IPv6 could change things - Was: DMCA takedowns of networks

Tue Oct 27 18:29:18 UTC 2009

To expand on this from a programmers perspective, usually at the kernel/network stack level, a "patricia" radix-style trie is used for fast ipv6 lookups.

The benefit of the patricia trie being that if you only have a difference keylength of 8 bits (/120) then the ip lookup only takes 8 steps in a worst-case scenario.

The same concept applies to ipv4 cidr as well, but it is less obvious.

William
------Original Message------
From: Adrian Chadd
To: Jeroen Massar
Cc: North American Network Operators Group
Subject: Re: IPv6 could change things - Was: DMCA takedowns of networks
Sent: Oct 27, 2009 10:39 AM

On Tue, Oct 27, 2009, Jeroen Massar wrote:

> But yes, the network stack itself is a different question, then again,
> you can just route a /64 into the loopback device and let your apache
> listen there... (which also allows you to do easy-failover as you can
> move that complete /64 to a different box ;)

Funny you should mention that.

A couple of tricks I've seen:

* instead of a linked list and O(n) searching of interface aliases, use
  some kind of tree to map local IP -> interface.
* hacks to do a "bind to all damned IP addresses and let userspace sort
  it out".

I've done the former for a few thousand aliases with no degredation
in performance. The hacks available for freebsd-4.x for the Web Polygraph
software did something similar.

2c,

Adrian

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