Subject: Re: Session Stability (was multi-homing vs route aggregation)

From: Jessica Yu <[email-masked]>
Date: Tue, 03 Aug 1999 17:06:05 -0400

Francis,

> In your previous mail you wrote:
>
>   But I am really concerned about the requirement of multi-address per host,
>   especially N (N>2) addresses per host is required if the site multihoming
>   to N ISPs.  
>   
>=> RFC 2260 (again) explains in its section 6 why a multi-homed site
>>should have multiple prefixes (then multi-address per host).
>The text is about IPv4 with CIDR and the aggregation constraints of
>IPv6 are far stronger then this requirement will remain...

	I do not think RFC2260 suggests anything that multiple addresses 
	should be assigned to each host as you mentioned.  Please read it 
	(again) carefully.

>In fact with IPv6 any interfaces should get two or more addresses,
>even on a mono-homed site, because of scoped addresses.
>Multi-address per host is an IPv6 fact and there are many available
>or proposed tools (like autoconfigurations, A6 and router renumbering)
>which should help us.

	I (again) suggest that before we jump into the multi-addressing 
	per host scheme, let's throughly evaluate the complication and 
	operation complexity associated with that.

	We can ignore the issue but it won't go away.  Didn't we tried
	it before with the multihoming routing issue?  Now, we still
	have to face it. 

	In the end, it's the network operators/engineers who are deciding
	if IPv6 should be deployed in their networks. If they are not
	convinced it's operational viable, what will happen?
>
>   I think it'd lead confusion in routing in the site and host management in 
>   general.  The software of hosts and routers has to be more sophiscated.  
>
>=> I agree, the common multi-address support shows its limits (or its bugs)
>but it can (should!) be fixed (even by leading vendors in routing software :-).

>   Anyway, I suggest that before we jump into the multi-addressing scheme, 
>   let's throughly evaluate the complication and operation complexity 
>   associated with that.  
   
>=> multihoming just makes it worse but this issue is there from the
>beginning of IPv6 (then it should be no more a real issue?)
>
>Thanks

>[email-masked]

>PS: Web "virtual-hosting" is another reason to support multi-addressing
>and one can put hundreds of addresses (=> performance issue too).

	We are talking about scaling here.  Operational complexity is
	far different between managing some multi-addressed 'web-hosting' 
	servers vs. managing hundreds and thousands of multi-addressed 
	hosts in a site.

cheers!
						--Jessica
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From: Francis Dupont <[email-masked]>
Date: Wed, 04 Aug 1999 14:13:11 +0200

=> there are two sections about address allocation and assignment
in RFC 2260. The section 6 explain why a single address space or prefix
is not a good solution (with two cases: an independent prefix or
the prefix of one ISP) and the arguments are still (ie even more)
valid in the IPv6 framework.
 The section 4 says "a particular node (host) may be assigned address(es)
out of a single prefix, or may have addresses from different prefixes".
Then RFC 2260 seems a bit ambiguous about this question (which is not
in fact addressed by it)... 

=> we jumped into it as soon as aggregation became the important thing
in addressing...

=> this issue is not ignored but I expect this is solved in host and
router kernels (modulo address selection which is still open).

=> I believe you have two concerns:
 - bugs in kernel code, for instance in router software with
   "secondary addresses"
 - management costs
First point should be fixed (but I'd like to have a confirmation from
head router vendors :-). Second point is supposed to be dealt with
autoconfigurations, A6 RRs and router renumbering.
In any cases we should try this in the reality then to switch to
the 6bone mailing list?
   
Regards

[email-masked]