The Domain Name System [DNS] is a distributed database, arranged hierarchically, containing records for domain names. The DNS system's main aim is to match a domain name to an IP Address. In order to fulfill this role, the DNS Server contains Records [called as Resource Records] in a Zone File, which contains the domain name and IP address mappings for computers contained within that Zone. All Resource Records have a TTL [Time To Live], specifying the number of seconds other DNS servers and applications are allowed to cache the record.

Most Web Hosting companies, do not provide you with an interface to manage your own DNS Records and/or the ability to select multiple providers for various Services like Web Hosting, Mail Hosting, etc.

JBC Dynamics gives you complete control over the following Resource Records by using our Managed DNS Service:

Address Record [A Record] - The A Record is the most basic and the most important DNS record type. They are used to translate human friendly domain names such as "www.domain.com" into IP-addresses such as 1.2.3.4 (machine friendly numbers).

When you wish to host your domain name, you will be provided with an IP address that needs to be set as an A Record for that particular domain name.

Mail Exchanger [MX] Record - An MX Record identifies the mail server(s) responsible for a domain name. When sending an e-mail to user@xyz.com, your mail server must first look up the MX Record for xyz.com to see which mail server actually handles mail for xyz.com (this could be mail.xyz.com - or someone else's mail server like mail.isp.com). Then it looks up the A Record for the mail server to connect to its IP-address.

An MX Record has a Preference number indicating the order in which the mail server should be used (only relevant when multiple MX Records are defined for the same domain name). Mail servers will attempt to deliver mail to the server with the lowest preference number first, and if unsuccessful continue with the next lowest and so on.

Canonimical Name [Alias / CNAME] Record - CNAME Records are domain name aliases. Often computers on the Internet have multiple functions such as Web Server, FTP Server, Chat Server, etc. To mask this, CNAME Records can be used, to give a single computer multiple names (aliases).

Sometimes a single server computer hosts many different domain names (take ISPs), and so CNAME Records may be defined such as www.abc.com = www.xyz.com.

The most popular use of the CNAME Record type, is to provide access to a Web Server using both the standard www.domain.com and domain.com (without the www). This is usually done by creating an A Record for the short name (without www), and a CNAME-record for the www name pointing to the short name.

CNAME Records can also be used when a computer or service needs to be renamed, to temporarily allow access through both the old and new name.

Authoritative Name Server [NS] Record - NS Records identify DNS servers responsible (authoritative) for a Zone. A Zone should contain one NS Record for each of its own DNS servers (primary and secondaries). This mostly is used for Zone Transfer purposes (notify). These NS Records have the same name as the Zone in which they are located.

But the most important function of the NS Record is Delegation. Delegation means that part of a domain is delegated to other DNS servers.

You can also delegate sub-domains of your own domain name (such as subdomain.yourname.com) to other DNS servers. An NS Record identifies the name of a DNS server, not the IP Address. Because of this, it is important that an A Record for the referenced DNS server exists, otherwise there may not be any way to find that DNS server and communicate with it.

If an NS Record delegates a sub-domain (subdomain.yourname.com) to a DNS Server with a name in that sub-domain (ns1.subdomain.yourname.com), an A Record for that server (ns1.subdomain.yourname.com) must exist in the Parent Zone (yourname.com). This A Record is referred to as a Glue Record, because it doesn't really belong in the Parent Zone, but is necessary to locate the DNS Server for the delegated sub-domain.

Start of Authority [SOA] Record - Each Zone contains one SOA Record, which holds the following properties for the Zone

Name of Primary DNS Server
The domain name of the Primary DNS Server for the Zone. The Zone should contain a matching NS Record.

Mailbox of the Responsible Person
The email address of the person responsible for maintenance of the Zone.

Serial Number
Used by Secondary DNS Servers to check if the Zone has changed. If the Serial Number is higher than what the Secondary Server has, a Zone Transfer will be initiated. This number is automatically increased by our Servers when changes to the Zone or its Records are made.

Refresh Interval
How often Secondary DNS Servers should check if changes are made to the zone.

Retry Interval
How often Secondary DNS Server should retry checking, if changes are made - if the first refresh fails.

Expire Interval
How long the Zone will be valid after a refresh. Secondary Servers will discard the Zone if no refresh could be made within this interval.

Minimum (default) TTL
Used as the default TTL for new records created within the zone. Also used by other DNS Server to cache negative responses (such as record does not exist, etc.).