[Serusers] Curious interop bug.

[Jan Janak]

Hello,

The packet dump and your description does not match. The messages in the
dump do not seem to go through SER at all, not even the INVITE.  200 OK
contains no Route header fields thus the gateway sends the ACK directly
to the other endpoint.

  Jan.

On 11-10-2005 17:20, David Gilbert wrote:
Content-Description: message body text
> For those of you who want to follow along, the packet dump in question
> is at http://strike.dclg.ca/~dgilbert/22-3-filtered ... it's a pcap
> format file.
> 
> I'm using a 0.9.4 copy of ser, compiled by hand on debian stable.
> Only the core portion of ser is being used, and I have simple config
> file (attached).
> 
> So, roughly, a call comes in level3, they make it SIP and forward it
> to my SER on port 5070.  SER turns around and forwarded it to asterisk
> on port 5060 of the same machine and then asterisk forwards it on to a
> linksys ATA.
> 
> In short, the problem is that level3 abuses the RFC by sending from a
> port and expecting you to reply on another port (specified in the
> Contact: header).  This goes almost right except for level3's equally
> literal read of the Contact header that SER sends.
> 
> Packet			    Sip Command	    Contact
> ======			    ===========	    =======
> level3:38999 ser:5070	    INVITE	    sip:+1416...@<level3 ip>:5060
> ser:5070 level3:38999	    100 Trying	    sip:+1866...@<ser ip>
> (ser invites asterisk, not in dump)
> asterisk:5060 ata:5060	    INVITE	    sip:+1416...@<asterisk ip>
> ata:5060 asterisk:5060	    100 Trying	    None
> ata:5060 asterisk:5060	    180 Ringing	    None
> (asterisk relays 180 to ser, not in dump)
> ser:5070 level3:38999	    180 Ringing	    sip:+1866...@<ser ip>
> ata:5060 asterisk:5060	    200 OK	    sip:604...@<ata ip>:5060
> asterisk:5060 ata:5060	    ACK		    sip:+1416...@<asterisk ip>
> (asterisk relays 200 OK to ser, not in dump)
> ser:5070 level3:5060	    200 OK	    sip:+1866...@<ser ip>
> level3:5060 ser:5060 !?!    ACK		    sip:+1866...@<level3 ip>:5060
> 
> Now... the problem is that each time ser repsonds, the contact line
> should be appended with ":5070" and it is not.  Therefore, being the
> literal people they are, level3 repsonds to port 5060 with their ACK.
> This means that the ACK goes directly to asterisk rather than to SER
> and it means that when the call ends, the BYE notification from
> asterisk goes directly to the wrong port at level3.
> 


Content-Description: message body and .signature
> 
> 
> Dave.
> 
> -- 
> ============================================================================
> |David Gilbert, Independent Contractor.       | Two things can only be     |
> |Mail:       dave at daveg.ca                    |  equal if and only if they |
> |http://daveg.ca                              |   are precisely opposite.  |
> =========================================================GLO================

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