Dynamic DNS

While most geeks probably know about this one, with the advent of cheaper and more widespread broadband, the concept deserves to be reviewed for both newcomers and seasoned experts.

First the problem: DSL, cable, and most other broadband home and small business connections to the Internet are not fixed unless you asked specifically for it, and paid a little to a lot more. So when you connect to the Internet, you are going to be handed a random address from a set of addresses that are associated with your physical connection. This is very similar to the original phone numbering scheme: a geographical region was assigned a "substation" prefix (in the first half of the 20th, it was usually given the name of that region, shortened to a two letter prefix, which is why letters are on the dial - CHelsea 5-4151, for example, was 245-4151), then up to 10,000 individual lines could be accessed by routing the traffic first to the substation, and then to the individual line.

IP addresses work the same way, but are "purchased" in a block of up to four groups by the Internet Service Providers (ISPs) for re-issue to their customers. Each block of number runs from 0 - 255, with some blocks set aside for non- or internal use. To see what your current IP address is, with respect to the Internet, visit this page. If you do a little math, four groups of up to 256 address combinations, subtracting the set-side reserved ones for interal use, yields what looks like a massive amount of numbers...but thinking again with the allegory of the existing phone system, we get area codes (the highest "subnet" of routing) added or broken apart each year as our population expands. Each area code can theorectically contain 10 million numbers, but each substation is given a three-digit prefix...and there are probably only a few places that physically have a thousand substations. The gist of this allegory is that some years back, all of the publically existing IP addresses were "owned" -- and only the ones belonging to the ISPs would be available for public use.

With the Internet, every device that speaks requires an individual and unique address -- either to itself, or to a gateway/router device that will act as a go-between. Broadband providers will rent or sell you a "modem" that is sometimes smart enoough to act as that go-between, but usually it only acts as a modem...a connector. So how do we take a limited set of addresses and give them out to anyone who needs them? Some ISPs start by putting gateways in place to "reuse" their banks of numbers, but most have to charge more for use. Once DSL picked up in people's minds, no everyone could be on at the same time...so people began to be "knocked off" while in use -- the Internet equivalent of the party line.

Log off the Internet and then back on and revisit the myipaddress.com page. It won't be long before you see this address to your machine changes -- possibly every time you do it, if you are in a high-density usage area. So long as you can get to the Internet, what does it matter, right? Ah, but suppose you are a small business wanting to access your computers from the road...or an individual wanting to host a web site on their computer. This address changing means you can't give the sequence to your friends or clients...they might end up with someone else! And such a string of numbers to remember...shouldn't you be able to provide a normal kind of Internet name, like "www.mywebsite.com"?

Enter a slick trick called dynamic DNS. DNS stands for domain name service, and is the way we link an Internet-kind of name to a unique IP address. Dynamic DNS is a way for that name resolution to always provide the right number...no matter how many times it changes. A simple program (the client) is installed on your computer, and periodically sends its current IP address back to a DNS hosting service, thus keeping the association up to date. No matter how many times it changes...even if it doesn't...dynamic DNS works.

Just like the hosting and name registration services, dynamic DNs also has many to choose from. KAUi's recommendation is the oldest and most reliable - DynDNS.com. Registering for a free dynamic DNS service is available, or for a small fee, it can be linked for any domain name. With the free service, you are limited to a block of domain name suffixes (such as dyndns.org...but you can put in anything for the first piece - myhomesite.dyndns.org). The site doesn't sell the client, but provides links to many free and low-cost software clients. Before you go and purchase one of these, check your router/gateway, as many of the newer ones have dyndns access built-in.

Once you have the client installed and configured, anyone in the world, by typing in the domain you set up, could theoretically access your machine. We say "theoretically" because if you have firewalls turned on in your computer or your router, or the ISP has such things blocked, the traffic may never get there. To turn on web hosting, for example, you will need to "open" port 80 in any or all of these walls. And if you are sharing your home or small business network through a single ISP connection, you will also have to create a port mapping between the router and the hosting machine, so that web traffic goes to the right one. These settings vary so much between vendors' equipment that we cannot go into detail here, but please feel free to contact us with assistance in getting this process set up at your location.

Dynamic DNS allows your static or mobile machine to have a "presence" on the Internet that others can find and use. Until the next generation of IP addressing (IP6) becomes available, it will be the only way to provide such services for the broadband "party line" users.


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by KAUi Software, Inc. Last modified 08/15/16