[conex] ConEx credit & audit: status update

Bob Briscoe <bob.briscoe@bt.com> Thu, 17 October 2013 08:26 UTC

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To: Marcelo BAGNULO BRAUN <marcelo@it.uc3m.es>, Nandita Dukkipati <nanditad@google.com>
From: Bob Briscoe <bob.briscoe@bt.com>
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Cc: ConEx IETF list <conex@ietf.org>
Subject: [conex] ConEx credit & audit: status update
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ConEx chairs,

David Wagner, Mirja Kuehlewind & I have been meeting over the past 2 
days to sort out whether the approach to credit the w-g agreed is 
correct and feasible.

You may recall that last July we agreed at the working group meeting 
in Berlin to go with David Wagner's idea of requiring audit to check 
for a non-negative balance of (credit - (loss or ECN)) as well as 
(re-echo - (loss or ECN)), so the source has to effectively 'pay' 
twice for congestion, with credit and with re-echo.
(See draft-wagner-conex-credit-00 Section.3.3. "Credit As Congestion 

The more I think about the idea, the more I like it - I'm grateful to 
David for thinking up this idea - it's solved an otherwise major 
problem. We all agree that there are still some niggles with it, 
which we will write up by updating David's draft (above).

But more importantly (if the relevant co-authors agree) we will 
reflect this change in thinking with the relevant normative text in:
         draft-ietf-conex-destopt and

For these expt track docs, we aim to issue new revisions before 
Monday's deadline, even there is no ConEx meeting planned for Vancouver.

We intend to write up a full (Informational) spec of audit and credit 
by revising
         draft-wagner-conex-credit-00 (we may use a new filename to 
include the word audit).

This will document all the potential attacks against ConEx and the 
way the audit function handles them. We'll need to build a new 
implementation to test it, then we can include reference pseudocode 
in the draft (all the ideas from the auditor in my PhD that Toby 
Moncaster implemented are just as applicable to these attacks, even 
with the change in the definition of credit).

Matt Mathis & I will also be making the few promised updates to
         conex-abstract-mech (Informational)
before Monday.


Bob Briscoe,                                                  BT