23-03-2012, 12:11 PM
Domain Name Service
Domain Name Service.docx (Size: 122.17 KB / Downloads: 36)
Overview to DNS in Microsoft Windows 2000
To facilitate communications between computers, computers can be given names within a name space. The specific name space defines the rules for naming a computer, and for how names are resolved into IP addresses. When one computer communicates with other computers, it must resolve, or convert, a computer name into an IP address based on the rules of the name space being used. This resolution will be done by a name-resolution service.
There are two main name spaces, and name-resolution methods, used within Windows 2000: NetBIOS, implemented by Windows Internet Naming Service (WINS) (described in Chapter 17), and the DNS, described in this chapter. Windows 2000 also provides support for other name spaces, such as Novell Netware and Banyan Vines, although discussion of these is outside the scope of this book.
What Is DNS?
The DNS is an IETF-standard name service. The DNS service enables client computers on your network to register and resolve DNS domain names. These names are used to find and access resources offered by other computers on your network or other networks, such as the Internet. The following are the three main components of DNS:
• Domain name space and associated resource records (RRs) A distributed database of name-related information.
• DNS Name Servers Servers that hold the domain name space and RRs, and that answer queries from DNS clients.
• DNS Resolvers The facility within a DNS client that contacts DNS name servers and issues name queries to obtain resource record information.
Key DNS Terms
This section describes the key components of the DNS and defines key DNS terms.
Domain Name Space
The domain name space is a hierarchical, tree-structured name space, starting at an unnamed root used for all DNS operations. In the DNS name space, each node and leaf in the domain name space tree represents a named domain. Each domain can have additional child domains. Figure 16-1 illustrates the structure of Internet domain name space.
Resource Records (RR)
A resource record is a record containing information relating to a domain that the DNS database can hold and that a DNS client can retrieve and use. For example, the host RR for a specific domain holds the IP address of that domain (host); a DNS client will use this RR to obtain the IP address for the domain.
Each DNS server contains the RRs relating to those portions of the DNS namespace for which it's authoritative (or for which it can answer queries sent by a host). When a DNS server is authoritative for a portion of the DNS name space, those systems' administrators are responsible for ensuring that the information about that DNS name space portion is correct. To increase efficiency, a given DNS server can cache the RRs relating to a domain in any part of the domain tree.
There are numerous RR types defined in RFCs 1035 and 1036, and in later RFCs. Most of the RR types are no longer needed or used, although all are fully supported by Windows 2000. Table 16-2 lists the key RRs that might be used in a Windows 2000 network. (For more detail on the contents of specific RRs, see the "DNS Resource Records" section later in this chapter.)
Domain Name Service.docx (Size: 122.17 KB / Downloads: 36)
Overview to DNS in Microsoft Windows 2000
To facilitate communications between computers, computers can be given names within a name space. The specific name space defines the rules for naming a computer, and for how names are resolved into IP addresses. When one computer communicates with other computers, it must resolve, or convert, a computer name into an IP address based on the rules of the name space being used. This resolution will be done by a name-resolution service.
There are two main name spaces, and name-resolution methods, used within Windows 2000: NetBIOS, implemented by Windows Internet Naming Service (WINS) (described in Chapter 17), and the DNS, described in this chapter. Windows 2000 also provides support for other name spaces, such as Novell Netware and Banyan Vines, although discussion of these is outside the scope of this book.
What Is DNS?
The DNS is an IETF-standard name service. The DNS service enables client computers on your network to register and resolve DNS domain names. These names are used to find and access resources offered by other computers on your network or other networks, such as the Internet. The following are the three main components of DNS:
• Domain name space and associated resource records (RRs) A distributed database of name-related information.
• DNS Name Servers Servers that hold the domain name space and RRs, and that answer queries from DNS clients.
• DNS Resolvers The facility within a DNS client that contacts DNS name servers and issues name queries to obtain resource record information.
Key DNS Terms
This section describes the key components of the DNS and defines key DNS terms.
Domain Name Space
The domain name space is a hierarchical, tree-structured name space, starting at an unnamed root used for all DNS operations. In the DNS name space, each node and leaf in the domain name space tree represents a named domain. Each domain can have additional child domains. Figure 16-1 illustrates the structure of Internet domain name space.
Resource Records (RR)
A resource record is a record containing information relating to a domain that the DNS database can hold and that a DNS client can retrieve and use. For example, the host RR for a specific domain holds the IP address of that domain (host); a DNS client will use this RR to obtain the IP address for the domain.
Each DNS server contains the RRs relating to those portions of the DNS namespace for which it's authoritative (or for which it can answer queries sent by a host). When a DNS server is authoritative for a portion of the DNS name space, those systems' administrators are responsible for ensuring that the information about that DNS name space portion is correct. To increase efficiency, a given DNS server can cache the RRs relating to a domain in any part of the domain tree.
There are numerous RR types defined in RFCs 1035 and 1036, and in later RFCs. Most of the RR types are no longer needed or used, although all are fully supported by Windows 2000. Table 16-2 lists the key RRs that might be used in a Windows 2000 network. (For more detail on the contents of specific RRs, see the "DNS Resource Records" section later in this chapter.)