Subject: RE: The state of IPv6 multihoming development

From: "Craig A. Huegen" <[email-masked]>
Date: Tue, 22 Oct 2002 16:56:06 -0500 (Central Daylight Time)

On Tue, 22 Oct 2002, Tony Li wrote:

> Because we've done nothing to eliminate the "tragedy of the commons".
>
> Under this scheme, which alternative is easier for users?  I would
> guess PI space.  And everyone would choose that and then tell us that
> they are sufficiently "special" to get PI space and then we end up
> back where we are today.
>
> A workable architecture has to constrain the users into doing The
> Right Thing automatically.  Because otherwise, users will optimize for
> their own benefit, at the cost of the network.

I agree that it's not something I would propose for all multi-homers.  I
agree there would be some folks who would want PI space when perhaps
multi-PA is indeed workable for them.  So it's all-or-nothing?  I don't
buy that.

The complexity and management of assigning multiple-PA prefixes to my home
network of 6 segments, or my mother's accounting firm with 20 segments, or
even a previous employer's network of 100 segments, is vastly different
than assigning multiple-PA prefixes to a network of tens of thousands of
segments worldwide, with multiple Internet igress/egress points.

I don't think it's just me who believes that IPv6 adoption isn't automatic
in large enterprises today, and is in fact hindered severely at this point
for lack of a multi-homing solution.

/cah

---
Craig A. Huegen, Chief Network Architect      C i s c o  S y s t e m s
IT Transport, Network Technology & Design           ||        ||
Cisco Systems, Inc., 400 East Tasman Drive          ||        ||
San Jose, CA  95134, (408) 526-8104                ||||      ||||
email: [email-masked]       CCIE #2100      ..:||||||:..:||||||:..

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From: Iljitsch van Beijnum <[email-masked]>
Date: Wed, 23 Oct 2002 00:21:38 +0200 (CEST)

> segments worldwide, with multiple Internet igress/egress points.

In my original message, which has stirred up a lot of discussion I'm
happy to see, I also mentioned working on a unified tunnelling/aliasing
mechanism.

If we look at a huge enterprise as one example of someone who needs
multihoming, and at a single host with two interfaces or one interface
with two addresses as another, it seems unlikely they could use the same
multihoming mechanisms. However, they could both use a multi address
solution.

For the enterprise, this could be something along the lines of Michel
Py's MHAP where the entire enterprise or good size chunks of it sit
behind clusters of aliasing/tunneling devices that provide the
multihoming functionality by rewriting (or tunnelling) traffic that
can't reach its destination otherwise over a backup address.

For the host, this could be something like Marcelo Bagnulo's extension
header, modified mobility, Peter Tattam's modified TCP or my own "BALTS"
idea. These all boil down to a host having several addresses and being
able to receive packets on a secondary address and trick the transport
layer into thinking it's still using the primary address.

Just recently it occurred to me that these solutions could very well
work together. There are just so many ways you can tunnel or aliaze a
packet, and it's fairly trivial to implement them all for sending. That
means everyone can implement whatever is most convenient for receiving.

For instance, if a multihomed host sends a packet to a multihomed
enterprise its server while the primary address is unreachable, the host
could replace the enterprise's primary prefix with a secondary (PA) one
which is received at a big de-multihoming box which replaces the
original prefix. When the target host (which doesn't have to know about
all of this) sends a packet back, the multihoming box can add a mobility
header and send the packet to the secondary address for the multihomed
host.

I think standardizing the interaction between different multi address
multihoming solutions will make this type of solution much more viable.

It would be great if we could have a discussion about this in Atlanta.

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From: "Tony Li" <[email-masked]>
Date: Tue, 22 Oct 2002 14:49:29 -0700

[ post by non-subscriber.  with the massive amount of spam, it is easy to
  miss and therefore delete mis-posts.  so fix subscription addresses! ]

|   > context." There's probably no single mechanism which is 
|   "the" answer to
|   > multi-homing; you probably need several, each with its own optimal
|   > applicability domain.
|   
|   So why not support PI for a limited subset of multihomers 
|   that have vast
|   networks while supporting multi-PA for the small networks 
|   that have a
|   minimal number of segments?

Tony