There is nothing in the SIP spec which mandates that responses are sent back
from the same address to which the packets where sent. The reason for
connecting the UDP socket is to detect ICMP errors. It cannot be relied upon
to receive the responses (although they may arrive there). This is not true
for TCP, however.
-Jonathan R.
---
Jonathan D. Rosenberg 72 Eagle Rock Ave.
Chief Scientist First Floor
dynamicsoft East Hanover, NJ 07936
[EMAIL PROTECTED] FAX: (973) 952-5050
http://www.cs.columbia.edu/~jdrosen PHONE: (973) 952-5000
http://www.dynamicsoft.com
> -----Original Message-----
> From: Charles Zeng [mailto:[EMAIL PROTECTED]]
> Sent: Friday, February 23, 2001 11:01 AM
> To: Benny Prijono
> Cc: Vijay Gurbani; [EMAIL PROTECTED]
> Subject: Re: [Sip-implementors] Re: [SIP] Change IP in one
> SIP Transation?
>
>
> Dear Benny and Vijay,
>
> Glad to get your suggestion. As our research, we believe in
> the SIP (draft-
> rfc2543bis-02), they prefer to use connect UDP. But they also
> said (it CAN
> be different listen port in the UA.)
>
> Anyway, Benny's case could be work if we use two UDP sockets.
> But we just
> wonder, if we build the server or UA support this case. It will lost
> inter-operablity
> if another vendor use one connect UDP socket instead of two
> UDP sockets.
>
> Other issue, I want make sure two different UDP can work.
> Since SIP need
> to concern the hacker packets. If the recieving IP is not
> list in the previous
> sending catch, maybe the transcation layer will filter it.
>
> Best regards
>
> Charles Zeng
>
>
> Benny Prijono wrote:
>
> > Vijay Gurbani wrote:
> > >
> > > Well, a lot depends on how the remote SIP terminal is
> coded. If for
> > > instance, it does a UDP connect() to 10.0.0.1 and then a
> send() to send the
> > > INVITE request and a recv() to get the responses, you
> maybe out of luck
> > > since it is expecting the responses on the connected
> socket to 10.0.0.1 and
> > > not 10.0.1.1.
> > >
> >
> > Except if the UAC uses two different UDP sockets, which I think is
> > quite common in implementations, one for sending UDP (with
> connect())
> > and another for receiving UDP datagram on port 5060. And because the
> > UAS will send the response to the addr/port specified in the topmost
> > Via, not to the source addr of the packet, the response
> will go to the
> > port 5060 in the UAC, which will be (happily?) received by the
> > receiving socket.
> >
>
> > > Is it possible for you send a 200 OK over the internal
> bus to 10.0.0.1 and
> > > have it send it out to the remote SIP terminal?
> > >
> > > - vijay
> > > --
> > > Vijay K. Gurbani vkg@{lucent.com,research.bell-labs.com,acm.org}
> > > Internet Software and eServices Group
> > > Lucent Technologies/Bell Labs Innovations 263 Shuman
> Blvd., Rm 1A-413
> > > Naperville, Illinois 60566 Voice: +1 630 224 0216
> Fax: +1 630 713 0184
> >
> > --
> > cheers,
> > Bennylp
>
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