That's true for ACK for a 200 response, not for an error response. In that case, ACK must be sent to the same address, port, and transport to which the original request was sent. Pl. see rfc 3261, sec. 17.1.1.2.
>-----Original Message----- >From: [EMAIL PROTECTED] >[mailto:[EMAIL PROTECTED] On Behalf Of >Rayees Khan >Sent: Tuesday, May 08, 2007 1:17 PM >To: Joerg Scholz; [email protected] >Subject: Re: [Sip-implementors] echot contact field in 401 > > >The ACK needs to be sent on the address that is mentioned in >the Contact header of reponse, unless it is overridden by >Record-Route etc. >I assume that there is some error in UAS here which is causing this. >However, if UAC acts according to protocol it would send ACK >to 172.20.16.1. > > >regards >Rayees > > >-----Original Message----- >From: [EMAIL PROTECTED] >[mailto:[EMAIL PROTECTED] On Behalf Of >Joerg Scholz >Sent: Tuesday, May 08, 2007 3:46 PM >To: '[email protected]' >Subject: [Sip-implementors] echot contact field in 401 > >Hi all, > >I have a quick question regarding the usage of the Contact >field in 401 message. In the trace here you can see that in >the 401 the contact field from the invite is just send back. >So for my understanding the ack to the >401 is send then to the own IP address in such a case. Is >there any rule for that specific behaviour? > > > >INVITE sip:[EMAIL PROTECTED] SIP/2.0 > >Max-Forwards: 50 > >Via: SIP/2.0/UDP >172.20.16.1:5060;rport;branch=z9hG4bK23268366631621974202502 > >From: <sip:[EMAIL PROTECTED]>;tag=723776519979065179735928398741 > >To: <sip:[EMAIL PROTECTED]> > >Call-ID: [EMAIL PROTECTED] > >CSeq: 1 INVITE > >Contact: <sip:[EMAIL PROTECTED]> > >User-Agent: TELES.VoIPBOX FX 13.0b 885 > >Allow: INVITE,ACK,CANCEL,BYE,UPDATE,REGISTER,PRACK,INFO,NOTIFY,REFER > >Timestamp: 1175605035 > >Content-Type: application/sdp > >Content-Length: 520 > >v=0 > >o=- 6 1 IN IP4 172.20.16.1 > >s=- > >c=IN IP4 172.20.16.1 > >t=0 0 > >m=audio 29000 RTP/AVP 18 18 18 18 4 0 8 > >a=rtpmap:18 G729/8000 > >a=fmtp:18 annexb=no > >a=ptime:20 > >a=rtpmap:18 G729A/8000 > >a=fmtp:18 annexb=no > >a=ptime:20 > >a=rtpmap:18 G729B/8000 > >a=fmtp:18 annexb=yes > >a=ptime:20 > >a=rtpmap:18 G729AB/8000 > >a=fmtp:18 annexb=yes > >a=ptime:20 > >a=rtpmap:4 G723/8000 > >a=fmtp:4 annexa=yes > >a=ptime:60 > >a=rtpmap:0 PCMU/8000 > >a=ptime:20 > >a=rtpmap:8 PCMA/8000 > >a=ptime:20 > > > >SIP/2.0 401 Unauthorized > > Via: SIP/2.0/UDP >172.20.16.1:5060;rport;branch=z9hG4bK23268366631621974202502 > > From: <sip:[EMAIL PROTECTED]>;tag=723776519979065179735928398741 > > To: <sip:[EMAIL PROTECTED]>;tag=GR52RWG346-34 > > Call-ID: [EMAIL PROTECTED] > > CSeq: 1 INVITE > > Contact: <sip:[EMAIL PROTECTED]> > > WWW-Authenticate: Digest realm="192.168.1.1", >nonce="1D9C86B49DD0C77FB73188939DA7E174", >opaque="9CCC512F6BCF46A90987581E8F4FCCD9", algorithm=md5 > > User-Agent: TELES.VoIPBOX FX 13.0b 885 > > Timestamp: 1175605035 > > Content-Length: 0 > > > >Thanks in Advance > >Joerg > > > >_______________________________________________ >Sip-implementors mailing list >[email protected] >https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors > >______________________________________________________________________ >This email has been scanned by the MessageLabs Email Security System. >For more information please visit >http://www.messagelabs.com/email >______________________________________________________________________ > > > > >--------------------------------------------------------------- >------------------- >IMPORTANT The information contained in this e-mail any >attachments is intended only for the named recipient and may >be privileged or confidential. > >If you are not the intended recipient, please notify us >immediately on +44 (0)1908 425000 and do not disclose, copy, >distribute or take any action based on the contents of this e-mail. > >You should understand and accept that, when communicating with >us by e-mail, it is not a totally secure communication medium. > >We accept no liability for any direct, indirect or >consequential loss arising from any action taken in reliance >on the information contained in this e-mail and give no >warranty or representation as to its accuracy or reliability. > >DIGITALK has the facility to monitor and read both incoming >and outgoing communications by e-mail. 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