I am also confident that the discovery method can be devised. However, I
think the first question to the WG is:

Any interested in defining a stateless tunnel protocol that works behind
legacy NATv4?

The whole idea of defining this protocol is to provide a lightweight
implementation to allow ISP to introduce v6 to their customers w/o upgrading
the network and home gateway.

If the answer is YES. Then we can work on the technology.

Regards,
Yiu


On 6/10/10 3:16 AM, "Brian E Carpenter" <[email protected]> wrote:

> Konrad,
> 
>> It is in my opinion useful, but only because it is simpler. The real
>> benefit will only show up once the discovery method is clear.
> 
> Maybe, but isn't the first question whether this approach is
> preferable to either a full SAM implementation, or to
> draft-lee-softwire-6rd-udp? I'm pretty confident a discovery
> method can be devised.
> 
> Regards
>    Brian
> 
> On 2010-06-10 01:01, Konrad Rosenbaum wrote:
>> On Wed, June 9, 2010 11:27, Brian E Carpenter wrote:
>>> On 2010-06-08 23:30, Konrad Rosenbaum wrote:
>>>> On Mon, June 7, 2010 09:41, Brian E Carpenter wrote:
>>>>> This is another approach to stateless tunnels across subscriber NATs.
>>>> There is of course the big question of how to discover a SAMPLE server.
>>>> I
>>>> doubt they would get any use if the user needed to enter anything in
>>>> his/her configuration.
>>> Well, that depends on the customer, but in general I think it needs to be
>>> a one-click operation.
>> 
>> Actually, for Joe-Average-User it should be zero-click. Teredo only gets
>> used because it is on per default and requires no configuration
>> whatsoever.
>> 
>>> At the moment we say
>>> 
>>>   "The SAMPLE interface in the host MUST be configured with the IPv4
>>>    address and UDP listener port number of the SAMPLE server."
>> 
>>> From the users perspective this makes it more complicated than Teredo.
>>> From an implementers perspective it makes yet another tunnel protocol.
>> 
>> Only from a network and security perspective it has some limited merit,
>> since it is somewhat simpler than teredo.
>> 
>>> There are various ways of automating that, so maybe we can defer the
>>> discussion until we know whether the method is useful.
>> 
>> It is in my opinion useful, but only because it is simpler. The real
>> benefit will only show up once the discovery method is clear.
>> 
>> [cut]
>>>> Maybe a centralized registry?
>>> Or SLP. Or an IPv4 DHCP option.
>> 
>> Neither is very useful, since they are both designed to work on the LAN.
>> We need a protocol that can easily cross the NAT box without changing it.
>> So:
>> 
>> * no multicast (SLP)
>> * no broadcast (DHCPv4)
>> * no use of private addresses as target IP
>> * no DNS magic(*)(**)
>> 
>> (*)some NATs drop what they call "unknown query type" packets
>> (**)some users use alternative DNS servers as forwarders, which means any
>> heuristic to find out where you are will fail for them
>> 
>> That leaves either a very simple request via TCP or via UDP - maybe as
>> some kind of directory lookup.
>> 
>>>> Also I would change the address format:
>> [cut]
>>> Well, the draft uses as closely as possible the Teredo format. Also
>>> we need to respect the u/g bit, which in your proposal means stuffing
>>> 2 bits into the V4ADDR field (more comments below). I'm not sure this
>>> is worthwhile to avoid hairpinning.
>> 
>> I see.
>> 
>> 
>>     Konrad
>> 
>> 
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