Misconceptions, was: IPv6 RA vs DHCPv6 - The chosen one?

Masataka Ohta mohta at necom830.hpcl.titech.ac.jp
Thu Dec 29 06:46:22 CST 2011


Ray Soucy wrote:

> Sounds like we have one group saying that IPv6 is too complicated and
> that all the "overhead" of IPv6 had resulted in slow adoption.
>
> Meanwhile we have others saying it doesn't have enough functionality,
> and should also include IGP.

Not at all. It is wrong that ND is so complicated that it even
act as IGP proxy.

To simplify the situation, let separate address resolution and
IGP, which is the conventional wisdom of IPv4.

ND became too complicated unnecessarily trying to offer incomplete
and incorrect assistance from routers to nodes, even though the
nodes should take care of themselves using information provided
through IGP.

Having a default router is fine if there is only one router.

However, with multiple routers, default routers and ICMP
redirects are nothing more than an incomplete proxy of IGP.

> There is a lot of academic and theoretical argument being made here,
> but not so much on the practical application side.

Though NANOG may not be a good place to discuss about practical
application side, it may be helpful to mention IPv6 is totally
broken for the side.

That is, as the length of IPv6 extension headers is unlimited
and there are extension headers inserted automatically without
application control, there is no guaranteed minimal payload
size left for the transport layer.

As PMTUD of IPv6 is proven to be inoperational:

	http://meetings.apnic.net/__data/assets/file/0018/38214/pathMTU.pdf

we must assume MTU of 1280B. But, as IPv6 extension headers can
be as lengthy as 1000B or 2000B, no applications are guaranteed
to work over IPv6.

						Masataka Ohta



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