Overview of computer communication and Networking Communication VS transmission Computer Network Types of networks Network Needs Standards

Communication VS transmission Sender Medium Receiver Sender Medium Receiver Common Protocol Transmission Communication

Computer Network ‘A computer network is a collection of computers and other devices (nodes) that use a common network protocol to share resources with each other over a network medium.’ computersdevicesprotocol medium

Computers Referred to as hosts, –Servers –Workstations Operating system required

Devices Used to represent any entity connected to network May be terminals, printers, computers, switches, routers May be local or remote Nearly all have to be uniquely identified

Medium Cable –Twisted pair –Coaxial –Fiber optic Wireless –Radio( microwave & satellite) –Infrared

Protocols Set of procedures, rules, or formal specifications governing specific behavior or language. Define data »Formatting »Integrity »transmission

Types of networks Network can be classified in many ways: –The area they encompassarea –Their topologiestopologies –Type of communicationcommunication

Area LAN (Local area network) 10 Km or less in length or radius (room, college, etc…) WAN(Wide area network) 8 Km or more, resources are widely separated (town, county, countries, etc..) GAN (Global area network) refers to a collection of WANs that span the globe PAN (Personal area network) small home network SAN (Storage area network) dedicated exclusively to store data

Topologies Point to point Broadcast Multidrop Topologies refers not only to the way the nodes are connected but also to the way they communicate

Point to point Nodes can only communicate with adjacent nodes (Only one hop) Source node sends a message that is passed serially through intermediate nodes until it reaches destination (Bridging or Routing) Star Loop Complete loop Tree

Broadcast Nodes share a single communication channel (Contention) Data is sent by one machine and received by all. Hosts need to verify if the message is intended for them (addressing) Bus Ring Satellite

Star Central processing hub All data must pass through hub Single point of failure

Loop nodes are connected via dedicated wiring instead of through a centralized hub, (only one connection between any 2 nodes. A single link failure does not cause the entire network to fail.

Complete Loop Each node is connected to every other node in the network, thus making every node adjacent to every other node. Commonly referred to as a fully meshed design

Tree Hierarchical configuration that consist of a root node or hub that is connected to second-level nodes or hub

Bus All computers are connected one another usually using coaxial cable One connection break and the whole network is down

Ring All nodes are connected to the same ring, which serves as the shared medium Can be physically designed as a star In a classic ring topology, messages are passed from node to node around the ring

Satellite Data transmission from land based antenna to satellite is usually point to point All nodes that are part of the network can receive a downlink transmission

Multidrop Master / Slave concept Master controls the network functions and slaves request access Nodes are all connected to a common cable plant, (similar to bus) but are assigned communication numbers

Switched Networks Involve partially or fully meshed topology and use specially designed network devices (switches) to interconnect links Circuit switched network Packet switched network

Circuit Switched networks A dedicated physical circuit is first established between source and destination before any transmission can take place The path is point to point Circuit dedicated to current transmission and released when transmission completed

Packet switched network Message is partitioned in packets Each packet carries destination node and sequence number As a packet arrives at a switch, it determines with path to take to get to the next switch Each packet is stored and then forwarded Link sharing promoted by using either virtual circuits or datagram transportvirtual circuits datagram

Virtual circuit packet switching Logical communication path instead of a physical one Each packet follows the same communication path in sequence as if traveling along a dedicated circuit Links in the circuit can also be used for other transmission at the same time

Datagram Packet Switching Packets are transmitted independently from one another at any time Different packets can take different communication routes to get to the destination Packets can be transmitted and received out of sequence (destination node is responsible to reassemble them in the proper order)

Network needs(1) Addressing: involves assigning a network node a unique address that allows other systems to locate it Routing: involves determining the path a data packet takes as it travels between source and destination Reliability: refers to data integrity, data received must be identical to data sent –Error detection: Error correction through transmission Autonomous error correction

Network needs (2) Interoperability: refers to the fact that products from different vendors must be able to communicate efficiently over the network Security: refers to the proper safeguarding of every thing on the network: Data, media and equipment.

Network Standards De Jure: approved by formal accredited standards organization De Facto: have come into existence without any formal plan. Accepted because of their use Proprietary: Developed in a manufacturer specific manner Consortia: Similar to De Jure, but developed by multiple manufacturers or vendors