> -----Original Message-----
> From: Neumaerker Elke [mailto:[EMAIL PROTECTED]]
> Sent: Friday, May 18, 2001 6:42 AM
> To: '[EMAIL PROTECTED]'
> Subject: [Sip-implementors] ACK without Record-Route
>
>
> Hello,
>
>
> In the SIP specification is written :
>
> " The ACK request is forwarded as the corresponding INVITE
> request, based
> on its Request-URI and thus MAY take a different path than the
> original INVITE request,.. "
>
> and
>
> "The ACK request does not generate responses for any
> transport protocol."
>
>
> Assume that the ACK is not sent directly from a user agent
> client to a user agent server,
> but sent to a Proxy and the Record header is not present. In
> this case the ACK is processed
> in the same way as the original INVITE.
> Assume that the proxy contacted a Redirect Server for the
> INVITE, it may contact the Redirect Server
> for the ACK too. If the Redirect follows the rules (see
> above), it does not generate a response.
> The ACK will never reach the user agent server and the call
> setup will not be successfull.
THis won't ever happen. As was pointed out, the UAS has to insert a Contact.
There may also be record-routes from proxies. However, in either case, there
is always a route set with at least one URL (see bis-03 section 16), so that
the ACK is never sent to a proxy without a Route header indicating a next
hop that is either a proxy or the UAS.
>
>
> Regarding this problem there arise several questions :
>
> (1) Is this a realistic scenario in existing networks ?
No, as I point out above.
> (2) MUST the client send the ACK directly to the user agent
> server, if it is not willing (ignore the
> Record-Route header) or no able (Record-Route header is
> not present in the 200 OK)
> to insert the Route header into the ACK ?
Record-route and Route support is mandatory in bis. Lots of things won't
work if you ignore this (like firewall traversal).
> (3) Is it acceptable, that the call setup is terminated, if
> the user agent client does not follow the rules of (2) ?
I don't understand this question.
> (4) What is the real behavior of a Redirect Server ?
> Shouldn't the Redirect Server proxy the ACK, if it is
> not destined for itself ?
> Or should it answer the ACK, because the Redirect Server
> is considered to be a database
> the Proxy Server can use for look up ?
A redirect server will only ever receive an ACK to acknowledge the 3xx
response it generated. Because the redirect server doesn't record-route, it
won't ever get an ACK for a 2xx response.
-Jonathan R.
---
Jonathan D. Rosenberg, Ph.D. 72 Eagle Rock Ave.
Chief Scientist First Floor
dynamicsoft East Hanover, NJ 07936
[EMAIL PROTECTED] FAX: (973) 952-5050
http://www.jdrosen.net PHONE: (973) 952-5000
http://www.dynamicsoft.com
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