Computer Networks Introducing Computer Networks n A computer

Computer Networks

Introducing Computer Networks n A computer network consists of two or more computers linked together to exchange data and share resources. n A node is any device connected to a network v. Computer v. Peripheral (i. e. , a printer) v. Network device (i. e. , a router) 2

Networking Synergies in a Nutshell Reduced hardware costs n Users share equipment Connected people n People can work together without being at the same location n Groupware enables sharing of schedules and communications Shared applications n Users share software n File server enables all users to work with the same application program Building information resources n Users create common pools of data that can be accessed by employees 3

Types of Computer Networks Local area network (LAN) n Links computers within a building (close proximity). n Uses direct cables, radio, or infrared signals. Wide area network (WAN) n Links computers separated by a few miles or thousands of miles. n Uses long-distance transmission media. Metropolitan area network (MAN) n Links computers within a group of buildings. n Uses fiber-optic cables. NEXT SLIDE 4

Network Fundamentals n Physical media used in networks: v Cables– Telephone lines, coaxial cable, microwave, satellites, wireless, and fiber optic cables connect computers. v Routers– Devices that examine the data transmitted and send it to its destination. v Switches– High speed electronic switches maintain connections between computers. n Protocols– Standards that specify how network components communicate with each other. 5

Network Architecture n Network architecture is the overall design of a network. n The network design is divided into layers, each of which has a function separate from that of the other layers. 6

Local Area Networks (LANs) n LANs connect computers and peripherals within a building. n Users can access software, data, and peripherals. n LANs require special hardware and software. n Computers connected to a LAN are called workstations or nodes. n Different types of LANs: v Peer-to-peer v Client-server 7

LAN Hardware and Software Hardware n Network interface card (NIC)– Inserted into a computer’s expansion slot Software n Operating system that supports networking (Unix, Linux, Windows, Mac OS) n Additional system software 8

Peer-to-Peer Networks n All computers on the network are treated as equal. n There are no file servers. n Users decide which files and peripherals to share. n They aren’t suited for networks with many computers. n They are easy to set up. Example: Home networks 9

Client-Server Networks n Typical corporate networks are client-server. n They use various topologies or physical layouts. n The network requires file servers, networked computers (clients), and a network operating system (NOS). n Clients send requests to servers for programs and data, and to access peripherals. 10

Network Media LANs use a variety of media to carry network signals. n Twisted pair–Two insulated wires twisted around each other. The same type of wire as that used for telephones. n Coaxial cable– Consists of an insulated center wire surrounded by a layer of braided wire. The same type of wire as that used for cable TV. n Fiber-optic cable– A type of fiber glass cable that transmits data in the form of light impulses. It can carry more data for longer distances than other wire. n Infrared– A wireless system that includes a transmitter and receiver for sending and receiving signals. n Radio– A wireless system that uses radio signals to send and receive data. 11

Types of Telephone Transmission Media Fiber Optics Twisted Pair Copper Wire Satellites Microwave 12

Transmission Media n UTP cable: Most popular for wired Ethernet networks n Types of UTP cable v. Cat 5 E: Cheapest, designed for 100 Mbps v. Cat 6: Designed to support gigabit Ethernet network v. Cat 6 a: Designed for ultra-fast Ethernet networks 13

Network Components Transmission Media (cont. ) 14

Wide Area Networks (WANs) n WANs are similar to long-distance telephone systems. n They have a local access number called a point of presence (POP). 15

Point of Presence (POP) n A point of presence is a WAN network connection point that enables customers to access the WAN by making a local telephone call. n Media used to create a connection from an organization to a POP include: v 56 Kbps leased line v ISDN v ADSL v T 1 line v Permanent virtual circuit (PVC) 16

Bandwidth Transmission Media Bandwidth PSTN Twisted pair 56 Kbps ISDN 128 Kbps TV Cable 1 to 10 Mbps n Bandwidth: Maximum speed at which data can be transmitted between two nodes. n Throughput: Actual speed of data transfer achieved. n Throughput is always less than or equal to the data transfer rate. n It is measured in kilobits per second (Kbps), megabits per second (Mbps), or gigabits per second (Gbps). Copyright © 2003 Prentice Hall, Inc 17

Network Topology The physical layout of a network Node - each computer, printer, or server on network Three common topologies n n n Star Ring Bus 18

Network Topology - Star n n n n 19 - Uses Category 5 cable (cat 6 is used - Cat 5 cable uses an RJ-45 connector for the NIC card - Easy to install/not that expensive - Computers are concentrated into a star pattern using hubs or switches - Hubs broadcast data to all devices - Switches can be used instead of hubs - If there is a break in the cable it does not disturb the other computers

Network Topology - Ring n n n 20 - Uses different hardware - More expensive - Complex to install - Data is passed around the ring until it reaches its destination - Best at passing data with less collisions

Network Topology - Bus n n n - Least expensive/easiest to setup - Uses coax cable - Computers are daisy chained together in a linear bus - Data packets are sent along the coax cables - All computers hear data sent out 21