Internet Video Series, Part 1


Episode 12, Segment 01 of 11

NAT Routers Part 2

Connecting a multiple PCs to the worldwide Internet thru a single IP address

During the 1990s, as millions of small businesses and families all over the world discovered the Internet, demand for Internet Addresses surpassed the expectations of even the most enthusiastic Internet proponents of previous decades. Unfortunately, - "real" - Internet Addresses are a limited commodity, and back in the early days of the Internet, before it became clear that they would one day be of immense value, huge blocks of these Addresses were irretrievably allocated to a few influential universities, corporations, and government institutions. Millions more IP addresses were lost to inefficient allocation schemes as Internet architects tried to allocate address blocks in patterns that could help them clarify the logical locations of (and boundaries between) separate networks.

Back in the early days, people requesting Internet access got to choose between a "Class A" arrangement (with 16,000,000 Internet Addresses), a "Class B" arrangement (with 65,000 addresses), or a "Class C" arrangement (with 256 Internet Addresses).

Those days are gone forever. As the last blocks of Internet Addresses have been gobbled up, even "Class C" network access is now too expensive for small businesses, and the price is unthinkable for all but the wealthiest of families.

If you've already seen the movie entitled "Class C Commercial-Grade Internet Services", then you know that even this smallest of traditional arrangements can provide addressing for as many as 33 million communicating processes simultaneously running on as many as 253 different computers. That's a LOT of networking power!

A few years ago, as the first - "Internet Service Providers" ( ISPs ) opened their virtual doors for business, they all purchased blocks of address space and made plans to sell addresses, one by one, to families and individuals all over the world. By purchasing tens of thousands of IP addresses in a single block and then leasing single addresses, month-by-month, to individual homes and small businesses, they expected to be able to generate handsome profits. In fact, they even concocted schemes to lease access to more addresses than they actually owned, by gambling that most of their customers would switch their computers off when not in use. By keeping careful track of computers that were not active from moment to moment, and dynamically allocating addresses from a carefully managed "pool", they knew they might meet the likely demands of 20,000 homes with only 10,000 addresses. This practice has come to be known as "dynamic IP addressing, and it's the cause of some extra complexity and related challenges for small businesses and families using the Internet. (The opposite of - "dynamic IP addressing" - is - "static IP addressing". You can learn more about static and dynamic IP addressing from other movies here at

The customers of these ISPs ended up with just a single Internet address, with the implicit expectation that they would connect just one computer. As you will soon see, however, that single Internet address has hidden power to support all of the computers that an individual household might ever want: as many as 253 of them!

Episode 12, Segment 02 of 11