DNS Definition according to the terminology is the Domain Name System, a complex and difficult topic in networking system but understanding the concepts is very essentials in mastering Windows server networking infrastructure.
Regarding the name resolution in a networking system, DNS definition is a resolver – a mechanism to resolve computer names to the IP addresses. Unlike lower-level services, people and applications tend to connect to network computers by specifying a name rather than IP address. It is much more difficult for people to memorize numbers (IP addresses) rather than names. There are two naming systems coexist in Windows Server 2003 network: NetBIOS and DNS that require separate mechanisms to resolve their names to IP addresses.
Regarding the naming systems, DNS definition is a superior naming system which offers superior scalability, security, and compatibility with the Internet compared to NetBIOS. NetBIOS is often used as a backup name resolution method for computers located on the same network segment and it is compatible with older windows features. But in Windows Server 2003 networks, DNS name resolution takes priority over NetBIOS name resolution which prioritization is handled by the DNS Client service.
DNS Name Space
DNS definition regarding the naming services is based is a hierarchical and logical tree structure called the DNS namespace. In the root top-level domains are centrally managed, while the second-level domains and below are managed by the owners. Root DNS servers only maintain entries for top level as referral system.
DNS Name Space
The namespace of a DNS domain describes a relationship between hosts. If a host named Srv1 is in the domain Business.com, its fully qualified domain name, or FQDN, would be srv1.Business.com. Another host, Srv2, in the same domain would have an FQDN of srv2.Business.com
Domains can be joined into a hierarchy based on a contiguous namespace. A DNS domain named branch1.Business.com would be a child of the domain Business.com. The figure below shows an example DNS hierarchy with several child domains.
DNS hierarchy
DNS definition regarding the top domain, or root, in a DNS hierarchy is identified by a trailing dot (.) at the end of the FQDN. This dot serves the same purpose as the leading slash in a file system path. It defines the top of the tree. A DNS resolver parses the FQDN starting at the leftmost element of the name and ending at the root next to the dot at the right side of the FQDN.
The trailing dot at the end of a FQDN is not generally shown in DNS documentation, and Windows DNS tools add it automatically, so it’s easy to forget it’s there. When troubleshooting, though, it’s a good idea to add the trailing dot just to be on the safe side.
Hosts File
Before a client goes to the trouble to make a DNS query to resolve a host name into an IP address, it first consults a local file called Hosts. Here is an example Hosts file. The pound sign (#) denotes a comment:
10.1.1.1 dc01.business.com #domain controller in Business
10.1.1.2 dc02.business.com #another domain controller in Business
10.3.1.27 srv1.branch1.business.com #general purpose server in branch office
The host name specified by a TCP/IP application must exactly match the entry in the Hosts file to get a successful lookup. For example, using the preceding Hosts file, a ping to dc01 would not succeed, but a ping to dc01.Business.com would succeed. If the name is not in the Hosts file, the client then uses DNS to resolve the name.
Primary and Secondary Name Servers
DNS definition in a conventional DNS server stores its resource records in a zone file. Windows-based DNS servers give zone files a .DNS extension. For example, the zone file for the Business.com zone would be Business.com.dns. The zone files are stored in the \Windows\System32\DNS folder. A zone can also be integrated into Active Directory, in which case the resource records are stored as objects in the AD database.
For fault tolerance and performance, it is a good idea to install one or more secondary name servers. A secondary name server hosts a read-only copy of the zone file. The secondary servers pull copies of the zone from primary name servers or from other secondary servers.
A name server that simply caches the results of queries so it can pass the information along to its clients is called a caching-only name server.
This reliance on a single primary name server is a weakness of classic DNS. But, Active Directory Integrated zones overcome this weakness by making any domain controller running DNS a primary name server for its zones.
See also:
- Configuring the router
- Virtual LAN
- Cisco ASA5500 adaptive security appliance
- What is ISDN
- WAN Technologies
it was a good piece of knowledge.