North American Network Operators Group

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RE: multi-homing fixes

  • From: Daniel Golding
  • Date: Fri Aug 24 18:07:14 2001

Leo is exactly right. The real reasons that folks multihome are:

1) Backbone and/or routing instability striking one upstream provider
2) Local loop/fiber cuts

That's pretty much it. Although there might be a small element of fear that
a provider might go out of business, there is normally plenty of notice that
a provider is going down, provided you are using a reputable business ISP
and service, as opposed to DSL.

I don't think multhoming needs to be limited, currently. The size of the
routing table is increasing at a more or less linear rate, now. Even at a
higher than linear rate, modern core routers used by most carriers (i.e.
Juniper M-series and Cisco GSRs) can certainly handle a much large routing
table, even in base configurations, with no memory upgrades. The number of
routing updates is certainly not taxing router CPUs, either. We may run into
scalability problems with the algorithm at some point, but it hasn't hit us
yet. And, for now, CPU speed has been growing faster than the processing
requirements of the table.

The fact is, bandwidth is really cheap now. It is a "best practice" to have
multiple providers of any resource that has a long lead-in time and that
some or all of your business functions are dependant on.

This article in NW is part of a distressing genre of similar skreeds, which
have themes like "we are running out of IP address space, and must switch to
IPv6, right now" or "the routing table is too big and the internet will melt
down tomorrow". These articles appear in places like NW, Boardwatch, and
Interactive Week. A greybeard from IETF is almost always trotted out as part
of these tabloid-esqe little dramas. The uninformed and the semi-informed
have a moment (or longer) of panic, then resume their lives, occasionally
internalizing the misinformation. Multihoming is good for almost everyone
who needs it, and NW writers need to do better research.

- Daniel Golding

-----Original Message-----
From: [email protected] [mailto:[email protected]]On Behalf Of
Leo Bicknell
Sent: Thursday, August 23, 2001 6:33 PM
To: '[email protected]'
Subject: Re: multi-homing fixes

On Thu, Aug 23, 2001 at 03:23:24PM -0700, Roeland Meyer wrote:
> At $99US for 512MB of PC133 RAM (the point is, RAM is disgustingly cheap
> getting cheaper), more RAM in the routers is a quick answer. Router

You almost make some good arguments.  I pick up on this one for
two reasons:

1) You clearly haven't priced Cisco RAM lately. :-)

2) You've missed the issue completely.  You dance around ISP's
   providing more reliable service (eg, by adding RAM to their
   routers), and then dismiss that in the face of poor service and
   cheap prices people will buy multiple links.

Much like your $99 RAM argument, customers today can get two or
three T1's for the same price as one just a year ago.  More bandwidth,
more reliability, often less cost.  Who would say no?

Clearly ISP's should offer better service, but at the current
bandwidth prices even with an ISP that took every precaution I, as
a customer, would always buy from two people.  The price really is
that cheap.  Even if ISP's (from a backbone perspective) delivered
real 100% uptime, many people would buy two circuits (to different
CO's) to avoid localized fiber / cable cuts.

Multi-homing is here to stay, in a big way.  It will only become
more popular, no matter how good the ISP's become, for a number of
reasons.  Any future protocol or policy discussions should take
this as a given.

Leo Bicknell - [email protected]
Systems Engineer - Internetworking Engineer - CCIE 3440
Read TMBG List - [email protected],