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COURSE TITLE 9/5/2007

RIC-Learning Center Page 2 For Internal Circulation Only

Introductions!Introductions!

Participant IntroductionsParticipant Introductions

NameName

Position/ Function, Location (city)Position/ Function, Location (city)

How long with RelianceHow long with Reliance InfocommInfocomm

How long in the Telecom IndustryHow long in the Telecom Industry

Expectations from this courseExpectations from this course

InstructorInstructors Introductions Introduction


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Course LogisticsCourse LogisticsCourse Logistics

PowerPoint PresentationPowerPoint Presentation

Follow along with the trainerFollow along with the trainer

Student GuideStudent Guide

Student NotesStudent Notes

Support informationSupport information

LogisticsLogisticsLogistics

Breaks, LunchBreaks, Lunch Toilet, WaterToilet, Water

Mobile phones, InternetMobile phones, Internet


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Points to remember!Points to remember!

Far End (remote to the Instruc tor)Far End (remote to the Instructor)

Keep mike off unless Q&A sessionKeep mike off unless Q&A session

Keep NetKeep Net--meeting ONmeeting ON

Post offline questions on ChatPost offline questions on Chat

Report discomfort immediatelyReport discomfort immediately

Near End (local to the Instructor)Near End (local to the Instructor)

Give first chance to far endGive first chance to far end

Both EndsBoth Ends

Keep courseware ready for referenceKeep courseware ready for reference

Raise hand, identify yourself, ask questionRaise hand, identify yourself, ask question

Keep mobi les off/ silentKeep mobi les off/ silent

Avoid leaving/ jo in ing the class in betweenAvoid leaving/ jo in ing the class in between

Stick to break timingsStick to break timings

ASK QUESTIONSASK QUESTIONS


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CONTENTSCONTENTSCONTENTSData networks OSI Model, LAN, WAN, MAN

Physical Layer, PDH, SDH, LMDS

Data Layer, Ethernet, ATM, PPP

Network Layer, Connection oriented, Connection less

Data Communication devices Repeater, Hub

Bridge, Switch, Spanning Tree Protocol, VLan

Routers, Router Architecture

Internet Protocol IP Suite, TCP/IP, UDP, ICMP

IPv4 Addressing, Sub-netting, IPv6

Routing Distance Vector, RIP

Link State, OSPF, Area

Autonomous Systems, IGP, BGP

MPLS Traffic Engineering, Class of Service, Service Level Assurance

FEC, LSP, Label Stacking, LDP, Tunnels

Data Applications & Reliance Data Network VPN, Multicasting, VoIP

RDN, ADN, DCN


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Any Questions?Any Questions?Any Questions?

Are we supposed to knowAre we supposed to know .. to start this course?.. to start this course?

Yes, butYes, but ....

Are we gett ing handsAre we gett ing hands--on exercises?on exercises? Yes/ NoYes/ No

Will there be a test at the end?Will there be a test at the end?

No! There will be test at regular intervals and also at the endNo! There will be test at regular intervals and also at the end

Please ask any question that comes to your mindPlease ask any question that comes to your mind

Raise your hand!Raise your hand!

Ask on a break.Ask on a break.

The only dumb question isThe only dumb question is

the one that isthe one that is notnot asked!asked!


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Module 1Module 1

Voice Vs Data NetworksVoice Vs Data Networks

Module Objectives

After completion of this module you will be able to understand

Comparison between conventional circuit switched and Data Networks

Why voice over Data Networks is the need of the hour

The current Scenario

Evolution of Data Networks


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History of Data NetworkingHistory of Data NetworkingHistory of Data Networking

1. Sharing Resources

2. Interoperability

3. The Internet

Server

Collaboration among DEC, Intel Corporation, and Xerox Corporation at the Palo Alto Research Center(PARC). The results of this research included Ethernet and the Xerox Network Systems (XNS)protocol.

LANs allowed many computer systems to be interconnected, using a minimum of wiring and requiringlittle configuration.

The Internet was born in 1969 as a group of interconnected Honeywell computers located at fourdifferent universities and financed by the U.S. government's Department of Advanced ResearchProjects Agency (DARPA). This network, which grew quickly and came to be called ARPANET,interconnected the rapidly growing computing resources of the scientific, academic, andgovernmental communities.

In 1973, the Transmission Control Protocol (TCP) became a standard protocol for the ARPANET. By1980, TCP, the Internet Protocol (IP), and the other protocols of the TCP/IP protocol suite hadbecome the required standard for connection to ARPANET; the name of the network changed tothe Internet.

In 1982, TCP/IP was incorporated into a popular version of the UNIX operating system (BSD UNIX,after the center of its development, U.C. Berkeley). TCP/IP hosts evolved into gateways (later to be

called routers) to provide interconnectivity between different TCP/IP hosts over wide area network(WAN) links.

Standard networking applications, such as Telnet and File Transfer Protocol (FTP), allowed users onone machine to remotely control the resources of host systems anywhere in the Internet. All ofthese developments set the stage for the explosion in the development of local area networks(LANs), which came soon


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DATA visDATA vis----vis VOICEvis VOICE

VOICE COMMUNICATION

Fault tolerant

Delay sensitive

Circuit oriented

Fixed Bandwidth

Access

Switch Switch Access

Data and Voice communication have several similarities but are different in a few ways:

1. Voice communication is tolerance of minor failures and noise, as the transmitting andreceiving parties are human being (highly intelligent as compared to machines that

communicate). Data communication needs to be Fault sensitive as the M/cs cant make mucherror correction.

2. Voice Communication on the other hand is Delay sensitive. Human being feel veryuncomfortable if there is variable delay in transmitting successive parts of the speech. Humansenses are used to hearing only in the way they hear to direct voice. Machines however haveno such inhibitions and that reconstruct a communicated information from various parts of thesame.

3. From the above points one would intuitively realise that Voice communication is best suited toCircuit switching and Data to Packet switching. One a circuit is established between the twoparties there would be no variation in transmission delays. The only delay is that of electricalsignal traveling over the circuit, which is in negligible. No fault correction mechanism isimplemented. But in case of Data, information in sent in packets with suitable error detectingcodes and transmitted along with several other packets. Different packets could be of differentsizes, thereby producing differential delays in receiving subsequent packets for a node. Butthats not the problem.

4. Lastly for Voice, we are all bound by the 64 kbps bandwidth, even during silences. While inData communication the bandwidth for each channel can be set differently depending on theneed of the parties.


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DATA visDATA vis----vis VOICEvis VOICE

DATA COMMUNICATION

Fault sensitive

Delay tolerant

Packet oriented

Variable Packet size/ Bandwidth

RR

R

R

R

Data and Voice communication have several similarities but are different in a few ways:

1. Voice communication is tolerance of minor failures and noise, as the transmitting andreceiving parties are human being (highly intelligent as compared to machines that

communicate). Data communication needs to be Fault sensitive as the M/cs cant make mucherror correction.

2. Voice Communication on the other hand is Delay sensitive. Human being feel veryuncomfortable if there is variable delay in transmitting successive parts of the speech. Humansenses are used to hearing only in the way they hear to direct voice. Machines however haveno such inhibitions and that reconstruct a communicated information from various parts of thesame.

3. From the above points one would intuitively realise that Voice communication is best suited toCircuit switching and Data to Packet switching. One a circuit is established between the twoparties there would be no variation in transmission delays. The only delay is that of electricalsignal traveling over the circuit, which is in negligible. No fault correction mechanism isimplemented. But in case of Data, information in sent in packets with suitable error detectingcodes and transmitted along with several other packets. Different packets could be of differentsizes, thereby producing differential delays in receiving subsequent packets for a node. Butthats not the problem.

4. Lastly for Voice, we are all bound by the 64 kbps bandwidth, even during silences. While inData communication the bandwidth for each channel can be set differently depending on theneed of the parties.


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Circuit Switching

What is circuit switching?

It is a dedicated end-to-end pathfor your particular voice channeland no other voice traffictransmits on this dedicated pathfor the duration of your call.

Circuit Switching

Advantages

Highly reliable

Excellent voice quality (QoS)

Disadvantages

Dedicated Circuit

Wasted Capacity

High cost of ownership


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Packet SwitchingPacket Switching

What is Packet Switching?

Packet switching can be defined aseither connection oriented or

connectionless environmentIn packet switching, the sendingsystem converts the data into smallindividual chunks called as packetseach having its own destinationaddress.

At the receiving side the address isidentified and the packets arereassembled to form the original data

Advantages

Reduces network load

Simultaneous data reception form

more than two computers possible

Disadvantages

Not suitable for voice transmissiondue to packet loss and packet delay


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Module 2

Networking Models & Protocols

Module Objectives

After completion of this module you will be able to understand

The Need for Standards

OSI - ORGANISATION FOR STANDARDISATION

The OSI & TCP/IP reference Model

The Seven OSI reference model Layers

Introduction to Protocols on different Layers

Summary


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HistoryHistory-- The Network ModelThe Network Model

Need For Standardization

Different vendors, different

Hardware, software.-No Compatibility

ISO Starts working on aCommon NetworkingStandard/language for

interoperability

1984-The OSI Model Approved-enables internetworking irrespesctive

Of manufacturer/OS

The Developmentof the OSI Model

ForInternetworking


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Open System Interconnection - OSIOpen System InterconnectionOpen System Interconnection -- OSIOSI

Communication function is partitioned into logical hierarchy oflayers.

There are seven layers. Each function is distinctly implemented in one layer.

The OSI model divides the tasks of computer communications into a series of seven layers, with thelowest layer providing an interface to the physical medium and the highest layer providing an interfaceto the user application.

Each layer communicates with the immediately higher and lower layers by placing information inheaders added to the data. These headers often contain fields called service access points (SAPs),which act like mailboxes where a communication program can leave information for a program runningat a higher or lower layer.

The application, presentation, and session layers format the data for presentation to the userapplication and establish a communication session between the local and remote applications.

The transport layer typically guarantees the reliability of the transmissions between two end stationsby providing facilities for disassembly, assembly, error checking, sequencing, and retransmission. Thislayer also often provides a way to identify the application thatgenerated the message, using a specialSAP (called a socket in TCP/IP).

The network layer provides addresses for the sending and receiving stations that allow routing of themessage over a network composed of various physical networks.

The data link layer provides addresses for the sending and receiving stations that allow delivery fromone station to the next station on the same physical network. The data link trailer usually includes someform of checksum (an arithmetic sum used to verify data integrity).

The physical layer converts the bits of data hi each frame into electrical or optical signals, dependingon the physical medium, and sends it through the medium.


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OSI - A Layered Network Model

The OSI reference model divides the problem of moving

information between computers over a network medium intoSEVEN smaller and more manageable problems .

This separation into smaller more manageable functions is knownas layering.

The OSI Reference Model is composed of seven layers, eachspecifying particular network functions.

The process of breaking up the functions or tasks of networkinginto layers reduces complexity.

Each layer provides a service to the layer above it in the protocolspecification.

Each layer communicates with the same layers software or

hardware on other computers.


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A Layered Network Model

The lower 4 layers (transport, network, data link and physical Layers 4, 3, 2, and 1) are concerned with the flow of data from endto end through the network.

The upper four layers of the OSI model (application, presentationand sessionLayers 7, 6 and 5) are orientated more towardservices to the applications.

Data is Encapsulated with the necessary protocol information as itmoves down the layers before network transit.


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OSI 7 Layer ConceptOSI 7 Layer ConceptOSI 7 Layer Concept

A layer undertakes the function assigned to it in association with its peer.

Peer-to-peer communication is defined by a protocol. Protocol is a set ofrules.

Upper layers request for service and lower layers provide service.

Service from

lower layer

Protocol

Service to

higher layer

Data

DataHeader

DataHeader

DataHeader

Header contains the communication to peer entity.

Every layer thus adds its own header. This is called encapsulation


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Encapsulation/DecapsulationEncapsulation/Decapsulation


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Functions of LayersFunctions of Layers


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Open System Interconnection - OSIOpen System InterconnectionOpen System Interconnection -- OSIOSI

Physical

Data Link

Network

Transport

Session

Presentation

Application

Ph

DL

Network

Ph

DL

Network

Physical

Data Link

Network

Transport

Session

Presentation

Application

Ph

DL DL

Ph

Network Node(Router)

Network Node(Router)

End System End System

Media Media Media

Computer Computer

Router Router

Important to note at this point that while the two end systems need all the 7 layers to communicate thein-between elements (Network Elements/ Routers) need to use upto Layer three. The Lower threelayers therefore are also called NETWORK LAYERSwhile the upper four are called APPLICATIONLAYERS.

Also note the Physical layer or Data/Link Layer protocol is applicable from one Node to another and not

all across the network.


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Figure 3-3

WCB/McGraw-Hill The McGraw-Hill Companies, Inc., 1998

An Exchange Using the OSI Model

H

H

H

H

T

H

H

H

TH

H

H

encapsulation

decapsulation


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OSI Physical LayerOSIOSI Physical LayerPhysical Layer


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Physical LayerPhysical Layer

Physical Layer deals with the issues such as:

"Electrical/Optical interface to the physical medium

"Electrical, mechanical, procedural, and functionalspecifications for activating, maintaining and deactivating

the physical link between communicating network systems.

"Voltage levels, timings of voltage changes, physical data rates, maximumtransmission distances, and physical connectors.

Protocol functioning at this layer:

"RS-232,RS-449,V3.5,ISDN,xDSL

"Ethernet (Fast/GigE)"T1/E1, T3/E3"SONET/SDH/PDHHubs/Repeaters/MUX/DACS function at this level.


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Physical Layer: TopologiesPhysical Layer: TopologiesPhysical Layer: Topologies

RR

R

R

R

Connection: Simplex/ Duplex, Half/ Full Duplex

Topology: Ring, Star, Bus


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E1(G.703/G.704) Multiplexing HierarchyE1(G.703/G.704) Multiplexing HierarchyE1(G.703/G.704) Multiplexing Hierarchy

1890155,520STM1

302402,488,320STM16

1209609,953,280STM64

7560622,080STM4

63051,840STM0Synchronous DigitalHierarchy

48034,448E3

302,048E1

164DS0Plesiochronous DigitalHierarchy

Equivalent Telephone

lines

Bandwidth

(Kbps)

Digital LevelStandard

Basic Payload E1-32 Timeslots

E1-channelized/unchannelized

European std.s Synchronous Digital Hierarchy (SDH) and its North Americancounterpart SONET proposes a transport system with highly synchronised networkelements and OFC as the physical media. Thereby the concept of bit-interleaving isreplaced by a Byte interleaved system. Also the bandwidths are defined upto much

higher range making it suitable for modern data & broadband communication.

SDH/ SONET defines to types of packaging one for the electrical network calledSynchronous Transmission Module/ System (STM-n/ STS-n) and another for theoptical network called Transport Unit (TU-n)/ Optical Carrier (OC-n).

STM-n has now been defined from STM-1 (63 E1s) to STM-256 (16128 E1s).Proposal for STM-1024 is under examination for standardising. That would take us toan amazing 160 Gbps.

Technically there is no difference between SDH and SONET. Some terms differ andsome details in Overhead definitions defer but that doesnt come in the way of makingthese to standards compatible to each other.


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Standards: Electrical Media & TransceiversStandards: Electrical Media & TransceiversStandards: Electrical Media & Transceivers

CO-AXIAL THINNET:

0.25 Cables for 10MB, 185m

RG-58/ U - Solid Copper CoreRG-58 A/U - Stranded Copper CoreRG-58 C/U - Mil spec. for RG58 A/URG-59 - Broadband transmission (TV)RG-62 - ArcNetNetwork Cable

CO-AXIAL THICKNET:

0.5 Cables for 10MB, 500m

RG-12

SHIELDED TWISTED PAIR:Cables up to 100m

Cat 2 - 4 Mbps, Cat 3 - 10 MbpsCat 4 - 16 Mbps, Cat5 - 100 Mbps

RS232C:

One to One Full Duplex communicationCommon mode connection.Baud Rate upto 19.2 kB

RS422:

One to One Full Duplex communication.Differential mode connection.Baud Rate upto 10 MB

RS485:

Multi-drop Half Duplex communication.Differential mode connection.Baud rate upto 10 MB.

BANDWIDTH-DISTANCE PRODUCT:

The product of bandwidth (thereby the baud-rate) & the distance between transmitter & receiver isgenerally constant for any particular type of cable.

So while the type of cable determines the bandwidth-distance product, for any cable the bandwidth isinversely proportional to the distance.

While bandwidth determines speed, distance gives coverage, thereby these two are very important forany network design.


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Ethernet LANs are referred to as

10Base5, Thick coaxial cable ethernet 10 Mb, baseband, 500 meters

10Base2, Thin coaxial cable ethernet 10 Mb, baseband, 200 meters

10Base-T, Twisted pair ethernet 10 Mb, baseband, 100 meters

Fast ethernets

100Base-Tx,2 twisted pair (CAT 5) 100 Mb, 100 meters

100Base-FX, 2 optical fibres 100 Mb, 2000 meters

100Base-T4, 4 CAT3 pairs 100 Mb, 100 meters

Gigabit ethernets

1000Base-SX, 2 multimode fibres 1 Gb, 550 meters

1000Base-LX, 2 multi/mono fibres 1 Gb, 550/5000 meters

1000Base-CX, STP 1Gb, 25 meter

Ethernet (802.3) The MediaEthernet (802.3) The Media

802.3 Now encompasses

Original 802.3: 10BASE-T 10BASE-5 10BASE-2 10BROAD-36

802.3u Fast Ethernet: 100BASE-TX 100BASE-FX 100BASE-T4

802.3x: Flow Control 802.3z Gigabit Ethernet: 1000BASE-SX / -LX / -CX

802.3ab Copper Gigabit Ethernet: 1000BASE-T

802.3ac Frame Tagging for VLAN support

802.3ad Link Aggregation

802.3ae 10 Gigabit Ethernet: Completion by March 2002

802.3af DTE Power via MDI: Completion by Sept 2001


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Business Customer

Application

Base Station

Micro Cell FeedingApplication

Terminal Station

Radio To The Building(RTTB) Application

3.5 GHz3.5 GHz

10.5 GHz10.5 GHz

26 GHz26 GHz

Microwave systems

LMDS-10.5GHZUBR-2.4GHZWIFI- 2.4 GHZWIMAX- 3.4GHZ

Standard: ETSI EN 301 021 (TM4)

Frequency Band: 10.15- 10.65 GHz

FDD Separation: 350 MHz

Range: 10KmReceiver Sensitivity: -87dbm @ BER 10-9

Emitted Power:

Terminal Station: 15 dbm

Base Station: 15 dBm(per carrier)

RFU: 27 dBm

Antenna Characteristics:

Terminal Station 80, 25 dBi

Base Station 900, 15. dBi, 4 sectors600, 18 dBi


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SS for Peer-to-PeerCommunications in Ad Hoc Network

WLAN (IEEE: 802.11)WLAN (IEEE: 802.11)WLAN (IEEE: 802.11)

BS Provides Campus-Wide Coverage

WLANs can be used either to replace wired LANs, or as an extension of the wired LAN infrastructure.The basic topology of an 802.11 network is shown in Figure 1. A Basic Service Set (BSS) consists oftwo or more wireless nodes, or stations (STAs), which have recognized each other and haveestablished communications. In the most basic form, stations communicate directly with each other ona peer-to-peer level sharing a given cell coverage area. This type of network is often formed on a

temporary basis, and is commonly referred to as an ad hoc network, or Independent Basic Service Set(IBSS).

In most instances, the BSS contains an Access Point (AP). The main function of an AP is to form abridge between wireless and wired LANs. The AP is analogous to abasestationused in cellular phonenetworks. When an AP is present, stations do not communicate on a peer-to-peer basis. Allcommunications between stations or between a station and a wired network client go through the AP.APs are not mobile, and form part of the wired network infrastructure. A BSS in this configuration issaid to be operating in the infrastructure mode.

The Extended Service Set (ESS) shown in Figure 2 consists of a series of overlapping BSSs (eachcontaining an AP) connected together by means of a Distribution System (DS). Although the DS couldbe any type of network, it is almost invariably an Ethernet LAN. Mobile nodes can roam between APsand seamless campus-wide coverage is possible.

Radio Technology

IEEE 802.11 provides for two variations of the PHY. These include two (2) RF technologies namelyDirect Sequence Spread Spectrum (DSSS), and Frequency Hopped Spread Spectrum (FHSS). TheDSSS and FHSS PHY options were designed specifically to conform to FCC regulations (FCC 15.247)for operation in the 2.4 GHz ISM band, which has worldwide allocation for unlicensed operation.

Region Allocated Spectrum

US 2.4000 2.4835 GHz, Europe 2.4000 2.4835 GHz, J apan 2.471 - 2.497 GHz, France 2.4465 -2.4835 GHz, Spain 2.445 - 2.475 GHz


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Wireless LAN Layer 1 for 802.11Wireless LAN Layer 1 for 802.11

802.11g

OFDM

802.11b

HR-DSSS

802.11a

OFDM

802.11

DSSS

802.11

FHSS

802.11

Infrared

802.3802.3802.3802.3802.3802.3

MAC

subla

yer

Datalinklayer

Upperlayers

Logical link control


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Wireless LAN (IEEEWireless LAN (IEEE--802.16)802.16)

IEEE 802.16 (2001)

Air Interface for Fixed Broadband Wireless Access System MAC andPHY Specifications for 10 66 GHZ (LoS)

Single Carrier

IEEE 802.16a (January 2003)

Amendment to 802.16 for 2 11 GHz (NLoS)

IEEE 802.16d (Jul y 2004)

Combines both IEEE 802.16 and 802.16a

IEEE 802.16e (November 2005)

Amendment to 802.16-2004 Modifications for limited mobility (60Kmph)

Evolution of the 802.16 standard

RCOM is presently (2007) deploying WiMAX (2004) for static use


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Data Link LayerData Link LayerData Link Layer

33H, 96H =00110011(oP=1)10010110(oP=1)

001100111100101101..oP=1? Yes..oP=1? Yes

Communication OK. 33H, 96H

The Data layer Protocol lays down such simple guidelines like what would bethe size of frame, how to detect start of frame or end of frame, how to detect

a transmission failure (Parity, CRC, etc.) and so on.

In simple words its about how to get your bits transmitted meaningfully.

Data/ Link layer makes networking possible within a limited physical area,called Local Area Network (LAN).

Parity bit: One bit that gives the value of (even/ odd) parity of the attached payload.

CHECK-SUM: Sum of values of all the data bytes.

PACKET: Collection of Data bytes, parity, check-sum, packet size, header/ footer,

etc.

SOT, EOT: Header & Footer of a Packet given by pre-defined signature bytes.

CRC: Cyclic Redundancy Check - a code attached to each packet for error checking.


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Data Link LayerData Link Layer

Data Link Layer deals with such matters

"Framing

"Error Detection

"Flow Control

Addressing

Contention Resolution/Media Access Control

Divided into two sub layers, MAC and LLC

Protocols listed at this layer:

"Ethernet, ATM, Frame-Relay, PPPSwitches function at this layer.


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Layer 2 EncapsulationLayer 2 Encapsulation


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Data networks - layer 2 Protocols


Network

Wide Area NetworkLocal Area Network

Point To Point WANs Point To Multipoint WANs

Protocol-Ethernet

Protocol-HDLC,PPP,MEN- Ethernet

Protocol-ATM, Frame Relay


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Figure 2-16


Local Area Network


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Figure 2-17


Metropolitan Area Network


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Ethernet: MAC AddressEthernet: MAC AddressEthernet: MAC Address

MAC Address Format

Ethernet MAC addresses are 48 bits in length. The IEEE assigns the first 24 bits to organizations requestingthem, typically, equipment vendors. Vendors are then responsible for placing a unique value in the remaining 24

bits, yielding a globally unique MAC address for every physical interface.

Unicast Address:

A Unicastaddress is simply a MAC address with the Multicast bit set to zero. Unicast addresses must be uniquewithin the network.

Broadcast address:

A Broadcast address at the MAC level is simply an address of all 1's. In hexadecimal notation this would beexpressed as FF-FF-FF-FF-FF-FF.

Multicast Address:

If the Multicast bit is set to 1 then the MAC address represents a multicast destination. There are severalreserved multicast addresses that are used by well known protocols.

There are several bits within the MAC address that have special meanings:

The least significant bit (LSB) of the first byte is the Multicast bit. AP11002-01 15- - - If it is set to 1,the MAC address is a multicast address.

If the Multicast bit is 1, then the most significant bit (MSB) of the third byte is either:

0 representing the Internet Multicast Address, or1 which is assigned by IANA for other uses


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Metro Ethernet: OverviewMetro Ethernet: OverviewMetro Ethernet: Overview

A. Primaril y Point to Point Links

B. Can be Switch or Router

C. WAN links (e.g. SONET/ SDH)

D. Various Service types (P2P, MP2MP, P2MP), BW from 1 Mbps to 1 Gbps

E. Various protection technique for Network Resilience

F. QoS both End-to-End and Node-to-Node

A. Links are primarily point-to-point and can be any speed of Ethernet.

B. Nodes can be either switches or routers, depending on their location in the MEN,the nature of the services being provisioned, and the level of service resilience(network protection). Nodes are meshed to whatever degree necessary to provide the

desired connectivity, services, and protection.

C. WAN links connectMENs together across large distances.

D. Ethernet services can be topologically classified into point-to-point (as shown inthis illustration), multipoint-to-multipoint, or point-to-multipoint. Services are thenfurther classified according to the bandwidth provisioned and used. This bandwidthusage can be exclusive or shared across multiple users. Bandwidth is provisioned ondemand from 1 Mbps to 1Gbps, in increments as fine as 1 Mbps.

E. Varying degrees of service resilience are obtained by implementing a combinationof network protection techniques. Protection can be end-to-end (as shown in thisillustration) or node-to-node.

F. Quality of Service (QoS) is realized using a combination of various techniques toprovide both hard and soft bandwidth and packet-loss guarantees. QoS can beend-to-end (as shown in this illustration) or node-to-node. From an enterprise end-customer perspective, QoS is visible as a technical/operational Service LevelSpecification (SLS), which is underwritten by a commercial Service Level Agreement(SLA).


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Frame Relay HistoryFrame Relay History

Before frame relay era, large organizations were interconnected by:

X.25 Leased Lines

Long network processing time Point to point

connectivity

Low bandwidth (max. 64kbps) Expensive, there is no

Charge per traffic bandwidth sharing

Required mult iple port

routers

Fixed price

As the 1980s came to close a new demands from the wide area networkswitching began to appear:

Growth in high speed, high speed throughput application.

Sophistication of the end user devices, equipment with processingability.

This new wide area switching technology required high speed, lowdelay, portsharing and bandwidth sharing on a virtual circuit basis.

These characteristics implemented in Frame Relay make Frame Relay idealsolution for the burst traffic sources found in LAN-WAN internetworking.

Frame Relay is a high-speed communication technology, which enables tosend information over the WAN by dividing the information into frames andpackets.

Frame Relay is not a single physical connection between two end points, but

a logical path is defined within the network.No Bandwidth is allocated to thepath until actual data needs to be transmitted. Then, the Bandwidth within thenetwork is allocated on a packet-by-packet basis, This logical path called VC(Virtual Circuit).


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X.25 VS. Frame RelayX.25 VS. Frame Relay


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Frame Relay Network (cont.)Frame Relay Network (cont.)

User Node

Router

User Node

Router

User Node

Router

User Node

Router

FR

switch

NetworkNode

FR

switch

FR

switch

NNINetwork to Network Interface

UNIUser to Network Interface

Network nodes (FR switches)User nodes (usually routers)

Switched Virtual Circui ts

Switched virtual circuits (SVCs) are temporary connections used in situationsrequiring only sporadic data transfer between DTE devices across the FrameRelay network. A communication session across an SVC consists of the

following four operational states:Call setupThe virtual circuit between two Frame Relay DTE devices isestablished.

Data transferData is transmitted between the DTE devices over the virtualcircuit.

IdleThe connection between DTE devices is still active, but no data istransferred. If an SVC remains in an idle state for a defined period of time,the call can be terminated.

Call terminationThe virtual circuit between DTE devices is terminated.

Permanent Virtual Circui ts

Permanent virtual circuits (PVCs) are permanently established connectionsthat are used for frequent and consistent data transfers between DTEdevices across the Frame Relay network. Communication across a PVCdoes not require the call setup and termination states that are used withSVCs. PVCs always operate in one of the following two operational states:


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Frame Relay Packet StructureFrame Relay Packet Structure

Frame Relay Header: 2 bytes of FR address and control

Information Field: Users data

FCS: 32 bits of Cyclic Redundancy Check (CRC)

Flag : 2 identical bytes made of 6 ones and 2 zeros.

Data transferData is transmitted between the DTE devices over the virtualcircuit.

IdleThe connection between DTE devices is active, but no data istransferred. Unlike SVCs, PVCs will not be terminated under anycircumstances when in an idle state.

DTE devices can begin transferring data whenever they are ready becausethe circuit is permanently established.

Differences with X.25

Less robust

Assumes more reliable medium =>

No retransmission of lost data

No windowing

Error control handled by higher layers

Higher performance and transmission efficiency


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Frame Relay: FormatFrame Relay: Format

FlagsFCSDataAddressFlags

8 16 Variable 16 8

Flags: Delimits the beginning and end of the frame. The value of this field is always the same and isrepresented either as the hexadecimal number 7E or as the binarynumber 01111110.

Address: Contains the following information:

DLCIThe 10-bit DLCI is the essence of the Frame Relay header. This value represents the virtualconnection between the DTE device and the switch.

Extended Address (EA)The EA is used to indicate whether the byte in which the EA value is 1 is thelast addressing field. If the value is 1, then the current byte is determined to be the last DLCI octet.

C/RThe C/R is the bit that follows the most significant DLCI byte in the Address field. The C/R bit isnot currently defined.

Congestion ControlThis consists of the 3 bits that control the Frame Relay congestion-notification

mechanisms. These are the FECN, BECN, and DE bits, which are the last 3 bits in the Address field.

Data:Contains encapsulated upper-layer data. Each frame in this variable-length field includes a user dataor payload field that will vary in length up to 16,000 octets.

Frame Check Sequence: Ensures the integrity of transmitted data.

Switched Virtual Circuits

Switched virtual circuits (SVCs) are temporary connections used in situations requiring only sporadicdata transfer between DTE devices across the Frame Relay network. A communication session acrossan SVC consists of the following four operational states:

Call setupThe virtual circuit between two Frame Relay DTE devices is established.

Data transferData is transmitted between the DTE devices over the virtual circuit.

IdleThe connection between DTE devices is still active, but no data is transferred. If an SVC remainsin an idle state for a defined period of time, the call can be terminated.

Call terminationThe virtual circuit between DTE devices is terminated.

Permanent Virtual Circuits

Permanent virtual circuits (PVCs) are permanently established connections that are used for frequentand consistent data transfers between DTE devices across the Frame Relay network. Communicationacross a PVC does not require the call setup and termination states that are used with SVCs. PVCsalways operate in one of the following two operational states:

Data transferData is transmitted between the DTE devices over the virtual circuit.

IdleThe connection between DTE devices is active, but no data is transferred. Unlike SVCs, PVCswill not be terminated under any circumstances when in an idle state.

DTE devices can begin transferring data whenever they are ready because the circuit is permanentlyestablished. Differences with X.25

Less robust, Assumes more reliable medium =>

No retransmission of lost data, No windowing, Error control handled by higher layers

Higher performance and transmission efficiency


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Leaky Bucket Algorithm (cont.)Leaky Bucket Algorithm (cont.)

Bc+BeBc

Each VC has several parameters needed to be configured:

CIR (Committed Information Rate)

CIR is the "worst-case" throughput that the frame relay network

provider attempts to guarantyCIR bandwidth is guaranteed. In overload situations,transmission will occur over a reasonable time span (usuallyover a span of seconds)

Transmission is monitored using "leaky bucket algorithm."

Bc (Burst Committed)

Value which indicated how many bits can be transmitted at acertain time interval and the system obligate to transmit them.

Be (Burst Exceeded)

The amount of bits which were transmitted over the Bc at thedefined time interval.

Tc (Time Committed)

The time interval


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Frame RelayFrame Relay

BS

TS

TS

FRAD

FRADFR

switch

FRAD

m*DLCI's

max(m)=200

n*DLCI'smax(n)=30

FrameRelayNetwork

DLCI 101

DLCI 102

FR

switch

Rdn n/w

FR USERS

Congestion Notification Mechanism is helping us to avoid a situation where a node reaches acertain point which it cant deliver data any more due to a sever congestions. In Frame Relaythere are several ways to avoid congestions:

Explicit Congestion Notification

Discard Eligibility

Discard Eligibility

Due to the use of the CIR which is an obligation for the quality of service to thecustomer, in case of a problem any frame which is send through the network abovethe CIR can be discarded. And will not effect the guarantied Quality of Service.

Frame Relay benefits over alternative technologies:

Lower cost of ownership

Well-established and widely adopted standards that allow open architecture andplug-and-play service implementation.

Low overhead, combined with high reliability.

Network scalability, flexibility and disaster recovery.

Interworking with other new services and applications, such ATM.


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DLCIDLCI--SUBNET MAPPINGSUBNET MAPPING

10.20.30.0192.20.30.0

10.20.31.0


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ATM: Desire for IntegratedATM: Desire for Integrated

ServicesServices

Economies of integration: voice, data, video

Minimize delays and delay variation

FDDIIntegratedNetwork

PBX

Data

Voice

Video

FDDI

PBX

Data

Voice

Video


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ATM BasicsATM Basics

Traditional voice/video technology: Time Division Multiplexing (TDM)

Fixed time slots give isochronicity

Traditional data technology: Packet / Frame Switching (PSDN)

Variable-size data units give flexibility and efficiencyATM technology: Cell switching

Small, fixed-size cells

Combined benefits of TDM and PSDN

Voice Video Data

Cells

ATMNetwork

Header

5 Octets

Payload

48 Octets

53

Octets

VCI: Virtual Channel Id PTI: Payload Type Indicator

VPI: Virtual Path Id CLP: Cell Loss Priority

UNI: User Network Interface HEC: Header Error Check

GFC: Generic Flow Control (undefined )

Al lows fo r 256 VPs and 65,536 VCs

Byte1

2

3

45

GFC VPI

VPI VCI

VCI

VCI PTI CLP

HEC

8 7 6 5 4 3 2 1 Bits

- Octets sent in

increasing order

(start at Octet 1)

- Within the Octet,

the MSB (8) is sent

first

Byte1

2

34

5

VPI

VPI VCI

VCIVCI PTI CLP

HEC

8 7 6 5 4 3 2 1 Bits

VCI: Virtual Channel Id PTI: Payload Type Indicator

VPI: Virtual Path Id CLP: Cell LossPriority

NNI: Network Network Interface

Allows for 4,096 VPs and 65,536 VCs

No GFC Field

More VPI bits for trunking


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ATM FEATURESOne technology for voice, data, video and multimedia

Bandwidth on demand as needed

Scalable as needs dictate

Quality of Service (QoS) is well defined

Management Systems and services pre-built into ATM

Hardware based switching instead of complicated routing and softwareschemes

ATM is connection oriented protocol and makes use of

one of the two connection types

PVC Permanent Virtual Circuit

SVC Switched Virtual Circuit

There is a logical mapping of connections in the network

The connection is built into a routing table and in each of the switchesinvolved with the connection from end to end

The switches needs to lookup a table for the incoming port and channel andthen determine the mapping


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ATM Sub layersATM Sub layers

Physical Layer

Transfers cells from one interface to another viacommunication channel

Supports both optical and electricalcommunication channelLAN data rates suppor ted are from 25 to 622Mbpsfor copper & Fiber

WAN data rates supports the data rates ofSONET/SDH

ATM Layer

Performs cell multiplexing/de-multiplexing andswitching

Provides virtual connection between end points

Manage cell headers

AAL ATM Adaptation Layer

AAL1(A) - Suppor ts connec tion oriented constantbit rate data

AAL2(B) - Suppor ts connec tion oriented vari able

bit rate dataAAL3/AAL4(C) -Supports connec tion or iented andconnection less data

AAL5(D)- Suppor ts bursty data which use highlevel protocol for error control


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t

BitRate

Average NaturalInformation Rate

Maximum Natural Information Rate

Bandwidth Wasted

Loss of Quality

(Bandwidth potential lost)

ATM Adoption Layer (AAL)ATM Adoption Layer (AAL)

TCP/IP, SMDSCBR, Voice, VideoVBR, Voice, VideoCBR, Voice, VideoExample

Connection-lessConnectionoriented

Connectionoriented

Connection orientedConnection

VariableVariableVariableConstantBit rate

Not RequiredNot RequiredRequiredRequiredTUNING

5, 3/45, 3/421TYPE

Class DClass CClass BClass AAAL

Higher Layers

ATM Adaptation

Layer

ATM Layer

Phy

Higher Layers

ATM Adaptation

Layer

ATM Layer

Phy

ATM Endpo int ATM Endpo int

ATM Network Interfaces

ATM

Switching

ATM

Switching

ATM Layer

Phy Phy

ATM Layer

Phy Phy

Peer Layer Communication


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Physical Layer (Fiber)

Virtual Path (VP)

Virtual Channel (VC)

Network A

Network B

ATM: Virtual Path & ChannelATM: Virtual Path & Channel

Virtual Channel

>Assigned at call-setup time

>Has only local significance>May be used for multi-component services e.g. video telephony with separatevoice and video VCI streams

Virtual Path

>Carry a bundles of Virtual Channels

>Virtual Path service from Carriers allows reconfiguration of virtual channelswithout service order changes to the Carrier


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Virtual Paths and Virtual ChannelsVirtual Paths and Virtual Channels

VCI1

VCI2

VCI3

VCI4

VC Switch

VCI 1

VCI 2

VP Switch

VCI 1

VCI 2

GFC VPI

VPI VCI

VCI

VCI PTI C

HEC

Empty cell s ind icated by VPI/VCI = 0NNI : 4,096 VPs and 65,536 VCsUNI : 256 VPs and 65,536 VCs

VPI 1

VPI1'

VCI 3

VPI3'

VPI2'

VPI 3VPI 3

VPI3'

VPI3'VPI4'

VCI 4

VPI 5VCI 1

VCI 2

VPI 4

VPI 4


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ATM Frame FormatATM Frame Format

GFC Generic Flow Control Controls the flow of data across the UNI

permitting multiple ATM devices to be attached to the same network interface

VPI Virtual Path Identifier Part of the network address used to identifygrouping of channels

VCI Virtual Channel Identifier Pointer that identifies the virtual channel the

system is using on a virtual path

PT Payload Type Indicates the type of information contained in the cell

CLP Cell Loss Payload Specifies whether or not to discard the cell in thepresence of congestion

HEC Header Error Control Provides error correction for single bit errors anderror detection for multiple bit errors in the cell.


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Sample ATM Network LayoutSample ATM Network Layout


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HDLC/PPPHDLC/PPP

High Level Data Link Control

Popularly used as a point to point WAN encapsulation protocol for

dedicated links and circuit switched type of connections.

-HDLC is an ISO standard that encapsulates data on synchronous ,

Serial data links.


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Point to Point ProtocolPoint to Point Protocol

The Point-to-Point Protocol (PPP) originally emerged as an

encapsulation protocol for transporting IP traffic over point-to-pointlinks.

PPP uses:

the High-Level Data Link Control (HDLC) protocol as a basis for

encapsulating datagrams.

An extensible LCP to establish, configure, and test the data link

connection.

A family of NCPs for establishing and configuring different network

layer protocols. PPP is designed to allow the simultaneous use of

multiple network layer protocols.


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Point to Point ProtocolPoint to Point Protocol

PPP is capable of operating across any DTE/DCE interface. Examples:

Asynchronous serial Synchronous Serial

ISDN

HSSI (High Speed Serial Interface)

PPP uses Frame of International Organization for Standardization (ISO)

HDLC procedures 3309:1984/PDAD1 :


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THE NETWORK LAYERTHE NETWORK LAYER


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Network LayerNetwork Layer

Network Layer deals with:

"Routing packets from source to destination subnet addresses.

Logical Addressing

"Control communication and forwarding information between routers

"Mapping MAC addresses to there Network addresses

Protocol Functioning in this layer include

IP,ICMP,ARP,RARP,RIP,OSPF,BGP

Routers function at this level


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Internet Protocol (IP)Internet Protocol (IP)

Used to route data from its source to destination

encapsulates or surrounds its payload

utilizes a header structure prefixed to the payload

individual packets are passed through the IP network on a best-effort basis

no guarantee of packet delivery

no guarantee of packet order

IP makes minimal demands on network

Routers make local forwarding decisions based upon the datagrams destination

address

Routers are not required to keep historical data on previous packet destination

paths

IP makes minimal demands on the network


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IP: Frame FormatIP: Frame Format

Source Address

Destination Address

Type-of-service Total Length

Fragment Offset

Protocol

FlagsIdentification

Header ChecksumTime-to-live

Options (+padding)

Data (Variable)

IHLVersion

32 bits

VersionIndicates the version of IP currently used.

IP Header Length (IHL)Indicates the datagram header length in 32-bit words.

Type-of-ServiceSpecifies how an upper-layer protocol would like a current datagram to be handled,and assigns datagrams various levels of importance.

Total LengthSpecifies the length, in bytes, of the entire IP packet, including the data and header.IdentificationContains an integer that identifies the current datagram. This field is used to help piecetogether datagram fragments.

FlagsConsists of a 3-bit field of which the two low-order (least-significant) bits control fragmentation.The low-order bit specifies whether the packet can be fragmented. The middle bit specifies whether thepacket is the last fragment in a series of fragmented packets. The third or high-order bit is not used.

Fragment OffsetIndicates the position of the fragment's data relative to the beginning of the data inthe original datagram, which allows the destination IP process to properly reconstruct the originaldatagram.

Time-to-LiveMaintains a counter that gradually decrements down to zero, at which point thedatagram is discarded. This keeps packets from looping endlessly.

ProtocolIndicates which upper-layer protocol receives incoming packets after IP processing iscomplete.

Header ChecksumHelps ensure IP header integrity.

Source AddressSpecifies the sendingnode.

Destination AddressSpecifies the receiving node.

OptionsAllows IP to support various options, such as security.

DataContains upper-layer information.


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The Transport LayerThe Transport Layer


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Transport Layer

The Transport layer is basically responsible

For making sure that the data is delivered error-free and in the

proper sequence.

Other responsibilities are:

Segmentation

"Sequencing

Retransmission (Error Correction)

Acknowledgements

Windowing / End to End flow control for connection oriented and

connectionless applications (Flow Control)"Port addressing, identifying upper layer protocols

Main protocols functioning here are TCP and UDP


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TCP OverviewTCP Overview

End-to-end protoco l that implements:

Reliability, sequencing, flow control and streaming

Bi-lateral duplex protoco l

Allowing only two parties on the same connection to share data

The same port number can be associated with a number of

distinctconnections by utilizing the source and destination

address fields

Low numbered ports are associated with defined services

Higher numbered ports are associated with dynamic

services

With stream data transfer, TCP delivers an unstructured stream of bytes identified by sequencenumbers. This service benefits applications because they do not have to chop data into blocks beforehanding it off to TCP. Instead, TCP groups bytes into segments and passes them to IP for delivery.

TCP offers reliability by providing connection-oriented, end-to-end reliable packet delivery through aninternetwork. It does this by sequencing bytes with a forwarding acknowledgment number that indicates

to the destination the next byte the source expects to receive. Bytes not acknowledged within aspecified time period are retransmitted. The reliability mechanism of TCP allows devices to deal withlost, delayed, duplicate, or misread packets. A time-out mechanism allows devices to detect lostpackets and request retransmission.

TCP offers efficient flow control, which means that, when sending acknowledgments back to thesource, the receiving TCP process indicates the highest sequence number it can receive withoutoverflowing its internal buffers. Full-duplex operation means that TCP processes can both send andreceive at the same time. Finally, TCP's multiplexing means that numerous simultaneous upper-layerconversations can be multiplexed over a single connection.

TCP Connection Establishment

To use reliable transport services, TCP hosts must establish a connection-oriented session with oneanother. Connection establishment is performed by using a "three-way handshake" mechanism.

A three-way handshake synchronizes both ends of a connection by allowing both sides to agree uponinitial sequence numbers. This mechanism also guarantees that both sides are ready to transmit dataand know that the other side is ready to transmit as well. This is necessary so that packets are nottransmitted or retransmitted during session establishment or after session termination.


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TCP AdaptabilityTCP Adaptabili ty

TCP manages the reliable exchange of data

TCP utilizes a basic flow-control algorithm Increasing the data flow rate until the network signals saturation

Packet loss

TCP flow rate is reduced

When reliable transmission occurs

Data flow begins to increase again

If no reliable flow is established

Flow rate backs off until initial probe of single packet occurs

Entire flow control process starts again

Allows a highly, efficient network to be utilized

Positive Acknowledgment and Retransmission (PAR)

A simple transport protocol might implement a reliability-and-flow-control technique where the sourcesends one packet, starts a timer, and waits for an acknowledgment before sending a new packet. If theacknowledgment is not received before the timer expires, the source retransmits the packet. Such atechnique is called positive acknowledgment and retransmission (PAR).

By assigning each packet a sequence number, PAR enables hosts to track lost or duplicate packetscaused by network delays that result in premature retransmission. The sequence numbers are sentback in the acknowledgments so that the acknowledgments can be tracked.

PAR is an inefficient use of bandwidth, however, because a host must wait for an acknowledgmentbefore sending a new packet, and only one packet can be sent at a time.

TCP Sliding Window

A TCP sliding window provides more efficient use of network bandwidth than PAR because it enableshosts to send multiple bytes or packets before waiting for an acknowledgment.

In TCP, the receiver specifies the current window size in every packet. Because TCP provides a byte-stream connection, window sizes are expressed in bytes. This means that a window is the number of

data bytes that the sender is allowed to send before waiting for an acknowledgment. Initial windowsizes are indicated at connection setup, but might vary throughout the data transfer to provide flowcontrol. A window size of zero, for instance, means "Send no data."

In a TCP sliding-window operation, for example, the sender might have a sequence of bytes to send(numbered 1 to 10) to a receiver who has a window size of five. The sender then would place a windowaround the first five bytes and transmit them together. It would then wait for an acknowledgment.


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TCP Data TransferTCP Data Transfer


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TCP Frame FormatTCP Frame Format

Source Port Destination Port

Sequence Number

Acknowledgement Number

Data Offset Reserved Flags Window

Checksum Urgent Pointer

Options (+padding)

Data (Variable)

Source Port and Destination PortIdentifies points at which upper-layer sourceand destination processes receive TCP services.

Sequence NumberUsually specifies the number assigned to the first byte of datain the current message. In the connection-establishment phase, this field also can be

used to identify an initial sequence number to be used in an upcoming transmission.

Acknowledgment NumberContains the sequence number of the next byte of datathe sender of the packet expects to receive.

Data OffsetIndicates the number of 32-bit words in the TCP header.

ReservedRemains reserved for future use.

FlagsCarries a variety of control information, including the SYN and ACK bits usedfor connection establishment, and the FIN bit used for connection termination.

WindowSpecifies the size of the sender's receive window (that is, the buffer spaceavailable for incoming data).

ChecksumIndicates whether the header was damaged in transit.

Urgent PointerPoints to the first urgent data byte in the packet.

OptionsSpecifies various TCP options.

DataContains upper-layer information.


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UDPUDP

Physical

Data Link

IP ICMP

UDP TCPApplication

UDP is a connectionless transport-layer protocol

UDP is basically an interface between IP andupper-layer processes.

UDP adds no reliability, flow-control, or error-recovery functions to IP.

UDP headers contain fewer bytes and consume lessnetwork overhead

UDP is useful in situations where the reliabilitymechanisms of TCP are not necessary, such as in caseswhere a higher-layer protocol might provide error andflow control.

UDP is the transport protocol for several well-known

application-layer protocols, including Network FileSystem (NFS), Simple Network Management Protocol(SNMP), Domain Name System (DNS), and Trivial File

Transfer Protocol (TFTP).

The User Datagram Protocol (UDP) is a connectionless transport-layer protocol(Layer 4) that belongs to the Internet protocol family. UDP is basically an interfacebetween IP and upper-layer processes. UDP protocol ports distinguish multipleapplications running on a single device from one another.

Unlike the TCP, UDP adds no reliability, flow-control, or error-recovery functions toIP. Because of UDP's simplicity, UDP headers contain fewer bytes and consume lessnetwork overhead than TCP.

UDP is useful in situations where the reliability mechanisms of TCP are notnecessary, such as in cases where a higher-layer protocol might provide error andflow control.

UDP is the transport protocol for several well-known application-layer protocols,including Network File System (NFS), Simple Network Management Protocol(SNMP), Domain Name System (DNS), and Trivial File Transfer Protocol (TFTP).


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TCP/UDP Port NumbersTCP/UDP Port Numbers

Each internet application (FTP, HTTP, Telnet) relates to particular port in asession. Main internet application maintain well known port numbers, while mostport numbers are dynamically assigned.


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TCP/UDP PORTSTCP/UDP PORTS

Port nos above 1024 are generally allocatedFor source port as port nos below 1024 haveBeen assigned for popular applications by IETF.Every application running in a PC will have aUnique source port while all similar applications(ex. http, telnet, ftp etc.) will have the sameDestination port.


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TCP/UDP Port AddressesTCP/UDP Port Addresses


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The Session LayerThe Session Layer


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Session Layer

Protocols at this layer are necessary for

Establishing, maintaining and ending sessions between user

applications.

They are basically flow chart applications which guide the user into the

various functional/control aspects of an application.


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The Presentation LayerThe Presentation Layer


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Presentation Layer

The presentation layer ensures that

The communication passing through are in the appropriate form for therecipient.

Programs in the presentation layer address three aspects ofpresentation.

"Data formats for example ASCII or binary formats

"Compatibility with host operating system

"Encapsulation of the data into message envelopsfor transmissionthrough the network.


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The Application LayerThe Application Layer


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Application Layer

This layer is closest to the user providing network services to

application programs to ensure communication with other applicationprogram

The Application layer is NOT the application itself that is doing thecommunication; it is the service layer that provides these services.

"Makes sure that the other party is identified and can be reached.

"If appropriate, authenticates either the message sender or receiver orboth.

"Makes sure that necessary communication resources exist.

"Ensures agreement at both ends about error recovery procedures data

integrity, and privacy.

"Determines protocol and data syntax rules at the application level.

!It may be convenient to think of the Application layer

as the high level set-up services for the application

program.


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The TCP/IP Protocol Suite

A set of standard data communication protocols also

known as the Internet Protocol suite used on the internet world wide.

The suite was originally developed for the US Department of Defense

Advanced Research Project Agency (DARPA)

TCP/IP is a layered protocol based on the DoD model where each layerbuilds upon the layer below it, adding new functionality.


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TCP/IP Protocol Suite

TCP/IP is designed to use a client server model of

communication in which a client request is provided a service (such assending a web page) to by another a computer(server) in the network.

TCP/IP has only four layers i.e. when compared to the OSI referencemodel the upper four layers (4-7) is integrated into one and is called as

Application layer.

All the TCP/IP applications resides at this layer.

Lower layers (1-3) purely are concerned with sending and receiving

data using specific n/w hardware.


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TCP/IP VS OSI MODELTCP/IP VS OSI MODEL


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TCP/IP Protocol Suite


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FTPFTP

File Transfer Protoco l

FTP is most widely used protocol for moving files reliably across networksof various platforms.

You need to logon to the FTP server with a password,

however publicly available files are easily accessed using anonymousFTP.

A user can use FTP commands from a prompt, or a graphical userinterface to download programs selected from a web page or an FTPserver.

Using FTP, one can also update (delete, rename,move and copy) files

at sever

To ensure reliability, FTP uses TCP at the transport layer


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HTTPHTTP

Hyper Text Transfer Protocol

HTTP is the fundamental protocol used by the World Wide Web

It defines how messages and files are formatted and transmitted and

what actions web server and browser should take in response tovarious commands.

A web browser is a client program that uses HTTP to make requests of

web servers throughout the internet on behalf of the browser user.

A web browser use the Uniform Resource Locator (URL) to link files toother websites.

To ensure reliability HTTP uses TCP at the transport layer


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SNMPSNMP

Simple Network Management Protoco l

Application layer protocol for managing complex networks

It allows a host (NMS) acting as an SNMP Manager to poll and

configure managed network devices SNMP agents

Agents routinely reports unsolicited events notifications to theirmanagers known as Traps.

Management Information Base (MIB) is a collection of managed objectsresiding in the agent.

SNMP uses UDP at the transport layer


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SMTPSMTPSimple Mail Transfer Protocol

The host that is configured with

this protocol is called as theSMTP server.

The SMTP server hand les

outgoing mails

Whenever you send a piece

of e-mail, your email client

interacts with your SMTP

server to handle sending of

the mail

The SMTP server then

contacts other SMTP server

to actually deliver the mail

To ensure reliabili ty SMTP

use TCP at the transport layer


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POP3POP3

Post Office Protoco l

It the most popular TCP/IP mail

access protocol

It implements the Off-Line access

model, allowing users to retrieve

mail from their SMTP server.


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TELNETTELNET

TELNET

Telnet is the terminal emulation program that allows you

to remotely access someone elses computer across the network,

assuming they have given you permission

To start a telnet session the client must log in to a server by entering avalid username and password

After you get authenticated you will be presented a command promptwhere you can execute the commands, you feel as if you are on thesever console

To ensure reliability, Telnet uses TCP at the transport layer


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Module Summary


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Module ReviewModule ReviewModule Review

1. Node to Node Communication is provided by Layer

2. Parity & CRC are .. layer tools.

3. .. layer takes care of end to end reliable delivery of data.

4. RS232C and RS485 are layer standards.

5. .layer takes care of packet transfer between logical networks.

6. .layer takes care of forms, formats, fonts, etc.

7. .layers are broadly categorized as the Network LayersandLayers are categorized as Application Layersin OSI model.

8. Which layers take part in data communication in Networking Devices

We had see this page before: As information is passed through the network, the topfour layers are only required at the end-points. The bottom three (Physical, Data &Network) are required at every node that the information pass through. Nodes whichcan process upto Layer 3 (Network layer) information are called Routers.

Routers are essentially element that determine the Route to to taken for end-to-endinformation Transfer. This they do by creating and maintaining either a Static orDynamic Routing Table. Modern Routers are capable of maintaining several RoutingTables, some Static and some Dynamic.


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Bus TopologyBus Topology

The Ethernet started in a bus topology:

Main Cable

TerminationTermination

COLISSIONS IS A PROBLEM,ANS INFO TRANSMITTED BY ONE GOESTO ALL,THIS IS A COMMON BROADCAST DOMAIN,AND THE BUS HASTO BE TERNINATED OTHERWISE THERE WILL BE VOLATAGEREFLECTIOSN

this is called a common broadcast domain


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Bus TopologyBus Topology

The bus topology found out to have a lot of disadvantages:

Cut in the Coax cable can cause disconnecting several stations.

Fault in Coax cable can disturbed the service.

Incorrect / no termination

Fault in the ground

NoTermination

Termination

Termination

Termination


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RIC-Learning Center Page100 For Internal Circulation Only

Star TopologyStar Topology

In order to over come the problem issued in a bus topology, star

topology was used for the Ethernet connection. If a single cable cut/fault only one node is disconnected.

Usage of a cheaper unshielded twisted pair cable than a coaxialcable.

The usage of the star topology introduced the bus in a boxequipmentwhich is known as an Hub.

SO THE HUB WAS DEVELOPED.THE MEDIA IS STILL SHARED BUTUNDER OUR CONTROL.ALL PORTS ARE PARALLEL,SO BREAK IN LINKWILL NOT RESULT IN ALL STATIONS OUTAGE.


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L1 DevicesL1 DevicesL1 Devices

Repeater

Used in local area networks. It is a physical layer device thatregenerates the electrical signal.

Extend the distance between remote nodes

Increase the total number of nodes on a network.

Repeater amplifies the signal and removes any distortion.

Maximum 5 spans

Repeaters let you extend the distance between remote nodes and increase the totalnumber of nodes on a network. The physical layer defines the rules for the media(such as electrical or fiber optic cable) that interconnect network devices. Electricalsignals become weaker over distance (called attenuation) and may become distorted

by exposure to interference (EMI and RFI). The rules provided by the physical layerprotocol ensure that the signal remains strong enough for the most remote end nodesto exchange data.

A repeater amplifies the signal and removes any accumulated distortion. The onlypossible values for a digital signal are 0 or 1, so it is easy to restore it to its originalcondition. Because a repeater deals with signal reproduction, it is considered tooperate at the OSI physical layer.

Besides limiting the length of the segment, physical layer specifications also state themaximum number of nodes per segment for different media types. For instance, amaximum of 30 attachments are permitted on an 802.3 network using 10BASE2 (thin

Ethernet) coaxial cable.

Repeaters allow you to interconnect multiple segments of the same media type andthe same data link layer protocol. This interconnection increases the number of nodesallowed and extends the maximum distance permitted between the most distant endnodes in the network.


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HubHubHub

Hubs provide both Physical layer and Repeaters function.

Hubs do not isolate collision domains , they extend them.This means a node may collide with any other node residing at anysegment in the LAN.

Segment A/ Accounts Department Segment B/ Sales Department


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CSMA/CDCSMA/CD

Although Metclafe and his colleagues establish a

connection they had one major problem Collisions.Through out the years a protocol was added to theEthernet network in order to reduce the collisions.

This protocol called CSMA/CD (Carrier Sense MultipleAccess / Collision Detection).

The CSMA/CD describes the following scenario

Laptop computerWorkstation IBM Compatible

IBM CompatibleIBM laser printer

SO THE TERMINAL WILL FIRST ENSURE WETHER MEDIA IS FREE ORNOT TO AVOID COLLISIONS

to avoid collisions the csma/cd protocol is defined


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CSMA/CDCSMA/CD

Node A prior the transmission to node B needs to listento the media

in order to check whether the media is free or not.

AB

C

A wants to t ransmit to BA listen to the Media is it free?The Media is free O.K to transmitThe Media is occupied wait a random period o f time and try again.


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CSMA/CDCSMA/CD

CSMA/CD is not immune to collisions because at the same time

that A listensto the media C could have also been listeningto the media and both of them will transmit on the same time.

In a collision scenario the Ethernet system has a way to knowthat collision happened. Both node stopping their transmissionand back-offfor a random time period.


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Full / Half DuplexFull / Half Duplex

Half Duplex Only one node may transmit on the line. Half duplex

is a must in shared media scenario (e.g hub).Full Duplex A station can receive and transmit on the same time,only in a none shared media environment.


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L2 DevicesL2 DevicesL2 Devices

Bridge

Bridge is a layer 2 device.

It interconnects two LAN segments.

The two LANs can be of different technologies e.g. Ethernet, token ring.

A bridge is also used to segment a LAN so that messages meant for onesegment are not sent to other segments (Filtering capability).

Segmentation of a LAN can be done department wise in an organization.Security policy can be implemented.

Bridge can be self learning i.e they learn addresses of stations on differentsegments by looking at the frames that flow in a segment.

LAN 1 LAN 2

In telecommunication networks, a bridge is a product that connects a local area network (LAN) toanother local area network that uses the same protocol (for example, Ethernet or token ring).

You can envision a bridge as being a device that decides whethera message from you to someoneelse is going to the local area network in your building or to someone on the local area network in thebuilding across the street. A bridge examines each message on a LAN, "passing" those known to bewithin the same LAN, and forwarding those known to be on the other interconnected LAN (or LANs).

In bridging networks, computer or node addresses have no specific relationship to location. For thisreason, messages are sent out to every address on the network and accepted only by the intendeddestination node. Bridges learn which addresses are on which network and develop a learning table sothat subsequent messages can be forwarded to the right network.

Bridging networks are generally always interconnected local area networks since broadcasting everymessage to all possible destinations would flood a larger network with unnecessary traffic. For thisreason, router networks such as the Internet use a scheme that assigns addresses to nodes so that amessage or packet can be forwarded only in one general directionrather than forwarded in alldirections.

A bridge works at the data-link level of a network, copying a data frame from one network to the next

along the communications path.

A bridge is sometimes combined with a router in a product called a brouter.


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BRIDGE BasicsBRIDGE Basics


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BridgeBridgeBridge

Transparent bridges integrate LANs into a logical network by activelylistening to each frame on each network and forwarding those frames with

a destination on the remote LAN.

To interconnect physical networks, bridges perform four basic functions:

Listen

Learn

Filter

Forward

The bridge listens to all messages transmitted on the networks to which it is connected. A bridge learnsdevice addresses by building a forwarding table mapping the source address from each frame itreceives to the port on which it is received. A bridge filters traffic, ignoring frames with destinationaddresses mapped to the same port on which they are received. (The bridge can be configured toperform additional filtering based on various criteria.) Finally, a bridge forwards traffic to the appropriate

ports to allow data to reach its destination.

A transparent bridge examines the destination address of all messages transmitted on each network towhich it is connected. If the destination address is associated with the port on which it was received,the message is not forwarded to transmitting ports. If the destination address is known and is notassociated with the port on which it was received, the bridge forwards the frame to the port associatedwith the destination. For instance, in Figure 3-3, a message with the destination addressAA receivedon port 1 is i

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