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The ins and
outs of DNS and how it effects your
domain:
Understanding
DNS and Name Servers:
This is an area, which causes a
great deal of confusion amongst both webmasters and end user
clients. Before we go any further, let's look at this quick
analogy: DNS can be considered something similar to that of
a phone book. When you move from one location to another,
your last name stays the same, but your phone number may
change. In order to point your name to the new phone number,
you must contact the telephone service provider, which will
assign you the new phone number. In addition, they update
all directory information data basis to reflect you as
pointing to this new phone number.
What
is DNS?
DNS stands for "Domain Name Server." The domain name server
acts like a large telephone directory in that it's the
master database, which associates a domain name such as
(http://www.mydomain.com) with the appropriate IP number.
Consider the IP number something similar to a phone number:
When someone calls http://www.myhost.com/, your ISP looks at
the DNS server, and asks "how do I contact myhost.com?" The
DNS server responds, it can be found at: 157.238.46.231. As
the Internet understands it, this can be considered the
phone number for the server, which houses the
http://www.myhost.com web site.
Where
are all of the DNS records
kept?
This is slightly more complicated, but for the purpose of
this overview, we'll try to keep it as general as possible.
There are 2 basic places DNS records reside:
International Root name servers (13 exist throughout the
world though this is increasing)
Your domain register, where your current DNS settings
reside.
When you register/purchase your domain name on a particular
"register's name server", your DNS settings are kept on
their server, and in most cases point your domain to the
Name Server of your hosting provider. This Name Server is
where the IP number (currently associated with your domain
name) resides.
The entire hierarchy is somewhat involved, but in short, the
world Root Name Servers can be considered the master listing
of all DNS records, and there are currently 13 of them in
the world. These name servers are where all the master DNS
records are kept. The DNS server of your ISP will typically
query the Root Name Servers once every 24-hours. This is how
they update all of their DNS tables, which in turn, resolve
www requests to the IP number of the server they reside
on.
Changing
your Name Server settings, so your domain points to your
host account:
Your "Name Server Settings" must be updated to point to your
account on your host company server. You originally
purchased your domain name from a register, and this
register is where your current DNS settings reside. That is,
unless you transferred your domain name to an alternate
register, in which case, you would control your DNS settings
from there.
The "Register" your domain resides on, communicates your
'current' DNS settings with the International Root name
servers, which is turn share this information with ISP's,
routers, and cache engines around the world. In essence,
it's like a worldwide directory that other computers can
refer to when they want to match a domain name with its
associate IP number. This IP number is how the particular
server your website resides on is located.
Accessing
your domain
manager:
Simply go to your domain register's web site, and look
around for links, which point to something like, domain
manager, manage domain, or something of that administrative
nature. In your welcoming email, you were sent DNS settings,
which look similar to this example:
NS1.MYHOST.COM
NS2.MYHOST.COM
Most of the newer registers have turned this into a 5-minute
process. You simply login to the register, select 'manage
domain' and you'll be presented with an option to update
your new DNS numbers. Contrary to popular belief, Network
Solutions 'now' also provides an online interface to change
these settings, so this process with them is no longer as
complicated as it use to be, however it's still not as
simple as the OPEN SRS based systems. If your
particular register 'does not' provide a domain manager of
some type, then you'll need to send them a message
requesting a change of DNS. This is an unlikely scenario, as
most every register now allows you to manage your own domain
settings from a web based interface.
Once you've accessed the "management interface" of your
domain name, look for a setting, which says "change or
manage DNS settings." In most cases, you can simply cut and
paste the DNS settings we've sent you directly into the
spaces, which correspond to your DNS management settings.
Remember, the DNS settings we're displaying here are an
"example."
The 3
to 4 day propagation period - Understanding what happens
during this time
frame:
In short, patience is a virtue. Remember what we talked
about earlier in this chapter regarding the shear size and
scope of the worlds DNS system? In short, when you change
your DNS settings, these new settings must propagate
throughout the worlds DNS servers. It also means that every
ISP (Internet Service Provider), must update their DNS
records to reflect these new changes, which in most cases,
is done automatically every 24 hours, but not always
however...
Where
do the Root Name Servers receive their information
from?
The Root Name Servers will query "domain registers" several
times a day. Domain Registers, being entities such as
Network Solutions, and the newer OPEN SRS based systems. The
Root Name Servers will gather this information from the many
registers now in existence, and update their master records
accordingly. Now your ISP must access the Root Name Servers,
and update their DNS records, which reside on their 'local'
DNS server. This process is fully automated and most ISP's
will check the Root Name Servers for updates every 24-hours.
Beware however, that some lame ISP's will delay this process
for as much as 2 to 4 days in some cases. If that happens,
it will no doubt cause additional confusion, as everyone
else will be reaching your new account on our servers except
you. This is because your ISP has not updated their DNS
records, and or have not cleared their DNS cache, which
means they'll still be pointing your domain name to your old
server. If it's a new domain name you've registered, then
you'll receive a blank "Site Not Found Page."
DNS Cache
and your ISP:
There is also the issue of DNS cache, which is something we
won't go into great detail about here, but here's the short
version. Every time you access a site from your ISP, they
cache the URL, as well as its associated IP number. If their
network is properly setup, these DNS cache records should
"Expire" at least every 24-hours. If they did not (which is
often the case), you'll experience this: You enter your
http://www.mydomain.com/
URL, and it keeps taking you back to your old server
account.
In a large number of cases, it's the result of an ISP who
"Did Not" configure their servers to "Expire" the DNS cache
records at the appropriate intervals. Unfortunately, this
adds additional confusion to their clients, and especially
the ones whom are trying to point their domain name to a new
server. Yes, it will make you want to scream sometimes,
however if you understand whom is actually at fault, then
you'll know who to scream at :)
The
DNS propagation process is not limited to
ISP's!
HA.. Just when you thought you had it all figured out!
Unfortunately, there's more folks. The Internet itself must
update/clear its DNS cache as well. When we say the
Internet, we mean the numerous intermediate "points of
access" you're routed through before reaching your final
destination. For the most part, these intermediate points of
access consist of "Internet Routers" and "Internet Caching
Engines." These too, maintain their own DNS cache, which
assists them in routing traffic/resolving URL's to the
correct destination IP's. Don't worry though, as Internet
routers are usually faster at clearing their DNS cache than
ISP's are.
What
to expect during this 2 to 4 day propagation
period:
In most cases, the propagation process will take at least 48
hours to complete. The first thing that happens is the
"World Root Name Servers" will check all of the various
"Domain Registers for updates. Ok, so now the Root Name
Servers have done their job. The rest of it is up to the
many ISP providers who "should be" updating their DNS
records (at least every 24 hours), but a number of them will
not.
Side
effects that can be expected during the propagation time
frame:
It's perfectly normal for strange things to happen within
the 48-hour propagation period, but sometimes longer. While
we could provide a full list of all the anomalies that can
occur during the DNS propagation period, we'll stick to some
of the most common scenarios that most people
experience:
HELP! My friends can reach my
new site, but I'm still being directed to the OLD ONE!
This is a class case of your friends ISP (who did update
their DNS records), but yours unfortunately did not. As a
result, your ISP is still pointing your domain name to the
old DNS record, which is your old hosting account. Wait a
couple of more days, and if it appears that everyone but you
can access your new account, then contact your ISP and tell
them to expire their old DNS cache records.
WOW! http://www.mydomain.com
was taking me to my new hosting account just a minute ago,
but when I try it now, I'm being taken back to my old
hosting account - what's up with this?
In all likelihood, your ISP may be in the process of
clearing their DNS cache, and or updating their local DNS
server records. During this small interval, it's normal to
fluctuate between the new and old web site, as the old DNS
records may not have completely expired from their cache
yet. Give it another several hours and it should be
fine.
HEY! My new site comes up
for me, but my friends are being directed to my old
one!
Break out the coffee and donuts, and consider yourself
lucky. Your ISP is on the ball and updates DNS records/
clears DNS cache in short regular intervals. Your friends
may be using an ISP, which is not as fast, and or efficient
at doing so. The only remedy for this is time. Eventually,
the other ISP's DNS cache will expire and be replaced with
the updated DNS records.
What's going on with my email?
When I try to access it, I receive a "host does not exist"
or a "cannot authenticate" error
message.
This can happen for a number of reasons, but in most cases,
it's because your new DNS records have not fully completed
the propagation process yet. Consequently, you may be trying
to access your old email account on your "old server", which
you may have already cancelled, or it's in a state of DNS
flux, which means it points to the new server one moment,
and the next, points back to the old server.
Give it some more time and it will eventually settle
down.
It's been over a week.
Everybody else can access my new site except
me!
Was your domain originally hosted by your ISP? If so, they
may not have deleted this entry in their DNS files. This
results in you, and or anyone else accessing the net from
this "particular ISP" being directed to your old web site on
their servers. A number of ISP's forget this small detail,
which can result in weeks of utter confusion and
frustration. If this is happening to you, contact your ISP
and make sure they've made the necessary changes to their
DNS records.
Checking
your DNS update
status:
In the event you're becoming impatient, and or are wondering
if the rest of the world outside of your ISP can access your
new site, you can proxy yourself to another network and test
it there. In many cases, you'll be surprised to see your
site responding perfectly, yet when you attempt it directly
from your ISP's servers, it does not exist.
There are several services, which allow anonymous surfing
across the net. While this is not the intent here, they can
be used for trouble shooting domain resolution problems.
How? Because they proxy you through their network,
which means your URL requests are controlled by "their" DNS
cache records. These services update/expire their DNS cache
far more often than ISP's, which makes them well suited for
testing your domain name through a network, which operates
with the latest DNS updates across the web.
To run this check, you can try accessing your site through
http://www.anonymizer.com/
They allow you to enter an URL, and
proxy your request through their servers. If your site is
accessible from their servers, then chances are your ISP has
yet to expire their old DNS cache records.
Checking
when the DNS propagation period is
over:
One easy way to check and see if your domain is answering to
our servers yet, is checking the URL http://www.yourdomain.com
and see if it shows our holding page. When it does, you'll
know your domain name is answering to your account on our
servers, and has been officially transferred. If it is not
yet complete, you will get an error message.
The
personal DNS (for advanced webmasters).
Let's say your company was www.acmewebhost.com. If you
desire, you could setup your own custom branded DNS, which
could display as:
DNS1.MYWEBHOST.COM
DNS2.MYWEBHOST.COM
This provides a somewhat more professional look to your
customers. In addition, if someone does a WHOIS lookup on
your domain name, it appears as your personal DNS, as
opposed to your hosting company. Not really a big deal, but
some webmasters do not want to advertise the host they're
with, as they feel it does not portray a professional and
independent look.
There is no superior advantage to having your own name
server unless you're a reseller, and or a web designer who
is also planning on hosting the websites they
build.
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