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[Sip] Open Issue #179: Multicast to unicast REGISTER



Issue:

The spec allows for clients to multicast their registrations. Presumably,
refreshes are also sent multicast. Sometimes this is the right thing, but if
the purpose of multicast REGISTER is just discovery, the client should
probably unicast after it discovers, and then revert to multicast again only
if that server becomes unavailable. However, the spec is silent on this
case. Should we discuss?

Discussion points:

A 301 can be sent by the registar, providing a unicast address (this is only
now possible in bis-05 due to the new multicast treatment). However, the 301
would be cached indefinitely at the client, and its not clear what the
behavior is for cached redirects on failure. If we specify that it retries
the original request that generated the 3xx, then the registrar has a
mechanism it can use.

Proposal:

 * add text to 301 section saying that if a cached contact fails, try the
original URI again

 * add text in the registration section, mentioning that this is a useful
thing to do. Otherwise, people may not be prepared to have their
registrations redirected, even though the spec does allow it.

-Jonathan R.

---
Jonathan D. Rosenberg, Ph.D.                72 Eagle Rock Ave.
Chief Scientist                             First Floor
dynamicsoft                                 East Hanover, NJ 07936
jdrosen@dynamicsoft.com                     FAX:   (973) 952-5050
http://www.jdrosen.net                      PHONE: (973) 952-5000
http://www.dynamicsoft.com
 

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