Computer Networks and The Internet

1. Computer NetworksandThe Internet

2. Definition - Network • In information technology, a network is a series of points or nodes interconnected by communication paths. Networks can interconnect with other networks and contain subnetworks. Whatis Encyclopedia

3. Topologies • The most common topology or general configurations of networks include the bus, star, and Token Ring topologies. Networks can also be characterized in terms of spatial distance as local area networks LAN, MAN and WAN. (more later on this!) Whatis Encyclopedia

4. More Characterizations • A network can also be characterized by the type of data transmission technology in use on it (for example, a TCP/IP network) by whether it carries voice, data, or both kinds of signals; by who can use the network (public or private); by the usual nature of its connections (dial-up or switched, dedicated or non-switched, or virtual connections); and by the types of physical links (for example, fiber optics, coax, UTP) • Large telephone networks and networks using their infrastructure (such as the Internet) have sharing and exchange arrangements with other companies so that larger networks are created. Whatis Encyclopedia

5. Additional Definitions • Computers on a network are sometimes called nodes. Computers and devices that allocate resources for a network are called servers. • Networking means to connect two or more computers together with the ability to communicate with each other.

6. More Definitions… • Protocol – The language used for devices to communicate on the network. The protocol defines a common set of rules and signals that computers on the network use to communicate. Examples are: • TCP/IP • IPX/SPX

7. Definitions – Protocol Cont. • An agreed-upon format for transmitting data between two devices. The protocol determines the following: • the type of error checking to be used • Data compression method, if any • How the sending device indicates it’s finished sending a message. • how the receiving device will indicate that it has received a message

8. More Definitions… • Architecture - Networks can be broadly classified as using either a peer-to-peer or client/server architecture. • A design. The term architecture can refer to either hardware or software, or to a combination of hardware and software. The architecture of a system always defines its broad outlines, and may define precise mechanisms as well.

9. Definitions • Ethernet – A LAN architecture developed by Xerox in cooperation with DEC and Intel in 1976. Ethernet uses a bus or star topology and supports data transfer rates up to 1gig. A newer version of Ethernet, called 100Base-T (or Fast Ethernet), supports data transfer rates of 100 Mbps. And the newest version, Gigabit Ethernet supports data rates of 1 gig (1,000 megabits) per second.

10. More Definitions… • Media - Devices can be connected by twisted pair, coax, or fiber optic cables. Some networks do without connecting media altogether, communicating instead via radio waves.

11. Types of Computer Networks • LAN – Local Area Network • The computers are geographically close together (that is, in the same building). • WAN – Wide Area Network • The computers are farther apart and are connected by telephone lines or radio waves. • CAN – Campus Area Network • The computers are within a limited geographic area, such as a campus or military base.

12. Types of Computer Networks • MAN – Metropolitan Area Network • A data network designed for a town or city. • HAN – Home Area Network (very new term) • A network contained within a user's home that connects a person's digital devices.

13. LAN • A computer network that spans a relatively small area. Most LANs are confined to a single building or group of buildings. However, one LAN can be connected to other LANs over any distance via telephone lines and radio waves. A system of LANs connected in this way is called a WAN.

14. LANs continued… • Most LANs connect workstations and personal computers. Each node (individual computer ) in a LAN has its own CPU with which it executes programs, but it also is able to access data and devices anywhere on the LAN. This means that many users can share expensive devices, such as laser printers, as well as data. Users can also use the LAN to communicate with each other, by sending e-mail or engaging in chat sessions.

15. LAN Transmissions • LANs are capable of transmitting data at very fast rates, much faster than data can be transmitted over a telephone line; but the distances are limited, and there is also a limit on the number of computers that can be attached to a single LAN.

16. WANs • A computer network that spans a relatively large geographical area. Typically, a WAN consists of two or more LANs. Generally if a LAN crosses a router, it is now a WAN.

17. WAN’s • Computers connected to a wide-area network are often connected through public networks, such as the telephone system. They can also be connected through leased lines or satellites. The largest WAN in existence is the Internet.

18. CANs • Acronym for campus-area network. An interconnection of LANs within a limited geographical space, such as a school campus or a military base.

19. HANs • Short for home area network. A HAN is a network contained within a user's home that connects a person's digital devices, from multiple computers and their peripheral devices to telephones, VCRs, televisions, video games, home security systems, "smart" appliances, fax machines and other digital devices that are wired into the network.

20. MANs • Short for Metropolitan Area Network, a data network designed for a town or city. In terms of geographic breadth, MANs are larger than LANs but smaller than WAN’s. MANs are usually characterized by very high-speed connections using fiber optic cable or other digital media.

21. Topologies • The geometric arrangement of the network. Bus, Star and Ring are common.

22. Bus Topology • All devices are connected to a central cable, called the bus or backbone. Bus networks are relatively inexpensive and easy to install for small networks. Ethernet Systems use a bus topology.

23. Ring Topology • All devices are connected to one another in the shape of a closed loop, so that each device is connected directly to two other devices, one on either side of it. Ring topologies are relatively expensive and difficult to install, but they offer high bandwidth and can span large distances.

24. Star Topology • All devices are connected to a central hub. Star networks are relatively easy to install and manage, but bottlenecks can occur because all data must pass through the hub.

25. Topologies… • These topologies can also be mixed. For example, a bus-star network consists of a high-bandwidth bus, called the backbone, which connects a collections of slower-bandwidth star segments.

27. The Internet! • Bunches of WANs interconnected! • Operates on the public network • Most common user interface is the web, with http as its protocol. • Other Internet protocols include ftp, smtp, etc

28. Definitions • ISP – Internet Service Provider. • ISPs give you access to the Internet. They usually add value with email, anti-spam software, etc.