Biggest mistake for IPv6: It's not backwards compatible, developers admit

[Fred Baker]

On Mar 31, 2009, at 5:05 AM, John Payne wrote:

>> And hence I raise my question. There are a number of alternatives  
>> on the table today that give one both multihoming and ISP  
>> independence. Who has given them five minutes though before  
>> rejecting them out of hand?
>
> What alternative gives you multi-homing and leaves the traffic  
> engineering[*] in the hands of the network team and not the end- 
> users or server folk?


On Mar 30, 2009, at 10:32 AM, Fred Baker wrote:
> As I see it, there are six major proposals on the table.
>   - provider-independent addressing (aka PI)
>   - provider-dependent addressing (aka PA)
>   - provider-dependent addressing with multiple prefix overlays in  
> multihomed networks (shim6)
>   - private addressing with NAT, converting to provider-dependent  
> addressing at a DMZ
>   - private addressing with Network Prefix Translation (GSE)
>   - exchange-based addressing (aka Metropolitan addressing)


With PI, you can do what you do today with PI.

With PA, you can do what you do today with provider-allocated addresses.

With shim6, you can do what you do today with provider-allocated  
addresses. It, however, depends on the end system's choice of a source  
and destination address (they are provider-allocated, but the end  
system may have multiple addresses from multiple providers) to  
determine which ISPs the traffic will transit, which is I think what  
you are concerned about.

With NAT, you can do what you do today.

With GSE, the edge network (not the host, the administration of the  
network the host is using) is in control of the edge network routing,  
and to the ISP that the edge network chooses it looks/works just like  
PA, because it is.

Exchange-based addressing is something where the routing issues are  
not all worked out, so I have to insert a caveat here in that regard.  
But one would expect it to work much like today's routing with the  
exception that the sender's contracts in effect select the transit ISP.

Your complaint, as I understand it, is with shim6, and speaking for  
myself I agree with your concern. From the perspective of the network,  
the rest devolve to PA, and you can manage routing the way you do with  
PA. Not that I am asking you to be happy with today's routing  
protocols, but I view them as a separate question.

Traffic engineering can be improved, no doubt. Personally, I would  
like to see that handled via a new routing protocol, one that  
explicitly addresses the issue. Why? Because it is a routing problem.  
But coming back to the question I have been responding to in this  
thread, the solutions on the table all address the issue of the  
allocation of addresses for multihoming, with the exception of PI.