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Reference: Cisco: Internetworking Basics
After receiving your assigned network number and giving IP addresses to your hosts, the next task is to assign names to the hosts and determine how you will handle name services on your network. You will use these names when you initially setup your network and, later, for expanding your network through routers or PPP.
The TCP/IP protocols locate a machine on a network by using its IP address. However, humans find it easier to identify a machine if it has an understandable name. Therefore, the TCP/IP protocols (and the Solaris operating environment) require both the IP address and the host name to uniquely identify a machine.
From a TCP/IP perspective, a network is a set of named entities. A host is an entity with a name. A router is an entity with a name. The network is an entity with a name. A group or department in which the network is installed can also be given a name, as can a division, a region, or a company. In theory, where is virtually no limit to teh hierarchy of names that can be used to identify a network and its machines. There term for these named entities is domain.
Many sites simply allow users to pick their own host names for their machines. Servers also require at least one host name, which is associated with the IP address of its primary network interface.
Network administrators must ensure that each host name in your domain is unique. In other words, no two machines on your network could both have the name "jeff", although the machine "jeff" might have multiple IP addresses.
When planning a network, make a list of IP addresses and their associated host names for easy access during the setup phase. The list can help identify and verify that all host names are unique.
Using popular operating systems like Solaris and Linux, you are already provided with the options of four types of name services - local files, NIS, NIS+, LDAP, and DNS. Name services maintain crucial information about the machines on a network, such as the host names, IP addresses, Enternet addresses, and the like.
When installing the operating system on most systems, you will need to supply the host name and IP address of the server, clients, or standalone machine as part of the procedure. The installation program will enter this information into a network database called the hosts database. The hosts database is one of a set of network databases that contain information necessary for TCP/IP operations on your machine. These databases are read my the name service you select for your network.
Setting up the network databases is a critical part of network configuration. Therefore, you need to decide which name service to use as part of the network planning process. Moreover, the decision to use name services also affects whether or not you organize your network into an administrative domain.
The NIS, NIS+, LDAP, or DNS name services maintain network databases on serveral servers on the network.
If you do not implement NIS, NIS+, LDAP, or DNS, the network will use local files to provide name service. The term "local files" refers to the series of files in the /etc directory that the network databases use.
If you decide to use local files as the name service for your network, you can easily set up another name service at a later date.
Many networks organize their hosts and routers into a hierarchy of administrative domains. If you are going to use NIS, NIS+, LDAP, or DNS name services, you must select a domain name for your organization that is unique worldwide. To ensure that your domain name is unique, your should register it with InterNIC. This is especially important if you plan on using DNS.
The domain name structure is hierarchical. A new domain typically is located below an existing, related domain. For example, the domain name for a subsidiary company could be located below the domain of the parent company. If it has no other relationship, an organziation can place its domain name directly under one of the existing top-level domains. Below is a list of several commonly used top-level domains.
When deciding on whether to implement administrative subdivisions on your network, consider the size and amount of control that can be efficiently distributed to other groups of administors. The more hosts and servers you have in a network, the more complex your management tasks will be. You may wish to handle such situations by setting up additional administrative divisions in the form of more additional networks of a particular class or by dividing existing networks into subnets. The decision as to whether to set up administrative subdivisions for your network hinges on the following factors:
What is the size of the network?
A single network of serveral hundred hosts, all in the same physical location and requiring the same administrative services, can be handled by a single administrative subdivision. On the other hand, a network of fewer machines, divided into a number of subnets and physically scattered over an extensive geographic area would be likely to benefit from the establishment of serveral administrative subdivisions.
Do users on the network have similar needs?
For example, yoy may have a network that is configured to a single building and supports a relatively small number of machines. These machines are divided amount a number of subnetworks, each supporting groups of users with different needs. Such a case could call for an administrative subdivision for each subnet.
Jeffrey Hunter is an Oracle Certified Professional, Java Development Certified Professional, Author, and an Oracle ACE. Jeff currently works as a Senior Database Administrator for The DBA Zone, Inc. located in Pittsburgh, Pennsylvania. His work includes advanced performance tuning, Java and PL/SQL programming, developing high availability solutions, capacity planning, database security, and physical / logical database design in a UNIX / Linux server environment. Jeff's other interests include mathematical encryption theory, tutoring advanced mathematics, programming language processors (compilers and interpreters) in Java and C, LDAP, writing web-based database administration tools, and of course Linux. He has been a Sr. Database Administrator and Software Engineer for over 20 years and maintains his own website site at: http://www.iDevelopment.info. Jeff graduated from Stanislaus State University in Turlock, California, with a Bachelor's degree in Computer Science and Mathematics.
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