[6bone] Re: IPv6-only IXP's are absolutely wrong

[Arien Vijn]

On 21-10-2002 17:50PM, "Bill Manning" <bmanning@ISI.EDU> wrote:

[..]

> 
> reasons to split v4 and v6:
> 
> multicast - v4 and v6 treat this differently.
> fabric "optimizations" - framing support, buffer sizing, MTU, etc.
> a decent L2 fabric will be able to accomodate the larger MTUs
> of native v6 and won't complain about divergent framing.
> "Smart" fabrics tend to be tuned to IPv4.
> 

Certainly things to consider when choosing your equipment.

> then there are issues wrt RA/ND on an exchange... having all the
> participants trying to "stamp" the fabric with their version of
> which prefix to use is noisy at best and an effective DOS at worst.
> 

In practice this is not an issue, at least in my experience. We explicitly
tell everyone that RA messages are not wanted on the shared medium. If you
have a Cisco you have to be suppress them explicitly (we now that). Junipers
you have to switch it on so no problem, same goes for most Zebra boxes.

RA messages are easy to monitor. Once they occur we politely ask the
technical contacts to stop these messages. Up to now we never had a problem
with that. Most are techies quite happy with the attention they get :-)

Even when they occur it doesn't seem a big issue since most routers do not
seem listen to them at all.

> then there are mgmt issues. most L2 fabrics do not have up to date
> v6 mib support, so the stats/traffic collection is not as accurate
> as it should be.
> 

This is a quite annoying problem indeed. Not only limited to v6 MIB support
BTW. However I do not see how a separate v6 exchange will solve that.

Except that one just can count the port statistics which is exactly what you
can do when everyone hooks up a separate IPv6 router.

> these things, in addition to the issues with the connecting gear
> (v4 in HW, v6 in SW), tend to argue that a mixed-mode exchange may
> be less stable / harder to troubleshoot than an single use
> facility. 

We actually had a separate v6 VLAN for a number of years and concluded that
it was not a problem at all to use both protocols in the same VLAN. The
benefit of doing that is that members can use dual stack routers which is
exactly what most v6 enabled IXPs do.

Kind regards, Arien


-- 

Arien Vijn
Amsterdam Internet Exchange
http://www.ams-ix.net