1. NETWORK FUNDAMENTALS
THE THREE MAJOR TYPES OF NETWORKS

There are three major types of networks they are (in ascending order; based upon physical size from smallest to largest):

LAN (Local Area Network)

LAN--is an acronym for Local Area Network. It is the physically smallest type of computer network and, is usually, confined within the boundaries of a single building or complex.

Originally, LANs were limited in their range and maximum number of computers. Today, much larger LANs are possible. For easier administration LANs are now broken up into small, logical pieces or areas called WORKGROUPS.

A WORKGROUP--is a collection of computers that share the same FILES and DATABASES over a LAN. Think of it as a mini-network.

MAN (Metropolitan Area Network)

MAN-- is also known as a Metropolitan Area Network, or regional network, and is the next largest type of network. It is:

WAN (Wide Area Network)

WAN--is Wide Area Network and is the largest type of network. The INTERNET is the most famous WAN of them all. Some of the qualities that a WAN possess are that it:

  1. Is a network that uses ROUTERS and PUBLIC NETWORK LINKS.
  2. Covers enormous amounts of distance and crosses metropolitan, regional, and/or national boundaries.
  3. It can be, either, a CENTRALIZED WAN or a DISTRIBUTED WAN. A centralized WAN consists of a central computer to which other computers and DUMB TERMINALS (a monitor and keyboard that is connected to a microcomputer, a main frame, or another large computer; it has no hard drive of its' own) connect. A distributed WAN is made up of many interconnected computers in many different locations; for example, the Internet.

WANs differ from LANs and MANs for the following reasons:

  1. Because of the greater distances involved a WAN is generally slower then other types of networks.
  2. WANs utilize both connection on demand and permanent connectivity. LANs have, only, permanent connections between workstations.
  3. WANs can use either public OR private network transports to facilitate communication. LANs use, only, private network transports and MANS use, mostly, public network transports.
  4. WANs can use either FULL-DUPLEXING or HALF-DUPLEXING communications (see below). LANs, usually, use only half-duplexing.
FULL- AND HALF-DUPLEXING

All communications can be defined as being, either, half-duplex or full-duplex.

In half-duplexed communications one computer sends a signal while the other one receives; then they switch sending and receiving. Think of it as being similar to communicating over a walkie-talkie or primitive intercom system.

In full-duplexed communications signals are sent and received, by each computer at the same time. This is similar to communicating over a telephone; where people on each end of the line can speak at the same time.

NETWORK COMPONENTS:
CLIENTS / WORKSTATIONS

A CLIENT is any network component that can request and use NETWORK RESOURCES. While this is usually used to describe a computer it can be any network device, including printers.

A WORKSTATION is a specialized type of client. The term workstation is used to describe any computer that is connected to a network and is operated by a user to do work. This term is related to the term workgroup.

SERVERS

A SERVER is the other side of the client/server relationship. While a client requests resources from a network; a server is what stores, runs, and/or provides services to the client.

A server can run many different types of services but, performance is increased when a server is assigned a single service to provide. Such single-tasking servers are also referred to as DEDICATED SERVERS, for obvious reasons.

Some examples of dedicated servers are:

HOSTS

In the strictest sense of the word a HOST is any network device that has a TCP/IP network address (Transmission Control Protocol/Internet Protocol; more on this later). This can be a personal computer, a server or any other network device.

PEER-TO-PEER VS. CLIENT/SERVER ARCHITECTURE

How a network shares resources depends upon the architecture of the operation system being used. Two of the most common network types are peer-to-peer and client/server.

PEER-TO-PEER NETWORKS

Peer is another word for "equal" and in peer-to-peer networking (also known as p2p) there is no centralized authority. The benefit of this type of network is that any computer on it has the ability to be both a client and/or a server. One of the drawbacks is that is not SCALABLE, in other words, there are only a limited and finite number of computers that can be on a peer-to-peer network. Also, because of a lack of centralized authority data backup and security is administered on a computer by computer basis, this can be a hassle.

Windows 95/98 or a network using Windows NT workgroup functionality are examples of peer-to-peer networks. KaZaA, Morpheus, and Napster are some other examples of programs that make use of peer-to-peer networking functionality.

CLIENT/SERVER NETWORKS

In a client/server network authority is located at a centralized network server. Clients make requests of the server and the server, after verifying user permissions and making other security checks, responds with the data or allows access to a resource. Due to this centralized server data backup and security for the network is much more manageable. Also, client/server networks can scale almost infinitely. Some client/server networks number in the tens of thousands of workstations.


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