Re: An alternative to 6to4 and teredo

["Fred L. Templin" <ftemplin@IPRG.nokia.com>]

Christian Huitema wrote:
> Even if you solved the set up issue, there would still be the matter of cost. Tunnel brokers are only "cost
> neutral" if they are provided by the user's ISP. On the other hand, if the tunnel broker has to be accessed
> over the Internet, then there is a direct bandwidth cost: the tunnel broker essentially becomes a secondary
> ISP. The cost may not be quite as large as the primary ISP, as there is less equipment involved, but it is of
> the same order of magnitude -- maybe 1/4th of the price of a regular subscription. You are unlikely to finance
> that kind of of cost with advertisements alone.

There is also the cost issue of the number of messages required to set
up the tunnel. There needs to be a reasonably persistent flow of messages
from a source to a particular destination (or, from a source *through* a
particular tunnel broker) before the cost for tunnel setup can be amortized.
Thus, I agree with Christian that tunnel brokers provided by the ISP are
one example in which the cost is justified. In other cases, e.g., when the
source sends only a few messages to a particular destination) automatic
tunnelling mechanisms are more cost-efficient.

> Rather than opposing tunnel brokers and automatic solutions, we should consider them complementary. Something
> like, use autoconfiguration by default, switch to a provisioned tunnel if one is available. In the case of
> 6to4, this essentially boils down to replacing the default "anycast" route by the specific address of a
> configured (or brokered) relay. In the case of Teredo, this requires provisioning a "configured" mode.

I agree with the complementary observation. Automatic tunneling
can provide the default behavior and configured tunnels (or,
"semi-automatic" tunnels) can be established when/if needed.
(Longest-prefix-match will steer packets to the appropriate
interface.)

Fred Templin
ftemplin@iprg.nokia.com