[EMAIL PROTECTED] wrote:
> From: sudhagar NAGARAJAN <[EMAIL PROTECTED]>
>
> Can anyone clarify whether Cseq is always incremented by 1 inside a
> dialog? for all new requests inside the dialog.
>
> At some place in the RFC, it says that the CSeq should be incremented
> by 1.
>
> But -- if the UA incremented the CSeq by more than 1, the other UA
> would behave the same way, as it is required to presume that an
> intermediate request had been lost by the network.
>
> But -- incrementing the CSeq by more than 1 would not be useful, and
> would tend to consume the available CSeq space. Admittedly, a dialog
> has a minimum of 2^31 (IIRC) CSeq numbers available, but if the UA
> decides to increment by 2^28, it might run out of numbers.
The received CSeq can increase by more than one due to lost messages.
I have also heard of a couple of techniques (hacks) that result in the
numbers increasing by more than one. For instance, a "proxy" that wants
to become a B2BUA for purpose of terminating a call can try sending a
BYE with a very large CSeq (up near 2^32) and so avoid having to keep
track of the CSeq otherwise.
Paul
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