Lesson 11 Network Essntials - II

Agenda Network Topology Catagories of Network Commonly used Terminologies Computing Model The Standards The OSI Network Security

Network Topology A network Topology determines How the NOS manages the network How Information flows The level of fault tolerance Trouble shooting method

Basic Topologies MESH STAR TREE BUS RING

MESH TOPOLOGY

Advantage Every device has dedicated point-to –point link which can carry its own load If one link becomes unusable it does not effect the overall network Message sent is on dedicated line so only the intended recipient gets it. Physical boundaries prevents other users from access to the message Privacy & security is highly maintained Since point to point links makes fault finding easy.

Disadvantage Installation & reconfiguration are difficult Large amount of cabling required Many I-O ports are required The H/w link makes it costly

STAR TOPOLOGY Centralised controller HUB

Star Topology The device can link to each other thru the centralised controller called the HUB. Star topology does not allow direct traffic between devices The HUB offers centralized resource management.

Star Topology - Advantages Each device needs one link & one I-O port to connect to any number of devices The link which becomes unusable then only that link is affected. It is a robust topology Fault identification and isolation is easy Less expensive than Mesh Topology

Star Topology - Disadvantage Since each device is connected to centralised link, the distance gets restriction. H/w requirement is costly than other topologies

Tree Topology Active HUB Secondary HUB

Tree Topology - Advantages & Disadvantages are same as star Topology. The Secondary Hubs increase the strength of the signal to travel longer distance with the help of repeaters. It allows the Network to isolate and prioritize communications from different computers. Hence time-sensitive data need not wait.

BUS Topology Cable End – Terminator TAP Drop Line Main Cable - BACK BONE

Bus Topology As the message passes each station it checks the address and then the station receives the message. Takes longer time to travel and thus generates heat making the signal weaker Limited number of Taps

Bus Topology As the message passes each station it checks the address and then the station receives the message. Takes longer time to travel and thus generates heat making the signal weaker Limited number of Taps

Bus Topology - Advantages Easy to Install and efficient Uses less cabling as compared to Mesh, Star & tree Each drop Line has to reach the nearest main Cable

Bus Topology - Disadvantage Fault identification and Isolation is difficult. Difficult to add node as optimal efficiency is calculated before installation A fault or break in the cable stops all transmission

Bus Topology As the message passes each station it checks the address and then the station receives the message. Takes longer time to travel and thus generates heat making the signal weaker Limited number of Taps

Ring Topology Each Device has point- point line configuration with only 2 device on each side There are no terminated ends The signal travels along the loop in one direction until they reach the destination Each device has a repeater which repeats the signal passing thro it. > > > < < < V V

Ring Topology - Advantages Easy to Install and reconfigure Each device is linked only to its immediate neighbour so adding or remoing a device requires moving of only 2 connections. Fault isolation is very easy & simple The signal circulates thru the ring, hence the device not receiving for a specified period triggers an alarm to the network administrator.

Bus Topology - Disadvantage A fault or break in the cable stops all transmission

Categories of Network LAN MAN WAN

LAN

Is usually owned by private owner Device linked in a single office, campus or building Can be as simple as 2 PCs to the entire office Size is Limited to less than a mile Can be distinguished from other network by its transmission media as LAN uses only one type of transmission medium. Has data rates ranging from 16 mbps to 100 mbps

LAN Applications Information Sharing among workgroups, divisions, companies, worldwide) Hardware Sharing – printers, fax,… Software Sharing (licensing issues!) Where good response time is needed Where local control is desirable

Wired LAN

MAN Designed to extend over a city Can be a single cable network or may be connecting several LAN Owned and operated by a private organisation Many telephone companies provide popular MAN service Data rate ranges from 1.54 mbps to mbps

WAN

Provides long distance transmission of data, voice, image and video. Network connects large geographical areas like a county to country or a continent to continent. May comprise of a public, private or leased communication device Wholly owned by a single company