RE: PReserving ids when changing providers (was:RE: to be draft-ohta-multi6-8plus8-00.txt)

["Christian Huitema" <huitema@windows.microsoft.com>]

> Christian,
> 
> How does SIP differ conceptually at the application layer from what
> MIPv6 does at the IP layer?
> 
> Eliot

SIP separates signaling from media transmission. I will invite you to a
session, the signaling traffic will pass through the system of SIP
servers, but the media should flow directly between the two "end
points". In contrast, MIPV6 handles just one kind of traffic; packets
may flow directly between the current locations, or it may remain "non
optimized" and flow through the home agents.

SIP separates the logical identity from the media endpoints. It is
perfectly reasonable to have a session between two logical identities,
say Alice and Bob, but to have the media flow between different pairs of
cameras and screens, mikes and speakers, etc. The choice of the media
endpoint is based on the application, e.g. choose between headset on my
mobile phone and loud speakers on my stereo. In contrast, MIPv6 assumes
that the COA is 'equivalent' to the HA, and that any choice is based
purely on connectivity considerations.

SIP includes an explicit negotiation of the session parameters. The
negotiation is mostly based on the capacities of the end points, such as
the medias and codecs supported by the end point, but it may also take
into account transmission issues, e.g. what is the available bandwidth.
In contrast, MIPV6 does not perform any such negotiation.

-- Christian Huitema