Subject: Padding TLV issue in draft-ietf-6man-segment-routing-header

From: David Lebrun <[email-masked]>
Date: Wed, 17 Jan 2018 16:19:04 +0000

Hi,

I was made aware of the fact (thanks to Mathieu in CC) that it is
impossible to correctly pad the SRH when the current length modulo 8
is equal to 6. That would require a padding of 2 or 10 bytes. However,
the Length field of the Padding TLV must be between 1 and 7 included,
which yields possible padding sizes between 3 and 9 (accounting for
the 2-byte TLV header).

It is thus impossible to use a single Padding TLV in that case. Using
two Padding TLVs would work but that would be a waste of space.

A possible fix is to extend the definition of the Padding TLV Length
field to allow values from 0 to 7. Would that make sense ?

Thanks,

David

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From: "Darren Dukes (ddukes)" <[email-masked]>
Date: Fri, 19 Jan 2018 19:04:17 +0000

Hi David thanks to you and Mathieu for spotting that.  We’ll add 0-7 in the next revision to cover all cases from length mod8 = {1..7} with a single padding TLV, which was the intent.

Darren

> On Jan 17, 2018, at 11:19 AM, David Lebrun <[email-masked]> wrote:
> 
> Hi,
> 
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