RE: ISATAP, v6inv4 and 6to4 tunnel interworkings [RE: ISATAP vs a lter natives in 3GPP [Re: comments on draft-ietf-v6 ops-3gpp-analysis-0 9 .txt] ]

[Pekka Savola <pekkas@netcore.fi>]

I haven't been following the discussion, so I may be missing something 
-- but a few comments..

On Wed, 31 Mar 2004, Fred Templin wrote:
> OK, if you must know it then I believe it is possible to run both 6to4 and
> ISATAP from a single interface. Let's say a node wants to send a packet
> to a 6to4 destination with prefix 2002:C001:0203::/48, i.e., a node that
> is reached via a 6to4 router with unicast IP address 192.1.2.3 (neglecting
> for the moment that 192.1.2.3 is non-global and used only as example).
> If the node has, e.g., a route in its routing table such as:
>  
>    2002:C001:0203::/48 -> fe80::0200:5EFE:C001:0203 (via isatap0)
>  
> then the packet will go out the isatap0 interface using ISATAP encapsulation
> based on the link-local ISATAP address from the routing table as the next-hop
> toward the 6to4 router, and the 6to4 router will be unable to tell whether the
> encapsulator used 6to4 or ISATAP.

The encapsulation part should be trivial, as it can be set by the
longest-prefix match by the system.  If it is set improperly, it's
only a problem of the implementation/operator.  Decapsulation is the
tricky part.

> In terms of receiving packets, if we view every global IPv4 address as a
> "Potential Router", then the ISATAP decapsulation checks amount to
> exactly the same (optional) checks suggested for 6to4 and, again, either
> interface could be used to receive the packet with no differences.

I don't think that's accurate.  For example, you don't use link-locals
on top of 6to4.  With ISATAP, you'd be accepting link-local traffic
from everyone.
  
> The difference comes when operational deployments will begin to use
> non-6to4 global IPv6 prefixes, in which case sending nodes will need to,
> e.g., add routes such as:
>  
>    3FFE:EXAMPLE::/48 -> fe80::0200:5EFE:C001:0203 (isatap0)
>  
> Then, the ISATAP router at 192.1.2.3 will appear the same as
> if it were a 6to4 relay router that relays from the 6to4 domain to the
> 3FFE:EXAMPLE::/48 prefix space. 

Yep, though in 6to4 the relay router is typically reached through the 
6to4 pseudo-interface.  

[...]
> In this case, however, the only
> choice would be to use an ISATAP interface, since 6to4 interfaces only
> encapsulate packets sent to a 2002:EXAMPLE::48 prefix.

Uh, no.  6to4 relay routers are also reachable through the 6to4 
interface, right?
 
-- 
Pekka Savola                 "You each name yourselves king, yet the
Netcore Oy                    kingdom bleeds."
Systems. Networks. Security. -- George R.R. Martin: A Clash of Kings