[ppml] Buying time...

michael.dillon at bt.com michael.dillon at bt.com
Wed Apr 25 03:55:40 EDT 2007

>(ISPs require packet
> forwarding in hardware, and not all hardware that forward 
> IPv4 traffic in
> hardware can also forward IPv6 in hardware).  

That's an oversimplification. For one, not all routers in an ISP network
need to forward in hardware, particularly at the edge where there is an
opportunity to pick and choose. For instance, use new edge routers for
IPv6 customers and old ones for IPv4-only customers. Also, MPLS can be
used in the core where traffic levels are high.

But it is true that some shortsighted ISPs have boxed themselves into a
corner because their CTOs made mistakes, or their CEOs decided that they
would bet the farm. If these companies run into economic difficulties,
that is OK because that is how the free market system is supposed to

> Large networks can take a long time to upgrade if a fork-lift 
> upgrade is required (think 2-3 years).  

I've never come across a large ISP that would even consider a fork-lift
upgrade. The reality is that upgrades are phased and they never really
complete because there are always parts of the network where the older
hardware causes no pain. Those old boxes will sit and work there for
another 10 years until someone decides that it is too risky to continue
to use boxes that are years past their end-of-life.

IPv6 will not be a forklift upgrade because there are too many ways to
make IPv6 and IPv4 coexist in the same network. Pseudowires, MPLS,
tunneling, dual stack, diverse layer 3 networks.

--Michael Dillon

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