NETWORKING CONCEPTS

Data Communication Communication is for sharing information Sharing can be local or remote Local communication between individuals is face to face Remote communication takes place over distance Telecommunication means communication at a distance includes telephony,telegraphyetc

Data-refers to information presented in whatever form agreed upon by the parties creating and using the data. Data communication –Exchange of data b/w two devices through some form of transmission medium such as wire cable.

SIMPLIFIED NETWORK MODEL Networks: Computer network A collection of computing devices that are connected in various ways in order to communicate and share resources Usually, the connections between computers in a network are made using physical wires or cables However, some connections are wireless, using radio waves or infrared signals

The generic term node or host refers to any device on a network Node can be a computer,printer,or any other device capable of sending or receiving data generated by other node on the network Data transfer rate The speed with which data is moved from one place on a network to another

Distributed Processing Most n/w use distributed processing. Ie.a task is divided among multiple computers Instead of one single large m/c responsible for all aspects of a process,separate computer handles a subset

Network Cryteria A n/w must meet a no of cryterias 1. Performance 2. Reliability 3. Security

Performance Measured in different ways like 1.Transit Time 2. Response time Transit Time: Amount of time required for a message to travel from one device to another Response Time Elapsed time between an enquiry and a response

Performance depends on no of factors including no of users,type of transmission medium,capabilities of connected h/w,efficiency of s/w etc. Performance is evaluated by using measures like 1.Throughput 2.Delay We need more throughput and less delay when we send more data to n/w we can increase the throughput but increase in delay due to congestion in n/w

Reliability Measured by frquency of failure,the time take a link to recover from a failure Security Security issues include protecting data from unauthorized access,damage,implementing policies and procedures for recovery from data losses

Simplified Network Model

PHYSICAL STRUCTURES Types of Connection n/w is 2 or more devices connected through links Link is a connecting pathway that transfers data from one device to other Imagine link as a line drawn b/w 2 points For communication to occur the two devices must be connected to same link at the same time

2 possible type of connection Point to point Provides dedicated link between 2 devices Entire capacity is reserved for transmission between those two devices Multi Point Also called multi drop connection More than specific device share a single link Capacity of channel is shared

Point to Point and Multipoint

PHYSICAL TOPOLOGY Refers to way in which a n/w is laid out physically 2 or more devices connect to a link 2 or more links form a topology ie. Topology means it is a representation of relationship of all the links and linking devices(nodes) to one another

CATEGORIES OF TOPOLOGY MESH STAR BUS RING

CATEGORIES OF TOPOLOGY

MESH TOPOLOGY Every device has dedicated point to point link to every other device The link carry traffic only b/w the two devices it connects In a mesh n/w no of links with n nodes is n(n-1) If physical link is in duplex mode we need n(n-1)/2 duplex mode links

MESH TOPOLOGY WITH 5 DEVICES

MESH TOPOLOGY Advantages Use of dedicated link guarantees that each connection can carry its own data load and thus eliminates traffic problems that can occur when links must be shared by multiple devices Roubst: if one link become unusable it does not in capacitate entire system Privacy/Security:every message travels only through dedicated line.only intended recipient can see it

MESH TOPOLOGY Advantages Point to point link makes fault identification and fault isolation easy Traffic can be routed to avoid links with suspected problems This facility enables n/w manager to discover the precise location of the fault & aids in finding the cause and solution

MESH TOPOLOGY Disadvantages Amount of cabling and I/O ports are very high because each device must be connected to each device and also installation and reconnection are difficult Bulk wiring is greater than available space h/w for connecting I/O ports is expensive

STAR TOPOLOGY Each device has a dedicated point to point link to a central controller usually called a hub Devices are not directly linked to one another Does not allow direct traffic b/w devices If one device wants to send data to other it sends data to controller and then send data to other device

STAR TOPOLOGY

Advantages Each device needs only one link and one I/O port to connect to it to any no of others.So it is easy to install and reconfigure Less cabling is needed. Addition and deletion involve only one connection. Between device and hub Robstness If one link fails other links are active,only one is affected Help easy fault identification and fault isolation

STAR TOPOLOGY Disadvantages Depending to one single point known as hub If hub is down whole system is down

BUS TOPOLOGY A multipoint connection One long cable act as a backbone to link all devices in a n/w

BUS TOPOLOGY Nodes are connected to bus cable by drop lines and taps Dropline: connection running b/w device and main cable Tap: Connector that splices into the main cable

BUS TOPOLOGY Advantages Ease of installation Less cabling than mesh ie. Backbone cable can be laid along the most efficient path,then connected to nodes by droplines of various lengths

BUS TOPOLOGY Disadvantages Difficult reconnection and fault isolation A bus is usually designed to be optimally efficient at installation so it is difficult to add devices Signal reflection at the tap can cause degradation in quality This degradation can be controlled by limiting no and spacing of devices connected to backbone so, Adding new devices include changing backbone Fault or break in bus cable stops all transmission

RING TOPOLOGY Each device has a dedicated point to point connection with only the two devices on either side of it A signal is passed along the ring in one direction from device to device until it reaches destination Each device in the ring incorporates a repeater When a device receives a signal intended for another device its repeater regenerates the bits and passes them along.

RING TOPOLOGY

Advantages Easy to install and configure Each device is connected to only its immediate neighbour To add or delete a device requires changing only 2 connections Fault isolation is easy Generally a signal is circulating all times.if one device does not receive a signal within a specified period it can issue an alarm The alarm alerts the n/w operator and its isolation

RING TOPOLOGY Disadvantages A break in a ring (eg:disabled station) can disable the entire n/w

HYBRID TOPOLOGY