Sometimes, IP numbers are assigned automatically by a Host Computer with something called "Dynamic Host Configuration Protocol" (DHCP) or "BOOTP" on the Unix side. Either way, every computer needs a different number to be unique.

Soon after the IP numbering scheme came out, there came a way of identifying machines by names. So every computer had a Hosts file, located with the system files, that named every machine with a resolution of every IP number on the network. For example, "Rocky" might be 192.168.217.20 and "Bullwinkle" might be 192.168.217.21 . A Hosts file might look like this:

rocky IN A

192.168.217.20

bullwinkle IN A 192.168.217.21

In this Unix-type Hosts file, "IN" means Internet and "A" means Address. In a Windows environment, things are a little different. For example:

192.168.217.20 rocky

192.168.217.21 bullwinkle

After a while, there was so much upkeep in having every machine having a current copy of the updated Hosts file that there had to be a better way. So they came out with Domain Name Service or DNS. This is a service that runs on one computer and does all the updating throughout the Network. Soon, though, this was not enough to keep track of all the machines on the network, so they expanded it so other machines also ran this service, and the DNS machines replicate to themselves. This worked and has worked ever since.

Another reason for DNS is to have a reverse lookup table to assure that each address is authentic. So we would enter in DNS a IN.ADDR.ARPA with the reverse address. Like this:

217.168.192.IN.ADDR.ARPA table

with every address within the domain.

There is a problem, though. The numbering scheme of four numbers ranging from 0 to 255 separated by a dot is running out of numbers. That's right, there are so many machines on the Internet that there are not enough numbers to go around.

So the Internet Standards Committee has come up with a new standard called IP version 6, or IPv6. It changes the scheme from a 32-bit numbering scheme in IPv4, the current scheme, to a 128-bit scheme. For example, instead of having four numbers separated by a dot, with a range of 0 to 255, now we will have eight sets of numbers, all separated by a dot. The numbers will be hexadecimal and will run from 0 to 65,535. For example, 39fd:8a51:9422:4ee5:87c2:0543:ff3b:10ab might be a valid IP address with the new IPv6.

As far as reverse lookup, you have to include the new IP6.INT. instead of the normal IN.ADDR.ARPA version 4 designation. So in the above example, b.a.0.1.b.3.f.f.3.4.5.0.2.c.7.8.5.e.e.4.2.2.4.9.1.5.a.8.d.f.9.3.IP6.INT. would be used.

Notice that each digit is separated by a dot, so the reverse lookup can be resolved by a nibble at a time. You won't have to have boundaries ending in 32-bit, 16-bit, or 8-bit subnets.

Find out more about IPv6, RFC1881, IPNG, IPv6 (3Com), and IPv6 (Digital).

With the deployment of the new IPv6, it will be many years before we come close to running out of numbers for every machine on the Internet. However, I wouldn't count your blessings just yet, because there is talk about connecting many types of appliances to the Internet as well. Your refrigerator might soon send you a message stating that your milk is going bad or that your roast has been in there longer than it is supposed to be.

Well, that is about it for this month's Tech Talk. See ya next month!