Differences between Network Types
The two basic types of network are the LAN and WAN. LAN stands for local area network and WAN stands for wide area network. There are obvious differences between the two network types. To begin with local area networks. They are smaller networks, usually within an office base. Connections between the workstations are physical, with cables, and all the office resources are shared and distributed between the network workstations. The most common type of LAN is that of Ethernet. This is a family of frame-based computer networking technologies for LANs.
WAN, or wide area networks, are broader geographic networks, like one city to another. They are more of a collection of interconnected LAN networks. Other WANs, provided by service providers, connect local networks to the Internet. In actual fact the Internet is more a specific Internetwork, not a straight WAN.
While LANs are smaller, collectively they can be linked to create the WAN.
Network Services
The whole point of a network is to allow computers to share resources, such as hard drives and printers and to allow communication. On major networks this requires a “server” and a “client”, both together provide the following services:
- E-Mail
- File Transfer
- On Line Databases
- Bulletin Boards
- Conferencing
E Mail
Electronic mail (email) offers all of the facilities provided by fax and teletex but is paperless.
Electronic mail; offers the additional advantage of being able to store messages even when the destination terminal is busy.
E Mail Features
Terminal to prepare and store messages
A communication link with other workstations within the network
A central controlling computer which will be your email server
A directory of addresses
A central mailbox
A system which dates the messages
A function that notes that a message has been received by the addressee
A facility to multiple-address, so that all members of a particular working group can be sent a message simultaneously
A prioritising system, so that messages can be identified as either important or routine
A storage facility in order to keep, in the memory, those messages that have not yet been received.
Compatibility with existing equipment and computer systems.
E Mail Advantages
Savings on stationery and paper costs.
Savings on telephone costs.
Rapid transmission.
Integration with other systems.
The recordings of all transmissions so that accurate costings can be obtained.
Allowing addressees to peruse their own electronic mail at leisure.
File Transfer
Facility which enables a user to transfer files electronically to another computer or to a printer.
Transfer across the internet from FTP sites is also common
Online Database
Internet Search Engines
Online catalogues
Support Sites
Forums
Online Data Storage
Bulletin Boards
Bulletin boards operate rather like a notice board,
Allows individuals to leave messages,
Various information, such as notices or memoranda to all staff can be found on an internal bulletin board
A bulletin board may be setup by a service or product provider to keep users or purchasers informed of new developments
Internet, bulletin boards, either free or requiring a subscription, which hold some very useful information which can be accessed and downloaded by any user.
Conferencing
In its most primitive form, conferencing allows number of individuals to speak to one another simultaneously over telephone network.
Video-conferencing
Chat rooms
Telephone conferencing
Network Topology
The term topology or more specifically network topology refers to the physical layout of computers, cables and other components on the network. This is commonly known as the design of network. Referred to as:
- Physical Layout
- Design
- Diagram
- Map
The design or network topology choice can impact the:
- The type of equipment the network needs
- Capabilities of the equipment
- Network growth
- The way it is managed
Standard topologies
In this topology, all computers and devices are connected to cable that forms a closed loop. Each computer on this type of topology acts like a repeater and boosts the signal before sending it to the next computer. It transmits data by passing a “token” around the network. Hence this type of network is commonly called a token ring network. Similar to the Bus topology, if one computer fails, the entire network goes down.
All computers and devices are connected to a centrally located hub or switch. The hub or switch collects and distributes the flow of data within the network. It’s better to use a switch than a hub because a switch transmits the data to the intended recipient rather than to all hosts on a network.
All computers and devices are connected in series to a single linear cable called a trunk or sometimes called a backbone. Both ends of the trunk must be terminated to stop the signal from bouncing back up the cable. Because the bus topology does not have a central point it is difficult to troubleshoot problems. Also, a break at any point along the bus can cause the entire network to go down.
Protocols
Protocols are rules and procedures for communicating, for communication to be successful computers must agree on protocols.
Purposes and Functions of Protocols
There are different types of protocols and each Protocol has different purpose and function. Networking protocols enable computers to exchange data with each other in a meaningful, organized, and efficient way. Computers rely on protocols to ensure each computer "understands" what the other computer is sending it. Both computers must use the same protocol if they are to exchange information with each other successfully. Most common protocol is TCP/IP used by the Internet and pretty much all operating systems.
Protocol Suites
