Re: [conex] ConEx credit & audit: status update

David Wagner <> Fri, 18 October 2013 13:28 UTC

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From: David Wagner <>
Organization: University of Stuttgart (Germany), IKR
To: Bob Briscoe <>, Matt Mathis <>
Date: Fri, 18 Oct 2013 15:28:10 +0200
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Subject: Re: [conex] ConEx credit & audit: status update
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Hi *, 

we now are sure to understand that credit will not allow to completely avoid handling time estimations in the audit, but rather represents a risk for future congestion. Therefore, I think we should change the respective section in abstract-mech and we even could change the term to something more distinct like "congestion risk". 

I'd propose to keep the word credit to not cause (more) confusion but to make clear the meaning of that signal in the abstract-mech draft. I would then refer to that text in the audit draft. 



On Wednesday 16 October 2013 19:52:29 Bob Briscoe wrote:
> 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 
> Surcharge")
> 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
>          draft-ietf-conex-tcp-modifications.
> 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
> ________________________________________________________________
> Bob Briscoe,                                                  BT 
> _______________________________________________
> conex mailing list

Dipl.-Inf. David Wagner
Institute of Communication Networks and Computer Engineering (IKR)
University of Stuttgart
Pfaffenwaldring 47, D-70569 Stuttgart, Germany

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