[e2e] A implementation question on TFRC algorithm

[Magnus Westerlund]

Hi Heejune,

I think the missing question here is, what transport protocol are you
trying to implement TFRC over? RTP/UDP? In that case you will have some
problems. Standard RTP does not have sufficient information to implement
TFRC over. You will require certain extensions, and also there is the
big question if your manage to get the feedback to report frequently
enough per the TFRC requirements.

The IETF AVT WG are currently looking into what would be required to
implement TFRC over RTP. There is an initial proposal in the draft:
http://www.ietf.org/internet-drafts/draft-ietf-avt-tfrc-profile-00.txt

Please note that this is very initial work and will require more
discussion.

Cheers

Magnus

Heejune AHN wrote:

>  Hi,  while implementing a streaming server, I am currently doing TFRC 
> transport adaptation module.
>  
> After reviewing several papers of Sally Floyd and A. Zakhor,  I sill 
> cannot implement it just because
> I cannot understand one thing:
>  
> "How to calculate Round-trip time in Receiver?"
> --------------------------------------------
> it is written in her paper how to get Roud Trip time in Sender, measuing 
> the feedback for same sequence num.
> (now my quetion, when the Rx decide to reply it?)
>  
> I need this value because
> "Rx should report feedback to the sender at least once per round-trip 
> time if it has received packets in that interval"
> (page 3 of SIGCOM 2000  publication, Equation-based Congestion control 
> for Unicast Application, Sally Floyd et al).
> I checked it from D. Tan and A. Zakhor papers in IEEE multimedia, 
> but the mechanism is not clear.
>  
> Maybe I can check with Sally's ns-2 simulation script, but it is too 
> much her computer-setting dependent script.
> I think it is not a big problem on their work, but I just want to know 
> how they implemented it.
>  
> Thanks.
>  

-- 

Magnus Westerlund

Multimedia Technologies, Ericsson Research EAB/TVA/A
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