Re: How is the FEC instance ID field in the EXT_FTI headerdefined?

Magnus,

Yes, that interpretation is correct. The field is present but set to zero in the already-defined fully-specified schemes.

...Mark

Sent from my BlackBerry wireless handheld.

-----Original Message-----
From: Magnus Westerlund <[email protected]>
Date: Thu, 19 Jan 2006 11:33:43 
To:Mark Watson <[email protected]>
Cc:[email protected]
Subject: Re: [Rmt] How is the FEC instance ID field in the EXT_FTI headerdefined?

So the correct interpretation of RFC 3926 in this regard for existing 
schemes (for example Raptor and No-compact code) is that the FEC 
Instance ID field is present but always set to 0?

The text that I cited could have been interpretead either way.

Cheers

Magnus

Mark Watson wrote:
> Magnus,
> 
> Actually, ETX_FTI is formally defined in (the new) ALC, but that just
> defines the Header Extension Type (64) and says that the content is the
> "Encoded FEC Object Transmission Information" which (according to the
> FEC BB) MUST be defined independently by each FEC Scheme.
> 
> So, for FEC Schemes with FEC Encoding ID < 128 they do not need to
> include the (redundant) FEC Instance ID.
> 
> However, for the previously defined FEC Schemes then in
> draft-ietf-rmt-bb-fec-basic-schemes-revised-01.html I defined the
> "Encoded FEC Object Transmission Information" to match the previous
> definition - in particular for the Compact No-Code, the bytes
> corresponding to the FEC Instance ID are included but marked as
> reserved. So, we have backwards compatibility for the existing FEC
> Schemes and flexibility for future ones.
> 
> Regards,
> 
> Mark
> 
> 
> 
> -----Original Message-----
> From: [email protected] [mailto:[email protected]] On Behalf Of
> Magnus Westerlund
> Sent: Wednesday, January 18, 2006 9:25 AM
> To: [email protected]
> Subject: [Rmt] How is the FEC instance ID field in the EXT_FTI
> headerdefined?
> 
> Hi,
> 
> Due to the missing LCT revised specification draft version 01 I do have 
> to ask this question. It might be answered by that draft, that I don't 
> know as I can't get hold of it.
> 
> But the real question is: Is the FEC Instance ID field present or not in
> 
> the EXT_FTI header when the FEC encoding ID is less than 128? The RFC 
> 3926 text:
>     FEC Instance ID, optional, 16 bits:
> 
>     This field is used for FEC Instance ID.  It is only present if the
>     value of FEC Encoding ID is in the range of 128-255.  When the value
>     of FEC Encoding ID is in the range of 0-127, this field is set to 0.
> 
> 
> Which says both that it shouldn't be there and have a value. Please 
> clarify this for me.
> 
> Cheers
> 
> Magnus Westerlund
> 
> Multimedia Technologies, Ericsson Research EAB/TVA/A
> ----------------------------------------------------------------------
> Ericsson AB                | Phone +46 8 4048287
> Torshamsgatan 23           | Fax   +46 8 7575550
> S-164 80 Stockholm, Sweden | mailto: [email protected]
> 
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-- 

Magnus Westerlund

Multimedia Technologies, Ericsson Research EAB/TVA/A
----------------------------------------------------------------------
Ericsson AB                | Phone +46 8 4048287
Torshamsgatan 23           | Fax   +46 8 7575550
S-164 80 Stockholm, Sweden | mailto: [email protected]

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