Service Identification

Jonathan Rosenberg

Cisco

Examples• Contrived chess example• PoC• Game that uses voice for

comments vs. telephony with IMs– Both use audio and MSRP but

• QoS for voice would be different

• Features would be different• Billing might be different

• Instant Messaging vs. Software Update– Both use MESSAGE but are

different• Different dispatch in the

phone• Different billing

• IPTV vs. Video Conferencing– Both use audio and video– Both use same codecs– But might be unidirectional– But we would want

• Different dispatch on the phone

• Different billing• Different QoS treatment

How is Service Identification Used?

• For the network to invoke application servers– PoC “supplementary

services” different than multimedia telephony

• For dispatch to the right application software in a client

• Inclusion in accounting records for purposes of billing

• To determine level of network QoS

• To identify additional context required to process a request– PoC and the chess

example

• For the user to explicitly ask its network to invoke application servers– Please insert a recording

server for this call

• Set of supported services a caller could use

How is Service ID Determined?

• Asserted by client

• Determined by network based on inspection of request

• Determined by network at perimeter and then asserted by network

Why are folks bothered so much by this?

• If many aspect of system behavior drive off of this single parameter– QoS, charging, feature servers, app dispatch, etc.

• What happens when– A ‘regular’ SIP phone calls a SIP phone in a provider

network that requires these service tags?– A call takes place between two providers that have

different tags for the same service?– A call takes place between two providers that have

different services but overlap in some way (both use IM, audio, etc.)?

Some Observations

• Some of the things people want to use service tags for are for information usually in SIP but sometimes not there in corner cases– Offerless INVITEs– Missing media properties (latency)

• If these were always present, and two SIP INVITEs for different services looked the same, you must have missed something– Do What I Say and *not* Do What I Mean

• So if they were always different, the service is really a ‘summarization’ of what is there

Proposal

• Investigate specific use cases where SIP message is lacking information to provide service identification– Missing Require tag for PoC– Latency requirements on SDP m-lines

• Define a provider asserted service ID that– Is defined only within a trust domain– Can always be determined by examining information

in SIP messages– This allows for either localized services or global

agreement with perfect interoperation with regular SIP clients