Re: Yet a different perspective on NAT

At 12:34 PM 08/05/2003 +0200, Bob Arctor wrote:
>the main reason you don't get static ip's with unlimited expansion of address
>space possiblity is to stop your network from growing.

With all due respect, that's nonsense, from both technical and business 
standpoints.
The reason they usually don't do static is that DHCP is easier to manage
(and they don't have to talk the low-tech user through configuring IP 
addresses on their PC.)

>NAT isn't routable. period.
>telcos are in fear that users will make better infrastructure using [Wireless]
.....

>then using proper routing tables you could have 'own' , independent internet,
>i.e . having 1Mbit broadband to the world , and 1Gbit to all towns around.

Here's where you're wrong, because you're not understanding routing protocols.
Suppose you decide to colonize the unused Class A network 1.0.0.0/8
on your wireless side, with 1.1.1.1 as your wireless interface
and you've got ISP service at 24.24.24.24, and
one of your wireless users 1.2.3.4 wants to use Google 216.239.53.100.

If you set up your routing tables properly, if that wireless user
sends you a packet for Google on your wireless interface,
you'll ship it out your DSL or cable connection and vice versa.
And if you and your fellow wireless users have set up the
routing tables on the wireless network appropriately,
the user at 1.2.3.4 may know that you've got an ISP connection that
can reach Google.

But Google doesn't know that 1.2.3.4 is hidden behind your cable modem,
because you're not running BGP with your cable modem company and
don't have a mechanism to tell them that you can reach 1.0.0.0/8 and
they won't know to advertise it to Google.
So Google won't send packets to your cable modem to reach your wireless,
so they won't get the connections they wanted.

By contrast, if you're running NAT on your box,
Google won't get a request from 1.2.3.4, it'll get one from
your cable modem at 24.24.24.24, and it'll send its reply back to you,
and you'll NAT the packets and send them back to the 1.2.3.4 wireless user.

Consumer and dial ISPs don't run routing protocols with their users.
Business ISP connections (typically T1 and above) can run routing protocols,
but usually only do that for customers who are multi-homed,
and almost all ISPs filter the routes to only allow legitimate ones
(so if you've got registered address space, you could use it for your 
wireless.)

>with NAT'ed connections you're stuck with your ISP, and as an 'extra' both
>ends are behind firewall.





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