Tue, 21 Oct 2008
/Admin/dynamicDNS:
Dynamic DNS Basics
You already have a broadband internet account at home, you have some
unused hardware laying around, you know how to setup and configure a
server, so why not save a few bucks and run your server at home?:
- The first reason tends to be more of a myth then a reason, really,
for most people in most parts of the world: "there is too much
downtime". I think most people's downtime is measured in minutes per
day. For a low-volume / hobbyist website: not a problem.
- Most cheap(er) retail broadbrand accounts are assigned a "Dynamic
IP"[1] which means the "address" of your server is constantly changing.
This needs to be taken care of using a "Dynamic DNS"[2] service, but
that tends to be not too difficult, and there are a number of free such
services out there to do just that.
- Many large and popular public e-mail services automatically classify
all e-mail coming from an e-mail server running on a Dynamic IP as SPAM,
so running an e-mail server on your home-based server is probably not a
good idea.
So if you are not intending on using an e-mail server on your server
at home, and whatever service(s) you were planning on providing
(website?) can absorb a little downtime from power and ISP outages, it
is a go. Especially if you want to run some very particular software
that is not commonly available from cheap hosting services, leaving you
with the relatively more expensive option of renting your own server.
Dynamic DNS is really very simple. Computers understand numeric IP[4]
("Internet Protocol") addresses of the form 111.222.333.444. Humans
understand alphanumeric internet addresses of the form www.myname.com.
When you type www.myname.com into your web browser (or any other network
application) www.myname.com must be pointing at the correct
111.222.333.444 for it to work. That is all DNS ("Domain Name Service")
really is. "Dynamic DNS" just refers to the situation where the numeric
IP address changes frequently, and the slightly specialized methods used
to keep www.myname.com and 111.222.333.444 in sync when this is the
case.
In your home, you will be faced with two general options:
- Use a commercial off-the-shelf router, with your server operating
behind the router.
- Build your own router from one of your own computers (also not
terribly difficult if you use my method[3]) or in fact allow your server
to perform the functions of both router and server.
Why would you want the added complication of the second option?
Because somewhere on your network you must run a piece of software that
will update www.myname.com with the new 111.222.333.444 whenever the
latter changes. That piece of information is a property of the network
interface that is directly connected to the internet, located on your
router. If you are using a commercial off-the-shelf router, that
information can be hard or impossible to extract from it. Some routers
are pre-configured to talk to certain Dynamic DNS providers, and maybe
some of them actually work in this role. I have so far not been so lucky
as to find one that does. If the router is your own machine, whose
hardware and software you have complete control of, everything tends to
be a bit easier.
That said, if you are sharing an internet connection, you might not
have a choice in the router department.....
Just to be clear, while probably achieving the opposite, the usual
way to tell your Dynamic DNS service that you have a new numeric IP
address is to send it a very simple message using http, and that message
AUTOMATICALLY must contain your current public IP address (your new
numeric address). The Dynamic DNS service then just strips this new IP
out of the message. The complication is, most Dynamic DNS services do
not want you to waste their resources by sending them this http message
every two minutes. Most will freeze your account if you do. They want to
hear from you only when the address really has changed, which is why the
Dynamic DNS software client running on your network must know when your
IP address changes, so that it then will know it is time to tickle the
Dynamic DNS service provider.
[1] http://en.wikipedia.org/wiki/Dynamic_ip
[2] http://en.wikipedia.org/wiki/Dynamic_DNS
[3] http://blog.langex.net/index.cgi/Admin/LAN/build-your-own-router.html
[4] http://en.wikipedia.org/wiki/Ip_address
posted at: 11:30 | path: /Admin/dynamicDNS | permanent link to this entry
