Subject: IPv6 Source address selection..

From: Markku Savela <[email-masked]>
Date: Tue, 25 Apr 2000 17:21:23 +0300 (EET DST)

Just throwing some ideas and questions... the draft

  draft-ietf-ipngwg-default-addr-select-00.txt

uses at one stage CommonPrefixLen(SA, D) as a comparison value to
select between candidate source addresses (prefixes). This is simple
common bits counted from left ("most significant end"), right?

In our code we use following ComparisonValue(SA, D), returns

  prefixlength, if the common bits covers the prefix,
and
  (common bits - prefixlength), when match is less (e.g. this value is
  always negative)

This prefers the longest prefix that matches fully. If none matches,
it prefers the prefix with least differing bits in the "routing
part".

"My version" differs only when none of the prefixes match fully. For
example, if D=xxxyyy... (x = 4bit unit)

SA= xxxzzzz/32  CommonPrefixLen=12 ComparisonValue= -20
SB= xxz/12      CommonPrefixlen=8  ComparisonValue= -4

CommonPrefix would select SA, ComparisonValue would select SB.

Just food for thoughts ... :)

-- 
Markku Savela ([email-masked]), Technical Research Centre of Finland
Multimedia Systems, P.O.Box 1203,FIN-02044 VTT,http://www.vtt.fi/tte/staff/msa/
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