Subject: [Autoconf] ABC problem redux

From: Alexandru Petrescu <[email-masked]>
Date: Tue, 27 Oct 2009 21:56:11 +0100

The ABC problem we discussed about recently is about this (substitute A, 
B and C for the PRs below).

MANETARCH draft pictures:
>           Communication
>               Range
>          <~~~~~~+~~~~~~>   <~~~~~~+~~~~~~>
>    Single       | <~~~~~~+~~~~~~> |
>    MANET      +-|-+    +-|-+    +-|-+
>    Interface  |PR1|    |PR2|    |PR3|
>               +---+    +---+    +---+
> 

This may cause a problem because, if PR3 and PR1 have the same LL 
address (PR2 different), the DAD executing on PR3 and PR1 won't hear 
each other, so they'll continue using the same LL.

Probably, PR2 will get two entries in its NC having the same LL address 
(of PR1 and 3), yet different MAC addresses.  Which may cause problems 
(not sure which).

Link-local addresses are required to be unique on a single link.  In 
this sense - is the medium between PR1-2-3 a single link?  I believe no, 
at least the picture tells me so.

If we put two distinct links: one between PR1-2 and one between PR2-3 
then the fact that those LLs are duplicated will be less of a problem - 
each is unique on its own link.  Would this solve the ABC problem?

Alex