introduction to network structure and protocol

8/2/2019 Introduction to Network Structure and Protocol

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Fundamentals of Networking:

Introduction to Network Structureand Protocol

Dr. Hania Farag


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Overview

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Monday, September 12, 2011

Basic concepts in communications

Understanding Networking.

Understanding Transmission Medium (Network

Cables) Understanding Network Hardware

Understanding Network Protocols


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Overview

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Basic concepts in communications Understanding Networking.


Cables)

Understanding Network Hardware



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Basic Concepts in Communication

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Communicationsactivity associated with distributingor exchanging information

Telecommunicationstechnology of communications at

a distance that permits information to be created any

where and used everywhere with little delay Today it, involves

Data: digital and analog

Voice: spoken word

Video: telelcommunication imaging


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Essentials for Communications

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Message

Transmitter / Receiver Medium

Message must be understood

Some level of security

Source Transmitter Transmission Receiver Destination

Source System Destination System

Workstation/PCWorkstation/PC

Medium


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Overview

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Cables)


WAN and LAN



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What do you see here for a typical network?

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Key Network Terminology Explained (1)

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Networks needs to interconnect at a distance by aform of point to point or point to multiple point

connected media

Networks that are interconnected have proven to be

low cost, reliable, and efficient means of

communicating at a distance


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Node: anything connected to the network, usually a

computer, but it could be a printer or a scanner

Segment: any portion of a network that is separated by a

switch, bridge or a router from another part of a network.

Backbone: the main cabling of a network that all of thesegment connect to. Usually, the backbone is capable of

carrying more information than the individual segments.

Topology: The way each node is physically connected to

the network


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Simplex: information flows in only one direction

Half-duplex: information flows in two directions, but

only in one direction at a time.

Full-duplex: information flows in two directions atthe same time


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Basic Signal Terminologies

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Bit: binary digit, either 0 or 1

Baud : one electronic state change per second

Bit rate :a method for measuring data transmission

speedbits per second

Mbps : millions of bits per second (data speed;measure of bandwidth = total information flow over

a given time) on a telecommunication medium

8 bits = 1 byte

Teraflops : trillion operations per second


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TYPES OF NETWORKS

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LANLOCAL AREA NETWORK IS A SMALL

GEOGRAPHICAL AREA SUCH AS OUR SCHOOLBOARD.

MANMETROPOLITAN AREA NETWORK IS A

NETWORK OVER A LARGER GEOGRAPHICAL AREA

SUCH AS THE PROVINCIAL GOVERNMENT.

WANWIDE AREA NETWORK IS A NETWORK USED

OVER AN EXTREMELY LARGE GEOGRAPHICAL AREA

SUCH AS THE FEDERAL GOVERNMENT.


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Topologies

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Physical layout of network devices

Four types: mesh, bus, ring, and

star


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Mesh Topology

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Mesh Topology

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It is also called apoint-to-pointtopology. Each device is connected directly to all other

network devices.

It provides fault tolerance.

It is only found in wide area networks.


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Bus Topology

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Bus Topology

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It is a multipointtopology. Each device shares the connection.

The bus has one starting and one ending point.

Packets stop at each device on the network. Only one device at a time can send.


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Ring Topology

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Ring Topology

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It is a circle with no ends. Packets are sent from one device to

the next.

It does not slow down as more

devices are added.


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Star Topology

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Star Topology

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All devices are connected to a central device(hub).

The hub receives and forwards packets.

It is the easiest topology to troubleshoot and

manage.


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Hybrid Topologies

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They are variations of two or more topologies.

Star busused to connect multiple hubs in astar topology with a bus.

Star ringwired like star, but functions like a

ring.


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Star Bus Topology

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Design Considerations

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The best topology involves matchingwith the environment it is to be usedin.

The physical arrangement ofcomputers do not dictate the necessarytopology.


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Overview

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Cables)


WAN and LAN



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Basic transmission medium concepts

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Medium is the physical path between transmitter and

receiver in a data transmission system

Guided Medium: waves are guided along a solid

medium path (twisted pair, coaxial cable, and optical

fiber). Unguided medium: waves are propagated through

the atmosphere and inner/outerspace (satellite, laser,

and wireless transmissions).


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Medium examples by type

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Conductive: twisted pairs and coaxial cables

Electromagnetic: microwave

Light: lasers and optical fibers (need clear line of

sight)

Wirelessinner/outerspace; satellite(omnidirectional security issues)


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Coaxial cable (1)

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Widely installed for use in business and corporation

ethernet and other types of LANs. Consists of inter copper insulator covered by

cladding material, and then covered by an outer

jacket

i l bl


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Coaxial cable (2)

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Applications:

TV distribution (cable tv); long distance telephonetransmission; short run computer system links

Local area networks

Transmission characteristics: Can transmit analog and digital signals

Usable spectrum for analog signaling is about 400

Mhz

T i d P i C bl


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Twisted Pair Cable

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T i d P i C bl
http://upload.wikimedia.org/wikipedia/commons/2/21/FTP_cable3.jpg


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Twisted Pair Cables

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Physical description:

Each wire with copper conductor

Separately insulated wires twisted together to reduce cross talk

If enclosed in a sheath then is shielded twisted pair (STP) otherwise often

for home usage unshielded twisted pair (UTP). Must be shield from

voltage lines

Application: Common in building for digital signaling used at speed of 10s Mb/s

(CAT3) and 100Mb/s (CAT5) over 100s meters.

Common for telephone interconnection at home and office buildings

Less expensive medium; limited in distance, bandwidth, and data rate.

C i f T i d P i C bli S


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Categories of Twisted Pairs Cabling System

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Category Maximum datarate

Usual application

CAT 1 Less than 1 Mbps analog voice (plain old telephoneservice) Integrated Services DigitalNetwork Basic Rate Interface in ISDNDoorbell wiring

CAT 2 4 Mbps Mainly used in the IBM Cabling Systemfor token ring networks

CAT 3 16 Mbps Voice and data on 10BASE-T Ethernet(certify 16Mhz signal)

CAT 4 20 Mbps Used in 16Mbps Token Ring

Otherwise not used much

CAT 5 100 Mbps 100 Mbps TPDDI

155 Mbps asynchronous transfermode (certify 100 Mhz signal)

O ti l fib


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Optical fiber

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O ti l Fib
http://en.wikipedia.org/wiki/File:Fibreoptic.jpghttp://en.wikipedia.org/wiki/File:Fiber_optic_illuminated.jpg


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Optical Fibers

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Physical Description:

Glass or plastic core of optical fiber = 2to125 m

Laser or light emitting diode provides transmission lightsource

Applications:

Long distance telecommunication Greater capacity; 2 Gb/s over 10s of Km

Smaller size and lighter weight

Lower attenuation (reduction in strength of signal)

Electromagnetic isolationnot effected by externalelectromagnetic environment.

Wi l T i i


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Wireless Transmission

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Frequency range (line of sight): 26 GHz to 40 GHz: for microwave with highly directional

beam as possible

30 MHz to 1 GHz: for omnidirectional applications

300MHz to 20000 GHz: for infrared spectrum; used for pointto point and multiple point application (line of sight)

Physical applications: Terrestrial microwavelong haul telecommunication service

(alternative to coaxial or optical fiber)

Propagation via towers located without blockage from trees,etc (towers less than 60 miles apart)

O i


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Overview

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Cables)


WAN and LAN


Hubs


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Hubs

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A hub is the place where data converges from one or

more directions and is forwarded out in one or more

directions.

Seen in local area networks

Gateways


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Gateways

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A gateway is a network point that acts as an entranceto another network.

Routers


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Routers

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A router is a device or a software in a computer that

determines the next network point to which a packetshould be forwarded toward its destination.

Allow different networks to communicate with eachother

A router creates and maintain a table of the availableroutes and their conditions and uses this informationalong with distance and cost algorithms to determine thebest route for a given packet.

A packet will travel through a number of network points

with routers before arriving at its destination.

Bridge


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Bridge

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a bridge is a product that connects a local area

network (LAN) to another local area network that

uses the same protocol (for example, Ethernet or

token ring).

A bridge examines each message on a LAN,"passing" those known to be within the same LAN,

and forwarding those known to be on the other

interconnected LAN (or LANs).

What is the difference between?


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What is the difference between?

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Bridge: device to interconnect two LANs that use the

SAME logical link control protocol but may use

different medium access control protocols.

Router: device to interconnect SIMILAR networks,

e.g. similar protocols and workstations and servers Gateway: device to interconnect DISSIMILAR

protocols and servers, and Macintosh and IBM LANs

and equipment

Switches


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Switches

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Allow different nodes of a network to communicate

directly with each other.

Allow several users to send information over a

network at the same time without slowing each other

down.

Circuit Switching Technologies


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Circuit Switching Technologies

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Circuit switching is a dedicated communications path established

between two stations or multiple end points through nodes of the WAN Transmission path is a connected sequence of physical link between

nodes.

On each link, a logical channel is dedicated to the connection. Data

generated by the source station are transmitted along dedicated path as

rapidly as possible.

At each node, incoming data are routed or switched to the appropriate

outgoing channel without excessive delay. However, if data processing

is required, some delay is experienced.

Example of circuit switching above is the telephone networks.

Packet Switching Technologies


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Packet Switching Technologies

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Data are sent out in a sequence of small chucks, calledpackets.

Each packet, consisting of several bits is passed through thenetwork from node to node along some path leading from thesource to the destination

At each node along the path, the entire packet is received,

stored briefly, and then transmitted to the next node. At destination all individual packets are assembled together

to form the complete text and message from the source. Eachpacket is identified as to its place in the overall text forreassembly.

If packet errors occur, the packet is retransmitted.

Frame Relay Techniques


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Frame Relay Techniques

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Each packet included additional bits and each node performed

additional processing to insure reliable transmission. Frame relay has removed the overhead bits and additional processing.

It has become unnecessary to invoke these overhead checks andthereby enables higher capacity transmission rates.

Frame relay takes advantage of these high rates and low error rates.

Frame relay networks are designed to operate efficiently at user datarates of 2 Mb/s and higher. (packet switching originally designed witha 64 Kb/s data rate to the end user).

Frame relay achieves these higher rates by stripping out most of theoverhead involved with error control.

Asynchronous Transfer Mode (ATM)


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Asynchronous Transfer Mode (ATM)

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Evolution from frame relay and circuit switching.

Major differences: Frame relay uses variable length packets

called frames. ATM uses fixed length packets called

cells.

ATM provides little overhead for error control like frame

relay, and depends on inherent reliability of the transmissionsystem and on higher layers of logic in the end systems to

identify and correct errors.

ATM is designed to operate in range of 10s to 100 Mb/s

compared to frame relay (2 Mb/s)

ISDN and


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ISDN and

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Integrated services digital network (ISDN) was intended to

be a world wide public telecommunication network toreplace existing public telecommunication networks anddeliver a wide variety of services.

ISDN has standardized user interfaces, implemented a set ofdigital switches and paths supporting a broad range of traffictypes and providing a value added processing service

ISDN is multiple networks, but integrated to provide userwith single, uniform accessibility and world wideinterconnection.

Broadband ISDN Technology


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Broadband ISDN Technology

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First generation ISDN was narrowband, 64 Kb/s

channel of switching and circuit switchingorientations. Frame relay resulted from the ISDNnarrowband efforts.

Second generation is broadband ISDN. It supports

high data rates of 100 Mb/s and has a packetswitching orientation. ATM resulted from thebroadband ISDN efforts.

What is ethernet?


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What is ethernet?

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A group of standards for defining a local areanetwork that includes standards in cabling and the

structure of the data sent over those cables as well as

the hardware that connects those cables.

Independent of the network architecture

Network Interface Card (NIC)


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Network Interface Card (NIC)

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Every computer and most devices (e.g. a network

printer) is connected to network through an NIC. Inmost desktop computers, this is an Ethernet card (10

or 100 Mbps) that is plugged into a slot on the

computer motherboard.

How does Ethernet work?


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How does Ethernet work?

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Using MAC addresses to distinguish betweenmachines

What is a MAC Address?


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Media Access Control (MAC) Addressare thephysical address of any device.

The MAC address has two parts of 3 bytes long. The

first 3 bytes specify the company that made the NIC

(Network Interface Card) and the second 3 bytes arethe serial number of the NIC.

Overview


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Cables)



Protocols of Computer Communications anN t k


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Networks

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Protocol are used for communication between computers in different

computer networks. Protocol achieves:

What is communicated between computers?

How it is communicated?

When it is communicated?

What conformance (bit sequence) between computers?

Key elements of a protocol are:

SYNTAC: Data format and signal levels

SEMANTICS: Control information for coordination and error handling

TIMING: Synchronization, speed matching, and sequencing

Examples of protocols:

WAN Protocol: TCP/IP LAN Protocol: Media Access Control; Contention; Token Passing

ISO/OSI Reference Model (1)


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( )

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Open Systems Interconnection

No one really uses this in the real world.

A reference model so others can develop detailed

interfaces.

The reference model defines 7 layers of functions

that take place at each end of communication and

with each layer adding its own set of special related

functions.

ISO/OSI Reference Model (2)


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( )

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How to transmit signal; codingHardware means of sending and receiving data on a carrier

Two party communication: Ethernet

Routing and Forwarding Address: IP

End-to-end control & error checking

(ensure complete data transfer): TCP

Establish/manage connection

ASCII Text, Sound (syntax layer)

File Transfer, Email, Remote Login

What is TCP/IP?


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Transmission Control Protocol (TCP)uses a set of rules to

exchange messages with other Internet points at theinformation packet level

Internet Protocol (IP)uses a set of rules to send and receive

messages at the Internet address level

TCP (example)


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p

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Web Server: serves HTML pages

TCP layer in the server divides the file into one or morepackets, numbers the packet, then forward packetsindividually to IP.

Note: each packet has the same destination IP address, itmay get routed differently through the network.

TCP (on the client) reassembles the individual packetsand waits until they have arrived to forward them as asingle file.

Connection-oriented protocol

IP


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Connectionless protocol (I.e. no established

connection between the end points that arecommunicating.)

Responsible for delivery the independently treated

packet !!!!

TCP responsible for reassembly.

Overview


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Cables)




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