The Interworking of IP Telephony with Legacy Networks ? ISUP is used in PSTN, ISDN, MSC/GMSC of GSM and the gateway of IS-41.
– ISUP is the 'almighty' signaling for inter-connecting the different telephony networks • In IP Telephony networks, the signaling is SIP, H.323 or MGCP/MEGACO. • The signaling of Interworking:
– 1, SIP-ISUP – 2, H.323-ISUP – 3, MGCP/MEGACO-ISUP(also TCAP) 1
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SIP-ISUP
• SIP overview:
–
SIP URLs –
Format= User@host
–
examples:
•
[email protected] •
[email protected]
–
2
Locating a SIP Server: Client request( E.g. INVITE) is sent to SIP server –
Either default local proxy SIP server
–
Or SIP server for called party
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SIP-ISUP
• PSTN? IP ? PSTN
–PSTN1 calls MGC1 The signaling is the ISUP
PROXY VoIP Network
–MGC1 calls MGC2 PROXY
The signaling is the SIP
–MGC2 calls PSTN2
MGC2
MGC1
The signaling is the ISUP • SIP looks like a transparent media for ISUP.
SS7/C7
PSTN2
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SS7/C7
PSTN1
PSTN
SIP-IP
MGC#1 PROXY MGC#2
PSTN
IAM INVITE
• PSTN? IP ? PSTN
IAM 100 TRYING
Call flow: 183 SESSION Pro
ACM
ACM ANM 200 OK ANM ACK
Conversation
REL BYE REL RLC 200 OK RLC
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SIP-ISUP
• PSTN ? IP
–PSTN calls the MGC The signaling is ISUP
PROXY VoIP Network
– MGC calls the SIP server and SIP phone
SIP server
The signaling is SIP Note:
MGC
– The SIP phone should already register to a SIP server. – SIP server could be a proxy or a redirect server 5
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SS7/C7
SIP phone
PSTN
PSTN
SIP-IP
MGC
P R O X Y SIP-phone
IAM INVITE
• PSTN ? IP
INVITE 100 TRYING
Call Flow:
180 RINGING 180 RINGING ACM 200 OK 200 OK ANM ACK ACK
Conversation
REL BYE BYE 200 OK 200 OK RLC
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SIP-ISUP
• IP ? PSTN
–SIP phone calls the MGC SIP server
The signaling is SIP
VoIP Network
–MGC calls the PSTN The signaling is ISUP
PROXY
MGC
SS7/C7
PSTN
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SIP phone
SIP-phone
SIP-IP
PROXY
MGC
PSTN
INVITE INVITE
• IP ? PSTN
IAM 100 TRYING
ACM 183 SESSION 183 Session ANM 200 OK 200 OK ACK ACK Conversation BYE BYE REL RLC 200 OK BYE
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H.323-ISUP
H.323:
–H.225.0: Call Signaling and media packetisation Specifies call setup message which are based on Q.931
–H.245: Call control MGC:
–Map the ISUP signaling to H.225 signaling and H.225 signaling to ISUP for call setup.
–Map the ISUP signaling to H.245 signaling and H.245 signaling to ISUP for call control.
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H.323-ISUP MGC
MGC Q.931 Channel H.245 Channel
• Q.931 channel
–Carries call setup messages to set up H.245
–Can be closed as soon as H.245 Channel set up 10
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• H.245 channel
–Exchange audio/video capabilities
–Master/slave determination –initiate setup of RTP sessions
–Terminate call
MGCP/MEGACO-ISUP
• Gateway Decomposition
–Scalability –Seamless PSTN Integration –SS7/C7 connectivity –Availability • 2 kind of Gateway
–Trunk(TGW) Connects PSTN to IP network
–Residential(RGW) Connects residential telephone an IP network 11
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MGCP/MEGACO-ISUP
• Call agent
–Controls TGW and RGW using MGCP/MEGACO –Handles SS7/C7 signaling for trunks that interconnect PSTN with IP network
–Interacts with SCPs over SS7 networking support of various services
–May support SIP/H.323 signaling • In UMTS All-IP Core Network, the Call agent is ' Call Processing Server' (CPS)
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MGCP/MEGACO-ISUP
Here is a example of MGCP-ISUP MGCP/MEGACO also support the mapping of TCAP
Call agent
Call Agent
MGCP MGCP Internet
MGCP RGW
SS7GW RGW
TGW
PSTN
SS7/ TCAP, SS7/ ISUP
STP
Signal Voice
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SCP
Caller
MGCP/MEGACO-ISUP
Call agent TGW
RGW Off-hook
Call Flow of the MGCP-ISUP
SS7
I:Off-hook C:Provide dialtone and collect digits
Dial tone Digits
I:Digits dialled C:Create connection I: RGW IP address, UDP Port
C:Modify Connection to send to TGW IP address, UDP port
C:Create Connection sending to RGW IP address, UDP port I: TGW IP address, UDP Port IAM ACM
Ringing from PSTN ANM
ACM RTP voice packets
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UMTS All-IP Core Network
Here is The UMTS All-IP Core Network . In UMTS All-IP Core Network , R-SGW is used for the MAP connection to the Legacy 2G Network for Roaming.
HSS GPRS HLR UMS
CPS CSCF MGCF
SGSN
IP Network
GW T-SGW R-SGW
BSS
MGW MRF
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