Query on when to open RTP ports during offer/answer

Hello All ,
Once I send an offer in in INVITE I am supposed to be ready
to listen to
media.
However If I start getting media packets before getting the
answer , I
do not know for sure whether the called
Party is playing me the media or somebody else is playing me
the media.
What do I do in this case ? Should I be rejecting the media
packets till
I get an answer ?

Also if the called party plays the media from a different IP
address
from the one which he provides in the the SDP (for receiving
media)how
can I be sure it's not some kind of attack on my UA ?
Regards ,
Sayan


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Sayan,
 Dont you have to wait for a response 183 or 200 OK before
you open your RTP ports?

Siddhardah


sayan.chowdhurywipro.com wrote: 

Hello All ,
Once I send an offer in in INVITE I am supposed to be ready
to listen to
media.
However If I start getting media packets before getting the
answer , I
do not know for sure whether the called
Party is playing me the media or somebody else is playing me
the media.
What do I do in this case ? Should I be rejecting the media
packets till
I get an answer ?

Also if the called party plays the media from a different IP
address
from the one which he provides in the the SDP (for receiving
media)how
can I be sure it's not some kind of attack on my UA ?
Regards ,
Sayan


The information contained in this electronic message and any
attachments to this message are intended for the exclusive
use of the addressee(s) and may contain proprietary,
confidential or privileged information. If you are not the
intended recipient, you should not disseminate, distribute
or copy this e-mail. Please notify the sender immediately
and destroy all copies of this message and any attachments.

WARNING: Computer viruses can be transmitted via email. The
recipient should check this email and any attachments for
the presence of viruses. The company accepts no liability
for any damage caused by any virus transmitted by this
email.

www.wipro.com

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Sip-implementorscs.columbia.edu
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*******************************************************
Siddhardha N. Garige
Tampa, FL.
Ph: (813)-298-4236.

www.pbase.com/garige

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On Thu, 2006-05-25 at 13:15 +0530, sayan.chowdhurywipro.com
wrote:
> Once I send an offer in in INVITE I am supposed to be
ready to listen to
> media.

Yes.

> However If I start getting media packets before getting
the answer , I
> do not know for sure whether the called
> Party is playing me the media or somebody else is
playing me the media.

You don't know even then, as more than one source could be
sending
packets to the port, and one of them could be malicious.

> What do I do in this case ? Should I be rejecting the
media packets till
> I get an answer ?

No, you are required to receive them.

> Also if the called party plays the media from a
different IP address
> from the one which he provides in the the SDP (for
receiving media)how
> can I be sure it's not some kind of attack on my UA ?

You cannot.

If you want security in the media stream, use some form of
secure RTP.
But it's not possible in ordinary SIP/SDP/RTP.

Dale

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