IXP

Fri Apr 24 17:46:53 UTC 2009

In a message written on Fri, Apr 24, 2009 at 05:06:15PM +0000, Stephen Stuart wrote:
> Your argument, and Leo's, is fundamentally the complacency argument
> that I pointed out earlier. You're content with how things are,
> despite the failure modes, and despite inefficiencies that the IXP
> operator is forced to have in *their* business model because of your
> complacency.

I do not think that is my argument.

I have looked at the failure modes and the cost of fixing them and
decided that it is cheaper and easier to deal with the failure modes
than it is to deal with the fix.

Quite frankly, I think the failure modes have been grossly overblown.
The number of incidents of shared network badness that have caused
problems are actually few and far between.  I can't attribute any
down-time to shared-network badness at exchanges (note, colos are
a different story) in a good 5-7 years.

On the contrary, I can attribute downtime already to paranoia about
it.  When I had an ethernet interface fail at a colo provider to
remain nameless I was forced to call the noc, have them put the
port in a "quarantine" vlan, watch it with tcpdump for a hour, and
then return it to service.  Total additional downtime after the bad
interface was replaced, 2 hours.  I have no idea how watching an
interface in a vlan with tcpdump supposedly protects a shared
network.

Remember the 7513's, where adding or removing a dot1q subinterface
might bounce the entire trunk?  I know of several providers to this
day that won't add/remove subinterfaces during the day, but turning
up BGP sessions on shared lans can be done all day long.

The scheme proposed with private vlan's to every provider adds a
significant amount of engineering time, documentation, and general
effort to public peering.  Public peering barely makes economic
sense when its cost is as close to free as we can get it, virtually
any increase makes it useless.  We've already seen many major
networks drop public peering all together because the internal time
and effort to deal with small peers is not worth the benefit.

Important volumes of traffic will be carried outside of a shared
switch.  The colo provider cannot provision a switching platform
at a cost effective rate to handle all cross connects.  So in the
world of PNI's, the public switch, and shared segment already select
for small players.  You may want to peer with them because you think
it's fair and good, you may do it to qualify up and comers for
PNI's, but you're not /public peering/ for profit in 99% of the
cases.

All this is not to say private VLAN's aren't a service that could be
offered.  There may be a niche for particular size networks with
particular sized flows to use them for good purposes.  Colo providers
should look at providing the service.

A replacement for a shared, multi-access peering LAN?  No. No. No.

-- 
       Leo Bicknell - bicknell at ufp.org - CCIE 3440
        PGP keys at http://www.ufp.org/~bicknell/
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