Hi Nagaraj,
If the connection is TCP, then A might get the response from the Proxy unless there is some kind of check.
The transaction structure may have maintained only the socket descriptor for the TCP connection from A with the Proxy (@ the PROXY ) and hence i feel the socket descriptor will be used blindly to send Responses (back to A) , but in the case of UDP, the Responses might go to B, as the IP and port in the Via Header are parsed and given to the Callback for sending messages in the stack (As this is Connection-less). (In case of TCP, even if the IP and port are parsed from the Via Header and passed, it might be ignored and the Socket Descriptor in the transaction structure might be used directly to communicate with the UAC (i.e A ) as there is already an Open connection with A)
The Proxy could detect these cases, by adding the received or sent-by or some field which iam not sure of, Please refer Sec. 18 of 3261.
Feel free to correct me ,if iam wrong :-)
Cheers.
Simith
Nagaraj S <[EMAIL PROTECTED]> wrote:
Hi,
I got it, I will explain the situation clearly,
1. Softphone 'A' sent a SIP REQUEST with a "via header field containing
a
IP address 'IP_B' other than the IP addres of softphone 'A' ".
2. A proxy 'P' received this Request and routed the request to the
destination Softphone say 'C'.
3. Softphone 'C' sent a response to this request. The response reached
our proxy 'P' safely.
4. Now the Proxy 'P' gets the IP address present in the via header field
of the response which
is not the IP address of softphone A which initiated this
transaction, but some other IP address 'IP_B'.
In this case, if the proxy 'P' is using a TCP connection for handling
the transaction initiated by 'A',
should it create a new TCP connection with the IP address 'IP_B' to
send the response or
should it identify this mismatch in the IP address being! used for this
transaction and the one mentioned in via
header field and treat the condition appropriately ?
hope i am not confusing u people...
----- Original Message -----
From: Markus Hofmann <[EMAIL PROTECTED]>
To: Nagaraj S <[EMAIL PROTECTED]>
Cc: <[EMAIL PROTECTED]>
Sent: Friday, June 25, 2004 3:14 PM
Subject: Re: [Sip-implementors] Doubt in handling via ....
> "Nagaraj S" <[EMAIL PROTECTED]>schrieb am 25.06.04 11:15:15:
>
> Hi , I have a doubt in handling "via and contact" header fields, AS
per the RFC 3261, "Via header field tells other elements where to send the
> response and the Contact header field tells other elements where to
send future requests." If a softphone A sends a INVITE message with a
"via header field containing the IP adress of some other softphone say B ,
then the response for this INVITE will be sent to B or not ?. ----
>
> No, t! here is a misunderstanding. Only A is able to stamp its address in
the via header or a proxy where the message is forwarded to. The response of
B will use the last via header and send back to this address. If this
address is a proxy, the proxy will remove its address and send to next via
header until a will reach.
>
> A will also set the contact header with its contact ([EMAIL PROTECTED] or
[EMAIL PROTECTED])
>
>
> Rgds
> Nagaraj S
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