Subject: RE: [Rmt] How is the FEC instance ID field in the EXT_FTI headerdefined?

From: "Mark Watson" <[email-masked]>
Date: Wed, 18 Jan 2006 11:45:13 -0500

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-masked] [mailto:[email-masked]] On Behalf Of
Magnus Westerlund
Sent: Wednesday, January 18, 2006 9:25 AM
To: [email-masked]
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
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From: Magnus Westerlund <[email-masked]>
Date: Thu, 19 Jan 2006 11:33:43 +0100

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

-- 

Magnus Westerlund

---

From: [email-masked]
Date: Thu, 19 Jan 2006 13:14:53 +0000 GMT

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

Cheers

Magnus

-- 

Magnus Westerlund