Subject: Re: [Sipping] [Sip] INVITE dialogs

From: [email-masked]
Date: Mon, 6 Oct 2008 22:42:53 -0400 (EDT)

From: Paul Kyzivat <[email-masked]>

   I then looked at your notes. I found it very interesting that through 
   formal means you have identified a number of race conditions. I gather 
   you are not aware of:

   http://www.ietf.org/internet-drafts/draft-ietf-sipping-race-examples-06.txt

   That document has been done without benefit of formal models. But it 
   appears that there is substantial agreement about the set of race 
   conditions. (I wish you had been around when we did that work.) That 
   document is largely done, so it is likely impractical to get your input 
   into it. But take a look. It has resolutions to most of the races. If 
   you find any errors, please speak up.

It would be a very interesting "live fire demonstration" of the value
of the formalism if it discovered race conditions that we hadn't
identified by informal means.

Dale
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From: "Saverio Niccolini" <[email-masked]>
Date: Fri, 24 Oct 2008 09:07:45 +0200

> It would be a very interesting "live fire demonstration" of 
> the value of the formalism if it discovered race conditions 
> that we hadn't identified by informal means.

I would not be surprise to discover that race conditions identified by
informal means are much less than the ones identified using a formalism
(even if one using simplifications).

Paul was saying there is not chance to touch the
draft-ietf-sipping-race-examples

is there any plan to address the identified new race conditions
in another draft then? (Pamela was speaking of about 40 more...)

Saverio

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From: Paul Kyzivat <[email-masked]>
Date: Fri, 24 Oct 2008 08:10:21 -0400

I think it is up to the wg and the chairs whether the draft is opened up 
for inclusion of more races. I haven't had time to examine Pamela's 
document in detail, so I can't speak to the specific races she has found 
right now. I would not be terribly surprised if there are more. But I am 
surprised if there are 40 more. Perhaps many of those are variants on a 
theme and might be viewed by others as some smaller number.

	Thanks,
	Paul

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From: "Mary Barnes" <[email-masked]>
Date: Fri, 24 Oct 2008 09:00:39 -0500

I think we also need to consider that some of these may be corner cases.
The idea of the doc in SIPPING was to document the most common race
conditions and the ones that had plagued folks in the past. If we can
get feedback from folks that these other cases occur "in the wild" and
are not rare cases (and not when there's buggy SW), then it might be
quite reasonable to bring this doc back to the WG.

Regards,
Mary. 

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On
Behalf Of Paul Kyzivat
Sent: Friday, October 24, 2008 7:10 AM
To: Saverio Niccolini
Cc: [email-masked]; [email-masked]; [email-masked]
Subject: Re: [Sipping] [Sip] INVITE dialogs

	Thanks,
	Paul

> informal means are much less than the ones identified using a 
> formalism (even if one using simplifications).
> 
> is there any plan to address the identified new race conditions in 
> another draft then? (Pamela was speaking of about 40 more...)
> 
> Saverio
> This list is for NEW development of the application of SIP Use 
> [email-masked] for questions on current sip Use 
> [email-masked] for new developments of core SIP
> 
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This list is for NEW development of the application of SIP
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---

From: Paul Kyzivat <[email-masked]>
Date: Fri, 24 Oct 2008 13:00:38 -0400

Mary,

I suppose there may be someplace to draw a line, but these race 
conditions are mostly corner cases. In my experience, any corner case 
you can find, as improbable as it might seem, will be observed in 
practice, probably much more often than you think.

If these things are real, and are not just variants of the ones we have 
already identified, and covered by them, then it *may* be worth revisiting.

I have exchanged several messages with Pamela on this, but have not 
examined her work in detail. She has made a number of simplifying 
assumptions that IMO are not realistic ones to make in practice. But I 
*think* that if she is finding races under those simplifying assumptions 
then they presumably should continue to be real under looser conditions.

But I haven't had the time to understand her formalisms to make a 
meaningful judgment on what she has found. Maybe somebody else has time?
(Perhaps someone like Iñaki (hint hint) who seems to have an interest in 
arcane things.)

	Thanks,
	Paul