Tuesday, October 23, 2012

Windows Server 2012 - Using Domain Name System

DNS is a name-resolution service that resolves computer names to IP addresses. Using DNS, the fully qualified host name computer84.cpandl.com, for example, can be resolved to an IP address, which allows it and other computers to find one another. DNS operates over the TCP/IP protocol stack and can be integrated with WINS, Dynamic Host Configuration Protocol (DHCP), and Active Directory Domain Services.
DNS organizes groups of computers into domains. These domains are organized into a hierarchical structure, which can be defined on an Internet-wide basis for public networks or on an enterprise-wide basis for private networks (also known as intranets and extranets). The various levels within the hierarchy identify individual computers, organizational domains, and top-level domains. For the fully qualified host name computer84.cpandl.com, computer84 represents the host name for an individual computer, cpandl is the organizational domain, and com is the top-level domain.

Top-level domains are at the root of the DNS hierarchy; they are also called root domains. These domains are organized geographically, by organization type, and by function. Normal domains, such as cpandl.com, are also referred to as parent domains. They’re called parent domains because they’re the parents of an organizational structure. Parent domains can be divided into subdomains that can be used for groups or departments within an organization.

Subdomains are often referred to as child domains. For example, the fully qualified domain name (FQDN) for a computer within a human resources group could be jacob.hr.cpandl.com. Here, jacob is the host name, hr is the child domain, and cpandl.com is the parent domain.

Active Directory domains use DNS to implement their naming structure and hierarchy. Active Directory and DNS are tightly integrated, so much so that you should install DNS on the network before you can install domain controllers using Active Directory. During installation of the first domain controller on an Active Directory network, you’re given the opportunity to install DNS automatically if a DNS server can’t be found on the network. You are also able to specify whether DNS and Active Directory should be fully integrated. In most cases, you should respond affirmatively to both requests. With full integration, DNS information is stored directly in Active Directory. This allows you to take advantage of Active Directory’s capabilities. The difference between partial integration and full integration is very important:

» Partial integration With partial integration, the domain uses standard file storage. DNS information is stored in text-based files that end with the .dns extension, and the default location of these files is %SystemRoot%\System32\Dns. Updates to DNS are handled through a single authoritative DNS server. This server is designated as the primary DNS server for the particular domain or an area within a domain called a zone. Clients that use dynamic DNS updates through DHCP must be configured to use the primary DNS server in the zone. If they aren’t, their DNS information won’t be updated. Likewise, dynamic updates through DHCP can’t be made if the primary DNS server is offline.

» Full integration With full integration, the domain uses directory-integrated storage. DNS information is stored directly in Active Directory and is available through the container for the dns Zone object. Because the information is part of Active Directory, any domain controller can access the data and a multimaster approach can be used for dynamic updates through DHCP. This allows any domain controller running the DNS Server service to handle dynamic updates. Furthermore, clients that use dynamic DNS updates through DHCP can use any DNS server within the zone. An added benefit of directory integration is the ability to use directory security to control access to DNS information.

If you look at the way DNS information is replicated throughout the network, you can see more advantages to full integration with Active Directory. With partial integration, DNS information is stored and replicated separately from Active Direc¬tory. Having two separate structures reduces the effectiveness of both DNS and Ac¬tive Directory and makes administration more complex. Because DNS is less efficient than Active Directory at replicating changes, you might also increase network traffic and the amount of time it takes to replicate DNS changes throughout the network.

To enable DNS on the network, you need to configure DNS clients and servers. When you configure DNS clients, you tell the clients the IP addresses of DNS servers on the network. Using these addresses, clients can communicate with DNS servers anywhere on the network, even if the servers are on different subnets.

When you install the DNS Server service on an RODC, the RODC is able to pull a read only replica of all application directory partitions that are used by DNS, includ¬ing ForestDNSZones and DomainDNSZones. Clients can then query the RODC for name resolution as they would query any other DNS server. However, as with direc¬tory updates, the DNS server on an RODC does not support direct updates. This means that the RODC does not register name server (NS) resource records for any Active Directory–integrated zone that it hosts. When a client attempts to update its DNS records against an RODC, the server returns a referral to a DNS server that the client can use for the update. The DNS server on the RODC should receive the updated record from the DNS server that receives details about the update using a special replicate-single-object request that runs as a background process.

Windows 7 and later releases add support for DNS Security Extensions (DNSSEC). The DNS client running on these operating systems can send queries that indicate support for DNSSEC, process related records, and determine whether a DNS server has validated records on its behalf. On Windows servers, this allows your DNS serv¬ers to securely sign zones and to host DNSSEC-signed zones. It also allows DNS serv¬ers to process related records and perform both validation and authentication.

Source of Information : Windows Server 2012 Pocket Consultant 2012

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