Re: [Autoconf] Autoconf addressing model

"Charles E. Perkins" <> Tue, 03 March 2009 21:30 UTC

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Date: Tue, 03 Mar 2009 13:30:35 -0800
From: "Charles E. Perkins" <>
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To: Alexandru Petrescu <>
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Subject: Re: [Autoconf] Autoconf addressing model
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Hello Alex,

Alexandru Petrescu wrote:
> -I find it more advantageous to describe stable subnets, with prefixes
>  (between /48 and /64) exchanged around, rather than /128s.

That's fine, as long as the destination is addressable within
a subnet.  If the destination does not live on a subnet, why
not use a host route (i.e., /128 address)?

> -I would avoid the assumption that an ad-hoc router maintains a
>  stable IP address while moving around.

Then you will have trouble.  There is no free lunch.
(a) the IP address stays the same, and the routes change, or
(b) the IP address changes, and there is a resolver to
      associate the IP address with some other identifier.

Since the design of the resolver in (b) is an unknown and
arguably much more difficult, I'll take (a) with a great
sigh of relief.

> The churning aspect of host-based routes was just one argument against
> /128s and finally against loopback/virtual interfaces.

Are the other arguments easily summarized in a few words?

> Of course, host-based routes could work in some networks, mainly
> depending on their size and way of moving.

This is true.  I don't see what's wrong with it.

> BEcause we simply don't know the size of the network in which they could
> work.  And that apparently it is avoided to put any limit on size of any
> kind.

Who said we had to avoid size limits?

> Even approximative evaluations of the size of the network in which these
> host-based routes would work aren't preferred by many.

I must have missed that, sorry.  Those "many" didn't often assert
their preferences in the [manet] working group.

>> This magically "forgets" the last 10 years of development for ad hoc 
>> networking protocols.  Do you think this work was somehow invalid? 
>> Solving the problems you mentioned was, after all, the entire point 
>> of the work.
> Sorry for having sounded neglecting the results of ad-hoc networking
> protocols.  It was not the intention.  I believe some protocols could be
> used to propagate prefixes - instead of /128s - and may be more
> efficient, grow the network larger.

Well, to me it did sound very negative.  Moreover, I think it is just
fine to pass around subnet prefixes, if you have subnets.

Charlie P.