question about draft-ietf-6man-rfc3484bis-06.txt and CommonPrefixLen()
Karl Auer <kauer@biplane.com.au> Mon, 23 July 2012 23:24 UTC
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Subject: question about draft-ietf-6man-rfc3484bis-06.txt and CommonPrefixLen()
From: Karl Auer <kauer@biplane.com.au>
To: IETF IPv6 <ipv6@ietf.org>
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Date: Tue, 24 Jul 2012 09:24:12 +1000
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I don't fully understand this change (from section Appendix B): 1. Changed the definition of CommonPrefixLen() to only compare bits up to the source address's prefix length. The previous definition used the entire source address, rather than only its prefix. As a result, when a source and destination addresses had the same prefix, common bits in the interface ID would previously result in overriding DNS load balancing [RFC1794] by forcing the destination address with the most bits in common to be always chosen. The updated definition allows DNS load balancing to continue to be used as a tie breaker. I can see this for destination address selection, where you are working from a candidate set provided by a DNS server. But I don't see it for source address selection. If you have multiple source address candidates in the same prefix, they will "fall through" Rule 8 and the implementation then has to make a choice anyway, and that choice doesn't seem able to be related to DNS load balancing. That is, the design rationale for the new CommonPrefixLen() doesn't seem to apply to source address selection, which leads me to think that for source address selection, CommonPrefixLen() should not stop at the source address prefix length. Am I missing something obvious here? Regards, K. -- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Karl Auer (kauer@biplane.com.au) http://www.biplane.com.au/kauer http://www.biplane.com.au/blog GPG fingerprint: AE1D 4868 6420 AD9A A698 5251 1699 7B78 4EEE 6017 Old fingerprint: DA41 51B1 1481 16E1 F7E2 B2E9 3007 14ED 5736 F687
- question about draft-ietf-6man-rfc3484bis-06.txt … Karl Auer
- Re: question about draft-ietf-6man-rfc3484bis-06.… Karl Auer
- Re: question about draft-ietf-6man-rfc3484bis-06.… Arifumi Matsumoto
- Re: question about draft-ietf-6man-rfc3484bis-06.… Karl Auer
- RE: question about draft-ietf-6man-rfc3484bis-06.… Dave Thaler
- RE: question about draft-ietf-6man-rfc3484bis-06.… Karl Auer
- RE: question about draft-ietf-6man-rfc3484bis-06.… Dave Thaler