Moving to IPV6

[Louis Mamakos]

On Feb 7, 2011, at 8:15 AM, Robert E. Seastrom wrote:

> 
> Anyway, the *real* problem that IPv6 fails to fix is one that I'm
> surprised that Mike didn't mention since he had an IETF draft or three
> that would have fixed it.  That problem is one of routing table
> growth.  In the middle of the Internet are large routers - not like
> the one that you have on your cablemodem, but ranging in size from 2
> rack units tall and weighing some 40 pounds to several adjacent 42u
> racks and weighing a couple of tons.  They carry the routes for
> Internet provider allocations.  This is called the default-free zone
> or DFZ, because you don't carry a default route or gateway - you're
> supposed to know how to get everywhere.  A full routing table in IPv4
> land is 375k routes, approximately.  In IPv6 land it is 4500 routes.
> Both are growing exponentially.  Processing power on the routers'
> management systems to sort out the routing information is not.  You
> can see where this is headed...  eventually...

Processing power might be the easy part; it's the wicked fast,
horrifically expensive memory that contains the computed forwarding
tables that's also an issue.  You can dump route updates from your
neighbors, and churn away doing computations in normal old DRAM,
like in your computer.  But eventually the rubber must hit the
road, and that's (depending on the router's architecture) on a
line card that's got to do a route look-up for every packet that
arrives in very high speed memory. 

And you need to include enough memory bandwidth to be able to update
the forwarding tables, too (or add twice as much and swap back and
forth).  While the cost of all this exotic memory is one issue, it
also tends to consume relatively more power and generates heat that
must be removed, too.  Power and heat densities in the facilities
that contain these sorts of network elements are a real, er, issue.

louie
wa3ymh