Networks Adapting Computers to Telecommunications Media

Connecting to a Network Modems –most often used to connect to WANs Network Interface Cards (NICs) –used to connect to LANs

Modem a device that converts digital signals used in computers to analog signals that can be transferred over the phone lines –modulate – convert digital signals to analog –demodulate – convert analog signals to digital typical speeds , 28.8, 33.6, 56 kbps faxmodems, internal, external modem PC card

Wide Area Networks transmit information over a large geographic region –public –private - intranets connection is usually through a dial-up lines –modem, modem software –service providers Commercial Online Services ISP - Internet Service Provider –browser for Internet access higher speed connection options –Integrated Services Digital Network (ISDN) –DirecPC –T1, T3 dedicated lines

Local Area Networks a collection of computers and other devices connected with a dedicated line usually confined to one geographic location used for sharing resources –data –hardware –software privately run

A Network Interface Card... Prepare data from the computer for the network cable Send the data to another computer Control the flow of data between the computer and the cabling system Expansion slot RJ-45 jack Coaxial cable BNC connector Network interface card

Network Interface Cards... Ethernet (CSMA/CD) Token Ring (token passing) are designed to support a particular network standard and communication protocol......that determines how messages are distributed to workstations and other network devices.

Ethernet CSMA/CD Protocol Every workstation examines the address, but only the one to which it is addressed reads the message.

Ethernet CSMA/CD Protocol Collision and Resolution Two messages sent simultaneously Each sender waits

Token-Passing Network Protocol A signal speeds over the network.

Communications Protocol Examples for WANs WAN protocols – Transmission Control Protocol/Internet Protocol (TCP/IP) – Systems Network Architecture (SNA) – Fiber Distributed Data Interface (FDDI)

Network Software: Operating System allows users to access files and software from the server manages the software licenses controls network security manages the communication between the components of the LAN and WAN Novell Netware, Windows NT Server

Network Configurations (Type) Hierarchical network Client-server networks Peer-to-peer network

Hierarchical Local Network Connects with other networks, terminals, or workstations Terminal Hub Mainframe printer Mainframe host computer

Client-Server Networks File Server each workstation interacts with the server workstations do not directly interact with each other. processing done at the workstations Workstation

Client-Server Networks Database Server establishes an interaction between workstations and servers that alleviates heavy traffic from using large database files

Peer-to-Peer Network Some workstations act as both workstations and file servers. Users can access programs and data files from the file server or from other workstation acting as a file server. File server Workstation Workstation and server

Network Topologies (Shape) Star Bus Ring Combination topologies

Network Topologies

Communication Between Networks Repeaters Routers Bridges Gateways