introduction to signalling own

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Introduction to Signalling Switching Core Network Signalling

M14/U4



Signalling Concept



What is Signalling ?

Signalling is the exchange of information specifically

concerned with the establishment and control of connections, and with management,

in a telecommunications network.



Standardisation Bodies: The ITU (International Telecommunication Union)

UN

Secretary ITU-D

ITU

General ITU-R ITU-T

http://www.itu.int

http://www.itu.int/



Other Standardisation Bodies

www.3gpp.org is a collaboration agreement that was

established in December 1998. The

collaboration agreement brings together a

number of telecommunications standards

bodies which are known as “Organizational

Partners”. The current Organizational Partners

are ARIB, CCSA, ETSI, ATIS, TTA, and TTC

www.ietf.org Is an organised activity of Internet Society (ISOC).

ISOC is a not-for-profit organization

founded in 1992 to provide leadership in

Internet related standards, education, and policy.

ISOC is supported by more than

90 organizational members and 26,000 individual members

http://www.3gpp.org/

http://www.3gpp.org/Management/OP.htm

http://www.3gpp.org/Management/OP.htm

http://www.ietf.org/

http://www.isoc.org/standards/

http://www.isoc.org/educpillar/









• Easier network integration

• Compatibility between products of different

vendors

• Wider choice of network products from which to

choose

• Competition between suppliers, which leads to a

reduced price and better products

• For the subscriber, this results in quality, lower

price and wider network coverage

Advantages of following the recommendations



Signalling Types

Signalling is divided into three types:

•signalling within the exchange

•signalling between subscriber and exchange

•signalling between exchanges

see also courses CN3414 and CN3415: SCN Call Control



Exchange

A Subscriber B Subscriber

d) Page

e) Service Request

f) Setup

g) Alerting

h) Connect

i) Connect

Acknowledge

a) Service Request

b) Access Grant

c) Setup (Digits)

h) Connect

g) Alerting

i) Connect

Acknowledge

Simplified Signalling Between Subscriber and Exchange



PSTN MSC

Hey, I want to call number 2...

Hold on a second, who are you and what is your number?

I am a priority subscriber and my number is 214-123-4567

Ok, now give the rest of digits

Here they are, 14-987-6543

Ok, he answered

CONVERSATION I want to clear the call now

Got it, bye bye!

A-

subscriber

B-

subscriber

Signalling Between Exchanges Simplified



Historical signaling development

•DC Signaling

•AC Signaling

•MF Signaling (DTMF, CAS)

•CCS Signaling,

– Digital signalling based on data communication concept from OSI (Open System Interconnection).

– Now is CCS No. 7 (called also SS7, C7, …)

– This document will discuss only digital signalling



Common Channel Signalling Common Channel Signalling (CCS) is a signalling method in which signalling information is conveyed over a single channel by addressed messages.

CCS7 CCS7 is an internationally standardised Common Channel Signalling (CCS) system. It is optimised for operation in digital telecommunication networks such as GSM.



Data Communication Environment

application application

host A host B

transmission medium

Communication hardware/softwar

e

Communication hardware/softwar

e

user A user B



OSI Protocol Stack

application

host A

transmission medium

Communication hardware/software

application

host B

Communication hardware/software

OSI Stack

1 Physical Layer

2 Data Link Layer

3 Network Layer

4 Transport Layer

5 Session Layer

6 Presentation Layer

7 Application Layer

access to phys. medium

error detection and correction

addressing and routing

virtual connection and multiplexing

session creation

encryption, decryption,

compression, decompression

application interface



Protocols and Interfaces

1 Physical Layer

2 Data Link Layer

3 Network Layer

4 Transport Layer

5 Session Layer

6 Presentation Layer

7 Application Layer

application application

transmission medium

protocol

protocol

protocol

protocol

protocol

protocol

protocol

interface



Physical layer

Data link layer

Network layer

Transport layer

Session layer

Presentation layer

Application layer

MTP (levels 1-3)

User Part

(Common part) (PSTN, ISDN,

GSM)

User Part

OSI Reference Model Common Channel Signalling No. 7

Application Part

(GSM specific part)

SCCP

Layer

1

2

3

4

5

6

7

Level

1

2

3

4

CCS7 protocol stack vs. the OSI reference model (level and layer)



1972 CCITT Recommendation No.6

1976 CCIS introduced by Bell System

1980 CCITT Recommendation SS7 (Yellow Book)

1984 Enhancement to SS7 (Red Books)

1985 ANSI specification of SS7

1988 Enhancement to SS7 (Blue Books)

1992 Modifications to SS7 Architecture (White Books)

Landmarks in the Progress of CCS7 Signalling

Evolution of the SS No. 7 architecture since the Red Book (1984) increasingly

has been based on the Open Systems Interconnection (OSI) reference

Model.



The Yellow Book Architecture : MTP with only:

• Signalling Data Link Function

• Signalling Link Functions

• Signalling Network Function

• User Parts: TUP and DUP, with possibility for other user parts.

The Red Book Architecture

• SCCP introduced

• ISDN user part modified to ISDN-UP

• The SCCP served OMAP, with an application service part

in between, which provided services of the Presentation-,

Session- and the Transport layer

The Blue Book Architecture:

• Introduction of “Transaction Capabilities”

• The ISDN-UP modified to ISUP

• The MTP made compatible to serve other CCITT defined users

The White Book Architecture:

• The present-day CCS#7. TC modified to TCAP.



Signaling protocols in 2G/3G Core Networks



2G GSM/3G Rel.99 network structure

Network Subsystem (GSM +UMTS)

IN SCP

GGSN

2G SGSN

GPRS + UMTS

SIM card

GSM mobile

UMTS mobile

GSM / UMTS mobile

GSM + UMTS Base Station Subsystem

GSM BTS

UMTS (WCDMA) BTS

BSC BSC

RNC RNC

MSC MSC HLR HLR

MGW

SRR SRR

Internet (TCP/IP)

Landline NW (PSTN/ISDN)

3G SGSN



CCS7 protocols in GSM Network

MAP / INAP

TCAP

SCCP

MTP

BSSAP MAP/INAP

TCAP

SCCP

MTP

TUP NUP ISUP

SCCP

MTP

BSSAP

SCCP

MTP

MSC/VLR

HLR/EIR/AC

PSTN Exchange

BSC

TUP NUP ISUP



Protocol stack in MGW Rel.99

Iu A'

RNCRNC Media Gateway

Media Gateway MSCMSC

Iub

MTP-1

MTP-2

AAL5

SSCOP

SSCF-NNI

BB/NB MTP-3

BB/NB SCCP

RANAP / BSSAP

MTP-3

SCCP

MTP-1

MTP-2

BSSAP

TDMATMATM TDM

AAL5

SSCOP

SSCF-NNI

Broadband MTP-3

Broadband SCCP

RANAP

ATM Layer ATM Layer



New Protocols in SCN Rel4

• Radio Access Network Application Part (RANAP)

• SIGTRAN (M3UA and SCTP)

• Media Gateway Control protocol (H.248/MEGACO)

• Bearer independent call control (BICC)

• Session Initiation Protocol (SIP)

• AAL2SIG (AAL Type 2 Signalling) between RNC-MGW or MGW-MGW when using an ATM bearer

• IPBCP (IP Bearer Control Protocol), tunnelling for MGW-MGW when using an IP bearer



GSM/UMTS Rel4 network structure

SGSN

RNC

IN/SCE APSE

GSM

BSC

WCDMA

MGW

External IP networks

IP/ATM Backbone

MGW

PSTN/ISDN

Other PLMN

HLR/

HSS

MSC Server MSC Server

GGSN

A

A

Iu-CS

Iu-PS

H.248 H.248

BICC CS-2, SIP-I



MSS System Interfaces & Protocols

Iu-CS

RNC

MSS/ GCS

AAL2 ATM

TDM

H.248 IP

MSC Server

Mc

MGW

Nc

AAL2/AAL5 ATM Nb

Mc

BICC CS-2, SIP ATM/IP

HLR Services

MAP CAP

MGW RTP IP

PSTN

RANAP AAL5/ATM SS7

BSC

A

TDM

BSSAP

H.248 IP

User data over ATM, TDM or IP

BICC or SIP for call control H.248 for

MGW control

RANAP or BSSAP

towards radio network



RANAP ---Radio Access Network Application Part

L

MSS/VLR

RNC

RANAP

ATM

MGW

Maintains Iu-interface Control Plane, thus

handling activities between the RAN and CN.

Broadband CCS



RANAP

ATM

AAL5

SSCOP

SSCF

MTP3B

IP

SCTP

M3UA

IP

SCTP

M3UA

MSS MGW

SCCP

RANAP

ISUP

SCCP

TCAP

MAP

RANAP

RNC

ATM

AAL5

SSCOP

SSCF

MTP3B



BSSAP Signalling in Rel4

MTP

IP

SCTP

M3UA

IP

SCTP

M3UA

MSS MGW

SCCP

BSSAP

ISUP

SCCP

TCAP

MAP

BSSAP

BSC

MTP



SIGTRAN - Signalling over IP

SIGTRAN defines a standardized way of carrying any SS7 signalling over IP networks

Defines retransmission and reordering functionalities

Physical layer can be any layer 1 technology

Ethernet/SDH/etc.

IP

SCTP

M3UA

Application

Physical layer

Transport layer

Signalling adaptation: SIGTRAN

Sigtran signalling stack

Application can be ISUP, BICC, SCCP,

etc.



SIGTRAN Deployment in Rel4 MSC Server System

MSC Server

MGW

MSC Server

MGW

PSTN/ ISDN IP

BICC

M3UA

SCTP

HLR

SCCP

M3UA

SCTP

IP

TCAP

MAP

SMSC SCCP

M3UA

SCTP

IP

TCAP

MAP

ISUP

M3UA

SCTP

IP

ISUP

MTP3

RAN/BSS

SCCP

M3UA

SCTP

IP

BSSAP

SCCPb

M3UA

SCTP

IP

RANAP

MGWs act as Signalling GWs

IP



MEGACO / H.248 ---Media Gateway Control protocol

The H.248 protocol is used on the Mc interface between MSC Server and MGW Rel.4.

MSC Server controls the user plane terminations and contexts in MGW Rel.4 through the Mc interface.

L

MGW MGW

MEGACO/ H.248

ATM/IP/TDM

MSS/VLR



H.248

The MSC Server (MSS) can control the user plane Terminations and Contexts in Media Gateway (MGW), using the H.248 protocol

This protocol is used to

• reserve and connect terminations

• connect or release echo cancellers to terminations

• connect or release tones and announcements to terminations

• send/receive DTMF tones

Ta Tb

terminations

MGW

context C User data

User data

SCTP TCP

IPv4 or IPv6

H.248

L1

Protocol stack



Bearer Independent Call Control - BICC •Specified by ITU-T, required in Rel4 networks

•BICC is used for call control between two MSC servers in the Nc interface, allowing a backbone independent Control Plane and User Plane.

•Based on ISUP, includes extensions to carry bearer related information; due to the fact that BICC is supposed to control calls over ATM/IP connection instead of PCM-TSLs.

•The needed bearer specific information is transferred from MGW to MSS through the H.248 protocol


MGW MGW

IAM

.

. MGW address Codec: AMR mode 7 . . .

Bearer information carried in signalling messages

Bearer cntr Bearer cntr

MGW address



Two ways to establish a bearer

Bearer Control Signalling

MSS MSS Call Control Signalling

BICC or SIP

E.g, AAL2 signalling

In IP backbone, no separate bearer signalling is used. Instead, the information

about the bearer is tunneled in H.248 and SIP or BICC

via the MSC Servers. (IPBCP)

H.248

1) Use separate bearer control signalling (ATM)

2) Tunnel bearer information in call control messages (IP)

In ATM backbone, bearer is established via separate

bearer control signalling. In case of ATM AAL2 connections, AAL2 signalling is used.

H.248

MGW MGW



Session Initiation Protocol - SIP

•SIP specified by IETF

•SIP-T defines extensions to carry ISUP messages encapsulated in SIP messages (“SIP for Telephony”)

•Transport usually over UDP (can be e.g. SCTP as well)

•Can establish IP bearers only


IP

UDP/SCTP

SIP

MGW MGW

INVITE

.

. IP address: 192.168.3.2 Port: 5964 Codec: AMR mode 7 . . ISUP: IAM ….

Bearer information and ISUP carried in signalling messages

192.168.3.2/5964

Bearer cntr Bearer cntr



AAL2 paths AAL2 Switc

h

AAL2 Switc

h

Signaling channel

AAL2 ch = AAL2 path & CID

CID = 8-255

AAL Type 2 Signaling

AAL type 2 signaling protocol (Q.2630) is used between AAL2 switching capable network elements ("AAL2 switches"), e.g., RNC-MGW

Path = ATM VCC (Interface,VPI/VCI)

• AAL2 paths are configured (ATM VCC) as permanent virtual channels

• Dedicated signaling channel (ATM VCC with AAL5) is configured between switches for carrying Q.2630 signalling

• Signaling protocol controls AAL2 channel setup and tear down within AAL2 paths. AAL2 channel is identified by AAL2 Path ID and Channel Identifier (CID)

• AAL2 path can go through an intermediate ATM switch in ATM protocol level without switching in AAL2 protocol level

CID(x) CID(x)

SETUP

ATM Switc

h



CCS7 in 3G Rel 4 Network

MGW

GCS MAP/INAP

TCAP

SCCP

M3UA

BICC ISUP

HLR/EIR/AC

MAP / INAP

TCAP

SCCP

M3UA

MSS/VLR

RANAP MAP/INAP

TCAP

SCCP

M3UA

BICC ISUP

RNC RANAP

SCCP

MTP3b

PSTN Exchange

SCCP

MTP3

ISUP



Control Plane Protocol Stacks

Backbone

MSC Server

RNC

MGW

MGW

RANAP

BSSAP

BSC

MSC Server

PSTN

RANAP

SCCP

BSSAP

M3UA

SCTP

IP

SAAL SAAL

ATM ATM

Phy Phy

MTP3b MTP3b

SCCP

MTP

M3UA

SCTP

IP

H.248

SCTP

IP

BICC

MGW

Ethernet

Ethernet

Ethernet

H.248

SCCP SCCP

M3UA

ISUP



Signalling and protocols in MSS

MAP CAP INAP

TCAP BSSAP RANAP

SCCP BICC ISUP

M3UA H.248 SIP

SCTP TCP UDP

IPv4, IPv6

Ethernet



MSS Interfaces (1/2)

Interface Protocol

Specified

by Spec. Transport Physical TransportMGW-BSC (A)

MGW-BSC (Ater), Nokia proprietary BSSAPETSI GSM 08.0X

TDMSTM-1 (VC11/VC12)

E1/T1

TS 25.410 - 415 AAL5/ATM STM-1/VC4, E1/T1

TS 25.933 M3UA/SCTP/IP LAN

MGW-RNC (Iu-CS / User Plain) 3GPPCODEC/AAL2/ATM

CODEC/RTP/UDP/IP

STM-1 (VC11/VC12), E1/T1

LAN

ETSI GSM 09.02 TDM E1/T1

3GPP TS 29.02 IP (Sigtran) LAN

MSS/MSC-MSS/MSC (E) MAP-EETSI

3GPP

GSM 09.02

TS 29.02TDM

M3UA/SCTP

E1/T1

LAN

MSS-VLR (B) MAP-BETSI

3GPP

GSM 09.02

TS 29.02 Internal Internal

VLR-VLR (G) MAP-G

ETSI

3GPP

GSM 09.02

TS 29.02 Internal Internal

HLR - AuC (H) Internal Internal

TCP/IP LAN

SCTP

MSS - IM-MGW (Mn) H.248/Megaco3GPP

ITU/IETF

TS 29.332

RFC 3525 (H.248)

TCP/IP

SCTP LAN

MSS-MSS (Nc) BICC CS2 ITU-T Q.1901 M3UA/SCTP/IP LAN

MTP3b/AAL5/ATM STM-1/VC4

ISUP ITU-/ETSI Q.76x series MTP3/MTP2 E1/T1

SIP, SIP-I, SIP-TITU/IETF

/3GPPseveral UDP/IP LAN

MGW - MGW (Nb) / User Plain Codec/RTP/UDP/IP LAN (Gbit/FE)

Codec/AAL2/ATM STM-1

G.711/TDM E1/T1/STM-1

Broadband (Mb) (User Plane) - MGW Codec/RTP/UDP/IP LAN

MSS - SMSC MAP TDM E1/T1

SMRSE IP (Sigtran) LAN

X.25, TCP/IP X.21, LAN

RANAPMGW-RNC (Iu-CS / Control Plain) 3GPP

MSS/VLR - HLR/EIR (C,D,F) MAP -C/-D/-F

MSS - MGW (Mc) H.248/Megaco3GPP

ITU/IETF

TS 29.232

RFC 3525 (H.248)



MSS Interfaces (2/2)

Interface Protocol

Specified

by Spec. Transport Physical Transport

MSS/MSCI - Voice MailISUP/TUP/R2 ITU-/ETSI several TDM

STM-1 (VC11/VC12)

E1/T1

MSS/MSCI - CCBSFTAM

FTP, GTP'

OSI

IETFseveral

ISO-IP (OSI), X25

TCP/IP

LAN, E1/T1

LAN

MSS/MSCi/HLRi - NetAct X.25/TDM E1/T1

IP (Sigtran) LAN

TCP/IP LAN

MGW - ISDN/PSTN ISUP/TUP/R2 ITU-/ETSI several TDMSTM-1 (VC11/VC12)

E1/T1

PBX ( 30B+D ) - MSS/MSC

Euro ISDN (DSS1)

DPNSS1 ITU-T Q.921 TDM E1

SSF - SCF

Core INAP

CAPETSI

3GPP

CS-1 and CS-2

CAMEL

TDM

(IP) SIGTRAN

E1/T1

LAN

HLR - SCF MAP

ETSI

3GPP

GSM 09.02

TS 29.02

TDM

(IP) SIGTRAN

E1/T1

LAN

MSS - IMS (Mj,Mg) SIP 3GPP TS. 29.163 UDP/IP LAN

NVS AS - IMS (S-CSCF )ISC (SIP)

ITU/IETF

3GPPseveral UDP/IP LAN

SBC - NVS SIP ITU/IETF several UDP/IP LAN

NVS - NVS (Nokia propriatory use)SIP

ITU/IETF

3GPPseveral UDP/IP LAN

LDAP database - NVS LDAP IP SIP LAN

MSS - GMLC (Lg) MAP

ETSI

3GPP

GSM 09.02

TS 29.02

TDM

(IP) SIGTRAN

E1/T1

LAN

MSS - SMLC (Ls) MAP

ETSI

3GPP

GSM 09.02

TS 29.02

TDM

(IP) SIGTRAN

E1/T1

LAN

HLR - GMLS (Lh) MAP

ETSI

3GPP

GSM 09.02

TS 29.02

TDM

(IP) SIGTRAN

E1/T1

LAN

SGSN-BSC (Gb) GTP IP LAN

SGSN-RNC (Iu_PS) GTP IP LAN

Cell Broadcast Centre (CBC) - NC (Iu_BC)

severalSeveralQ3, FTAM,

VTERM,

XML over HTTP

introduction to signalling own

Documents

session initiation

user plane

aal2 switc

user plane

call control

msc server

user data

standardisation