplementary services

IP UNIGATEnetwork

MSC-VLR

STP STP

STP STP

SMS-C

SMS-C

HLR

HLR

SGw SGw

SGw SGw

MSC-VLR

60

119

Cisco Architecture: M2PA Cisco Architecture: M2PA adaptionadaptionprotocolprotocolSP SG (STP)

SS7Appl

MTP3

MTP2

MTP1

MTP2M2PA

SCTP

MTP1 IP

M2PA

SCTP

IP

SS7 IP

��

Peer to PeerMTP3

SP

SS7Appl

MTP3

MTP2

MTP1

MTP3

MTP2

MTP1

SG (STP)SS7

Transport

SCCP SCCPGTTGTT GTTGTT

SCTP Stream Control Transmission Protocol (RFC 2960)M3UA MTP3 User Adaptation (RFC 3332)M2UA MTP2 User Adaptation (RFC 3331)M2PA MTP2 Peer to Peer Adaption (IETF draft)

Documents

4' day SS7