Subject: [AVT] Address/port to which separate FEC stream is directed

From: Rajesh Kumar <[email-masked]>
Date: Thu, 31 Jan 2002 15:55:32 -0800

Jonathan, Henning

rfc2733 seems to mandate that a separate FEC stream, when produced, must be 
sent to a different port or IP address. Isn't is possible to send the FEC 
packets to the same port/address as the media packets? Even if this is 
do,  you cannot omit the parameters <port>, <network type>,  <address type> 
and <connection address>, right?

a=fmtp:<number> <port> <network type> <address type> <connection address>

Thanks

Rajesh Kumar
Cisco Systems

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From: Jonathan Rosenberg <[email-masked]>
Date: Thu, 31 Jan 2002 23:20:43 -0500

> and <connection address>, right?

Well, my recollection is fuzzy here, but I recall that we decided that a
separate RTP session was better. One reason that I remember was rtp
header compression/rohc, since the timestamp predictors would be wrong
every time a FEC packet was emitted. I suspect there are other reasons
too, but that is the one I remember. 

Anyway, rfc2733 does explicitly say that the FEC stream is sent as a
separate RTP session. Its in section 3:

 The FEC packets are not sent in the same RTP stream as the media
   packets. They can be sent as a separate stream, or as a secondary
   codec in the redundant codec payload format [5].

-Jonathan R.

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