[SIPForum-discussion] RTP before stablished a dialog

Hilyard, Trey A [CTO] Trey.A.Hilyard at sprint.com
Fri Mar 6 17:09:02 UTC 2015

Alberto –

According to RFC3264:

“Once the offerer has sent the offer, it MUST be prepared to receive
media for any recvonly streams described by that offer.  It MUST be
prepared to send and receive media for any sendrecv streams in the
offer, and send media for any sendonly streams in the offer (of
course, it cannot actually send until the peer provides an answer
with the needed address and port information).  In the case of RTP,
even though it may receive media before the answer arrives, it will
not be able to send RTCP receiver reports until the answer arrives.”

If the INVITE is being sent with an SDP offer with a recvonly or sendrecv, then this is perfectly acceptable (although I have never seen this happen in the wild until your trace).

Normally, I would have expected a 183 Session Progress with SDP to establish early media, but what you are seeing is allowed.


From: discussion-bounces at sipforum.org [mailto:discussion-bounces at sipforum.org] On Behalf Of Alberto Llamas
Sent: Tuesday, February 24, 2015 5:37 PM
To: discussion at sipforum.org
Subject: [SIPForum-discussion] RTP before stablished a dialog

Hi guys,

Its posible that a callee send RTP packets before the 200 Ok message?

Check this image:

[Inline image 1]
Alberto Llamas
Telecommunications Engineer
Digium Certified Asterisk Professional (dCap)
Linux Administrator


This e-mail may contain Sprint proprietary information intended for the sole use of the recipient(s). Any use by others is prohibited. If you are not the intended recipient, please contact the sender and delete all copies of the message.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://sipforum.org/pipermail/discussion/attachments/20150306/0c09d8d4/attachment-0002.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: image001.png
Type: image/png
Size: 41364 bytes
Desc: image001.png
URL: <http://sipforum.org/pipermail/discussion/attachments/20150306/0c09d8d4/attachment-0002.png>

More information about the discussion mailing list