Subject: Re: Source address selection insufficient?

From: Erik Nordmark <[email-masked]>
Date: Thu, 11 Mar 2004 17:55:57 -0800 (PST)

> > Once you modify the hosts at both ends why not also provide connection
> > rehoming?
> 
> Sure. But how does this relate to the problem at hand currently?

I'm trying to understand whether we need ingress filtering avoidance
(such as the general case of source-based routing) even once we
have a connection rehoming solution.

One reason we might need that is when only one end of the communication
implements multi6.

> > (There seems to be a large class of connection rehoming mechanisms
> > that can live with source locator rewriting instead of ingress 
> > filtering,
> > but that's the subject of a different email.)
> 
> Unfortunately we still have to deal with the packets that can't be 
> rewritten and I'm not sure if expecting all routers to be upgraded to 
> support this is reasonable.

I guess the question is about timing and transition.
It might be reasonable to expect that over time all routers will be
upgraded, but we still need some approach to handle the interim.

> > I agree that source based routing and relaxed filtering both work.
> > What is tricky is the middle between the small and the large; too small
> > a site to be able to convince the ISPs to relax ingress filtering
> > and too large a site for source based routing to be trivial.
> 
> For mid-sized sites the "use a default only" policy wouldn't be ideal, 
> but it should at least make sure there is always a working path. For 
> small sites the default-only policy has the disadvantage that only one 
> external link will be used for outgoing traffic, but in a site that has 
> several routers and subnets, different routers/subnets could use 
> different external connections so rudimentary load balancing would 
> still happen.

But I suspect the mid-size sites would like to benefit from some level
of load balancing across their ISPs.

  Erik

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From: "Kanchei Loa" <[email-masked]>
Date: Fri, 12 Mar 2004 10:29:40 -0700

> have a connection rehoming solution.

Could you please clarify "connection rehoming solution" ?

------------
Kanchei Loa
[email-masked]

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From: Erik Nordmark <[email-masked]>
Date: Fri, 12 Mar 2004 10:13:34 -0800 (PST)

> Could you please clarify "connection rehoming solution" ?

This is the component of a multihoming solution that allows the peers
in the communication to switch the locators that are used on the wire
without impacting anything above the transport layer.

Some of these components, for instance the ones in HIP and NOID,
base their security of the rehoming on something strong enough so
that they do not need to care which of the multiple locators are used
even during the initial setup of the communucation.
Hence I think they are capable of always allowing locator rewriting.

Does that make things more clear?

  Erik