Subject: Re: multi-homing vs route aggregation

From: [email-masked]
Date: Thu, 22 Jul 1999 11:51:57 -0800 (AKDT)

Justin <[email-masked]> wrote:
 > If there's no good current solution for massive amounts of multihoming,
 > ISPs should tell Joe User, who wants to give his dog's dog collar, his TV
 > remote, and his toaster global ipv6 addresses AND who wants multiple
 > ISPs, to go away.  Just because ipv6 has the theoretical ability to allow
 > more devices to be connected, doesn't mean that has to be encouraged, or
 > even allowed, until problems with it are fixed.  Exactly why does a 
 > toaster need a global ip, anyway?

For the immediate-to-medium term, we're not talking about Joe User.  We're
talking about small-to-medium ISPs and medium-to-large corps.  

 > Do all the ISPs for a multihomed site have to announce the route?
 > Couldn't only one announce, and when the others see a withdrawl of that
 > route, they compete (intelligently) to decide which next advertises it?  I
 > don't see this as an issue with ipv6 at all, I think it's an issue with
 > BGP4+.

Eeek!  Eeek!  No, because they aren't necessarily closely connected.
Primary ISP would be advertising a /24 or /35 or whatever, and not 
be *also* advertising the customers addresses.  There is no indication
that the link has failed in the global BGP tables.  At all.  Unless the
entire ISP fails, then the secondary ISPs could pick up the specific
routes.  But that would still be a major conceptual pain in the rear to
coordinate or even implement.

 > Plus, a solution to this could be made to solve renumbering as well; why
 > not have the customer use the same ips with both ISPs, then renumbering is
 > not necessary.  ISP2 can pick up the withdrawn route for ENTITY through
 > ISP1 since it knows ENTITY is a customer.  Routing updates propegate.  No
 > lost tcp connections.  "But this will cause massive routing churn!"  I
 > would think even a significant increase in route churn is much more
 > acceptable than requiring that all routers with global BGP views have 32GB
 > of memory or some other rediculous amount when ipv6 is deployed.  ...and I
 > would hope that anyone who wants to be multihomed would ensure that their
 > links are reliable, which would mean not many extra routing updates for
 > failed links.

Link reliability is often determined by the telco.  Yes, you can yell at
your telco, but that is like smashing your head into a brick wall.  This 
is why one gets to be multihomed, for when either your telco or upstream
explodes for no apparent purpose.

_______________________________________________________________________
|Aaron Dewell			===>		[email-masked]         |
|http://www.woods.net/~acd			http://www.woods.net/ |
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From: "Ben CROSBY" <[email-masked]>
Date: Fri, 23 Jul 1999 00:43:26 +0100

>talking about small-to-medium ISPs and medium-to-large corps.

I believe this is flawed. We are discussing immediate to medium term. What
about deployment of xDSL technologies ? Permanant IP(v6) links to homes
across the world, with services provided by a whole raft of different 
value-added
service providers. I can see a situation just around the corner, where I 
want to
be able to connect to my corporate lan on the one hand, and my video provider
on the other hand, maybe even to a VPN between some friends so we can play
video games. That gives me a very big reason to have my xDSL connected
(network or standalone) at home multi-homed under v6.

This is just one scenario, where end users can be multi homed, and it isn't for
resilience.

We really don't want to break the Route Aggregation.

My 0.02c.

Ben.

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From: Brian E Carpenter <[email-masked]>
Date: Thu, 22 Jul 1999 20:40:46 -0500

I don't understand this conversation at all.

The whole point is that we don't even think about advertising
anything more specific than a [sub]TLA prefix outside the ISP
that owns the given [sub]TLA. Longer prefixes just never get
out, and multihomed sites have multiple prefixes. If my house
has two ISPs, it has two /64s perhaps, but they never escape from
either ISP. In fact they probably never escape the two ISP's
nearest wiring closets.

Eliminate IPv4 thinking please! 

  Brian

-- 
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Brian E Carpenter (IAB Chair)
Program Director, Internet Standards & Technology, IBM Internet Div
On assignment for IBM at http://www.iCAIR.org 
Non-IBM email: [email-masked]

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From: "Matt Crawford" <[email-masked]>
Date: Fri, 23 Jul 1999 09:54:36 -0500

> out, ...

A small correction: they never get out globally, but any routing
peers are free to exchange any information they wish.  I may set up a
private link or tunnel between (sites or providers) FOO and BAR and
exchange some routing information without regard for TLA or other
bit-boundaries.
				Matt
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