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RE: The Gorgon's Knot. Was: Re: Verio Peering Question
From: smd () clock org (Sean M. Doran)
Date: Fri, 28 Sep 2001 15:44:38 -0700 (PDT)



| But, we all do, or we aren't talking BGP. The requirements here are not that
| large. A Cisco 2651 with 128mb is a valid BGP speaker, these days. That's a
| cheap router, indeed. And, router memory is dirt cheap.

BGP is based on TCP and thus has the fun property that a big
set of changes will pile up in front of a connection to a peer
that is slow at processing inbound announcements & withdrawals.
The slower you are at processing updates, the more likely you
are to be out of sync with reality in such a way that you will
begin to notice that you are forwarding some packets the wrong
direction into loops or black holes.   The slower you are, the
greater the backlog you have to chug through to catch up, 
making you busier for longer periods, which in turn leads to 
greater backlogs.   Slow down too much and the other side
will help you out by resetting the session.

We've seen this in the past - it's caused MASSIVE outages
affecting nearly EVERYONE for hours at a time.

Or you can say "smd is protecting his own personal interests"
and carry on arguing the equivalent of "ANYBODY can build
a modern router using a sufficient amount of ROM" which simply
underlines the point that dynamic global routing is an expensive 
luxury that many people have gotten used to.

| The common good is
| promoted by allowing these folks to multihome, which would be effectively
| prohibited if all networks implimented verio-style filter policies.

Think of it as a catalyst for more experimentation with alternative
ways of multihoming without the use of BGP.   There are several which
exist now, and several which are being discussed in multi6 which
could be made to exist now without universal software changes.
Some brainstorming could result in several other approaches, more
or less generalized, but what's the point when the normal cheap-seeming
thing to do is to announce CIDR holes to the world?

| The number of folks who multihome is large and growing. We should support
| this by promoting relatively open filtering policies and allowing /24s to be
| truly, globally routable.

I think we should encourage people to introduce individual /32s
into the network and flap them around a bit, to force some issues
which have been avoided becauase first Sprint and then Verio have
been willing to take a bunch of negative PR in the act of self-protection
(which has the side-effect of protecting alot of people who generate
the negative PR, and everyone else).

        Sean.


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