Domain Forwarding, Nameservers, Masking, Locking Exlained

Domain Forwarding

URL redirection is a technique on the world wide web for making a web page available under many URLs.

URL redirection may be used to redirect a URL to a page on the same web server, for example http://www.company.example/ may be the same as http://www.company.example/index.html.

Or it may be used to redirect a URL to a web page on another web server. This is typically used when virtual hosting is not available for some reason. For example, a customer of a web hosting company has a page at the URL http://www.hosting.example/~user/mybiz/ but wants to make that page available at the URL http://www.mybiz.example/. If the web hosting company does not offer virtual hosting, another company can provide a URL redirection service. (URL redirection is often called domain forwarding when used like this, but that term is misleading because the domain is not aliased in the Domain Name System; only the web pages at URLs using the domain are forwarded.
Forwarding just might be the best, hardest-working domain bargain going!

Now you can put any domain name to work, whether you've built a site for it or not. Just select a domain name (or names), add forwarding, and any visitor who types in that name will be redirected to the existing site you designate.

Forwarding is especially useful if you have a site with a long, complicated address. Now you can just register a simpler domain name (easily done using one of the less common top level domains, like .BIZ instead of .COM, for example) and then forward it. It's that easy.

Domain Masking

Domain masking lets you protect the address of a particular site, while still allowing customers to access the content. Here's how it works:

First, you register a domain name, say, domain1.com. This is only an address, though; domain1.com is not going to have its own web site. You use this address to display the content of another web site, say, forwarded-to.com.

So your visitors type in www.domain1.com and see the display from the forwarded-to.com web site. But they do not see the forwarded-to.com address.

NAMESERVER

This is a server that matches up the URL of a website (eg www.nictips.com) with its proper numeric IP address - it translates www.nictips.com into the unique numeric IP address (69.16.223.210). Whenever you request a web page the web browser must consult the domain name server to find out what the numeric translation of the URL is. This is necessary because computers only understand the numeric IP address, whereas we humans prefer to use meaningful and more memorable text.

The Domain NameServer provides a service very similar to the telephone directory. Humans remember names better than they do numbers. Computers can remember numbers easily and can process them faster than names. IP addresses are numbers that indicate the identity of a particular device on an internetwork. They are written as four decimal numbers separated by periods ("dots") and this is referred to as dotted notation.
It would be difficult to remember the IP address for Microsoft's World Wide Web server, but it is easy to remember "www.microsoft.com". The Domain Name Server acts like the white pages of the telephone directory. It maintains a list of network names and their corresponding IP addresses. So the entry for www.microsoft.com would look something like this

www.microsoft.com 192.205.171.10

The web browser, when given "www.microsoft.com" as a destination, requests the IP address from the Domain Name Server (DNS) daemon. The DNS daemon looks in its database for the name and returns the IP address. The web browser then sends its request to that IP address in order to retrieve the Microsoft home page. This is referred to as a forward DNS lookup.

Sometimes an IP address is given instead of a name. In this case, the DNS daemon performs what is referred to as a reverse DNS lookup. It has a database that is set up so it can be searched on the IP address in order to find the corresponding name. So the entry for 192.205.171.10 would look something like this

192.205.171.10 www.microsoft.com

This is similar to the phone lists that those annoying telemarketers use to call you during dinner to hawk their wares. The list contains phone numbers in numerical order, with the name of the resident to the right of the number. The reverse DNS lookup works the same way.

There are millions of IP addresses. A single DNS server could not possible be expected to contain all the addresses and their corresponding names, so the DNS databases are distributed in a hierarchical manner. There are "root" DNS servers that basically remember the locations of other name servers which are authoritative for their domains. This means that each individual network must maintain a DNS database and daemon for the IP addresses that can be reached via that network. In this way, a DNS search proceeds from the "root" name servers downward, getting progressively closer to the name server that actually knows the name and IP address of the destination in question.

If you see an IP address without a corresponding reverse DNS entry, it is because the site in question wants to hide the identity of the host at that address, or the network administrator is too busy to add the address to the reverse file. Spammers usually want to hide the name of the spam host to avoid the consequences of spamming. A few site administrators think that going nameless is a good security measure since it provides no additional information to potential attackers.

Some network servers will refuse a connection to a host that has no reverse DNS entry, since their administrator believes that any unidentified host accessing the site is a potential security risk.

There are usually two, and sometimes three, nameservers for a particular domain. The primary nameserver is consulted first by the resolver on a host machine in order to obtain DNS information. If the primary does not respond, the resolver will attempt to obtain the information from the secondary. If a tertiary nameserver is listed in the InterNIC database (and hence in the root nameservers' databases), it will be queried if the secondary nameserver does not respond. If no DNS server responds, you will see a "No DNS entry" error message from your application.

DNS uses both TCP and UDP. It uses UDP datagrams for DNS lookups. It uses TCP however for zone transfers. A zone transfer is the method used by secondary nameservers to obtain the latest DNS information from the primary nameserver.