Re: LL31 Probing intervals

Stuart Cheshire wrote:

> Christian, I'm not sure we're talking about the same thing.
>
 > ...
 >
> 
> The issue I'm raising is that in draft-08 we replaced that paragraph with 
> the one below, which I do not view as an improvement:
> 
>    When ready to begin probing, the host should then wait for a random
>    time interval selected uniformly in the range zero to one seconds,
>    and should then send three probe packets, spaced randomly, zero to
>    one seconds apart.
> 
> One material result of this change is as follows:
> 
> With draft-07, if an Ethernet switch vendor built a product where the 
> time from link-up to active forwarding was no more than five seconds, 
> then they would be sure to see at least the last of the four probe 
> packets. As long as they successfully forward that packet without 
> dropping it, then the host has a fair chance of getting reliable conflict 
> detection. Accordingly, the switch vendor could truthfully describe such 
> a product as being "Zeroconf compatible" or "Zeroconf friendly" (or some 
> such wording, which we will let the marketing department worry about).
> 
> With draft-08, there is no defined lower bound. The time from link up to 
> sending the last probe should average 1.5 seconds, but sometimes it could 
> be less than one second. Sometimes it could be less than half a second. 
> It could be much less, near-zero on occasion. No matter how fast the 
> switch vendor can make their product bring up the port, it can never be 
> fast enough to guarantee to see at least one of the probe packets. I fail 
> to see how this change improves the standard.

I'm on the same page as you - I just backtracked a little to much in my 
commentary - I've not trying to rehash things already settled down.

I share the same concerns as the times tend towards the lower end of 
what's permitted by the standard but may in fact cause some grief in 
actual implementation.



-- 
Chris Herzog                    Software Technologies Group, Inc.
mailto:[email protected]              http://www.stg.com
(708) 547-0110 x225             FAX (708) 547-0783