[SIPForum-discussion] RTP before stablished a dialog

[Hilyard, Trey A [CTO]]

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.

-Trey


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


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