IPv6 day and tunnels

Wed Jun 6 01:42:48 UTC 2012

Templin, Fred L wrote:

>> You can't carry a 65516B IPv6 packet in an IPv4 packet.
> 
> No, but you can carry a ((2^32 - 1) - X) IPv6 packet in
> an IPv6 packet.

I'm afraid you wrote:

>> General statement for IPv6-in-IPv4 tunneling, yes. But

and

>> What I am after is a tunnel MTU of infinity.

in a single mail.

>> Bigger packets makes it rather circuit switching than packet
>> switching. The way to lose.
>>
>> Faster is the way to go.
> 
> Why only fast when you can have both big *and* fast?

Because bigger packets makes it rather circuit switching than
packet switching, which is the way to lose.

> See
> Matt's pages on raising the Internet MTU:
> 
> http://staff.psc.edu/mathis/MTU/

A page with too narrow perspective.

> Time on the wire is what matters,

In senses you have never imagined, yes.

> and on a 100Gbps wire
> you can push 6MB in 480usec. That seems more like packet
> switching latency rather than circuit switching latency.

100Gbps is boringly slow.

Are you interested in only supporting slowgrams? IMHO,
go fast or go home!

At 1Tbps optical packet switched network, there is no
practical buffer other than fiber delay lines.

If MTU is 1500B, a delay for a packet is 12ns long, delay for
which requires 2.5m fiber. For practical packet lose probability,
delay for tens of packets is necessary, which is not a problem.

9000B may still be acceptable.

But, 6MB means too lengthy fiber.

That's how time matters.

Worse, at a 10Mbps edge of a network with 1Tbps backbone,
6MB packets means 4.8 seconds of blocking of other packets,
which is why it is like circuit switching.

Or, at a 1Tbps link in a super computer, 48usec is too much
blocking.

That's another way how time matters.

Are you interested in only supporting circuitgrams? IMHO,
go packet or go ITU!

					Masataka Ohta