Re: [DNA-BOF] Draft BoF agenda.

[Erik Nordmark <Erik.Nordmark@sun.com>]

> Would you elaborate more on "link instance"? I am thinking about what 
> does it mean 'to attach a network'.  
> 
> I think a network consists of three entities 1) Router, 2) Physical Medium 
> and 3) on-link Prefix. But there are some ambiguities.  

My point is that "link" (or "physical medium") could capture the type
of medium i.e. 802.11 might be a link.
The fact that there might be multiple overlapping instances of 802.11
is what I tried to capture with "link instance".

> Two routers advertise two different prefixes on their wireless interfaces. 
> Router1 advertises the prefix A:: and Router2 advertises the the prefix B::. 
>  And they inject the related routes to Internet. Router1 injects route for
> A::  and Router2 injects route for B::.  
> 
> But assume Router1 is implemented with the host-specific part of Prefix 
> Discovery. Hence it knows that the prefix B:: is assigned to the link by 
> hearing RAs from Router2. 
> 
> Then what is the Router1's on-link prefixes on the wireless link? 
> In this case, is the complete set of on-link prefixes  {Prefix A::} 
> or {Prefix A:: , Prefix B::}

I think the key question is what prefixes are assigned to the link
and in this case both A and B apply. The same would be the case of
both routers advertised both A and B, or if there was a single router
advertising A and B.

I think the confusion is caused by the attempt to overload on-link prefixes
to mean something different than intended. THeir meaning is: you can and
should perform address resolution for an address that falls in the on-link
prefix and send packets addressed to other routers to one of the default
routers.
RFC 2461 allows links that have no on-link prefixes i.e. where all packets
would be sent to a default router (with the ability to redirect to on-link
destinations).

Thus as RFC 2461 is designed it is problematic to overload the on-link
prefixes as some form of "link identifier".

I see two choices on how to proceed:
 - revisit RFC 2461 and make all routers on the link advertise the same set
   of on-link prefixes and require that at least one on-link prefix
   be advertised on every link.
 - introduce an explicit "link identifier" option in Neighbor Advertisements.

  Erik