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TELECOM ITALIA GROUP Signalling Systems for Future Telecom Networks Amsterdam – January 2011. Conveying ISDN User-to-user Information in SIP. Enrico Marocco enrico.marocco@telecomitalia.it. ISDN User-to-user Information. 2. Wait. Seriously??. Let's start over. TELECOM ITALIA GROUP
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TELECOM ITALIA GROUP Signalling Systems for Future Telecom Networks Amsterdam – January 2011 Conveying ISDN User-to-user Information in SIP Enrico Marocco enrico.marocco@telecomitalia.it
TELECOM ITALIA GROUP Signalling Systems for Future Telecom Networks Amsterdam – January 2011 Learning by ExampleTransitioning from PSTN to Future Telecom Networks: The UUI Case Enrico Marocco enrico.marocco@telecomitalia.it
POTS ISDN SIP H.323
Flaws (H.323 anyone?)
My desktop phone (Has good speaker and mic, why change?) Backward Compatibility
Q.931 ISDN User-to-user information Application-specific information that “is not known and understood by the ISDN network that transports it” Used in call centers, contact centers, public phones…
UUI in SIP – User Agent to User Agent Alice Proxy Bob INVITE (UUI) INVITE (UUI) 100 Trying 200 OK 200 OK ACK ACK
UUI in SIP – Retargeting Alice Proxy Carol INVITE sip:bob (UUI) INVITE sip:carol (UUI) 100 Trying 200 OK 200 OK ACK ACK
UUI in SIP – Redirect Alice Redirector Bob INVITE 302 Moved (UUI) 200 OK ACK INVITE (UUI) 200 OK ACK
UUI in SIP – Referral Alice Referrer Bob REFER (UUI) 202 Accepted Various NOTIFYs INVITE (UUI) 200 OK ACK
ISDN UUI in SIP – Why not in INFO? • SIP INFO Message was introduced specifically for ISUP interworking, but… • UUI needs to be carried at call setup/teardown • Network elements may want to make decisions based on it
ISDN UUI in SIP – Why not in MIME body? • Application data should naturally go in message bodies (just as in HTTP, SMTP), but… • Reality check: very few implementations support multipart MIME • Redirect? Referral?
ISDN UUI in SIP – Why not in URI param? • URI parameter are common in Contact headers to specify user agent characteristics, but… • UUI targets the user, not necessarily the user agent (i.e. 1 user, N UAs) • Retargeting?
ISDN UUI in SIP – New Header Field • Clear syntax and semantic (other than) • Mechanisms for encoding header fields in REFER and 302 messages already exist… and work! User-to-User: 56a390f3d2b7310023a;encoding=hex;purpose=isdn-interwork ;content=isdn-uui Contact: <sip:+12125551212@gateway.example.com? User-to-User=56a390f3d2b7310023a%3Bencoding%3Dhex%3Bpurpose%3D isdn-interwork%3Bcontent%3Disdn-uui> Refer-To: <sip:+12125551212@gateway.example.com? User-to-User=56a390f3d2b7310023a%3Bencoding%3Dhex%3Bpurpose%3D isdn-interwork%3Bcontent%3Disdn-uui>
IETF CUSS Working Group Roadmap • Working group chartered in September 2010 (despite standardization work begun 2/3 years earlier) • Problem statement and requirements • Mechanism specification (exp. in June) • ISDN application usage specification (exp. in June)
Possible Future Applications • Realtime credit information • Payments • ??