Subject: Question about multihoming

From: Nathan Lutchansky <[email-masked]>
Date: Thu, 18 Jan 2001 09:13:57 -0500 (EST)

Hi all,

I posed this question a few days ago on the IPv6 users list and didn't get
a reply, so perhaps this mailing list is a more appropriate place to ask.
I'm still very interested in the answer, and even just a pointer to a
website or reference book would be great.  Thanks.  -Nathan

---------- Forwarded message ----------
Date: Tue, 16 Jan 2001 11:15:17 -0500 (EST)
From: Nathan Lutchansky <[email-masked]>
To: "[email-masked]" <[email-masked]>
Subject: Question about multihoming

Hi,

I've just started learning about IPv6 over the past month, and I have a
question regarding multihoming that's not clearly answered in the RFCs.

What is intended to be the standard method of assigning IP blocks to sites
with service from multiple providers?  Since portable address blocks will
not be used in IPv6 in favor of provider-based assignments, there are
apparently two approaches that can be used.

One of the design goals for IPv6 is to allow easy renumbering of entire
networks, as well as promoting the use of multiple prefixes concurrently
to give each device one global IP address per prefix.  This would suggest
that a multihomed site would obtain a prefix from each provider.  In fact,
draft-ietf-ipngwg-default-addr-select-02 ("Default Address Selection for
IPv6") states, "In addition, multi-homing situations will result in more
addresses per node. For example, [...] a site may have multiple ISP
attachments with a global prefix per ISP."

However, draft-ietf-ipngwg-ipv6multihome-with-aggr-01 ("IPv6 Multihoming
with Route Aggregation") suggests that a multihomed site would only use
a prefix assigned by one ISP, then set up weaker routing entries in that
ISP to route through the second ISP for load-balancing and redundancy.
This would be similar to multihomed situations in IPv4 in which a site is
not using portable addresses.

I can see advantages and disadvantages to both techniques.  Are there
guidelines for determining which method to use?  In what situations might
each solution be necessary?  I can even envision cases in which both
methods could be used, i.e. a site uses two prefixes, and both ISPs can
route both of them.

Any comments would be appreciated.  I'm working on an introductory
transitional guide for IPv6, so I'd like to get this point right.  Thanks.
-Nathan

-- 
+-------------------+---------------------+------------------------+
| Nathan Lutchansky | [email-masked] |  Lithium Technologies  |
+------------------------------------------------------------------+
|  I dread success.  To have succeeded is to have finished one's   |
|  business on earth...  I like a state of continual becoming,     |
|  with a goal in front and not behind. - George Bernard Shaw      |
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From: [email-masked]
Date: Thu, 18 Jan 2001 23:23:20 +0900

>website or reference book would be great.  Thanks.  -Nathan

	I believe the best reference (to date) is
	http://playground.sun.com/ipv6/meetings.html, near "September/October
	1999".  We had two-day meeting just for multihoming in IPv6.  you will
	find meeting minutes there.  Also, there are couple of other
	internet drafts about the topic.

itojun