Thursday, October 16, 2014

Explain Network Administrative models. Or Short note: Workgroup,Binarybased, Domain,Directory services.

·         In computer networking, a workgroup is a collection of computers on a local area network (LAN) that share common resources and responsibilities. Workgroups provide easy sharing of files, printers and other network resources.
·         Being a peer-to-peer (P2P) network design, each workgroup computer may both share and access resources if configured to do so.The Microsoft Windows family of operating systems supports assigning of computers to named workgroups.
·         Macintosh networks offer a similar capability through the use of AppleTalk zones. The Open Source software package Samba allows Unix and Linux systems to join existing Windows workgroups.
·         Workgroups are designed for small LANs in homes, schools, and small businesses. A Windows Workgroup, for example, functions best with 15 or fewer computers.
·         As the number of computers in a workgroup grows, workgroup LANs eventually become too difficult to administer and should be replaced with alternative solutions like domains or other client/server approaches.
Binary Based:
·        The binary based model is one that is used by Novell NetWare versions up to NetWare 3.2 binary based networks follow the client/server model of networking.
·        Novell binary based servers still have a large presence in many networks to this day.  In a binary model, there is one server and many clients.
·        The server contains a flat user account database.  A flat user account database is one that contains the names of users, in one single list from A to Z who are allowed to log onto the system.
·        Also, this database of user accounts is used to assign who has rights or privileges to use different resources on the network.  These rights are either assigned on a user-by-user basic or a group-by-group basic.
·        The server is also responsible for containing all of the services on the network.  The client machines are not designed to provide any services at all.  This allows for a more centralized method of management of the network.
·        A client machine on this system is one that has a redirector installed on it, such that it will connect to a central server, and try to authenticate against that server’s user account database.
·        The user will supply a valid name that exists within the user account database(logon name) and an associated password.
·        If the name and password exist within the server’s user account database, the user is granted permission to use the network, and in turn, the user’s computer is given a “key” by the authenticating server.
·        This key is similar to a security badge that you may wear when touring a secured facility.

Limitation of binary model:
·        Binary models do not allow for the sharing of database lists between servers, as each server maintains its own user account database.
·        Because of this limitation, as more servers are added to the network, every time a new user account is created, it would have to be added to the user account database on each server that would contain a resource being shared out to that user.

·         The DNS translates Internet domain and host names to IP addresses. DNS automatically converts the names we type in our Web browser address bar to the IP addresses of Web servers hosting those sites.
·         DNS implements a distributed database to store this name and address information for all public hosts on the Internet. DNS assumes IP addresses do not change (are statically assigned rather than dynamically assigned).
·         The DNS database resides on a hierarchy of special database servers. When clients like Web browsers issue requests involving Internet host names, a piece of software called the DNS resolver (usually built into the network operating system) first contacts a DNS server to determine the server's IP address.
·         If the DNS server does not contain the needed mapping, it will in turn forward the request to a different DNS server at the next higher level in the hierarchy.
·         After potentially several forwarding and delegation messages are sent within the DNS hierarchy, the IP address for the given host eventually arrives at the resolver, that in turn completes the request over Internet Protocol.
·         DNS additionally includes support for caching requests and for redundancy. Most network operating systems support configuration of primary, secondary, and tertiary DNS servers, each of which can service initial requests from clients.
·         Internet Service Providers (ISPs) maintain their own DNS servers and use DHCP to automatically configure clients, relieving most home users of the burden of DNS configuration.

Directory Services:
·        A simple directory service called a naming service, maps the names of network resources to their respective network addresses. With the name service type of directory, a user doesn't have to remember the physical address of a network resource; providing a name will locate the resource.
·        Each resource on the network is considered an object on the directory server. Information about a particular resource is stored as attributes of that object.
·        The directory design process normally has a set of rules that determine how network resources are named and identified. The rules specify that the names be unique and unambiguous.
·        In X.500 (the directory service standards) and LDAP the name is called the Distinguished name (DN) and is used to refer to a collection of attributes (relative distinguished names) which make up the name of a directory entry.
·        A directory service is a shared information infrastructure for locating, managing, administering, and organizing common items and network resources, which can include volumes, folders, files, printers, users, groups, devices, telephone numbers and other objects.
·        A directory service is an important component of a NOS (Network Operating System).
·        In the more complex cases a directory service is the central information repository for a Service Delivery Platform. For example, looking up "computers" using a directory service might yield a list of available computers and information for accessing them.

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