Request to review type in draft-ietf-fecframe-interleaved-fec-scheme

[Magnus Westerlund]

Hi Bjoern,

Many thanks for the review. I expect the author to comment also. I will
respond due to my reasonable good familiarity with these issues as
ex-AVT chair.

Bjoern Hoehrmann skrev:
> * Magnus Westerlund wrote:
>> This document
>> http://www.ietf.org/id/draft-ietf-fecframe-interleaved-fec-scheme-06.txt
>> has been through an IETF last call. Unfortunately this hasn't been
>> announced on this list either in WG last call or when the IETF last call
>> started. Thus I would like a review before bringing this to the IESG. I
>> would be thankful if the review could happen before the 7th of January.
>> However, if a committed reviewer needs additional time due to the
>> holidays that can be granted. But please tell me so that I can postpone
>> the IESG review.
>>
>> Here is the media type template for the 4 types present in this document.
> 
> I think it's confusing to re-iterate the same text in each template; the
> templates in RFCs are not used out of context, later templates should
> just reference the first one. I could not immediately find a rationale
> for registering the same sub type under 4 different top level types. It
> would be helpful if someone could post one to this list, and it should
> be added in the introductory section 5.1.

I think that is an instruction that can be forwarded to AVT. However, I
do hope that people on this list do agree

The rational for registering this in the 4 top level types is that it
needs to be possible to combine this FEC RTP payload format with media
carrying RTP payload formats. As the media carrying RTP payload formats
have any of the 4 top-level types and only one top-level media type is
allowed in an RTP session. Thus the need to register this payload format
in all the top-level types that is used by other RTP payload formats.



> 
>>   Required parameters:
>>
>>   o  rate:  The RTP timestamp (clock) rate.  The rate SHALL be larger
>>      than 1000 Hz to provide sufficient resolution to RTCP operations.
>>      However, it is RECOMMENDED to select the rate that matches the
>>      rate of the protected source RTP stream.
> 
> I am not sure from this what the syntax is, the text makes it sound
> like rate="1001 Hz" might be it. Perhaps something like "The RTP time-
> stamp (clock) rate in Hz. The rate SHALL be larger than 1000 ..." to
> make it clearer. Alternatively "an integer ..." like some of the other
> parameters say.

Yes, I would agree, because the value is just the integer "rate=1001".

> 
>>   o  repair-window:  The time that spans the source packets and the
>>      corresponding repair packets.  An FEC encoder processes a block of
>>      source packets and generates a number of repair packets, which are
>>      then transmitted within a certain duration.  At the receiver, the
>>      FEC decoder tries to decode all the packets received within the
>>      repair window to recover the missing packets.  Assuming that there
>>      is no issue of delay variation, the FEC decoder SHOULD NOT wait
>>      longer than the repair window since additional waiting would not
>>      help the recovery process.  The size of the repair window is
>>      specified in microseconds.
> 
> Here the syntax definition is also just "time".
> 
>>   Applications that use this media type:  Multimedia applications that
>>   want to improve resiliency against packet loss by sending redundant
>>   data in addition to the source media.
> 
> That's perhaps a bit too promotional and unspecific.
> 
>>   Additional information:  None.
> 
> (I note that it is common for RTP-only types to omit this section.)

Well, the RTP payload format specifies what you need and you are in a
context that is much more bound then mail and HTTP.

Cheers

Magnus Westerlund

IETF Transport Area Director
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