[address-policy-wg] IPv6 PI resource question!

* Nick Hilliard:

> One of the more common hardware components for performing IP address
> lookups is called TCAM - ternary content addressable memory.  It
> performs a similar function to an associative array in a language like
> PHP, except it's implemented in hardware.  It's ridiculously fast and
> ridiculously expensive, and because it's so expensive, router
> manufacturers tend not to put large quantities into their lookup
> engines.

Very nice explanation, thanks!

Cost is probably not that much of an issue.  I suspect that the
bits-per-Watt number is still extremely poor for current TCAMs (data
sheets do not quote them), which means that you can only use a limited
number of them in parallel.

Especially for IPv6, alternative implementations are probably quite
competitive, such as hardware-assisted tries or hybrid schemes relying
mostly on DRAM.  You can also take a few shortcuts if you encode the
current IPv6 addressing architecture in silicon.

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Florian Weimer                <fweimer at bfk.de>
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