Subject: RE: [Rmt] EXP2ST: TSI length limitations with A flag - LCT/ALC

From: "Michael Luby" <[email-masked]>
Date: Mon, 1 Aug 2005 17:42:29 -0700

Another option is to just relax the requirement that the TOI + TSI must be
32-bit aligned only in the case when the remainder of the packet is
non-empty (carries data).  The alignment is really for accessing the data in
the payload of the packet, but if there is no data then the alignment does
not seem important.

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On Behalf Of
[email-masked]
Sent: Sunday, July 31, 2005 10:04 AM
To: [email-masked]
Subject: [Rmt] EXP2ST: TSI length limitations with A flag - LCT/ALC

TOI may be omitted for A flag packets with FLUTE (and also for a single
object transfer with ALC). LCT says TOI + TSI filed must be 32 bit aligned.
TSI may be 16, 32 or 48 bits length. Thus, the TOI field may not be omitted
for objects in sessions with TSI lengths of 16 or 48 bits. (for 16 bits, the
TSI can be increased to 32 bits just for A flag packets without TOI by
switching S, O, H flags - but this is not desirable and doesn't work for
48bit TSI).

Should we add a note to LCT (and/or ALC) that "Omitting the TOI field is
only feasible for packets with 32 bit TSI field length."?

BTW, an implementation option is to set TOI = 0 for A flag packets where TSI
is 16 or 48 bits length

Cheers, Rod.

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From: "Jani Peltotalo" <[email-masked]>
Date: Tue, 9 Aug 2005 09:12:55 +0300

Hi all,

>From implementation point of view it is important to see the header field
lengths from the header flags (e.g. S, O, H). In our implementation receiver
parses TSI and TOI values as informed with S, O and H flags, so if H flag is
set to one (and O is zero) then our receivers tries to parse TOI value also.
Then if there is no TOI field present, receiver needs extra information to
check if there is a header or packet error. The 'A flag' is not enough
because you can use that in non-empty packets also. And I think that we
should avoid extra complexity.      

Another side effect is that current receiver does not interoperate with
suggested idea.

Cheers, Jani

> Michael Luby
> Sent: 2. elokuuta 2005 2:42
> To: [email-masked]; [email-masked]
> Subject: RE: [Rmt] EXP2ST: TSI length limitations with A flag - LCT/ALC
>

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From: "Michael Luby" <[email-masked]>
Date: Wed, 17 Aug 2005 11:54:12 -0700

You make some good points Jani, and thus given this I think Rod's suggestion
is the best way to go unless anybody thinks of something better.

-----Original Message-----
From: Jani Peltotalo [mailto:[email-masked]] 
Sent: Monday, August 08, 2005 11:13 PM
To: 'Michael Luby'; [email-masked]; [email-masked]
Subject: RE: [Rmt] EXP2ST: TSI length limitations with A flag - LCT/ALC

Hi all,

Cheers, Jani