Subject: WG ACTION: 2 weeks to discuss [LL66] Additional statistical example

From: Erik Guttman <[email-masked]>
Date: Wed, 5 May 2004 01:20:50 +0200

Please post discussion of this issue to the mailing list over the 
next two weeks
ending May 18, 2004.  In order to accept this issued, we will need a strong WG
consensus given that this is very late in the process.

Please see http://www.drizzle.org/~aboba/ZEROCONF/issues.html for a list of
current issues and their status.

[LL66]

Description of Issue:		Additional statistical example
Submitter Name:                 Stuart Cheshire
Submitter Email Address:        [email-masked]
Date first submitted:           04 May 04
Reference:
Comment Type ['t'ech|'e'dit]:	t
Prio ['S' Must|1 should|2 may]:	1
Section:			1.3
Rationale/Explanation:
Lengthy Description:

>    When these address conflicts are detected, the subsequent forced
>    reconfiguration may be disruptive, causing TCP connections to be
>    broken. However, it is expected that such disruptions will be rare.
>    It should be relatively uncommon for networks to be joined while
>    hosts on those networks are active. Also, 65024 addresses are
>    available for IPv4 Link-Local use, so even when two small networks
>    are joined, the chance of collision for any given host is fairly
>    small.

A specific example with numbers: If two 100-host networks are joined,
there's still a better than 75% chance that not a single host on either
network will have to select a new address.

[Erik]

There has been no demand in successive reviews for further example.

[Stuart]

I calculated specific numbers to substantiate the previously vague
assertion.

I believe concrete facts are more informative than vagueness.

[Erik]

Thanks for the numbers.  My point is that we need to publish this
document with as few changes as possible.  This is not an editorial
change.  In my opinion 'fact' assertions generate a lot of debate.

Requested Change:

Add to section 1.3

    This specification is intended for use with small ad-hoc networks - a
    single link containing only a few hosts. Although 65024 IPv4 Link-
    Local addresses are available in principle, attempting to use all
    those addresses on a single link would result a high probability of
    an address conflict, requiring a host to take an inordinate amount of
    time to find an available address.

becomes

    This specification is intended for use with small ad-hoc networks - a
    single link containing only a few hosts. Although 65024 IPv4 Link-
    Local addresses are available in principle, attempting to use all
    those addresses on a single link would result a high probability of
    an address conflict, requiring a host to take an inordinate amount of
    time to find an available address.

    If two 100-host networks are joined,
    there's still a better than 75% chance that not a single host on either
    network will have to select a new address.

---

From: Ralph Droms <[email-masked]>
Date: Thu, 06 May 2004 06:46:35 -0400

Stuart - for my own understanding, can you explain the computation you made
for your statistical example?

- Ralph

At 01:20 AM 5/5/2004 +0200, Erik Guttman wrote:
>Please post discussion of this issue to the mailing list over the next two 
>weeks

---

From: "Philip Nye" <[email-masked]>
Date: Fri, 7 May 2004 12:27:30 -0000

I see no compelling need for an example here and it's too late in the day.

Philip

---

From: Ralph Droms <[email-masked]>
Date: Fri, 07 May 2004 17:32:30 -0400

I agree with Philip - and the concrete example can easily lead to
interminable debate about the assumptions and details of the computation.  I
do not support making this change.

- Ralph