Subject: RE: [SIP] UAC Record Routing in draft-ietf-sip-call-flows-01.txt

From: Jonathan Rosenberg <[email-masked]>
Date: Tue, 7 Nov 2000 03:08:52 -0500

> -----Original Message-----
> From: Neil Deason [mailto:[email-masked]]
> Sent: Friday, November 03, 2000 8:34 AM
> To: Sip List
> Subject: [SIP] UAC Record Routing in draft-ietf-sip-call-flows-01.txt
> 
> 
> The way the UAC builds the Route on a final 200 response 
> in 3.1.2 of the call flows draft doesn't look quite 
> right ...
> 
> 3.1.2 Successful SIP to SIP through two proxies
> 
>    User A          Proxy 1          Proxy 2          User B
>      |                |                |                |
>      |   INVITE F1    |                |                |
>      |--------------->|                |                |
>      |     407 F2     |                |                |
>      |<---------------|                |                |
>      |     ACK F3     |                |                |
>      |--------------->|                |                |
>      |   INVITE F4    |                |                |
>      |--------------->|   INVITE F5    |                |
>      |    (100) F6    |--------------->|   INVITE F7    |
>      |<---------------|    (100) F8    |--------------->|
>      |                |<---------------|                |
>      |                |                |     180 F9     |
>      |                |    180 F10     |<---------------|
>      |     180 F11    |<---------------|                |
>      |<---------------|                |     200 F12    |
>      |                |    200 F13     |<---------------|
>      |     200 F14    |<---------------|                |
>      |<---------------|                |                |
>      |     ACK F15    |                |                |
>      |--------------->|    ACK F16     |                |
>      |                |--------------->|     ACK F17    |
>      |                |                |--------------->|
> 
> F14 200 OK Proxy 1 -> A
> 
>    SIP/2.0 200 OK
>    Via: SIP/2.0/UDP here.com:5060
>    Record-Route: <sip:[email-masked];maddr=ss2.wcom.com>,
>     <sip:[email-masked];maddr=ss1.wcom.com>
>    From: BigGuy <sip:[email-masked]>
>    To: LittleGuy <sip:[email-masked]>;tag=314159
>    Call-ID: [email-masked]
>    CSeq: 1 INVITE
>    Contact: LittleGuy <sip:[email-masked]>
>    Content-Type: application/sdp
>    Content-Length: 134
> 
>    v=0
>    o=UserB 2890844527 2890844527 IN IP4 there.com
>    s=Session SDP
>    c=IN IP4 110.111.112.113
>    t=0 0
>    m=audio 3456 RTP/AVP 0
>    a=rtpmap:0 PCMU/8000
> 
> 
>    F15 ACK A -> Proxy 1
> 
>    ACK sip:[email-masked] SIP/2.0
>    Via: SIP/2.0/UDP here.com:5060
>    Route: <sip:[email-masked];maddr=ss2.wcom.com>,
>     <sip:[email-masked];maddr=110.111.112.113>
>    From: BigGuy <sip:[email-masked]>
>    To: LittleGuy <sip:[email-masked]>;tag=314159
>    Call-ID: [email-masked]
>    CSeq: 1 ACK
>    Content-Length: 0
> 
> The UAC should build the Route header in the ACK by 
> copying the 200 response Record-Route header, 
> reversing the order and then adding the Contact as 
> the last entry. (Note the 1st entry in the Route is
> subsequently removed when the client actually sends F15).
> But in this case the last entry has become an IP address. 
> Shouldn't the UAC just copy the Contact and not try 
> and do any resolution of it?

Correct. This behavior is really bad, actually. It depends on being able to
perform a resolution of the Contact address outside of the realm where it is
supposed to be resolved. If there is a private DNS running, or some kind of
local information is placed in the hostname, this resolution will fail at
the called party.

Alan - can you please fix?

Thanks,
Jonathan R.

---
Jonathan D. Rosenberg                       72 Eagle Rock Ave.
Chief Scientist                             First Floor
dynamicsoft                                 East Hanover, NJ 07936
[email-masked]                     FAX:   (973) 952-5050
http://www.cs.columbia.edu/~jdrosen         PHONE: (973) 952-5000
http://www.dynamicsoft.com

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---

From: Alan Johnston <[email-masked]>
Date: Wed, 08 Nov 2000 14:05:01 -0600

I will fix this.  I thought RFC2543bis read that the maddr was required, but I
see upon re-reading that this is only true for proxies.

Alan.