NAT Benefits for the ISP
A Dwindling Supply of Addresses
There are only so many IP Addresses in the world, and as an ISP you will
be issued far fewer than you would like. When you exhaust those that
you are given, you cannot connect another customer.
It has become all too automatic for an Internet Service Provider to give
a "Class C Network," or 256 addresses, to each customer, whether that is
appropriate or not. If you started with a Class B Network, you may
connect 255 customers.
Our NAT Products
Our NAT products let you loan the right number of IP Addresses
to your customers. In most cases, that number is one!
How does it work? Read on for the short answer, or follow this link to the
complete techie details?
Network Address Translation
The Short Answer
Each of our NAT products acts like an IP router. The Internet Service
Provider assigns an IP Address from his assigned numbers to the ISP's
side of the NAT. On "the other side" of the NAT (on the customer's
private Intranet), almost any IP Addresses may be used. If none are in
use yet, we recommend the "private" addresses from
RFC 1597.
When a customer computer sends a message to the outside world via the
NAT, the NAT keeps track of the actual "inside" address of that
computer, but substitutes the assigned "outside" address into the
message before it is sent into the Internet. When a reply comes back
from the outside, the NAT restores the actual address before sending the
reply to the customer computer.
There are cases that get more complicated than this, and if you are
interested, you should read the
complete techie details.
Internet Security
We're all concerned about security, and our NAT helps you here. Only
messages that exactly match a connection are permitted
into the customer's Intranet. This means that only messages that are in
response to their requests may enter their Intranet, unless the NAT
is configured to permit a service like WWW.
Competing NATs that provide a simple
mapping of IP Addresses may unintentionally give the hacker a window
into the customer's Intranet.
This page was last modified on April 19, 1996.
Copyright © 1996 Network Safety
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