Re: [AVT] Lack of clarity in RFC 3550 on packet loss

[Colin Perkins <csp at csperkins.org>]

Rajesh,

On 3 Jun 2005, at 21:07, Rajesh Kumar wrote:
> RFC 3550 does not explicitly say that the "fraction lost" and the  
> "cumulative number of packets lost" fields in RTCP sender reports  
> and receiver reports refer to packet losses after the effects of  
> RFC 2198 redundancy and RFC 2733 FEC have been taken into account.  
> However, this is a reasonable assumption to make, and is in sync  
> with RFC 3611, which does make such an assertion.
>
> Is this what the intent of RFC 3550 was?

No, that is exactly the opposite of the intent of RFC 3550.

The "fraction lost" and "cumulative number of packets lost" fields in  
RTCP SR and RR reports always refer to the number of packets lost on  
the wire.  The use of RFC 2198 redundancy or RFC 3722 FEC changes the  
amount of payload data received, but does not affect the pattern of  
packet loss on the network, and hence doesn't affect the packet loss  
statistics reported by RTCP (indeed, reporting loss after the effects  
of RFC 2198 or RFC 2733 would break applications that use RTCP RR  
packets to control the amount of redundancy they add).

Colin

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