Allocations for "always-on" ISPs

On Thu, 7 Dec 2000, Neil J. McRae wrote:

>> More like an uninvited guest, I would say. NAT severely restricts the
>> range of services you can offer and will give you problems in the
>> future.
>
>Perhaps you could expand on what NAT restricts and why it will
>give you problems?

Certainly.

NAT:ed addresses means that the customers' (private) address is not
reachable from outside the point in which you do the NAT. This point
resides within the primary (point of sale) operator's network.

Now, say that an ASP wants to offer some service to your customers
(generating traffic = revenue) which has a communication pattern in which
the ASP needs to connect to the customer's PC. Because of NAT, this is not
possible.

A common application is remote access by IPSEC connections from
mobile/residential users to the office. IPSEC+NAT is not a good
combination. It has been known to work through NAT under some
special circumstances, but typically gives you problems.

The fact is that the customers' addresses are not reachable from outside
the NAT:ed area. This limits your ability to provide services to your
customers.

NAT may be used successfully in some scenarios, and unsuccessfully in
others. In my opinion, it should be every operator's choice whether to
deploy NAT, and not regulated by eg RIPE, and hence should not be
considered as a solution for the "always-on" allocation problem.

Kindly,

-- Janne
------------- Elcom ------------- Network Operations Center ---------
Jan-Erik Eriksson		mailto: jee at alcom.aland.fi
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