On Mon, 2009-02-23 at 14:18 -0800, cool goose wrote:
> Sec 10.3 Point #7 specifies the below:
>  
> "If the Call-ID value in the existing binding differs from the
>          Call-ID value in the request, the binding MUST be removed if
>          the expiration time is zero and updated otherwise."
>  
> Does this mean that the Register requests from same UA can have
> different Call-IDs as long as the CSeq values are not the same?

If two requests have different Call-Ids, their CSeq values are not
related to each other.

In regard to registrations, if a series of REGISTERs have the same
Call-Id, then the CSeq values provide protection in case the messages
arrive out of order -- the message with the largest CSeq (which must
have been sent last) controls the result.

If a series of REGISTERs have different Call-Ids, then there is no
protection against message reordering, and the last one that arrives at
the registrar controls the result.  This is less desirable, but is the
only way to allow a UA that has been rebooted to remove "dangling"
registrations that the UA established prior to rebooting.

Dale



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