Gonzalo CamarilloAtlanta September 28th, 1999 Advanced Signalling Research Lab.
Fall ‘99 VONVON protocols - SIP
Gonzalo [email protected]
ASRLAdvanced Signalling Research Lab.
SIP / ISUP interconnection
Gonzalo CamarilloAtlanta September 28th, 1999 Advanced Signalling Research Lab.
Fall ‘99 VONVON protocols - SIP
Telephone Services
•GSTN (General Switched Telephone Network)
•IP Telephony
IP Telephony GSTN
Gonzalo CamarilloAtlanta September 28th, 1999 Advanced Signalling Research Lab.
Fall ‘99 VONVON protocols - SIP
• Brief SS7 introduction (architecture)
• Gateway architecture ( SG, MGC, MG )
Contents
• ISUP - SIP interworking issues and proposed solutions
Gonzalo CamarilloAtlanta September 28th, 1999 Advanced Signalling Research Lab.
Fall ‘99 VONVON protocols - SIP
Different architectures
GSTN architecture:Intelligence in the networkDumb terminals
SIP architecture:Move the intelligence to the edge
Gonzalo CamarilloAtlanta September 28th, 1999 Advanced Signalling Research Lab.
Fall ‘99 VONVON protocols - SIP
DSS 1 ISUP DSS 1
Signalling in GSTN
Signalling in the network (between switches)User to network signalling
Gonzalo CamarilloAtlanta September 28th, 1999 Advanced Signalling Research Lab.
Fall ‘99 VONVON protocols - SIP
DSS-1
Q. 931Protocol between the user and the networkMuch simpler than ISUP.
Q. 921Handles the transport of the messages
Gonzalo CamarilloAtlanta September 28th, 1999 Advanced Signalling Research Lab.
Fall ‘99 VONVON protocols - SIP
Signalling in GSTNSS7 (System Signalling No. 7)
MTP
ISUP TUPTCAP
SCCP
Level
4
3
2
1
Gonzalo CamarilloAtlanta September 28th, 1999 Advanced Signalling Research Lab.
Fall ‘99 VONVON protocols - SIP
General ISUP<->SIP Conversion
SG
SIP Client
SIP ServerSTP ISUP/MTP
E1/T1
SIP
SS7
Voice StreamSignalling
MG
RTP
MGCP SIP
SIP
IP network
ISUP/IP
MGC
DSS 1
Gonzalo CamarilloAtlanta September 28th, 1999 Advanced Signalling Research Lab.
Fall ‘99 VONVON protocols - SIP
Architecture of the distributed gateway
Signalling Gateway
Media Gateway Controller
Media Gateway
GSTN side
IP side
Voice stream Voice stream
ISUP
SIP
MGCP
ISUP/IP
Gonzalo CamarilloAtlanta September 28th, 1999 Advanced Signalling Research Lab.
Fall ‘99 VONVON protocols - SIP
Signalling Gateway
• To find the appropriate media gateway controllerFunction:
Signalling GW
ISUP/IPISUP/IPISUP/IP
ISUP/IP
ISUP
SIPMGCPSIPMGCPSIPMGCPSIPMGCP
MGC MGC MGC MGC
Gonzalo CamarilloAtlanta September 28th, 1999 Advanced Signalling Research Lab.
Fall ‘99 VONVON protocols - SIP
Media GatewayMapping between different voice formats
ControlProtocol
GSTN RTP
Gonzalo CamarilloAtlanta September 28th, 1999 Advanced Signalling Research Lab.
Fall ‘99 VONVON protocols - SIP
Media Gateway Controller for distributed
Media Gateways
• Actual mapping between protocols (ISUP-SIP)• Control the Media Gateway/s• Authentication, Authorization and Accounting (AAA)
Functions
Gonzalo CamarilloAtlanta September 28th, 1999 Advanced Signalling Research Lab.
Fall ‘99 VONVON protocols - SIP
Experiences implementing ISUP to SIP mapping
• Different flavours of ISUP (message flow)• Overlap signalling (SAMs)• In band announcements and ring-back tone• ISUP transparency• Billing in forwarding situations• Tracing calls (malicious, SOS)
Gonzalo CamarilloAtlanta September 28th, 1999 Advanced Signalling Research Lab.
Fall ‘99 VONVON protocols - SIP
ITU ISUP message exchange during a callLocal
ExchangeIAM
ACM
RLC
CPGANM
REL
Voice Transfer
LocalExchange
Different message flows
ANSI ISUP: CPG before ACM
Gonzalo CamarilloAtlanta September 28th, 1999 Advanced Signalling Research Lab.
Fall ‘99 VONVON protocols - SIP
Overlap signalling (SAMs)
European phone numbers does not have a fixed length.
Example: +358 9 299 1 Finland Helsinki Ericsson Front desk
+358 9 299 3371 Finland Helsinki Ericsson Camarillo’s
The ingress gateway cannot know when the number is complete.
Gonzalo CamarilloAtlanta September 28th, 1999 Advanced Signalling Research Lab.
Fall ‘99 VONVON protocols - SIP
Proposed solution
Ingress gateway waits for SAMs with more digitsa certain amount of time.
• Timer = 0 Heavy signalling traffic may be generated
• Timer = 5 secs ( inter-digit timeout) User is not that patient
Gonzalo CamarilloAtlanta September 28th, 1999 Advanced Signalling Research Lab.
Fall ‘99 VONVON protocols - SIP
In-band announcements and ring-back tones
•‘Your call is being forwarded to an automatic voice mail’• Ring-back tone• Busy tone
SIP Client
E1/T1
MG
RTP
DSS 1
Proposed solution: 183 SIP response
Gonzalo CamarilloAtlanta September 28th, 1999 Advanced Signalling Research Lab.
Fall ‘99 VONVON protocols - SIP
ISUP transparency(SIP bridging)
IP network
ISUP/MTP
E1/T1
Voice Stream
Signalling
STP
SIP
RTP
ISUP/MTP
E1/T1
STP
SGSG
MGMG
MGC MGC
MGCP MGCP
ISUP/IP ISUP/IP
Gonzalo CamarilloAtlanta September 28th, 1999 Advanced Signalling Research Lab.
Fall ‘99 VONVON protocols - SIP
ISUP transparecy( SIP bridging)
ISUP messages in SIP bodies (MIME),SIP INFO method, reliable 1xx responses ...
Trusted parties, confidentiality, ISUP flavours...
Gonzalo CamarilloAtlanta September 28th, 1999 Advanced Signalling Research Lab.
Fall ‘99 VONVON protocols - SIP
Billingscenarious
Isabel calls from Spain to my GSM mobile:+358 40 702 35 35 (Finland’s international prefix)
Isabel pays the call leg Spain-FinlandI pay the call leg Finland-Atlanta
SIP is end to end … where are the call legs??
Gonzalo CamarilloAtlanta September 28th, 1999 Advanced Signalling Research Lab.
Fall ‘99 VONVON protocols - SIP
Tracing calls
• SOS services ( physically closest center )• Malicious calls
An IP address or a SIP URL do not give any useful information for catching the “bad guys”.
Gonzalo CamarilloAtlanta September 28th, 1999 Advanced Signalling Research Lab.
Fall ‘99 VONVON protocols - SIP
Further information
• draft-ietf-sigtran-mime-isup-00.txt• draft-ietf-mmusic-sip-multipart-00.txt• draft-zimmerer-mmusic-sip-isup-mime-00.txt• draft-ietf-mmusic-sip-info-method-01.txt• draft-ietf-mmusic-sip-100rel-00.txt• draft-roach-mmusic-sip-provisional-media-00.txt• draft-donovan-mmusic-183-00.txt• draft-roach-mmusic-sip-pstn-require-header-00.txt• draf-zimmerer-mmusic-sip-bcp-t-00.txt• draft-roach-sip-isup-parameters-00.txt• draft-camarillo-mmusic-sip-isup-bcp.txt
IETF internet drafts ( www.ietf.org )