h002 computer networks

8/9/2019 H002 Computer Networks

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COMPUTERCOMPUTERNETWORKSNETWORKS

ByBy

HITESH MAHAPATRAHITESH MAHAPATRA


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INTRODUCTIONINTRODUCTION

Two or more than two computer systems connected by

means of a communication medium like cables is

termed as a Network.

Computer Network is a communication systems, which

links computers and their resources.

Computer Resources are storage devices e.g. HDD, tapedrive, CDROM, MODEM,RDBMS like Oracle, MS-SQL

etc and any other computing system (Mainframe,

Minicomputer etc.).


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BENEFITSOF A NETWORKBENEFITSOF A NETWORK

Following are the benefits of a networking which

help to increase the productivity:

Information Sharing

Printer Sharing

Hard Disk Sharing

Modem Sharing

Hardware Sharing

Software Sharing

Service Access

Easy Back-Up Management

Security

Centralized Administration and Support


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TYPESOFNETWORKTYPESOFNETWORK

LOCAL AREA NETWORK (LAN) :

LAN connects computers that are located near each other or at

the same location.

A corporate network consisting of several building in a campusan example of a LAN

WIDE AREA NETWORKS (WANLONG HAUL

NETWORKS) :

WAN connects a numbers of computers which are located at a

greater distance from one other or at different location.

Internet is an example of WAN


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The key characteristics, which are often used to differentiate

between these two types of networks, are as follows:

Geographic Distribution

Data Rate

Error Rate

Communication Link

Ownership

Communication Cost

Note:

Networks that share some of the characteristics of both LANsand WANs are sometimes referred to as Metropolitan AreaNetworks (MAN). The MANs usually cover a wider geographicarea than LANs. The main objective of MANs is to interconnectLANs located in a entire city or metropolitan area.


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NETWORKTOPOLOGYNETWORKTOPOLOGY

It refers to the physical layout of the network, especially the

location of the computers and how the cable is run between them.

The choice of the networks topology for installing a computernetwork depends upon a combination of factors, such as:

The desired performance of the system.

The desired reliability of the system.

Size of the system..

Expandability of the system.

Availability of communication lines.

Delays involved in routing information from one node to

another.


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The bus topology refers to a linear arrangement ofcomputers that are connected together by a single

cable referred to as the trunk or backbone. It is often

used when a network installation is small, simple or

temporary.Advantages:

Simple,Reliable,Easy to use and

understand.

Least amount of cable to connect

a computers.

Easy to extend a bus with the help of a repeater.

BUSTOPOLOGYBUSTOPOLOGY


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STARTOPOLOGYSTARTOPOLOGY

A star network consists of one central switch, hub or computerwhich acts as a router to transmit messages.

Advantages:

Good PerformanceEasy to set up and to expand.

Any non-centralized failure will have very

little effect on the network, whereas on a

ring network it would all fail with one fault.

Disadvantages:

Expensive to install

Extra hardware required

If the host com uter fails the entire system is affected.


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RINGTOPOLOGYRINGTOPOLOGY

A ring network is a topology of computer networks where eachconnected to node is two other nodes, so as to create a ring.

Advantages:

Data is quickly transferred without a bottle neck. (very fast, all

data traffic is in the same direction)

The transmission of data is simple as packets travel in one

direction only.

Adding additional nodes has very little impact on bandwidth

It prevents network collisions because of the media access method

or architecture re uired.


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Disadvantages:

Data packets must pass through every computer

between the sender and recipient therefore this makes it

slower.

If any of the nodes fail then the ring is broken and datacannot be transmitted successfully.

It is difficult to troubleshoot the ring.

Because all stations are wired together, to add a station

you must shut down the network temporarily.

In order for all computers to communicate with each

other, all computers must be turned on.


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TOKENRINGTOKENRING

A token ring is a type of computer network in which allthe computers are arranged (schematically) in a circle. Atoken, which is a special bit pattern, travels around thecircle. To send a message, a computer catches the token,

attaches a message to it, and then lets it continue totravel around the network.

Although it is considered a more reliable

system, a token ring network is slowerand offers less flexibility than schools

and other businesses need.

In a token ring, only one computer

may send information at a time.


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MEDIUM ACCESSCONTROLMEDIUM ACCESSCONTROL

PROTOCOLPROTOCOL

The Medium Access Control (MAC) protocol is used to provide

the data link layer of the Ethernet LAN system. It defines the

access method and access control in different local area networks.

The MAC layer provides an addressing mechanism called physical

address or MAC address. This is a unique serial number assigned

to each network adaptor, making it possible to deliver data packets

to a destination within a subnetwork.

Media access control is often used as synonym to multiple access

protocol, since the MAC sublayer provides the protocol and

control mechanisms that are required for a certain channel access

method.


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CMSA/CDPROTOCOLCMSA/CDPROTOCOL

In computer networking, Carrier Sense Multiple AccessWith Collision Detection (CSMA/CD) is a networkcontrol protocol in which a carrier sensing scheme isused.

A transmitting data station that detects another signalwhile transmitting a frame, stops transmitting that frame,transmits a jam signal, and then waits for a random time

interval (known as "backoff delay") before trying to sendthat frame again.

Ethernet is the classic CSMA/CD protocol.


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WANTECH

NOLOGIES

WANTECH

NOLOGIES


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WAN is Wide Area Network.

A WAN is a data communications network that

covers a relatively broad geographic area and that

often uses transmission facilities provided bycommon carriers, such as telephone

companies(coaxial cables) or communication

satellites.

WAN uses no fixed Network Topology.


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PACKETPACKET--SWITCHINGEXCHANGESSWITCHINGEXCHANGES

PSEs are hardware devices (special purpose

computers) dedicated to the task of data

communication.

Communication channels of the network

interconnect the PSEs.

A computer of a WAN only interacts with the PSE

of the WAN to which it is connected for sending

and receiving messages.


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AWAN of ComputersAWAN of Computers

3

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C

A

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PSE

PSEPSE

PSE1

2

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Computers


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SWITCHINGTECHNIQUESSWITCHINGTECHNIQUES

The process moving data from one interface and

delivering it through another interface, selecting

the best paths between machines that store

messages is known as switching.

There are a number of ways to perform switching:

Circuit SwitchingPacket Switching

Message Switching

Cell Switching


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CIRCUITSWITCHINGCIRCUITSWITCHING

A type of communication in which a dedicated

channel (or circuit) is established for the duration

of a transmission.

connection-oriented networks.

Ideal for communications that require data to be

transmitted in real-time or for long continuoustransmission.

Used in PSTN (Public Switched Telephone

Network).


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ADVANTAGES : ADVANTAGES :

No delay other than propagation delay.

Full capacity of the circuit is available.

Transmission time required to send a message can

be known and guaranteed.

DISADVANTAGES :DISADVANTAGES :

Additional overhead during circuit establishment

and circuit disconnection.

Channel bandwidths may be wasted.


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PACKET SWITCHINGPACKET SWITCHING

Packet Switching techniques switch packets of data

between destinations.

Each packet is then transmitted individually and can

even follow different routes to its destination (Store

and forward).

connectionless networks.

Used in X.25 public packet network and the internet.


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ADVANTAGES : ADVANTAGES :Efficient usage of channels (Bandwidths are

shared).

Alternate paths may be used (Failed paths may be

ignored).

Suitable for small data bursty in nature.

DISADVANTAGES :DISADVANTAGES :Each packet needs to be buffered and reassembled.

Inefficient for large messages.

Time taken depends on the route chosen.


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ROUTINGTECHNIQUESROUTINGTECHNIQUES

In a WAN, when multiple paths exist between thesource and destination computers of a packet, any

one of the path may be used.

Packets are routed to their destination as

determined by a routing algorithm.

An efficient routing techniqueReduces Network Latency.

Should be implementable in h/w.

Should not require Global State Info.


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Routi al orit s are classifie aseRouti al orit s are classifie ase

on t e following attri utes :on t e following attri utes :

Place where routing ecisions are a e.

Ti e c onstant of the infor ationupon

which the routing ecisions are ase .

Control echanis use for yna ic

routing.


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PLACEBASEDPLACEBASED

SOURCE ROUTING :Source computers PSE selects the entire path

before sending the packet

HOP-BY-HOP ROUTING :

Each PSE along the path decides only the next PSE

for the path.

HYBRID ROUTING :

Source comps PSE specifies certain major

intermediate PSEs of the complete path and the sub

aths are decided with ho -b -ho method.


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TIME CONSTANT BASEDTIME CONSTANT BASED

STATIC ROUTING (Fixed or Deterministic) :

Routing tables (stored at PSEs) are set once

and do not change for a very long time.

DYNAMIC ROUTING (Adaptive) :

Routing tables are updated relativelyfrequently, reflecting shorter term changes in

the network environment.


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CONTROLMECHANISMBASEDCONTROLMECHANISMBASED

ISOLATED MANNER :Individual PSEs update information in their

local routing table in an isolated manner.

CENTRALIZED MANNER :

Changes in the network

environment,connectivity, or performance are

constantly reported to one centralized PSE

based on which global table is maintained.

DECENTRALIZED MANNER :

Each PSE maintains a routing table and the

table updates are performed by mutual

interaction among the PSEs.


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INTERNETWORKINGINTERNETWORKING


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Interconnecting of two or more networks to form a

single network is called INTERNETWORKINGand the resulting network is called an

INTERNETWORK (eg. Internet).

INTERNETWORKS are heterogeneous networkscomposed of several network segments that may

differ in topology and protocol.

Goal of internetworking is to hide the details of

different physical networks so that resulting

internetwork functions as a single coordinated unit.


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INTERCONNECTIONTECHNOLOGIESINTERCONNECTIONTECHNOLOGIES

Internetworking schemes provide some common

point of reference for the two networks to

communicate with each other.This point of reference may be

High-Level protocol common to the twonetworks.

A Device that allows interconnection of differenttopologies with different physical and electrical

characteristics.

Protocol that allows operating environmentdifferences to be ignored


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BRIDGESBRIDGES

Bridges operate at the bottom two layers of the

OSI model (Physical and Data Link).

They are used to connect networks that use the

same communication protocols above the data-link

layer but may or may not use the same protocols atthe physical and data-link layers.


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ROUTERSROUTERS

Routers operate at the Network Layer of the OSImodel.

They are used to connect networks with the same High

Level protocols.

Routers unlike bridges only know which is the next

router for the data being transferred across thenetwork.

Routers choose the best route for data based on the

info in routing table.


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BROUTERSBROUTERS

Brouters are hybrid of Bridges and Routers.

They are complex,expensive and difficult to install.

They are used for connecting segments with the

same high level communication protocols.


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GATEWAYSGATEWAYS

Gateways are most sophisticated internetworking

tools.

Gateways operate at the top three layers of the OSI

model (Session, Presentation and Application).

They are used for connecting networks that are built

on totally different communication architectures.


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Communication Medium to beCommunication Medium to be

usedusedDEPENDS ON :

Location of the two networks.

Throughput desired.

OPTIONS AVAILABLE :

Leased Telephone Lines

Dedicated Telephone Lines

Public Data Networks

Communication Satellites


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Network Management TechnologiesNetwork Management Technologies

Network Management is monitoring and analysis of

network status and activities.

They monitor Data Throughput, Node and LinkFailures and other Global Occurrences on network.

They report existence and cause of the problem.

They should enfold all the protocols and devices on

a typical heterogeneous internetwork, should beeasy to use and should be intelligent.

Eg. SNMP,CMIP and DME


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CO

MMUN

ICA

TION

CO

MMUN

ICA

TION

PROTOCOLSPROTOCOLS


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The term protocol is used to refer to a set ofrules and conventions needed for

communication between communicating

parties.

Computer networks are implemented using the

concept of layered protocols.

Requirements of communication protocols for

network systems and distributed systems are

different.


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Protocols forNetwork SystemsProtocols forNetwork Systems

The OSI/ISO Reference Model

Provides a framework in which standards can bedeveloped for the services and protocols at each

layer.

It is a seven layer architecture in which a

separate set of protocols is defined for each

layer.


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The OSI/ISO Reference ModelThe OSI/ISO Reference Model

Application Layer

Presentation Layer

Session Layer

Transport Layer

Network Layer

Data Link Layer

Physical Layer


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Physical Layer:

Transmits raw bit streams between two sites.

Data Link Layer:

Detects and corrects any errors in the transmitted

data.

Network Layer:

Sets up logical path between two sites forcommunication to take place.

Two popular network layer protocols are X.25

protocol and Internet Protocol.


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Transport Layer:

Provides site-to-site communication and hides allthe details of the communication subnet from the

session layer by providing network independent

transport service.

The two most popular protocols are TCP andUDP.

Session Layer:

Provides the means by which presentation

entities can organize and synchronize their dialog

and manage their data exchange.


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Presentation Layer:

Represents message information to

communicating application layer entities in a way

that preserves meaning while resolving syntax

differences.

Application Layer:

Provides services that directly supports the endusers of the network.


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It is a modified reference model suitable for LANs

built by IEEE.

The layers in this model are similar to those of the

OSI model the only difference being that the last

two layers of the reference model are modified.

TheIEEE 802 LANReferenceTheIEEE 802 LANReference

ModelModel


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Application

LayerPresentation

Layer

Session Layer

Transport

LayerNetwork

LayerData Link

Layer

PhysicalLayer

Logical-LinkControl Layer

Medium-Access

Control Layer

Physical Layer

Relationship between theRelationship between the

IEEE LANMODEL & OSIMODELIEEE LANMODEL & OSIMODEL


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The physical layer defines interface protocols for thefour types of media that are commonly used in

LANs : baseband,broadband,fiber optics and

twisted pair.

The medium-access-control layer deals with

medium access control protocols for LANs.

The logical-link-control layer contains the IEEE

802.2 standard.


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Protocol forDi tri tedProtocol forDi tri ted

SystemsSystems

Requirements for distributed systems

TransparencyClient-server based communication

Group communication

Security

Network management

Scalability


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The VersatileMessageTransportThe VersatileMessageTransport

Protocol (VMTP)Protocol (VMTP)

It is a transport protocol designed for distributed

operating systems that has special features to

support request/response behavior between a client

and one or more server processes.

Entities are identified by 64 bit identifiers.

It provides selective retransmission mechanism.

It uses a rate-based flow control mechanism


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TheFast Local InternetTheFast Local Internet

Protocol (FLIP)Protocol (FLIP)

It is a connectionless protocol designed to supporttransparency, group communication, secure

communication and easy network management.

The following FLIP properties helps to achieve theefficiency requirements for distributed systems.


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FLIP identifies entities called network serviceaccess points (NSAPs)


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FLIP uses a one way mapping between the private

address, used to register an endpoint of a network

connection, and the public address used to

advertise the endpoint.

FLIP routes messages based on NSAP.

FLIP uses a bit in the message header to request

transmission of sensitive messages across trusted

networks.


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ATMNETWORKSATMNETWORKS


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FEATURESFEATURES

Enables high-bandwidth distributed applications.

Provides high transmission speeds for local and

wide-area networks and services.

Supports circuit switching and packetswitching.[CELL SWITCHING]

Uses the concept of virtual networking to pass

traffic between 2 locations.

Supports multi-casting.Enables use of single network to efficiently

transport a wide range multimedia data.

It is flexible since it grants access to bandwidth


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BASIC CONCEPTSBASIC CONCEPTS

Fundamental types of network traffic-CBR & VBR.

Connection oriented technology.

Cell Switching technology is based on the digital packet

switching technology which relays and routes traffic over

virtual path by means of an address contained within the

packet.

In ATM, a virtual path is essentially a bundle of virtual

channels that can be multiplexed together.


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ATM

Protocol Reference Model

ATM

Protocol Reference Model

Other layers not specified in ATM protocol

reference model

ATM Adaptation Layer (AAL)

ATM Layer

Physical Layer


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PHYSICALLAYERPHYSICALLAYER

By carrying cells as a synchronous data stream.

By carrying cells in the payload portion of an

externally framed transmission.

SONET (Synchronous Optical NETwork).


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ATMLAYERATMLAYER

Generic Flow Control (GFC)

Virtual Path Identifier (VPI)Virtual Circuit Identifier (VCI)

Payload Type Identifier (PTI)

Cell Loss Priority (CLP) Field

Header Error Control (HEC) Field


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4 bits 48 bits8 bits 16 bits 3 bits 1 bit 8 bits

Payload areaHeader area

GFC VPI VCI PTI CLP HEC Payload

ATM CE

LLFO

RMA

TA

TM CELL

FO

RMA

T


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ATM ADAPTATIONLAYERATM ADAPTATIONLAYER

Responsible for providing different types of services todifferent types of traffic according to their specific

requirements.

It packages various kinds of user traffics into 48-byte cells,

together with the overhead.

Four service classes defined by the ITU:

CLASS A: Applications having delay sensitive &

CBR traffic & are connection oriented.

CLASS B: Applications having delay sensitive &


CLASS C: Applications having delay sensitive &


CLASS D: Applications having delay sensitive &



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Four service classes defined by the ITU:

CLASS A:Applications having delay sensitive &

CBR traffic & are connection oriented. Ituses AAL1 protocol.

CLASS B:Applications having delay sensitive &

VBR traffic & are connection oriented. It

uses AAL2 protocol.CLASS C:Applications that are not delay

sensitive & VBR traffic & are connection

oriented. It uses AAL3/4 or AAL5 protocol.

CLASS D:Applications that are not delaysensitive & VBR traffic & are not

connection oriented. It uses AAL3/4 or

AAL5 protocol.


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ATMNETWORKSATMNETWORKS

ATM SWITCH

ATMSWITCH

ATMSWITCH

Host Computers


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THANK YOUTHANK YOU

h002 computer networks

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