Subject: RE: more comments (questions)aboutdraft-draves-ipngwg-router-selection-01.txt

From: "Richard Draves" <[email-masked]>
Date: Mon, 30 Apr 2001 10:21:34 -0700

> >> 1. what should a host do when it receives an RA with the 
> preference 
> >> field being set to 10 (i.e. reserved)?
> >> - ignore the entire RA.
> >> - accept the RA, but consider the preference value as
> >> another value?
> >> if so, high/medium/low?
> >> - other option?
> 
> > How about, treat the RA as if the RouterLifetime field is zero. I 
> > think this will produce the best compatibility with future 
> use of the 
> > reserved preference value.
> 
> Hmm, but, if all routers in a segment specify the reserved 
> value, then a host (which supports the router preference 
> field, but does not understand the reserved value yet) would 
> never be able to make off-link communications.  I don't think 
> it's a happy story.  (Ignoring the RA would also be a bad 
> choice for the same reason.)

My assumption is that if the reserved value is ever used, it will be to
define a "black-hole" preference value that means "do not send packets
to me". (I believe it was Robert Elz who suggested this.) So then for
the default route, there isn't too much difference between a zero
RouterLifetime and the "black hole" preference value.

Do you have some other possible future use in mind for the reserved
value?

Thanks,
Rich
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From: JINMEI Tatuya / 神明達哉<[email-masked]>
Date: Tue, 01 May 2001 02:52:11 +0900

>>>>> On Mon, 30 Apr 2001 10:21:34 -0700, 
>>>>> "Richard Draves" <[email-masked]> said:

> Do you have some other possible future use in mind for the reserved

I don't know, but if this (i.e. a "black-hole" preference) is the only
possibility, why don't you just define it in the (next revision of)
the draft?  It would ensure the best (future) interoperability.

					JINMEI, Tatuya
					Communication Platform Lab.
					Corporate R&D Center, Toshiba Corp.
					[email-masked]
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