Subject: RE: [NDProxy#16] Loop prevention, revisited

From: "Dave Thaler" <[email-masked]>
Date: Wed, 16 Feb 2005 09:59:55 -0800

Pekka Savola writes:
> > Proposed replacement text:
> >> An implementation MUST have some means of preventing loops.
> >> Loop prevention SHOULD be done by having the proxy implement the
> >> Spanning Tree Algorithm and Protocol as defined in [BRIDGE] on all
> >> proxy interfaces, as described below.
> 
> Is this strong enough for interoperability across ND-proxies from
> different vendors?  Loop prevention won't do much good unless every
> vendor implements an interoperable mechanism..
> 
> The text is also a bit contradictory: "An implementation MUST have
> some means.." and "The mechanism is required only if...".  Granted,
> there are some cases where it may be physically impossible (or
> extremely difficult) to use the implementation to form a loop, but in
> the general case, the implementor really cannot know how the devices
> will end up being used.  Maybe the first sentence needs to be reworded
> slightly to include an escape clause there as well.

Point taken. How about:
A proxy MUST ensure that loops are prevented, either by running
the Spanning Tree Algorithm and Protocol defined in [BRIDGE] on all
proxy interfaces as described below, or by being deployable only in
an environment where physical loops cannot occur.  For example, in a
cell phone which proxies between a PPP dialup link and a local Ethernet
interface, it is typically safe to assume that physical loops are not
possible and hence there is no need to support the Spanning Tree
Protocol (STP).

-Dave

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From: Pekka Savola <[email-masked]>
Date: Wed, 16 Feb 2005 21:57:20 +0200 (EET)

> possible and hence there is no need to support the Spanning Tree

This text looks fine by me.  Thanks!

-- 
Pekka Savola                 "You each name yourselves king, yet the
Netcore Oy                    kingdom bleeds."
Systems. Networks. Security. -- George R.R. Martin: A Clash of Kings

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From: Bill Sommerfeld <[email-masked]>
Date: Wed, 16 Feb 2005 23:01:17 -0500

On Wed, 2005-02-16 at 14:57, Pekka Savola wrote:

> > For example, in a

all well and good until someone strings together four such phones and two
ethernet hubs just to prove a point..

						- Bill