basics of communications

8/14/2019 Basics of Communications

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Basics ofBasics ofCommunicationsCommunications


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Elements of CommunicationElements of Communication

SystemSystem


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SignalsSignals

Analog SignalsAnalog Signals

Digital SignalsDigital Signals


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Pulse Code ModulationsPulse Code Modulations

It Converts Analog signal to DigitalIt Converts Analog signal to Digital

SignalSignal

Why PCM ?Why PCM ?

Practical implementationPractical implementation

SamplingSampling

QuantizingQuantizing EncodingEncoding


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SamplingSampling


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QuantizingQuantizing


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EncodingEncoding


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Contd..Contd..

PCM uses non-linear encoding, i.e., amplitudePCM uses non-linear encoding, i.e., amplitudespacing of levels is non-linear.spacing of levels is non-linear.

There is a greater number of quantizing steps for lowThere is a greater number of quantizing steps for lowamplitude.amplitude.

This reduces overall signal distortion.This reduces overall signal distortion. This introducesThis introduces quantizing error (or noise).quantizing error (or noise). PCM pulses are then encoded into a digital bitPCM pulses are then encoded into a digital bit

stream.stream.

8000 samples/sec x 8bits/sample = 64 Kbps for8000 samples/sec x 8bits/sample = 64 Kbps fora single voice channel.a single voice channel.


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DATA TRANSMISSIONDATA TRANSMISSION

Parallel TransmissionParallel Transmission

Serial TransmissionSerial Transmission

Synchronous TransmissionSynchronous Transmission Asynchronous TransmissionAsynchronous Transmission


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Parallel Transmission


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Serial Transmission


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Asynchronous Transmission


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Synchronous Transmission


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MultiplexingMultiplexing

Multiplexing Techniques:Multiplexing Techniques:Frequency Division MultiplexingFrequency Division Multiplexing

Time Division MultiplexingTime Division Multiplexing


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Frequency Division MultiplexingFrequency Division Multiplexing


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Why 4KHzWhy 4KHz

In Practical Communication AllottedIn Practical Communication Allotted

0-4KHz0-4KHz

In Frequency shifting process twoIn Frequency shifting process two

new Frequency Bands will be addednew Frequency Bands will be added

1.Lower Side Band (LSB)1.Lower Side Band (LSB)

2.Upper Side Band (USB)2.Upper Side Band (USB)


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Time Division MultiplexingTime Division Multiplexing

PCM Sampling in TimePCM Sampling in Time

The Samples are taken in Higher ratesThe Samples are taken in Higher rates

i.e. 8 Samples/Cycle in 1KHz.i.e. 8 Samples/Cycle in 1KHz.

So its 8KHzSo its 8KHz

Must Provided Synchronizing MechanismMust Provided Synchronizing Mechanism


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TDM in T1 CarrierTDM in T1 Carrier


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Error Detection and CorrectionError Detection and Correction

ERROR DETECTIONERROR DETECTION

errors caused by signal attenuation, noise.errors caused by signal attenuation, noise.

receiver detects presence of errorsreceiver detects presence of errors

ERROR CORRECTIONERROR CORRECTIONreceiver identifies and corrects bit error'sreceiver identifies and corrects bit error's

without resorting to retransmissionwithout resorting to retransmission

Types Of ErrorTypes Of Error

Single bit errorSingle bit errorMulti bit errorMulti bit error

Burst errorBurst error


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Single-bit error


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Multiple-bit error


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Burst error


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Error DetectionError Detection

EDC= Error Detection and Correction bitsEDC= Error Detection and Correction bits(redundancy)(redundancy)

D = Data protected by error checking,D = Data protected by error checking,

may include header fieldsmay include header fields

Error detection not 100% reliable!Error detection not 100% reliable!

protocol may miss some errors, but rarelyprotocol may miss some errors, but rarely

larger EDC field yields better detection andlarger EDC field yields better detection andcorrectioncorrection


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Contd..Contd..


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CRC


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Binary Division


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NATNAT


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NATNAT

Theoretically, you could haveTheoretically, you could have

4,294,967,296 unique addresses4,294,967,296 unique addresses i.e.3.2 to 3.3 millionsi.e.3.2 to 3.3 millions

explosion of the Internet and the increase inexplosion of the Internet and the increase in

home networkshome networks and business networksand business networks

number of available IP addresses is simply notnumber of available IP addresses is simply not

enoughenough

The Solution is Redesign the IP AddressesThe Solution is Redesign the IP Addresses
http://computer.howstuffworks.com/question549.htmhttp://computer.howstuffworks.com/question549.htmhttp://computer.howstuffworks.com/question549.htmhttp://computer.howstuffworks.com/home-network.htmhttp://computer.howstuffworks.com/home-network.htmhttp://computer.howstuffworks.com/home-network.htmhttp://computer.howstuffworks.com/question549.htm


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NAT RouterNAT Router


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Static RouterStatic Router

In static NAT, the computer with the IP address of

192.168.32.10 will always translate to 213.18.123.110.


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Dynamic RouterDynamic Router

In dynamic NAT, the computer with the IP address

192.168.32.10 will translate to the first available address in the

range from 213.18.123.100 to 213.18.123.150.


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Overloading (PAT)Overloading (PAT)

In overloading, each computer on the private network is translated to the

same IP address (213.18.123.100), but with a different port number

assignment


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Stub Domain TableStub Domain TableSource

Computer

Source

Computer's

IP Address

Source

Computer'sPort

NAT

Router'sIP Address

NAT Router'sAssigned

Port Number

A 192.168.32.

10

400 215.37.32.

203

1

B 192.168.32.13

50 215.37.32.2

03

2

C 192.168.32.15 3750 215.37.32.203 3

D 192.168.32.18

206 215.37.32.203

4


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Virtual PrivateVirtual Private

NetworksNetworks


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VPNVPN

The popularity of the Internet grew.The popularity of the Internet grew.

Intranets (password-protected sites)Intranets (password-protected sites)

Accommodate the needs of remoteAccommodate the needs of remoteemployees and distant officesemployees and distant offices

"virtual" connections"virtual" connections routedrouted throughthrough

the Internet from the company'sthe Internet from the company'sprivate network to the remote site orprivate network to the remote site or

employeeemployee
http://computer.howstuffworks.com/router.htmhttp://computer.howstuffworks.com/router.htmhttp://computer.howstuffworks.com/router.htm


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Typical VPNTypical VPN


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Makes of VPNMakes of VPN

Extend geographic connectivityExtend geographic connectivity Improve securityImprove security Reduce operational costs versus traditional WANReduce operational costs versus traditional WAN Reduce transit time and transportation costs forReduce transit time and transportation costs for

remote usersremote users Improve productivityImprove productivity Simplify network topologySimplify network topology Provide global networking opportunitiesProvide global networking opportunities Provide telecommuter supportProvide telecommuter support

Provide broadband networking compatibilityProvide broadband networking compatibility Provide faster ROI (return on investment) thanProvide faster ROI (return on investment) than

traditional WANtraditional WAN


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Features of VPNFeatures of VPN

SecuritySecurity

ReliabilityReliability

ScalabilityScalabilityNetwork managementNetwork management

Policy managementPolicy management


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Types of VPNTypes of VPN

Three typesThree types

Remote VPNRemote VPN

Intranet VPNIntranet VPN

Extranet VPNExtranet VPN

Examples of Three types


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IPv6IPv6


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IPv6IPv6 IPv6 is also called IPngIPv6 is also called IPng

It is decided on IETF on July 25, 1994.It is decided on IETF on July 25, 1994.

It is a 128 bits AddressesIt is a 128 bits Addresses

IPv6 Addresses FormatIPv6 Addresses Format

Three types of AddressesThree types of Addresses UNICAST AddressesUNICAST Addresses

ANY CAST AddressesANY CAST Addresses

MULTICAST AddressesMULTICAST Addresses


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Abbreviated addressAbbreviated address


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Abbreviated address with consecutive zerosAbbreviated address with consecutive zeros


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Example of the AddressesExample of the Addresses

1080:0:0:0:8:800:200C:417A - a uni cast1080:0:0:0:8:800:200C:417A - a uni castaddress FF01:0:0:0:0:0:0:101- a multicastaddress FF01:0:0:0:0:0:0:101- a multicastaddress 0:0:0:0:0:0:0:1 - the loop back addressaddress 0:0:0:0:0:0:0:1 - the loop back address

0:0:0:0:0:0:0:0 - the unspecified addresses0:0:0:0:0:0:0:0 - the unspecified addresses

This Addresses may be represented as:This Addresses may be represented as:1080::8:800:200C:417A - a uni cast address1080::8:800:200C:417A - a uni cast address

FF01::101 - a multicast addressFF01::101 - a multicast address

::1 - the loop back address::1 - the loop back address:: - the unspecified addresses:: - the unspecified addresses


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CIDR (CIDR (Class-less InterdomainClass-less Interdomain

Routing)Routing) addressaddress ipv6-address/prefix-lengthipv6-address/prefix-length

WhereWhere

ipv6-address - is an IPv6 address in any ofipv6-address - is an IPv6 address in any of

the notations listedthe notations listed

prefix-length - is a decimal value specifyingprefix-length - is a decimal value specifyinghow many of the leftmosthow many of the leftmost

contiguous bits of thecontiguous bits of the

address comprise the prefixaddress comprise the prefix


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Address structureAddress structure


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Provider-based addressProvider-based address


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Address hierarchyAddress hierarchy


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Unspecified addressUnspecified address

8 bits Source Addresses8 bits Source Addresses

Destination Addresses not specifiedDestination Addresses not specified

b k ddL b k dd


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Loop back addressLoop back address

The Unicast address 0:0:0:0:0:0:0:1 is calledThe Unicast address 0:0:0:0:0:0:0:1 is called

the loop back addressthe loop back address

It may be used by a node to send an IPv6It may be used by a node to send an IPv6

packet to itselfpacket to itself

To never be assigned to any physical interfaceTo never be assigned to any physical interface


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Compatible addressCompatible address

The IPv6 transition mechanisms [TRAN]The IPv6 transition mechanisms [TRAN]include a technique for hosts and routersinclude a technique for hosts and routers

to dynamically tunnel IPv6 packets overto dynamically tunnel IPv6 packets over

IPv4 routing infrastructure.IPv4 routing infrastructure.


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Mapped addressMapped address

This address is used to represent the addresses ofThis address is used to represent the addresses of

IPv4-only nodes (those that *do not* supportIPv4-only nodes (those that *do not* support

IPv6) as IPv6 addressesIPv6) as IPv6 addresses

A t bl Gl b l U i tA t bl Gl b l U i t


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Aggregatable Global UnicastAggregatable Global Unicast

Addresses (AGUR)Addresses (AGUR) This addresses designed to support toThis addresses designed to support to

both the current provider basedboth the current provider basedaggregation and a new type ofaggregation and a new type ofaggregation called exchanges.aggregation called exchanges.

3 13 8 24 16 64 bits3 13 8 24 16 64 bits

FP TLA RES NLAFP TLA RES NLA SLASLAInterfaceInterface ID IDID IDID IDID ID


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Contd..Contd..

WhereWhere001 - Format Prefix (3 bit) for001 - Format Prefix (3 bit) forAggregatable Global UnicastAggregatable Global UnicastAddressesAddresses

TLA ID -Top-Level AggregationTLA ID -Top-Level AggregationIdentifierIdentifier

RES - Reserved for future useRES - Reserved for future use

NLA ID - Next-Level AggregationNLA ID - Next-Level Aggregation

IdentifierIdentifierSLA ID - Site-Level AggregationSLA ID - Site-Level Aggregation

IdentifierIdentifier

INTERFACE ID - Interface IdentifierINTERFACE ID - Interface Identifier


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Link local addressLink local address

Local addresses are designed to beLocal addresses are designed to be

used for addressing on a single link forused for addressing on a single link for

purposes such as auto-addresspurposes such as auto-address

configuration, neighbor discovery, orconfiguration, neighbor discovery, orwhen no routers are present.when no routers are present.


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Site Local AddressesSite Local Addresses

Site-Local addresses are designed toSite-Local addresses are designed to

be used for addressing inside of a sitebe used for addressing inside of a site

without the need for a global prefixwithout the need for a global prefix


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Subnet AddressesSubnet Addresses

N bitsN bits 128-n bits128-n bits

Subnet Prefix Anycast address isSubnet Prefix Anycast address is

the prefixthe prefix which identifies awhich identifies a

specific linkspecific link

Subnet prefix 00000000000000


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Multicast addressMulticast address

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