OMB: IPv6 by June 2008

Thu Jul 7 16:04:22 UTC 2005

Joe Abley wrote:
> 
> On 2005-07-07, at 10:23, Andre Oppermann wrote:
> 
>> It was about a spot in the global routing table.  No matter if one  gets
>> PA or PI they get a routing table entry in the DFZ.  There is no  way 
>> around
>> it other than to make the routing protocols more scaleable.
> 
> With the hole-punching/CIDR abuse multihoming that is widely used in  
> IPv4, a slot in the DFZ gets burned each time an end site adds a  
> provider, regardless of whether they are using PA or PI addresses.  This 
> slot represents state information for the multi-homed site which  
> answers the question "how else can this set of addresses be reached?"
> 
> The shim6 approach shifts this state from the DFZ to the endpoints  
> which are exchanging unicast traffic. The endpoints exchange a set of  
> possible locators through a protocol element within the IP layer and  
> handle locator migration transparently to the transport layer above.  
> Hence the question "how else can this particular remote address be  
> reached" is answered using information on the host, not information  in 
> the network.
> 
> With shim6 an end site can multi-home using one PA prefix per  provider, 
> without taking up additional slots in the DFZ. Hosts within  the site 
> are given multiple addresses (locators), and the layer-3  shim handles 
> any change of locator needed for traffic exchanged  between any two hosts.
> 
> If one (or both) of the hosts exchanging traffic don't support shim6,  
> then the traffic is exchanged without transport-layer stability  across 
> re-homing events (and, potentially, without any optimisation  as to the 
> choice of endpoint addresses for the session).
> 
> So, the shim6 future of multihoming looks like this:
> 
> 1. ISPs multi-home exactly as people are used to doing today, using  PI 
> prefixes, and taking up a slot in the DFZ per transit provider.  
> Everybody is familiar with this already. There is no change for ISPs  in 
> this picture.
> 
> 2. Multi-homed end sites obtain one PA prefix per upstream ISP, and  
> hosts within those end-sites are assigned multiple addresses (in some  
> automated, secure and controllable fashion). There are no additional  
> slots burned in the DFZ by end site multi-homing. Hosts obtain  
> transport-layer reliability across re-homing events using shim6,  rather 
> than relying on the network to take care of it.

Ok, you don't think this thing will ever fly, do you?

-- 
Andre