Re:Teredo vs Silkroad

[Pekka Savola <pekkas@netcore.fi>]

On Fri, 21 May 2004, Eiffel Wu wrote:
> >On Fri, 21 May 2004, Eiffel Wu wrote:
> >> As compared with the Teredo, Silkroad has the following
> >> strongpoints:
> >>
> >> 2. Silkroad can deploy without the support of relay, while the
> >> Teredo needs the relay which advertises the reachability of Teredo
> >> Prefix.
> >
> >That's not really true, I think.  You can deploy Teredo using your 
> >own, arbitrary prefix, ("internal Teredo server"), and to the rest of 
> >the Internet, it looks like native IPv6 service.
> 
> Cited from Teredo:
> Teredo relays are IPv6 routers that advertise reachability of the
> Teredo service IPv6 prefix through the IPv6 routing protocols.
> 
> Teredo address format:
>   +-------------+-------------+-------+------+-------------+
>   | Prefix      | Server IPv4 | Flags | Port | Client IPv4 |
>   +-------------+-------------+-------+------+-------------+
>    
>    - Prefix: the 32 bit Teredo service prefix.
>    - Server IPv4: the IPv4 address of a Teredo server.

Yes, but look at the definitions:

========
2.5     Teredo IPv6 service prefix
   
   An IPv6 addressing prefix which is used to construct the IPv6
   address of Teredo clients.
   
2.5.1   Global Teredo IPv6 service prefix
   
   An IPv6 addressing prefix whose value is XXXX:XXXX:/32.
   (TBD IANA; experiments use the value 3FFE:831F::/32, taken from a   
   range of experimental IPv6 prefixes assigned to Microsoft.)
=========

in other words, there can be multiple Teredo IPv6 service prefixes.  
Anyone can establish one just if the operator has a /32 prefix to 
spare. Many probably don't :).

In addition to that, there is the _global_ service prefix which is 
used by default.

btw. Christian, in section 5.2.1:

 This prefix should be a valid Teredo IPv6 server prefix: the
   first 32 bits should contain the global Teredo IPv6 service prefix,
   and the next 32 bits should contain the server's IPv4 address.

==> here 'global' should be omitted, I think?   

> >> 3. Silkroad supports all types of NATs, while Teredo doesn't support
> >> symmetric NATs.
> >
> >Obviously, this could be added very easily to Teredo as well, but it 
> >would require that Teredo servers would act as tunnel endpoints, and 
> >there would not be direct tunneling.  That would burden the servers to 
> >that it would probably be undesirable.
>
> Whether or no, Teredo does not support symmetric NATs.

See section 6.  If you used Teredo just as a tunnel service, it would 
work with symmetric NATs as well.  I don't think many people would 
want to deploy the servers like that though.. :)

-- 
Pekka Savola                 "You each name yourselves king, yet the
Netcore Oy                    kingdom bleeds."
Systems. Networks. Security. -- George R.R. Martin: A Clash of Kings