Re: Shim6 proxies

["Jason Schiller (schiller@uu.net)" <jason.schiller@mci.com>]

On Thu, 20 Apr 2006, Scott Leibrand wrote:

> Date: Thu, 20 Apr 2006 09:58:58 -0400 (EDT)
> From: Scott Leibrand <sleibrand@internap.com>
> To: marcelo bagnulo braun <marcelo@it.uc3m.es>
> Cc: Per Heldal <heldal@eml.cc>, shim6-wg <shim6@psg.com>
> Subject: Re: Shim6 proxies
> 
> On 04/20/06 at 4:02pm +0300, marcelo bagnulo braun <marcelo@it.uc3m.es> wrote:
> 
> > you can still make source address based routing work in multiple hops
> > or you can use a mesh of tunnels to allow exit routers to forward the
> > packet to the proper exit router and so on...
> 
> If this is a requirement to implement shim6, it will not happen.  It
> doesn't scale, and is way too complicated to manage.  Either we find a way
> to automate source routing by IGPs, or we give up on letting hosts control
> its egress in networks with more than one broadcast domain.

I agree with Scott.

Source routing is expensive.  

1. Get the source to put the "right" source address in the packet
(e.g. it understands the IGP metrics or there is some routing oracle that
pushes enterprise wide source address preferences)    

OR 

2. Have the egrees router re-write it on exit.


> 
> > but, i guess that as the site grows, such approaches may collide with
> > other requirements
> 
> I don't think it requires any growth to get such collision.  I'll put it
> even more bluntly: almost anyone with enough routers to have an IGP and
> run BGP *will not* want to multihome with shim6 as currently specified.
> They may be fine with enabling shim6 on their hosts so they can talk with
> multihomed hosts at smaller sites, but for their own multihoming such
> sites will want to use traditional BGP techniques.
> 
> As I've said before, I think the shim6 design needs to recognize that it
> will not be the One and Only method for multihoming, and therefore it
> needs to be designed to ensure that hosts that don't use shim6 for
> multihoming can still interoperate with multihomed hosts and small sites
> that do want to use shim6.

Agreed.  To put it another way, if shim6 is not useful to largish
enterprise customers and content providers, then they are not likely to
turn it on, especially if it add complexity like policy routing or holding
lots of state on content servers.  So unless you only want shim6 to be
useful as a peer-to-peer technology for consumner customers figure out how
to eaither add value to the business enterprise customers and content
providers, or at least make it non-invasive to them as Scott is
attempting.

___Jason

> 
> -Scott
>