Subject: [bfcpbis] Gen-ART Telechat review of draft-ietf-bfcpbis-rfc4582bis-13.txt

From: Suresh Krishnan <[email-masked]>
Date: Mon, 2 Mar 2015 17:19:26 +0000

I am the assigned Gen-ART reviewer for this draft. For background on
Gen-ART, please see the FAQ at
<http://wiki.tools.ietf.org/area/gen/trac/wiki/GenArtfaq>

Please wait for direction from your document shepherd or AD before 
posting a new version of the draft.

Document: draft-ietf-bfcpbis-rfc4582bis-13.txt
Reviewer: Suresh Krishnan
Review Date: 2015/03/02
IESG Telechat date: 2015/03/05

Summary: This draft has significant issues that needs to be fixed before 
it is ready for publication as a Proposed Standard.

Major:

* Section 5.1:

This section mandates the receiver to ignore the F bit if it is set 
while running over reliable transport. In my opinion this is not 
sufficient as the length of the header is determined by the bit being 
set. I strongly believe that this is an error condition and the packet 
should not be processed further. At the bare minimum, the draft needs to 
specify if the receiver should process the COMMON-HEADER as having 12 
octets or 16 octets in this case.

* Section 6.2.3:

This section does not explicitly state that each of the fragments needs 
to have the COMMON-HEADER included, but it can be inferred since that is 
the most logical thing to do. I would prefer that it be explicitly 
stated though.

If my interpretation is correct, then the formula for calculating the 
number of fragments is wrong. Instead of

N=ceil(message size / MTU size)

it needs to be

N = ceil( (message size - X) / (MTU size - X) )

where X is the size of the COMMON-HEADER with fragment fields (i.e. 16) 
if the MTU size is the MTU for UDP. This is needed because the common 
header will be repeated on all the fragments.

e.g. Assume MTU size=1280 and message size=2560 (COMMON-HEADER 16 + 2544 
message) the current formula will yield N=2, while N should in fact be 3 
as the message will not fit in 2 fragments.

Thanks
Suresh