What is ManagedDNS and DNS zone?
Posted by Andy Williams, Last modified by on 28 June 2007 08:48 AM
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 Resource Records] in a Zone File, which contains the domain name and IP address mappings for computers contained within that Zone. This zone file is also referred to as 'DNS Zone'. A 'ManagedDNS' is a DNS zone file hosted at the domain name registry.
Indichosts.net gives you complete control over the following Resource Records by using our Managed DNS Service:
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 220.127.116.11 (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.
A MX Record identifies the mail server(s) responsible for a domain name. When sending an e-mail to email@example.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.
A 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.
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 companies register their multiple domain names for their brand-names but still wish to maintain a single website. In such cases, a CNAME Record maybe used to forward traffic to their actual website. For example, www.abc.in could be CNAMEd to www.abc.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 adding a CNAME-record for the www name pointing to the short name [while creating an A Record for the short name (without www)].
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.
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 a 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.
A Text Record provides the ability to associate some text with a domain or a subdomain. This text is meant to strictly provide information and has no functionality as such. A TXT Record can store upto 255 characters of free form text. This record is generally used to convey information about the zone. Multiple TXT records are permitted but their order is not necessarily retained.
For example, you may add a TXT Record for yourname.com with the value as "This is my mail server". Here if anybody was checking ALL or TXT records of yourname.com, they would notice the above text appearing in the TXT record.
TXT Record is also used to implement the Sender Policy Framework (SPF) and DomainKeys specifications.
Sender Policy Framework (SPF)
Sender Policy Framework is an extension to the Simple Mail Transfer Protocol (SMTP). SPF allows software to identify and reject forged addresses in the SMTP MAIL FROM (Return-Path), a typical nuisance in e-mail spam.
SPF allows the owner of a domain to specify their mail sending policy, e.g. which mail servers they use to send mail from their domain. The technology requires two sides to work in tandem -
DomainKeys is an e-mail authentication system (developed at Yahoo!) designed to verify the authenticity of the E-mail sender and the message integrity (i.e,. the message was not altered during transit). The DomainKeys specification has adopted aspects of Identified Internet Mail to create an enhanced protocol called DomainKeys Identified Mail (DKIM).
Each Zone contains one SOA Record, which holds the following parameters 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.).