Service Identification Jonathan Rosenberg Cisco. Examples Contrived chess example PoC Game that uses...

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