2005-1, good or bad? [Was: Re: Shim6 vs PI addressing]

Thu Mar 2 23:17:52 UTC 2006

AO> Date: Thu, 02 Mar 2006 21:42:49 +0100
AO> From: Andre Oppermann

AO> Doing longest-prefix match for high pps rates and high prefix counts
AO> in hardware is complex and expensive.

True, but...

AO> Way more so than doing perfect match on 32 bits (giving 4bn
AO> routeable slots).

...how many routers' FIBs are 32-bit perfect match right now?  Or even a 
24+8 radix tree?

That said, one can use a hybrid

	{ array + { btree | skip list } }

for O(k + log(N)) FIB lookups when hardware doesn't support full exact 
match.  Transition workload from logarithmic to scalar as technology 
permits.

Classful routing is simple.  Simplicity is good.  However, it's still 
not quite time to get carried away with huge tables.  (Of course, IPv6 
is a good chance to "start over" with a defragmented table in which a 
full table would have _fewer_ routes than IPv4.)

Eddy
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