Re: Question for IPv6 w.g. on [Re: IPv6 Type 0 Routing Header issues]

Bob Hinden wrote:
> [trimming this to just the IPv6 w.g.]
> 
> We think the question for the IPv6 working group on this topic is does 
> the working group want to do anything to address the issues raised about 
> the Type 0 routing header.  Possible actions include:
> 
>  1) Deprecate all usage of RH0
>  2) Recommend that RH0 support be off by default in hosts and routers

I see these two as being equivalent.  If RH0 is going to be off by 
default in routers, then it's for all intents and purposes unusable and 
should be fully deprecated.

>  3) Recommend that RH0 support be off by default in hosts

This is what everyone already expects the behavior to be, and even 
people on this list have shown surprise when they have discovered that 
this is not the case.  I'd completely agree with this.

>  4) Limit it's usage to one RH0 per IPv6 packet and limit the number of 
> addresses in one RH0.

The use case that I would want to use is allowing trace routes from a->b 
when you don't have access to either end, or for asking for a reverse 
trace route from a host back to yourself.  These don't require multiple 
RH0's.

If it's not done already (I've not had time to read the spec carefully), 
you should also check that the scope is the same (or possibly greater) 
to prevent people for example using RH0 to talk to hosts that only have 
link local addresses via a router that has a globally routable address.

So, I'd prefer disabling it for end hosts, enabling it by default on 
routers but limiting it to only one RH0 header with the same scope.

If that is not acceptable, then deprecate the entire feature.

--------------------------------------------------------------------
IETF IPv6 working group mailing list
ipv6@ietf.org
Administrative Requests: https://www1.ietf.org/mailman/listinfo/ipv6
--------------------------------------------------------------------