Re: [AVTCORE] Slight rewording on Selective Forwarding Middlebox

Magnus Westerlund <> Tue, 31 March 2015 08:46 UTC

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Date: Tue, 31 Mar 2015 10:46:35 +0200
From: Magnus Westerlund <>
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Subject: Re: [AVTCORE] Slight rewording on Selective Forwarding Middlebox
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Here is an update of the last two paragraphs taking care of some nits
and a rewording of the very last sentence. Thanks for Dan Wing for feedback.

   Note that this topology could potentially be seen as a media
   translator which include an on/off logic as part of its media
   translation.  The topology has the property that all SSRCs present in
   the session are visible to an endpoint.  It also has mixer aspects,
   as the streams it provides are not basically translated version, but
   instead they have conceptual property assigned to them and can be
   both turned on/off as well as being fully or partially delivered.
   Thus this topology appears to be some hybrid between the translator
   and mixer model.

   The differences between selective forwarding middlebox and a
   switching mixer (Section 3.6.2) are minor, and they share most
   properties.  The above requirement on having a large number of
   decoding instances or requiring efficient switching of decoder
   contexts, are one point of difference.  The other is how the
   identification is performed, where the Mixer uses CSRC to provide
   information on what is included in a particular RTP stream that
   represent a particular concept.  Selective forwarding gets the source
   information through the SSRC, and instead uses other mechanisms to
   indicate the streams intended usage, if needed.

I intended to submit an updated draft on Thursday if no objections are made.


Magnus Westerlund

Services, Media and Network features, Ericsson Research EAB/TXM
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