PAN African e-Network Project

PGDITNetworking Fundamental

Semester - II

Session - 2

Dr. A.V Singh

Networking Devices

Network Structure Define the elements of communication

3 common elements of communication message source the channel message destination

Define a network data or information networks capable of carrying many different types

of communications

Describe how messages are communicated Data is sent across a network in small chunks called segments

Define the components of a network Network components

hardware software

End Devices and their Role in the Network End devices form interface with human network & communications network Role of end devices:

client server both client and server

Identify the role of an intermediary device in a data network and be able to contrast that role with the role of an end device

Role of an intermediary device provides connectivity and ensures data flows across network

Define network media and criteria for making a network media choice Network media this is the channel over which a message travels

LAN Device SymbolsLayer 1

Transceiver

Hub

Repeater

LAYER 1Repeater

Cleans up (regenerates) and repeats the signal.

Used when a networks cabling extends beyond its capability.

LAYER 1Transceiver

Transmitter and Receiver of electronic signalsspecialized repeater.

Connects different media technologies

Also called a MAU (Media Attachment Unit)

FiberCat 5 UTP

LAYER 1Hub

Simply a multi-port repeater.

Used to connect multiple devices to the same network drop.

The Cloud

Hubs are multiport repeaters The difference between the two devices is the number of ports While a repeater has just two ports, a hub generally has from four to twenty-

four ports Sometimes hubs are called concentrators

Hubs come in three basic types: Passive A passive hub serves as a physical connection point only.

Passive hub does not need electrical power.

Active An active hub must be plugged into an electrical outlet because itneeds power to amplify the incoming signal before passing it out to theother ports

Intelligent Intelligent hubs are called smart hubs. These devicesfunction as active hubs and include a microprocessor chip and diagnosticcapabilities

LAN Device SymbolsLayer 2

Bridge

Switch

LAYER 2Bridge

Connects two LAN segments.

Keeps traffic local by filtering traffic based on MAC Addresses.

The bridge makes decisions about whether or not topass signals on to the next segment of a network

When a bridge receives a frame on the network, thedestination MAC address is looked up in the bridgetable to determine whether to filter, flood, or copy theframe onto another segment

LAYER 2Switch

Connects multiple LAN segments.

Can be called a multi-port bridge.

Provides full bandwidth out each port.

The Cloud

A switch is sometimes described as a multiport bridge

A bridge may have just two ports linking two network segments

All switching equipment performs two basic operations. Switching data frames Building and maintaining switching tables

Switching alleviates congestion and reduces traffic by increasing the number of collision domains.

Switches micro segment a network

Layer Three Devices

Router

LAYER 3Router

Can be used to connect different Layer 2 devices and different topologies.

Makes decisions based on network addresses (IP Addresses).

The Cloud

Transmission Terminology

Simplex Communication

A simplex system is a communication system inwhich the message can be send in one directiononly.

Radio and TV boardcasting are eg User Transmitter Receiver User

Half Duplex communication A half-duplex system provides for communication in both directions, but

only one direction at a time (not simultaneously). Typically, once a partybegins receiving a signal, it must wait for the transmitter to stoptransmitting, before replying.

An example of a half-duplex system is a two-party system such as a"walkie-talkie" style two-way radio, wherein one must use "Over" oranother previously-designated command to indicate the end oftransmission, and ensure that only one party transmits at a time, becauseboth parties transmit on the same frequency.

Full Duplex Communication A full-duplex, or sometimes double-duplex system, allows

communication in both directions, and, unlike half-duplex, allows thisto happen simultaneously. Land-line telephone networks are full-duplex, since they allow both callers to speak and be heard at thesame time. A good analogy for a full-duplex system would be a two-lane road with one lane for each direction. For example: Telephone,Mobile Phone, etc.

Bandwidth Bandwidth is defined as the amount of information that can flow through a

network connection in a given period of time.

Why Bandwidth is important:

It is limited by physics and technology.Bandwidth is not free.Bandwidth requirement are growing at a rapid rate.Bandwidth is critical to network performance.

Serial Communication Serial communication is the process of

sending data one bit at a time, sequentially, overa communication channel or computer bus.

Serial communication is used for all long-haulcommunication and most computer networks,where the cost of cable and synchronizationdifficulties make parallel communicationimpractical

Parallel Communication

Parallel communication is a method of sending severaldata signals simultaneously over several parallelchannels. It contrasts with serial communication; thisdistinction is one way of characterizing acommunications link

A parallel link transmits several streams of data (perhapsrepresenting particular bits of a stream of bytes) alongmultiple channels (wires, printed circuit tracks, opticalfibres, etc.) where as a serial link transmits a singlestream of data.

Analog Transmission

Analog transmission is a transmission method of conveying voice,data, image, signal or video information using a continuous signalwhich varies in amplitude, phase, or some other property inproportion to that of a variable.

There are two basic kinds of analog transmission, both based onhow they modulate data to combine an input signal with a carriersignal. Usually, this carrier signal is a specific frequency, and data istransmitted through its variations. The two techniques are amplitudemodulation (AM), which varies the amplitude of the carrier signal,and frequency modulation (FM), which modulates the frequency ofthe carrier

Benefits & drawback of analog Transmission

Analog transmission is still very popular, in particular for shorter distances,due to significantly lower costs and complex multiplexing and timingequipment is unnecessary, and in small "short-haul" systems that simply donot need multiplexed digital transmission.

However, in situations where a signal often has high signal-to-noise ratioand cannot achieve source linearity, or in long distance, high outputsystems, analog is unattractive due to attenuation problems. Furthermore,as digital techniques continue to be refined, analog systems areincreasingly becoming legacy equipment.

Recently, some nations, such as the Netherlands, have completely ceasedanalog transmissions on certain media, such as television,for the purposesof the government saving money.

Digital Transmission

A method of storing, processing and transmittinginformation through the use of distinct electronicor optical pulses that represent the binary digits0 and 1

Advantages of Digital

Less expensiveMore reliableEasy to manipulateFlexibleCompatibility with other digital systemsOnly digitised information can be transported

through a noisy channel without degradation Integrated networks

Transmission Media

Guided Media

Unguided Media

Guided Media Coaxial Cable

Twisted Pair Cable

Fiber-Optic Cable

Coaxial Cable

Coaxial cable consists of a copper conductor surrounded by a layerof flexible insulation.

The center conductor can also be made of tin plated aluminiumcable allowing for the cable to be manufactured inexpensively. Overthis insulating material is a woven copper braid or metallic foil thatacts as the second wire in the circuit and as a shield for the innerconductor. This second layer, or shield also reduces the amount ofoutside electromagnetic interference. Covering this shield is thecable jacket.

STP (Shielded Twisted Pair)

STP cable combines the techniques of cancellation,shielded, and twisted wires.

STP reduces electrical noise within the cable such aspair to pair coupling and crosstalk. STP also reduceselectronic noise from outside the cable such aselectromagnetic interference (EMI) and radio frequencyinterference (RFI). STP cable shares many of theadvantages and disadvantages of UTP cable. STPprovides more protection from all types of externalinterference. However, STP is more expensive anddifficult to install than UTP.

UTP (Unshielded Twisted Pair)

UTP is a four-pair wire medium used in a variety ofnetworks. Each of the eight copper wires in the UTPcable is covered by insulating material. In addition, eachpair of wires is twisted around each other.

This type of cable relies on the cancellation effectproduced by the twisted wire pairs to limit signaldegradation caused by EMI and RFI. To further reducecrosstalk between the pairs in UTP cable, the number oftwists in the wire pairs varies. Like STP cable, UTP cablemust follow precise specifications as to how many twistsor braids are permitted per foot of cable.

Wave Length

The wavelength of an electromagnetic wave is determined by how frequentlythe electric charge that generates the wave moves back and forth.

Facts About Wavelength

Wavelengths that are not visible to the human eye areused to transmit data over optical fiber.

These wavelengths are slightly longer than red light andare called infrared light. Infrared light is used in TVremote controls.

The wavelength of the light in optical fiber is either 850nm, 1310 nm, or 1550 nm. These wavelengths wereselected because they travel through optical fiber betterthan other wavelengths.

Electromagnetic SpectrumRadio, microwaves, radar, visible light, x-rays, and gamma rays are all types of electromagneticenergy. If all the types of electromagnetic waves are arranged in order from the longestwavelength down to the shortest wavelength, a continuum called the electromagnetic spectrum iscreated

Visible SpectrumHuman eyes were designed to onlysense electromagnetic energy withwavelengths between 700 nanometersand 400 nanometers (nm).

A nanometer is one billionth of a meter(0.000000001 meter) in length.Electromagnetic energy withwavelengths between 700 and 400 nmis called visible light.

The longer wavelengths of light that arearound 700 nm are seen as the colorred.

The shortest wavelengths that arearound 400 nm appear as the colorviolet. This part of the electromagneticspectrum is seen as the colors in arainbow

Fiber OpticsThe part of an optical fiber through whichlight rays travel is called the core of thefiber.

Light rays can only enter the core if theirangle is inside the numerical aperture ofthe fiber.

Likewise, once the rays have entered thecore of the fiber, there are a limited numberof optical paths that a light ray can followthrough the fiber. These optical paths arecalled modes.

Single-Mode Vs Multi-Mode

Multi-Mode and Single-Mode

Duplex Fiber

Fiber Optic ConnectorsConnectors are attachedto the fiber ends so thatthe fibers can beconnected to the ports onthe transmitter andreceiver.

The type of connectormost commonly used withmultimode fiber is theSubscriber Connector(SC).

On single-mode fiber, theStraight Tip (ST)connector is frequentlyused.

UNGUIDED MEDIA (WIRELESS)

Radio Waves

Microwaves

Infrared

Radio WavesComputers send data signals electronically. Radiotransmitters convert these electrical signals to radiowaves. Changing electric currents in the antenna ofa transmitter generates the radio waves.

Radio waves radiate out in straight lines from theantenna. However, radio waves attenuate as theymove out from the transmitting antenna. In aWLAN, a radio signal measured at a distance ofjust 10 meters (30 feet) from the transmittingantenna would be only 1/100th of its originalstrength.

Like light, radio waves can be absorbed by somematerials and reflected by others. When passingfrom one material, like air, into another material, likea plaster wall, radio waves are refracted. Radiowaves are also scattered and absorbed by waterdroplets in the air.

Microwaves Electromagnetic waves having frequencies

between 1 and 300 GHz are called microwaves. Microwaves are unidirectional. Microwave band is relatively wide, almost 299

GHz. Microwaves are used for unicast communication

such as cellular telephones, satellite networks,and wireless LANs.

Infrared Infrared signals, with frequencies from 300 GHz

to 400 THz (wavelength from 1mm to 770mm),can be used for short-range communication.

Cannot be used outside a building because theSuns rays contain infrared waves that caninterfere with communication.

Infrared signals can be used for short-rangecommunication in a closed area using line-of-sight propagation.

Wireless LAN Standards

802.11

A key technology contained within the 802.11 standardis Direct Sequence Spread Spectrum (DSSS). DSSSapplies to wireless devices operating within a 1 to 2Mbps range. A DSSS system may operate at up to 11Mbps but will not be considered compliant above 2Mbps.

802.11b 802.11b increased transmission capabilities to 11 Mbps.

802.11b may also be called Wi-Fi or high-speed wireless andrefers to DSSS systems that operate at 1, 2, 5.5 and 11 Mbps. All802.11b systems are backward compliant in that they also support802.11 for 1 and 2 Mbps data rates for DSSS only. This backwardcompatibility is extremely important as it allows upgrading of thewireless network without replacing the NICs or access points.

802.11b devices achieve the higher data throughput rate by using adifferent coding technique from 802.11, allowing for a greateramount of data to be transferred in the same time frame. Themajority of 802.11b devices still fail to match the 11 Mbps bandwidthand generally function in the 2 to 4 Mbps range.

802.11a

802.11a covers WLAN devices operating in the 5 GHZtransmission band. Using the 5 GHZ range disallowsinteroperability of 802.11b devices as they operate within2.4 GHZ.

802.11a is capable of supplying data throughput of 54Mbps and with proprietary technology known as "ratedoubling" has achieved 108 Mbps. In productionnetworks, a more standard rating is 20-26 Mbps.

802.11g 802.11g provides the same bandwidth as 802.11a but

with backwards compatibility for 802.11b devices usingOrthogonal Frequency Division Multiplexing (OFDM)modulation technology.

Cisco has developed an access point that permits802.11b and 802.11a devices to coexist on the sameWLAN. The access point supplies gateway servicesallowing these otherwise incompatible devices tocommunicate.

Internet AddressingA Technical Overview

Overview

Background Internet Address History Internet Address Allocators Conclusions

Addresses -- How to get here from there

Addresses provide information on how to locate something, e.g., what route to take from here to there.

Internet addresses combine a routing portion, known as the network part a name portion known as the host part

How to split an Internet address into the network part and the host part has changed over time

The Beginning Back when the TCP/IP protocols were first

being designed, there was a big argument between fixed length and variable length addresses Fixed length will always be limited

But if you make it big enough, no one will notice

Variable length will always take more cycles to process

But there are tricks you can play to minimize the difference

The decision was made for fixed, 32 bit addresses Rumor has it, by a flip of a coin...

IP version 4 Addresses 32 bit unsigned integers

possible values 0 - 4,294,967,295 Typically written as a dotted quad of octets

four 8 bit values with a range of 0-255 separated by . For example, 202.12.28.129 can be written as below

202

1 1 0 0 1 0 1 0 0 0 0 0 1 1 0 0 0 0 1 1 1 0 0 0 1 0 0 0 0 0 0 1

12 28 129. . .

Internet Addresses

A subset of IPv4 addresses One of an infinite number

Guaranteed globally unique by the IANA Generally allocated by delegated authorities such as Internet

service providers or regional registries Assumed to be routable

Bad assumption

Partitioned into two parts A host part that identifies a particular machine on a local or wide

area network A network part that gives routers information how to get to the

local or wide area network via the Internet

Internet Address Structure

Originally, the architects of the Internet thought 256 networks would be more than enough Assumed a few very large (16,777,216 hosts) networks They were wrong (in case you were wondering)

Addresses were partitioned as below 8 bit network part, 24 bit host part

Network Part Host Part

Classfull Addressing

Original addressing plan too limiting More than 256 networks with many fewer hosts

than 224

Solution was to create address classesNetwork Part Host Part

0

Network Part Host Part

1 0

Network Part Host Part

1 1 0

1 1 1 0

1 1 1 1

Class A128 networks16,777,216 hosts

Class B16,384 networks65,536 hosts

Class C2,097,152 networks256 hosts

Class DMulticast268,435,456Addresses

Class EReserved268,435,456Addresses

The Problem

Class A way too big 16 million hosts in a flat network is unthinkable

Class B too big Even 65536 host addresses is too many in most

cases Imagine 65534 hosts all responding to a broadcast

Class C too small Most sites initially connecting to the Internet were

large Universities, 256 was too small for them Need more flexibility!

Subnetting

Classfull addressing was a better fit than original but class A and B networks impossible to manage

Solution was to partition large networks internally into sub-networks (subnets) Typically class C (8 bit host part) sized subnets

although variable length subnets used too"Real" Host Part

"Subnet" PartNetwork Part "Effective" Host Part

Classless Addressing Forget what I just told you

Classfull addressing is officially Bad 3 sizes just dont fit all -- very wasteful

Better solution is to use variable length partitioning between the host and network parts Actual partitioning for a site provided by routing protocol notation is dotted quad followed by a / and the network part

length, e.g., 202.12.28.129/26 First host on 64 host network starting at 202.12.28.128

No need for subnets202

1 1 0 0 1 0 1 0 0 0 0 0 1 1 0 0 0 0 1 1 1 0 0 0 1 0 0 0 0 0 0 1

12 28 129

Network Part (26 bits) Host Part(6 bits)

Example of Classless Addressing

202.12.28.0/25128 hosts

202.12.28.128/2664 hosts

202.12.28.192/2664 hosts

202.12.28.128/25128 hosts

202.12.28.0/24256 hosts

202.12.29.0/24256 hosts

202.12.28.0/23512 hosts

202.12.30.0/24256 hosts

202.12.31.0/25128 hosts

202.12.31.128/25128 hosts

202.12.31.0/24256 hosts

202.12.28.30/23512 hosts

202.12.28.0/221024 hosts

Prefix 202.12.28.0/22 1024 host addresses announced as a single

network (important!)

Consists of 7 subnets 202.12.28.0/25 202.12.28.128/26 202.12.28.192/26 202.12.29.0/24 202.12.30.0/24 202.12.31.0/25 202.12.31.128/25

Summary

Internet addresses are 32 bit fixed length globally unique numbers One subset of all IPv4 address spaces

Internet addresses have evolved over time to be more flexible and to include hierarchy

Currently, classless addressing is in use providing arbitrary host and network part lengths.

Q1. The device used in a data communication network to perform the conversion between analogue and digital signals, is called a ....

a) Front end processor.b) Modem.c) Decoder.d) Multiplexer.

Q2. A router:a) Determines on which outgoing link a packet is to be forwardedb) Forwards a packet to all outgoing linksc) Forwards a packet to the next free outgoing linkd) Forwards a packet to all outgoing links, except the link upon which the

packet originated.

Multiple Choice Questions

Q3. The device operating at Data link layer isa) Bridgeb) Routerc) Repeaterd) None of the above

Q4. What is the central device in star topology?a) STP serverb) Hub/switchc) PDCd) Router

Q5. Why are pairs of wires twisted together in UTP cable?a. Twisting of the wires makes six pairs fit in the space of four pairs.b. Twisting of the wires makes it low expensivec. Twisting of wires makes it thinnerd. Twisting of wires reduces noise problems.

Q6. Which material is considered to be electrical semiconductora. Airb. Siliconc. Glassd. Gold

Q7. Which of the following are the parts that make UTP cables (choose two)a. Center core b. Cladding c. Twisted wire pairsd. Shielding e. Outer Jacketf. Buffer

Q8.Which of the following cable is used to connect to a router to the serial port of the PC

a. A roll over cableb. An inverted cablec. Cross over cable

d. Straight- through cable

Q9. Which of the followings are the parts of the fiber cable? a. Braidb. Corec. Cladding d. Twisted pair e. Bufferf. Shielding

Q10. Transmission media are usually categorized as a. Fixed or unfixedb. Guided or unguidedc. Determinate or indeterminated. Metallic or nonmetallic

Thank You

Please forward your query

To: avsingh@amity.eduCC: manoj.amity@panafnet.com