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1 © Nokia Siemens Networks Presentation / Author / Date / Document Number
For public use – IPR applies
Introduction to Signalling Switching Core Network Signalling
M14/U4
4 © Nokia Siemens Networks Presentation / Author / Date / Document Number
For public use – IPR applies
Signalling Concept
5 © Nokia Siemens Networks Presentation / Author / Date / Document Number
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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.
6 © Nokia Siemens Networks Presentation / Author / Date / Document Number
For public use – IPR applies
Standardisation Bodies: The ITU (International Telecommunication Union)
UN
Secretary ITU-D
ITU
General ITU-R ITU-T
http://www.itu.int
7 © Nokia Siemens Networks Presentation / Author / Date / Document Number
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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
8 © Nokia Siemens Networks Presentation / Author / Date / Document Number
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• 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
9 © Nokia Siemens Networks Presentation / Author / Date / Document Number
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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
10 © Nokia Siemens Networks Presentation / Author / Date / Document Number
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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
11 © Nokia Siemens Networks Presentation / Author / Date / Document Number
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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
12 © Nokia Siemens Networks Presentation / Author / Date / Document Number
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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
13 © Nokia Siemens Networks Presentation / Author / Date / Document Number
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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.
14 © Nokia Siemens Networks Presentation / Author / Date / Document Number
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Data Communication Environment
application application
host A host B
transmission medium
Communication hardware/softwar
e
Communication hardware/softwar
e
user A user B
15 © Nokia Siemens Networks Presentation / Author / Date / Document Number
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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
16 © Nokia Siemens Networks Presentation / Author / Date / Document Number
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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
17 © Nokia Siemens Networks Presentation / Author / Date / Document Number
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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)
18 © Nokia Siemens Networks Presentation / Author / Date / Document Number
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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.
19 © Nokia Siemens Networks Presentation / Author / Date / Document Number
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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.
20 © Nokia Siemens Networks Presentation / Author / Date / Document Number
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Signaling protocols in 2G/3G Core Networks
21 © Nokia Siemens Networks Presentation / Author / Date / Document Number
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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
22 © Nokia Siemens Networks Presentation / Author / Date / Document Number
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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
23 © Nokia Siemens Networks Presentation / Author / Date / Document Number
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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
24 © Nokia Siemens Networks Presentation / Author / Date / Document Number
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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
25 © Nokia Siemens Networks Presentation / Author / Date / Document Number
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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
26 © Nokia Siemens Networks Presentation / Author / Date / Document Number
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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
27 © Nokia Siemens Networks Presentation / Author / Date / Document Number
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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
28 © Nokia Siemens Networks Presentation / Author / Date / Document Number
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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
29 © Nokia Siemens Networks Presentation / Author / Date / Document Number
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BSSAP Signalling in Rel4
MTP
IP
SCTP
M3UA
IP
SCTP
M3UA
MSS MGW
SCCP
BSSAP
ISUP
SCCP
TCAP
MAP
BSSAP
BSC
MTP
30 © Nokia Siemens Networks Presentation / Author / Date / Document Number
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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.
31 © Nokia Siemens Networks Presentation / Author / Date / Document Number
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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
32 © Nokia Siemens Networks Presentation / Author / Date / Document Number
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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
33 © Nokia Siemens Networks Presentation / Author / Date / Document Number
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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
34 © Nokia Siemens Networks Presentation / Author / Date / Document Number
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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
MSC Server MSC Server
MGW MGW
IAM
.
. MGW address Codec: AMR mode 7 . . .
Bearer information carried in signalling messages
Bearer cntr Bearer cntr
MGW address
35 © Nokia Siemens Networks Presentation / Author / Date / Document Number
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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
36 © Nokia Siemens Networks Presentation / Author / Date / Document Number
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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
MSC Server MSC Server
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
37 © Nokia Siemens Networks Presentation / Author / Date / Document Number
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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
38 © Nokia Siemens Networks Presentation / Author / Date / Document Number
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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
39 © Nokia Siemens Networks Presentation / Author / Date / Document Number
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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
40 © Nokia Siemens Networks Presentation / Author / Date / Document Number
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Signalling and protocols in MSS
MAP CAP INAP
TCAP BSSAP RANAP
SCCP BICC ISUP
M3UA H.248 SIP
SCTP TCP UDP
IPv4, IPv6
Ethernet
51 © Nokia Siemens Networks Presentation / Author / Date / Document Number
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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)
52 © Nokia Siemens Networks Presentation / Author / Date / Document Number
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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,
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