Re: [Sip] FW: I-D Action:draft-kaplan-sip-session-id-00.txt

[Hadriel Kaplan <HKaplan at acmepacket.com>]

> -----Original Message-----
> From: sip-bounces at ietf.org [mailto:sip-bounces at ietf.org] On Behalf Of Paul
> Kyzivat
>
> Dale.Worley at comcast.net wrote:
> > In regard to adding a Session-Id to requests are not given one by the
> > UAC:
> >
>
> Specifically, *subsequent* requests in the same dialog won't carry the
> same value, at least until the node that inserted the value is reached,
> if it is reached. And even then the same value won't be inserted unless
> the inserting node is dialog stateful. That argues for only having
> dialog stateful elements insert the header.

Although the draft mentions a UUID as one option, it leaves the mechanism to be decided.  One thing we could do instead of UUID, for example, would be to make it a hash of the received call-id and local system/node ID and MAC or some such.  In other words take some non-volatile system data munged with the call-id, and hash it to get the 128 bits of output for the Session-ID header value.  That way a stateless proxy can re-generate the same value again for upstream and downstream requests and responses, without it compromising or being re-create-able just from the call-id value and giving a reason for folks to remove it.
But I'll have to ask some security folks about that.

-hadriel
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