Computer Networking (Appendix C) Objectives Understand networking fundamentals Understand network services and transmission media Understand network software and hardware

Networking Fundamentals Network consists of: Servers – provides services Clients – requests services Peers – both requests and provides services Types of networks Server-centric networks Peer-to-peer networks

Networking Fundamentals Network Services File services Print services Message services Applications services

Networking Fundamentals Network Operating System (NOS) Two parts: System software that runs on the server Client software on each workstation Examples Banyan Vines Novell NetWare Microsoft LAN Manager LANtastic

Networking Fundamentals Transmission Media The pathway to send data and information between two or more entities on a network Bandwidth: transmission capacity Attenuation: weakening of a signal over distance EMI: electromagnetic interference

Networking Fundamentals Cable Media Twisted pair cable Coaxial cable (“coax”) Fiber-optic cable

Networking Fundamentals Wireless Media Infrared line of sight High-frequency radio Pager – one way wireless Cellular phone – two way wireless Wireless LANs Microwave Terrestrial Satellite

Network Software and Hardware Media access control Rules that govern how a workstation gains access to the network Distributed access control Token passing Random access control “Listens” for network traffic

Network Software and Hardware Network topologies Star network Ring network Bus network

A star network topology Use: This topology is useful for applications where processing must be centralized and some can be performed locally. Advantages: Easy to lay out and modify. It is easy to diagnose problems at individual workstations. Problems: Costly, it requires the largest amount if cabling. Since all communication pass through the central computer, the communications in the network will stop if the host/hub computer stops functioning.

A ring network topology Use: This topology is useful in LANs. Advantages: It does not rely on central host. The connecting wire, cable, or optical fiber forms a closed loop. Data are passed along the ring from one computer to another and always flow in one direction. The message is regenerated and passed to the next computer if it is not for the previous computer. This regeneration process enables ring networks to cover much larger distances than star or bus networks. Disadvantages: A failure of any node on the ring network can cause complete network failure. It is difficult to modify and reconfigure the network.

A bus network topology Use: This topology is useful in LANs. Advantages: It does not rely on central host. This network can still function if one of the computers malfunctions. Other advantages: easy to wire, quick response, less expensive. Disadvantages: The main disadvantage is bad connection to the cable can bring down the entire network. Another problem: collision occurs when 2 nodes send messages simultaneously.

Network Software and Hardware Protocols: Set of rules ( format of transmitting data, error checking method, data compression technique) OSI model – open systems interconnection Ethernet TCP/IP

OSI RM

OSI RM

Network Software and Hardware Connectivity hardware Transmission Media Connectors: T-connector for coax cable and RJ-45 connectors for twisted pair Network interface card (NIC) Modems Repeaters Hubs Bridges Multiplexers Routers Brouters Channel service units (CSU): buffer between a LAN and a WAN Gateway