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MSC Server overview
Markus Martin
26.06.2003
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MSC Server - separates user and controlplane
MSCi - M11
MGW - U1.5
A'
Iu-CS
MSS
M12
MGW - U2
Packet basedBackbone (IP/ATM)
& TDM based PSTN
TDM basedBackbone & PSTN
A
A & Iu-CS
userplane
control plane
H.248/MegacoSigtran
MSC 3GPP Rel99
MGW is a part of 3G MSC GSM and 3G Circuit Switching Transmission is TDM
MSC Server 3GPP Rel4
MGW is separate from MSS GSM and 3G Circuit Switched services Transmission is IP (also ATM can be use Voice and signaling over IP
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All interfacessupported by
same elements
WCDMA
IP/ATMBackbone
PSTN/ISDN
Other PLMN
MSC Server
GSM
BSC
RNC
A
Iu-CS
MGW
H.248
IN/SCE HLR
MSC Server system
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Interfaces & ProtocolsRel.4 Network
Iu-CS
RNC
MSCServer
AAL2ATM
TDM
H.248IP
MSCServer
Mc
MGW
Nc
AAL2/AAL5ATM Nb
Mc SigtranIP
BICCATM/IP
RANAP/BSSAP for radio accesscontrol
Nc - BICC for call control (also SIP-T)
Mc - H.248 for MGW control
Nb - AAL2 for user data
Nb- RTP for user data over IP
AAL5 for signaling over ATM
Sigtran for transmitting SS7signaling over IP
HLRServices
MAP CAP
MGWRTPIP
PSTN
RANAPAAL5/ATM SS7
BSC
SigtranIP
A
TDM
BSSAP
H.248IP
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Support for All-IP Mobility CoreIMS-CS interworking
SS7
RTP
IP
PSTN
MSS/GCS
SIP
CPS
MGW
SIGTRAN
TDM
H.248
SIP
PS CN domain
Gi
Gi
Gi
GGSNSGSN
MGW can be used in IMS
environment forinterconnecting IMS andPSTN/PLMN networks
CPS = Connection Processing ServerGCS = Gateway Control Server
M13/ U2.1
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MSC Server overview
the MSC Server is a circuit-switched call controlproductoffering all GSM and 3G circuit-switched services.
the MSC Server allows operators to: provide same CS services as with an MSC combine transport of voice and data (GPRS)
in a single transport network optimize signaling and transport networks,
separatelypurchase call control and traffic capacity
have a clear evolution to IP backbone with theMGW
the MSC Server is a functionality which can beupgraded tothe MSCi and TMSCi network elements (2G or 3G)
6 NOKIA MSC Server marketing1.PPT / 26.9.2000/ATu/KN
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Integrated MSC Server
Upgrade from previous MSCi release to contain also MSCServer features
Still supports full MSCi functionality
Contains Gateway MSC Functionality Visited MSC Functionality
Media Gateway Control Function
MSCi - M11 MSCi - M12 MSS1) M12 upgrade 2) MSS activation
GMSC VMSC
MGCF
GMSC VMSC
Switching IWF IWFSwitching
GMSC VMSC
Switching IWF
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Standalone MSC Server
New delivery in M12 without user plane switching
Contains only MSC Server features and optimized hardware(e.g. no GSW, ET or modem pools)
Note though that same functionalities are present as inIntegrated MSC Server except MSCi user plane handling
Gateway MSC Functionality Visited MSC Functionality
Media Gateway Control Function Also possible to upgrade Integrated MSC Server to Standalone
MSC Server (MSSu) by removing user plane switching HW andfunctionality
MSS
GMSC VMSC
MGCF
New delivery
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Gateway Control Server
Gateway Control Server
New product Includes GMSC and MGCF functionalities Meant for operators who need transit MSC Server or
dedicated PSTN access for IP Telephony
MSS functionality also possible in TMSCi (probably not
relevant)
GCS
GMSC
MGCF
New delivery
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Location of new functionalities
MSC Server adds more signallings
CCSU
SIGU
BSU
Sigtran (M3UA/SCTP)
H.248
BICC
SIP/SIP-T
Sigtran (M3UA/SCTP)
RANAP
ISU
Sigtran (M3UA/SCTP)
H.248
AAL2 signalling
MSC S i l i d
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MSC Server in a multivendorenvironment
Nokia philosophy on the power of open interfaces also applies
in the MSC Server system Nokia has implemented all interfaces according to
standardization with the exceptions defined in the detailedinterface specifications
Standardization in all other interfaces apart from Mc is such thatno major IOT issues are foreseen.
Variations in H.248 packages (grouping of termination characteristics) Naming convention of the Termination Identity
IOT testing has not started yet for MSC Server system specific
interfaces It should be noted that it supports the same multivendor interfaces as the
MSCi First priority in IOT/MVI will be in Nc (MSS-MSS) and Nb (MGW-MGW)
interfaces
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MSS system topology
handlingshort intro
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IP Network Topology - User Plane
Using IP an operator can build a routable user plane with no
connection configuration UPD is the lowest level information that the MSC Server knows
about the user plane (no user plane IP addresses are known)
Signaling links still need to be configured (not for SIP)
MGW
MGW
MGW MGW
MGW
MGW
IP
UPD1UPD2
UPD3
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Finding an terminating MGW
MGW_
A
MSC Server
MSC Server
MGW_B
1. ADD.req2. ADD.resp
(IP_addr_A)
3. IAM(IP_addr_A)
4. ADD.req(IP_addr_A)
5. ADD.req(IP_addr_B)
6. APM(IP_addr_B)
7. MOD.req(IP_addr_B)
IP address information is tunneled between the MGWs
MGW does not need to know anything about the user planetopology
Routers need to be configured with their own subnets
R
R
Subnet 192.168.2.0/24Subnet 192.168.3.0/24
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IP Network Topology - Signalling
Sigtran links are created between Signalling Point Codes
Sigtran STPs are possible but do not make networkconfiguration easier at MTP3 level
Configuration consists of few MMLs, planning the PCM-TSLusage not necessary
MSC Server
MSC Server
MSC ServerMGW
SPC: 600H
SPC: 400H
SPC: 500HSPC: 300H
PSTNSPC=x
Sigtran
Sigtran
Sigtran
SGW funcionalityof the MGW used
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ATM Topology - User Plane
MGW
MGW
MGW MGW
MGW
MGW
ATM
UPD1UPD2
UPD3
ATM connections between MGWs have to be preconfigured
Between MGW and the ATM switch PVCs used
In ATM core S-PVC if supported by ATM switch vendor(PNNI1.0 signalling required)
Similarly as in IP case, UPDs have to be configured to the
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Finding an terminating MGW
MGW_
A
MSC Server
MSC Server
MGW_B
1. ADD.req2. ADD.resp(ATM_addr_A)
3. IAM(ATM_addr_A)
4. ADD.req(ATM_addr_A)
5. ADD.req(ATM_addr_B)
6. APM(ATM_addr_B)
7. MOD.req(ATM_addr_B)
ATM address information is tunneled between the MGWs
MGW does needs to find a route towards the terminating MGW ATM switches have been configured with PVCs (S-PVCs)
S
S
Route AAL2 ERQ towards ATM_addr_B
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ATM Topology - User Plane (cont.)
In large networks, to reduce the number of VCs to be
configured, either use two MGW per call, or the AAL2 nodal function can be used
MGW
MGW
MGW
UPD2
MSC Server
MGW
MGW
MSC Server
RAN
AAL2 Nodal function used!
2.
1.
RAN
MGWWeight - 50
Weight - 30
UPD1
MGW
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AAL2 Nodal Funtionality
MGW_B
RAN
ATM PVC betweenRNC and MGW
2. AAL2 ERQ
MGW_A
MSC Server
1. RAB ESTABLISHMENT REQ (NSAP_A)
4. AAL2 ERQ
ATM PVCbetween MGWs
3. NUMBERANALYSIS
5. NUMBERANALYSIS
The MGW will analyze the called party address of the incoming
AAL2 ERQ message If it is not destined for itself, it will route it forward
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ATM Topology - Signalling
Sigtran links are created between Signalling Point Codes like
in IP case IP based signalling carried
over IP over ATM tunnels or via SGW (using MTP3b)
MSC Server
MSC Server
MGW
SPC: 600H
SPC: 400H
SPC: 500HSPC: 300H
Sigtran
SGW funcionalityof the MGW used
MGW
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Virtual MGWs
MGW
MSC Server MSC Server
Single physical MGW can be controlled by more than one MSC
Server Improved resiliency at critical points of the network
E.g. a large Point of Interconnect
MGW can be split to 50 VMGWs (each ISU unit can be split tofive VMGWs)
H.248 H.248
MGW does not know whether it is controlledby a single or many MSS.
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Virtual MGWs (cont.)
MSC Server selected at MGW startup and registration
IP and ATM resources are common for all MSC Servercontrolling the MGW
TDM resources are dedicated to MSC Servers
ISU-1
MGW
Primary MSC Server: 192.168.26.1
Secondary MSC Server: 192.168.21.1
. . .
MSC ServerMGW DB
MGW name: OuluMGW1.operator.net
IP addr: 192.168.11.1
Routes: 101-105, 110
. . .
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Protocols and stack
short intro
U Pl P l S k
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User Plane Protocol Stacks
Backbone
MSC Server
MSC +
IP Trunk
RNCMGW MGW
Nb/IPNb/ATM
Nb-UP
AAL2
ATM
Phy
Nb-UP
RTP
UDP
IP
Phy
AMR (/EFR / FR)
Iu-UP
AAL2
ATM
Phy
RTP
UDP
IP
Phy
AMR/EFR/FR/G.711
G.711Phy
PSTNBSS
Iu_CS
AMR/EFR/FR/G.711
H 248
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H.248
Master-slave protocol The MGC (Media Gateway Controller) is the master and the MG (Media
Gateway) the slave MG registers with the MGC and the association is setup a one-to-one protocol, MG is controlled by one MGC can be ASN.1 binary codes or ASCII coded, MGC must support both,
MG chooses
Specified in IETF (Megaco) and ITU-T (H.248) In 3GPP mandated between MSS and MGW for Rel.4
In Rel.5/6 it is used between MGCF and MGW, and CSCF andMRF
Connection model based on termination and contextsTa Tb
terminations
MGW
context CUser data User
data
SCTP TCP
IPv4 or IPv6
H.248
L1
Protocolstack
Si lli T t (SIGTRAN)
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Signalling Transport (SIGTRAN)
Sigtran maps SS7 addressing (Signalling Point Codes orGT addresses) into IP addresses.
SCTP (Stream Control Transmission Protocol) providesreliable and redundant transport mechanism over IPspecial features suitable for signalling
Different adaptation layers possible M2UA (MTP2 user adaptation layer), Not supported M3UA (MTP3 user adaptation layer) SUA (SCCP user adaptation layer), FFS
M3UA supported in the 1st implementation of Rel4
The main function of the T-SGW is changeMTP L1 L3 signalling to correspond IPsignalling. SCTP and adaptation layers(e.g. M3UA) can be used for this purpose in the T-SGW.
IP
SCTP
SUA
TCAP
MAP
IP
SCTP
M3UA
SCCP
TCAP
MAP
B I d d t C ll C t l BICC
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Bearer Independent Call Control - BICC
Specified by ITU-T, required in Rel4 networks
Based on ISUP, includes extensions to carry bearer relatedinformation
Two parts Call control (signalling) Bearer Control (application in MSC Server)
Can establish ATM and IP bearers Transported over Sigtran
MSC ServerMSC Server
IP
SCTP
M3UA
BICC
MGWMGW
IAM
Sigtran
.
.IP address: 192.168.3.2Port: 5964Codec: AMR mode 7...
Bearer informationcarried insignalling messages
Bearer cntr Bearer cntr
192.168.3.2/5964
S i I iti ti P t l SIP
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Session Initiation Protocol - SIP
SIP specified by IETF, required in 3GPP All-IP networks
SIP-T defines extensions to carry ISUP messagesencapsulated in SIP messages (SIP for Telephony)
Transport usually over UDP (can be e.g. TCP as well, M13candidate)
Can establish IP bearers
MSC ServerMSC Server
IP
UDP/TCPSIP
MGWMGW
INVITE
.
.IP address: 192.168.3.2Port: 5964Codec: AMR mode 7..ISUP: 84FC 03FC .
Bearer informationand ISUP carried insignalling messages
192.168.3.2/5964
Bearer cntr Bearer cntr
Basic Call Cases in MSS system
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Basic Call Cases in MSS system
The basic call cases are described in the feature:
FN1327 Basic Call Cases in MSC Server
UE UE call ATM core (1/3)
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UE-UE call, ATM core (1/3)
MSC Server
MGW
RNC
MSC Server
MGW
RNC
PSTNPSTN
TDMTDM
Forward Establishment used, BICC between MSS
ATM Core
1. SETUP2. CALL PROCEEDING
3. IAM
4. SETUP5. CALL CONFIRMED
6. Add.req7. Add.resp (mgw_addr, binding id)
8. APM (mgw_addr, binding_id
9. Add.req (mgw_addr, binding_id)10. Add.resp
11. ERQ (mgw_addr, binding_id)
12. ECF
15. Notify.ind16. Notify.resp
UE UE call ATM core (2/3)
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UE-UE call, ATM core (2/3)
MSC Server
MGW
RNC
MSC Server
MGW
RNC
PSTNPSTN
TDMTDM
Forward Establishment used, BICC between MSS
ATM Core
17. Add.req18. Add.resp (mgw_addr, binding id)
19. RAB ASSIGNMENT REQ(mgw_addr, binding_id)
20. ERQ (mgw_addr, binding_id)
21. ECF
22. RAB ASSIGNMENT COMPLETE
23. COT
24. Add.req25. Add.resp (mgw_addr, binding id)
26. RAB ASSIGNMENT REQ(mgw_addr, binding_id)
29. RAB ASSIGNMENT COMPLETE
27. ERQ (mgw_addr, binding_id
28. ECF
30. ALERTING
33. ACM
31. Add.req (ringing tone)32. Add.resp
34. ALERTING
UE UE call ATM core (3/3)
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UE-UE call, ATM core (3/3)
MSC Server
MGW
RNC
MSC Server
MGW
RNC
PSTNPSTN
ATM/ AAL2
ATM/ AAL2
TDMTDM
Forward Establishment used, BICC between MSS
ATM Core
35. CONNECT
36. Modify.req (cut through) and remove tone37. Modify.resp
38. ANM
39. CONNECT
UE to UE call
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RNC
WCDMA MGWMGW
MSC ServerMSC Server
UE to UE call
WCDMA
RNC
Two MSC Servers, BICC signalling, IP user plane
1. RANAP: Setup
2. Digit analysis:outgoing call ->select MGW
3. H.248:Reserve userplane resources
4. BICC: IAM
8. BICC: APM
9. Bearer established
6. RANAP: Setup
5. Digit analysis:UE terminated ->Page, select MGW
7. H.248:Reserve userplane resources
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Network migration
example scenarios
MSC Server introduction (2G)
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( )as port and coverage expansion
MGW
MGW
MGW
CommonIP/ATM backbone
MSCi upgraded to
Integrated MSS
Existing MSC coverage
BSC
BSC
New coverage
PSTN
BSC
BSC
MGWs introducedin new area toprovide local
switching
MGWs introduced inexisting area to provideadditional port capacityand BB connectivity
PSTN
IWFIWF functionality
can be provided byMSS
MSC Server introduction (2G)
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as separate expansion
MGW
MGW
MGW
CommonIP/ATM backbone
MSCi
Existing MSC coverage
BSC
BSC
New coverage
PSTN
BSC
BSC
MGWs introducedin new area toprovide local
switching
MGWs introduced inexisting area to provideadditional port capacity
and BB connectivity
MSS introduced
to control newMGWs
ISUPPSTN
CDS
IWF functionalityprovided by CDS
MSC Server introduction (2G)
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Subrack MSC replacement
MSCi
Area1
BSC
BSC
Area 2
PSTN
BSC
BSC
MSS introduced
to control newMGWs
ISUPPSTNMSC
MSC
MSCISUP
ISUP
ISUP
3 subrack MSCs in twodifferent areas are beingreplaced by MGW andMSS
MSC Server introduction (2G)S SC
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Subrack MSC replacement
MGW
MGW
MGW
CommonIP/ATM backbone
MSCiBSC
BSC
PSTN
BSC
BSC
MGWs introducedin Area 2 to providelocal switching
MSS introduced to
handle subrack MSCcontrol plane
functions as eachMSC is swapped to a
MGW
ISUPPSTN
MGWs introduced oneby one to replacesubrack MSC user
plane functions.
PBX interfaces insubracks rehomed to
MSCi
CDS
IWF functionalityprovided by CDS.CDSU boards from
subrack MSCs can bereused.
Area1Area 2