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2009, Velocis Systems

Networking BasicsNetworking Basics

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How a LAN Is BuiltHow a LAN Is Built

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1-3Networking Fundamentals 2009, Velocis Systems

Local-Area NetworkLANLocal-Area NetworkLAN

What is a LAN?

A collection of computers, printers, and otherdevices that can communicate with eachother in a small area.

What are the components?Computers, operating system (OS),network interface card (NIC), and hubs

How is a LAN controlled?ProtocolsFormal descriptions of sets of

rules and conventions that govern how

devices on a network exchange information

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Local-Area NetworksLocal-Area Networks

LANs are designed to:Operate within a limited geographic area

Allow multi-access to high-bandwidth media

Control the network privately under localadministration

Provide full-time connectivity to local services

Connect physically adjacent devices

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Network Operating System (OS)Network Operating System (OS)

Software that allowscommunicating andsharing of data and

network resources

Examples:

AppleTalk

NetWare

Win NT

PC or Workstation

Loaded with NOS

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Network Interface CardNetwork Interface Card

Connector Port

PC or Workstation

Loaded with NOS

Network InterfaceCard (NIC)

Amplifies electronic signals

Packages data fortransmission

Physically connectscomputer to

transmissionmedia (cable)

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1990sGlobal Internetworking1990sGlobal Internetworking

19921 major backbone, 3,000 networks, 200K computers

1995Multiple backbones, hundreds of regional nets, tens of thousands

of LANs, millions of hosts, tens of millions of usersDoubling every year!

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The OSI ModelThe OSI Model

OSI Layer is meant for Networking

manufacturers and developers toprovide them a standard based onwhich they can make their products.

All OSI Layers are independent fromeach other, which makes introducingchanges easier as no other layers areeffected.

Ease of Troubleshooting.

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The Layered ModelThe Layered Model

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Devices Function at LayersDevices Function at Layers

7 Application

6 Presentation

5 Session

4 Transport

3 Network

2 Data Link

1 Physical

NIC Card

Hub

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Host LayersHost Layers

7 Application

6 Presentation

5 Session

4 Transport

Network

3 Data Link

1

Host layers:Host layers: Provideaccurate data delivery

between computers

Physical

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Media LayersMedia Layers

7 Application

6 Presentation

5 Session

4Transport

3 Network

2 Data Link

1 Physical

Host layers:Host layers: Provideaccurate data delivery

between computers

Media layers:Media layers:Control

physical delivery of messages

over the network

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Layer FunctionsLayer Functions

Provides network services to

application processes (such aselectronic mail, file transfer, and

terminal emulation)

Application7

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Application

Presentation

7 Network services to applicationsNetwork services to applications

Data representation6

Ensures data is readable by

receiving system

Format of data Data structures

Negotiates data transfer

syntax for application layer

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Application

Presentation

Session


6 Data representationData representation

5 Inter-host communication

Establishes, manages, andterminates sessions between

applications

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Application

Presentation

Session

Transport



5 InterInter--host communicationhost communication

4 End-to-end connection reliability Concerned with data transport

issues between hosts

Data transport reliability Establishes, maintains, and

terminates virtual circuits

Fault detection and recovery

Information flow control

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Application

Presentation

Session

Transport

Network




4 EndEnd--toto--end connection reliabilityend connection reliability

3 Addresses and best path

Provides connectivity and pathselection between two end

systems

Domain of routing

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7 Application

6 Presentation

5 Session

Transport4

Network3

Data Link2

InterInter--host communicationhost communication

Network services to applicationsNetwork services to applications

Data representationData representation

EndEnd--toto--end connection reliabil ityend connection reliability

Addresses and best pathAddresses and best path

Access to media Provides reliable transfer of data

across media

Physical addressing, network

topology, error noti fication, flow

control

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Application

Presentation

Session

Transport

Network

Data Link

Physical




4 EndEnd--toto--end connection reliabilityend connection reliability

3 Addresses and best pathAddresses and best path

2 Access to mediaAccess to media

1 Binary transmission

Wires, connectors, voltages,

data rates

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Peer-to-Peer CommunicationsPeer-to-Peer Communications

7 Application

6 Presentation

5 Session

4 Transport

3 Network

2 Data Link

1 Physical

Host A

Application

Presentation

Session

Transport

Network

Data Link

PhysicalBits

Frames

Packets

Segments

Host B

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Application LayerApplication Layer

This is where users communicate to the

computer. This is where communication between

two users are established.

This is a point where user or applicationinterfaces with the protocols to gain

access to the network. Examples are WWW, Telnet, FTP, TFTP,

E-mail, SNMP, DNS

Presentation LayerPresentation Layer

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Tasks like Translation, Encryption,decryption, compression, decompression areassociated with this layer.

It receives the data in native format &converts in standard format or receives datain standard format and converts in nativeformat, ie. EBCDIC to ASCII.

It is mainly responsible for how the data is to

be presented to the Application Layer.

Examples are PICT, TIFF, JPEG, MIDI, MPEG,GIFF etc.

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ASCIIEBCDIC

Encrypted

Text

Data

login:

PICTTIFF

JPEGGIF

Graphics

Visual images

Sound

VideoMPEG

QuickTime

MIDI

Provides code formatting and

conversion for applications

PROTOCOLS OF PRESENTATIONPROTOCOLS OF PRESENTATION

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PROTOCOLS OF PRESENTATIONLAYER

PROTOCOLS OF PRESENTATIONLAYER

PICT: This is picture format used by Macintosh or power PC

program for transferring quick draw graphics. TIFF: Tagged image file format is a standard graphic format for

high resolution, bitmapped images.

JPEG: the joint photographic express group brings this photo

standard to us. MIDI: the musical instrument digital interface is used for

digitized music. Other standard guide movies and sound:

MPEG: the moving picture experts groups standard for the

compression and coding of motion video for the CDsincreasingly popular. It provides digital storage and rates up to1.5 Mbps.

Quick time: this for use with Macintosh or PowerPC programs; it

manages audio and video application.

S i LS i L

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Session LayerSession Layer

Session Establishment

Establishes a session between two devices

before actual transmission of data.Dialog Control

Simplex

Half Duplex

Full Duplex

S i L

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Session Layer

Simplex

Data travels only one way.

Radio transmission is the best example of this.

Half DuplexBoth way but one at a time. By default all LAN Cards

(NICs) work on Half Duplex.

Full Duplex

Both way at the same time.

S

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Session LayerSession Layer

Network File System (NFS)

Structured Query Language (SQL)

Remote-Procedure Call (RPC)

X Window System

AppleTalk Session Protocol (ASP)

DEC Session Control Protocol (SCP)

Service Request

Service Reply

Coordinates applications asthey interact on different hosts

S SS O O OCO SSESSION LAYER PROTOCOLS

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SESSION LAYER PROTOCOLSSESSION LAYER PROTOCOLS

Network File System (NFS): Was developed by SunMicrosystems and used with TCP/IP and Unix workstations toallow transparent access to remote resources.

Structured Query Language (SQL): Was developed by IBM toprovide users with a simple way to define their informationrequirements on both local and remote systems.

Remote Procedure Call (RPC): A board client/server redirectiontool used for disparate service environments. Its procedure arecreated on client and performed on servers.

X Windows: Is widely used by intelligent terminals forcommunicating with remote Unix computers, allowing them as

though they were locally attached monitors. Apple Talk special Protocol (ASP): Is another client /server

mechanism, which both establishes and maintains session talksbetween apples talk client and sever machines.

Digital Network Architecture Session control protocol (DNASCP): Is DEC net session layer protocol

T t LT t L

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Transport LayerTransport Layer

Segments upper-layer applications

Establishes an end-to-end connection Sends segments from one end host to another

Optionally, ensures data reliability


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Transport Layer never actually transports the databut only prepares for transporting.

Uses Socket to define the services running on aparticular node, the data is associated with.

Responsible for the following :

Segmentation

End-to-end Communication

Flow ControlError Control

Multiplexing of Applications

TCP, UDP and SPX work at this layer

SocketSocket

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SocketSocket

Socket is a software component and points to a particular servicerunning on a particular node.

Structure of a socket

IP Address + Port Address

Each service has a unique Port address

Max. Port Addresses can be 65,536

Port address 1-1023 is reserved for specific Services l ike

WWW - 80FTP - 21

SMTP - 25

Port Addresses are reserved for standardization purpose.

P t N bP t N b

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Port NumbersPort Numbers

TCP

Port

Numbers

FTP

Transport

Layer

TEL

NET

DNS

SNM

P

TFT

P

SMT

P

UDP

Application

Layer

2121 2323 2525 5353 6969 161161

RIP

520520

SegmentationSegmentation

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SegmentationSegmentation

This is a mechanism wherein the data is divided into

multiple segments and sent over the network. By doing this different segments can use different l inks

for travelling across the network.

If one segment is lost the only segment is required to bere-sent and not the entire data.

Once all segments reach to the destination the receivedsegments have to be sequenced back, which is alsodone at this layer.


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Transport LayerSends Segments with Flow Control

Transport LayerSends Segments with Flow Control

Transmit

Buffer FullNot Ready

Stop Process

Segments

Buffer OKReadyGo

Resume Transmission

ReceiverSender

Flow ControlFlow Control

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Used while connection oriented communication

It helps to have a control on over flow of Buffer.

Advantages are:

The segments delivered are acknowledged if received

Any segment not acknowledged are retransmitted

segments are sequenced back upon their arrival

Congestion, Overloading and data loss are avoided

To achieve all this it uses the technique of Sliding

window or Windowing


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p yEstablishes Connection

p yEstablishes Connection

Synchronize

Synchronize

Acknowledge

Negotiate Connection

ReceiverSender

Data Transfer

Connection Established

(Send Segments)

End to End CommunicationEnd to End Communication

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End-to-End CommunicationEnd-to-End Communication

Connection Less Transmission

UDP is used

Not reliable

Faster

Connection Oriented Transmission

TCP or SPX is used

Reliable

Slower

Connection Oriented ProtocolConnection Oriented Protocol

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Connection Oriented ProtocolConnection Oriented Protocol

These protocols relies on Acknowledgement. Positive acknowledgement means data has

been received.

Negative acknowledgement means data islost no further data is sent till positive

acknowledgement is received. It is slow but Reliable.

Eg. TCP and SPX


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p yReliability with Windowing

p yReliability with Windowing

Window Size = 1

Sender

Send 1 Receive 1

Receiver

Ack 2

Send 2 Receive 2

Ack 3

Sender

Send 1

Send 2Receive 1Receive 2

Window Size = 3

Send 3 Receive 3Ack 4

Send 4

Receiver


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p yAn Acknowledgement Technique

yAn Acknowledgement Technique

Sender Receiver

Send 2Send 1Send 3

Ack 4

Send 5Send 4Send 6

Ack 5

Send 5 Ack 7

1 2 3 4 5 6 7 1 2 3 4 5 6 7

Connection Less ProtocolConnection Less Protocol

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Connection Less ProtocolConnection Less Protocol

They do not provide acknowledgementneither sequence numbers.

It is faster but not reliable

Eg. UDP

Network LayerNetwork Layer

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yy

It is responsible for communicating Networks

It recognizes Networks with the help of Netwok Addresses

Network Address is a logical address like IP Address or IPX

Address

It is common for a group of computers

It works only with Network IDs and has got nothing to do with host

Ids.

Path determination or Routing is performed at this layer.

Router works at this layer.

Network Layer: Path DeterminationNetwork Layer: Path Determination

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Network Layer: Path DeterminationNetwork Layer: Path Determination

Which Path?Which Path?

Layer 3 functions to find the best

path through the internetwork

Network Layer: Communicate PathNetwork Layer: Communicate Path

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Network Layer: Communicate PathNetwork Layer: Communicate Path

1

2

3

4

5

6

7

8

9

10 11

Addresses represent the path of mediaconnections

Protocol Addressing VariationsProtocol Addressing Variations

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Protocol Addressing VariationsProtocol Addressing Variations

Network Node

1 1

General

Example

Network Host

10. 8.2.48

TCP/IP

Example(Mask 255.0.0.0)

Network Node

1aceb0b. 0000.0c00.6e25

Novell IPXExample

Network LayerP t l O ti

Network LayerP t l O ti

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Protocol OperationsProtocol Operations

X Y

AA

CC

Each router provides its services to

support upper layer functions

Routed Versus Routing ProtocolRouted

Versus Routing Protocol

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Routed Versus Routing ProtocolRouted Versus Routing Protocol

Routed protocol

used between

routers to directuser traffic

Examples: IP, IPX,

AppleTalk

Routing protocolused only between

routers to maintain

routing tables

Examples: RIP, IGRP, OSPF

Static Versus Dynamic RoutesStatic Versus Dynamic Routes

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Static Versus Dynamic RoutesStatic Versus Dynamic Routes

Uses a protocol route that a network

administrator enters into the router

Static Route

Uses a route that a network protocol

adjusts automatically for topology ortraffic changes

Dynamic Route

Static Route ExampleStatic Route Example

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Static Route Examplep

Point-to-point orcircuit-switched

connection

Stub network

Only a single network

connection with no need

for routing updates

AA

BB

Fixed route to address reflects

administrators knowledge

Adapting to Topology ChangeAdapting to Topology Change

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p g p gy gp g p gy g

AA BB

CCDD

Can an alternate route substitute

for a failed route?


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AA BB

CCDDXX


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AA BB

CCDDXX

Can an alternate route substitutefor a failed route?

YesYesWith dynamic routing enabled

Data Link LayerData Link Layer

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yy

It uniquely identifies each device in the Network.

It translates data from Network Layer into bits for thePhysical layer to transmit.

It formats the messages into Data Frames

Adds a customized header containing Source andDestination hardware address

This layer works with Frames

This layer is logically divided in two sub-layers:

LLC (Logical Link Control)

MAC (Media Access Control)

DATA LINK LAYERDATA LINK LAYER

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FUNCTIONS OF ETHERNET

1) Arbitration: CSMA/CD algos

2) Addressing: 6 byte-long MAC address

3) Error detection: FCS in Ethernet trailer

4) Identify the type of packet inside the frame

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DOD MODELDOD MODEL

The DoD ModelThe DoD Model

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The Process / Application Layer

The Host-to-Host Layer

The Internet Layer

The Network Layer

The DoD & OSIThe DoD & OSI

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ApplicationApplication

Presentation

Session

Transport

Network

Data Link

Physical

Host-to-Host

Internet

Network

Access

DoDModel OSIModel

Process/Application LayerProcess/Application Layer

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The Process / Application layer definesprotocols for node-to-node application

communication and also controls user-interface specification.

A vast array of protocols combine at thislayer of DoDs Model to integrate theactivities and duties of upper layer of OSI.

Examples for this layer are :

Telnet, FTP, TFTP, NFS, SMTP, SNMP,

DNS DHCP, BootP etc.

Host-to-Host LayerHost-to-Host Layer

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The Host-to-Host layer parallels thefunctions of the OSIs Transport layer

It performs the following:

Defining protocols for setting up thelevel of transmission service forApplications

It tackles issues like creating reliable

ene-to-end communication.It ensures the error free delivery of data

It handles packet sequencing andmaintains data integrity.

Internet LayerInternet Layer

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Internet Layer corresponds to the OSIsNetwork Layer.

It performs the following:

Designating the protocols relating to thelogical transmission of packets over theentire network.

It takes care of the addressing of hostsby giving them an IP address.

It handles routing of packets among

multiple networks.

Network Access LayerNetwork Access Layer

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This layer is equivalent of the Data Link andPhysical Layer of OSI model.

It performs the following

It monitors the data exchange between thehost and the network.

Network Access Layer overseas hardwareaddressing and defines protocols for thephysical transmission of the Data.

Lets have a look on how TCP/IP Protocol suit relatesto the DoD model layers.

TCP/IP Protocol Suit at DoDTCP/IP Protocol Suit at DoD

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DoDModel

Process /Application

Host-to-Host

Internet

Network

Access

TCP/IP Protocol Suit

Telnet FTP LPD SNMP

X WindowNFSSMTPTFTP

TCP UDP

ICMP

Ethernet

ARP RARP

IP

Fast

Ethernet

Token

Ring FDDI

BootP

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EthernetEthernet

IntroductionIntroduction

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Ethernet is a methodology for accessing a media

It allows all hosts on a network to share the same

bandwidth of a link.

It is popular because :

It is easy to implement & TroubleshootIt is easy to add new technologies like Fast Ethernet

and Gigabit Ethernet to existing infrastructure.

Ethernet uses Data Link Layer and Physical LayerSpecification

It uses something called CSMA/CD

Ethernet OperationEthernet Operation

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AA BB CC DD


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AA BB CC DD

D

Data Link

NetworkTransport

Session

Presentation

Application

Physical


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AA BB CC DD

D

Data Link

NetworkTransport

Session

Presentation

Application

Physical

B and C

Data Link

NetworkTransport

Session

Presentation

Application

Physical

Ethernet LANs:How do they work?

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Multiple workstations

are connected to a

segment Each station has to take

turns sending traffic

All stations listen to all

traffic on their segment

Stations can only senddata (Ethernet Frames)

when no one else is

sending

Ethernet LANs:MAC Addresses

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Every workstation has

a Network Interface

Card (NIC) Every NIC has a unique

MAC address

Stations use MAC

addresses to send

Ethernet Frames to aspecific station

0000.0c12.3456

0000.0c12.11110000.1018.321a

Ethernet LANs:Unicast Frames

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Ethernet frames contain

the MAC address of the

station that the framewas sent to

These are called

unicast frames All stations receive the

Ethernet frame, but

ignore the frames that

are not addressed to

their MAC address

0000.0c12.3456

0000.0c12.11110000.1018.321a

Frame

To: 0000.0c12.3456

Ethernet LANs:Broadcast Frames

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Some Ethernet frames

are sent to all stations These are called

broadcast frames

All stations process

this frame

0000.0c12.3456

0000.0c12.11110000.1018.321a

Frame

To: FFFF.FFFF.FFFF

Ethernet LANs:Broadcast Frames

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Some Ethernet frames

are sent to all stations These are called

broadcast frames

All stations process

this frame

0000.0c12.3456

0000.0c12.11110000.1018.321a

Frame

To: FFFF.FFFF.FFFF

Ethernet Collisions

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Sometimes stations

transmitsimultaneously

Two frames on the

same segment coll ide

Collisions require

each station to waitand resend

Collision!

PacketFrame PacketFrame

Packe

t

Packe

tFrameFrame

Ethernet ReliabilityEthernet Reliability

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B C DAFigure 1

B C DDAAFigure 2

Collision


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Collision

CC

B C DDAA

BA D

JAMJAMJAMJAMJAM JAM


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B C DA

Collision

B C DA

JAMJAMJAMJAMJAM JAM

Carrier sense multiple access with

collision detection (CSMA/CD)

CSMA/CDCSMA/CD

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CSMA/CD stands for Carrier Sense Multiple Access /Coll ision Detect.

It is used by all NICs in Ethernet Networking

In this method all NICs first sense whether the cableis free or not.

If it is free the request is sent otherwise it waits.

Half Duplex EthernetHalf Duplex Ethernet

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It is defined in 802.3 Ethernet

specifications It uses only one wire pair for signals

running in both direction.

CSMA/CD is used to prevent collision.

Half Duplex typically 10base T is 50-60

% efficient. (In CISCO views)

In a large 10 base T network you only

get 3 to 4 MBPS at most.

Full DuplexFull Duplex

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Full Duplex Ethernet uses two pairs ofwires.

It uses Point-to-Point connection

There is no collision in Full Duplex Full Duplex is suppose to offer 100%

efficiency in both direction

Means you can get 20 MBPS in 10 MBPSor 200 MBPS in Fast Ethernet running

Full Duplex.

Ethernet AddressingEthernet Addressing

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Ethernet Addressing uses MAC Address

MAC addresses are burned on every NIC

It is a 48-bit address

It is written in the same format even if different

LAN Technologies are used.

Organizationally

Unique Identifier (OUI)

(Assigned by IEEE)

Vender Assigned

24 bits 24 bits

Ethernet Addressing using MAC Addresses

Ethernet and IEEE 802.3Ethernet and IEEE 802.3

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Benefits and background Ethernet is the most popular physical layer LAN technology because

it strikes a good balance between speed, cost, and ease ofinstallation

Supports virtually all network protocols Xerox initiated, then joined by DEC & Intel in 1980

Revisions of Ethernet specif ication

Fast Ethernet (IEEE 802.3u) raises speed from 10 Mbps to 100 Mbps Gigabit Ethernet is an extension of IEEE 802.3 which increases

speeds to 1000 Mbps, or 1 Gbps

Ethernet and IEEE 802.3Ethernet and IEEE 802.3

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Several framing variations exist for thiscommon LAN technology

Ethernet FramesEthernet Frames

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Frames are used at the Data Link Layer toencapsulate packets coming down fortransmission on a type of Media Access

Types of Media Access

Contention (Ethernet)

Token Passing (Token Ring or FDDI)We will be covering only Contention, as rest all are beyond the scope of our course.

LAN FUNDAMENTALSLAN FUNDAMENTALS

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Ethernet

It is a LAN protocol. Given by Xerox in early 1970s. Threecompanies modified it as E (II)

DEC, Intel & Xerox (DIX). IEEE made it standard as 802.3

Header of Ethernet

8bytes 6byts 6byts 2 byts variable 4byts

DAFlag SA TYPE DATA Flag

MAC SUB-LAYERMAC SUB-LAYER

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MAC Layer - 802.3

DataSource add FCSLengthDest add

# Bytes 8 6 2 Variable6 4

Preamble

Ethernet IIuses Type

here and

does not use

802.2.

0000.0C xx.xxxx

IEEE assigned Vendorassigned

MAC Address

PreamblePreamble

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It allows the receiving devices to lockthe incoming bit stream.

The Peamble is used to indicate tothe receiving station that the data

portion of the message will follow.

Destination Address (DA)Destination Address (DA)

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DA is used by receiving stations to

determine if an incoming packet isaddressed to a particular node.

Uses LSB (Least Significant Bit) first

Destination can be individual, multicastor broadcast

Broadcast will be all 1s or Fs and will besent to all.

Multicast wil l be sent to the specific subnet

Source Address (SA)Source Address (SA)

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SA is a 48 bit MAC Address suppliedby the transmitting device.

Broadcast and Multicast addressformats are illegal within the SAfields.

It uses LSB (Least significant bit first)

Length or Type FieldLength or Type Field

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802.3 uses length field where as Ethernetframe uses type field to identify thenetwork layer protocol.

802.2 can identify upper-layer protocol andmust be used with 802.3 frame.

DataData

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This is the packet sent down to theData Link Layer from the Networklayer.

The size can vary from 46-1500bytes.

Frame Check Sequence (FCS)Frame Check Sequence (FCS)

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FCS is a field at the end of the framethat is used to store the cyclicredundancy check.

Data Link Layer Functions (cont.)Data Link Layer Functions (cont.)

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DataDest

SAP

Source

SAP

DataSource add FCSLengthDest add

Variable11 802.2 (SAP)

Ctrl

1 or 2

3 2

Preamble

DataDest SAPAA

Source SAPAA

Variable11

802.2 (SNAP)

Ctrl03

1 or 2

OR

OUIID Type

# Bytes

# Bytes

MAC Layer - 802.3

802.2 Frame802.2 Frame

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802.2 Frame has two new fields

DSAP (Destination Service Access Pointer)

SSAP (Source Service Access Pointer)

802.2 frame type is nothing but 802.3frame with LLC information

Because of the LLC information we

know what upper layer protocol is.

SNAP FrameSNAP Frame

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The SNAP Frame has its own protocol field toidentify the upper layer protocol.

To Identify SNAP Frame:

DSAP and SSAP fields are always AA to indicatethat this is a SNAP header coming up.

it is an LLC data unit (sometimes called aLogical Protocol Data Unit (LPDU)) of Type 1(indicated by 03)

The SNAP header then indicates the vender via

the Organisational Unique Identifier (OUI) andthe protocol type via the Ethertype field

CISCO uses SNAP frame with their proprietaryprotocol CDP (CISCO Discovery Protocol)

EXAMPLE - SNAPEXAMPLE - SNAP

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In the example above we have the OUI as

00-00-00 which means that there is an Ethernet

frame, and the Ethertype of 08-00 whichindicates IP as the protocol.

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ETHERNET

CABLING

Network CablingNetwork Cabling

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Media connecting network components

NIC cards take turns transmitting on the cableLAN cables only carry one signal at a time

WAN cables can carry multiple signals

simultaneously

Three primary types of cabling

Twisted-pair (or copper)Coaxial cable

Fiber-optic cable

Twisted-Pair (UTP and STP)Twisted-Pair (UTP and STP)

STP only:

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Speed and throughput: 10/100 Mbps

Relative cost: Least costly

Media and connector size: Small

Maximum cable length: 100 m

RJ-45

Connector

Color-Coded

Plastic Insulation

Twisted-Pair

Outer Jacket

STP only:

Shielded Insulation

to Reduce EMI

Coaxial CableCoaxial Cable

Braided Copper Shielding

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Speed and throughput: 10/100 Mbps

Relative cost: More than UTP, but still low

Media and connector size: Medium

Maximum cable length: 200/500 m

OuterJacketBraided Copper Shielding

Plastic Insulation

Copper Conductor

BNC Connector

Fiber-Optic CableFiber-Optic Cable

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Outer JacketKevlar Reinforcing

Material

Plastic

Shield Glass Fiber

and Cladding

Speed and throughput: 100+ Mbps

Average cost per node: Most expensive

Media and connector size: Small

Maximum cable length: Up to 2 km

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UPPER LAYER

PROTOCOLS

UPPER LAYER

PROTOCOLS

What Is TCP/IP?What Is TCP/IP?

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A suite of protocols

Rules that dictate how packetsof information are sent across

multiple networks

Addressing

Error checking

TCP/IP ProtocolTCP/IP Protocol

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The Transmission Control Protocol/Internet Protocol(TCP/IP) suit was created by the Department of Defense

(DoD).

The Internet Protocol can be used to communicateacross any set of interconnected networks.

TCP/IP supports both LAN and WAN communications.

IP suite includes not only Layer 3 and 4 specificationsbut also specifications for common applications like e-mail, remote login, terminal emulation and file transfer.

The TCP/IP protocol stack maps closely to the OSImodel in the lower layers.

The DoD & OSIThe DoD & OSI

D D M d l OSI M d l

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Application

Application

Presentation

Session

Transport

Network

Data Link

Physical

Host-to-Host

Internet

Network

Access

DoDModel OSIModel

TCP/IP Protocol Suit at DoDTCP/IP Protocol Suit at DoD

DoDModel

TCP/IP Protocol Suit

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Process /

Application

Host-to-Host

Internet

Network

Access

Telnet FTP LPD SNMP

NFSSMTPTFTP

TCP UDP

ICMP

Ethernet

ARP RARP

IP

Fast

Ethernet

Token

Ring FDDI

BootP

TCP/IP ApplicationsTCP/IP Applications

Application layer

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Application layerFile Transfer Protocol (FTP)

Remote Login (Telnet)

E-mail (SMTP)

Transport layerTransport Control Protocol (TCP)

User Datagram Protocol (UDP)

Network layer

Internet Protocol (IP) Data link & physical layer

LAN Ethernet, Token Ring, FDDI, etc.

WAN Serial lines, Frame Relay, X.25, etc.

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Internet ProtocolInternet Protocol

P id ti l b t

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Provides connectionless,best -

effort delivery routing of datagrams.

IP is not concerned with the contentof the datagrams.

It looks for a way to move thedatagrams to their destination.

IP DatagramIP Datagram

1

Bit 0 Bit 15 Bit 16 Bit 31

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Version

(4)

Destination IP Address (32)

Options (0 or 32 if Any)

1 Bit 15 Bit 16 Bit 31

Header

Length (4)Type

of Service (8)Total Length (16)

Identification (16)Flags

(3) Fragment Offset (13)

Time-to-Live (8) Protocol (8) Header Checksum (16)

Source IP Address (32)

20

Bytes

Data (Varies if Any)

IP DatagramIP Datagram

Version Currently used IP version

Header Length Datagram header length

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g g g

TOS Level of importance assigned by a particular upper-layer protocol

Total Length- Length of packet in bytes including Data and Header Identification Identifies current datagram (Sequence Number)

Flags Specifies whether the packet can be fragmented or not

Fragment Offset Used to piece together datagram fragmentsTTL It maintains a counter that gradually decreases, in increments, to zero

Protocol It indicates which upper-layer protocol receives incoming packets

Header Checksum Calculated checksum of the header to check its integrity

Source IP Address Sending node IP Address

Destination IP Address Receiving node IP Address

Options It allows IP to support various options like security

Data U er la er information maximum 64Kb

Protocol FieldProtocol Field

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Transport

Layer

InternetLayer

TCP UDP

IP

176 Protocol

Numbers

Determines destination upper-layer protocol

Address Resolution Protocol(ARP)

Address Resolution Protocol(ARP)

ARP works at Internet Layer of DoD Model

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y

It is used to resolve MAC address with the

help of a known IP address.

All resolved MAC addresses are maintained

in ARP cache table is maintained. To send a datagram this ARP cache table is

checked and if not found then a broadcast is

sent along with the IP address.

Machine with that IP address responds and

the MAC address is cached.

Address Resolution ProtocolAddress Resolution Protocol

I need the

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172.16.3.1 172.16.3.2

IP: 172.16.3.2 = ???IP: 172.16.3.2 = ???

I need the

Ethernet address

of 176.16.3.2.


I need the

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172.16.3.1 172.16.3.2

IP: 172.16.3.2 = ???IP: 172.16.3.2 = ???

I heard that broadcast.

The message is for me.

Here is my Ethernetaddress.

I need the

Ethernet address

of 176.16.3.2.


I need the

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172.16.3.1

IP: 172.16.3.2

Ethernet: 0800.0020.1111

IP: 172.16.3.2

Ethernet: 0800.0020.1111

172.16.3.2

IP: 172.16.3.2 = ???IP: 172.16.3.2 = ???




I need the

Ethernet address

of 176.16.3.2.


I need the

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Map IP Ethernet

172.16.3.1

IP: 172.16.3.2

Ethernet: 0800.0020.1111

IP: 172.16.3.2

Ethernet: 0800.0020.1111

172.16.3.2

IP: 172.16.3.2 = ???IP: 172.16.3.2 = ???




I need the

Ethernet address

of 176.16.3.2.

DHCP (Dynamic Host Configuration Protocol)DHCP (Dynamic Host Configuration Protocol)

The DHCP server dynamically assigns IP address to hosts.

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All types of Hardware can be used as a DHCP server, even aCisco Router.

BootP can also send an operating system that a host canboot from. DHCP can not perform this function.

Following information is provided by DHCP while hostregisters for an IP address:

IP Address

Subnet mask Domain name

Default gateway (router)

DNS

Internet Control MessageProtocol

Internet Control MessageProtocol

ICMP messages are carried in IP datagrams and used to senderror and control messages.

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Application

Transport

Internet

Data-Link

Physical

Destination

Unreachable

Echo (Ping)

Other

ICMP

1

g

ICMP PingICMP Ping

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Transport Layer OverviewTransport Layer Overview

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Transmission Control

Protocol (TCP)

User Datagram

Protocol (UDP)

Transmission Control

Protocol (TCP)

User Datagram

Protocol (UDP)

Application

Transport

Internet

Data-Link

Physical

Connection-

Oriented

Connectionless

Transmission Control Protocol (TCP)Transmission Control Protocol (TCP)

TCP works at Transport Layer

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p y

TCP is a connection oriented protocol.

TCP is responsible for breaking messagesinto segments and reassembling them.

Supplies a virtual circuit between end-userapplication.

TCP Segment FormatTCP Segment Format


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Source Port (16) Destination Port (16)

20

Bytes

Sequence Number (32)

Acknowledgment Number (32)

HeaderLength (4) Reserved (6) Code Bits (6) Window (16)

Checksum (16) Urgent (16)

Options (0 or 32 if Any)

Data (Varies)

TCP Segment FormatTCP Segment Format

Source port Number of the calling port

Destination Port Number of the called port

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Destination Port Number of the called port

Sequence Number Number used to ensure correct sequencing of the

arriving data

Acknowledgement Number Next expected TCP octet

Header Length Length of the TCP header

Reserved Set to zero

Code Bits Control Functions (setup and termination of a session)

Window Number of octets that the sender is willing to accept

Checksum Calculated checksum of the header and data fields

Urgent Pointer Indication of the end of the urgent data

Options One option currently defined (maximum TCP segment size)

Data Upper layer protocol data

Port NumbersPort Numbers

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TCP

PortNumbers

F

T

P

Transport

Layer

T

E

L

N

ET

D

N

S

S

N

M

P

T

F

T

P

S

M

T

P

UDP

Application

Layer

2121 2323 2525 5353 6969 161161

R

I

P

520520

TCP Port NumbersTCP Port Numbers

S

Source D ti ti

Destination

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Source

Port

Source

PortDestination

Port

Destination

Port

Host A

10281028 2323

SP DP

Host ZTelnet Z

Destination port = 23.

Send packet to my

Telnet

application.

TCP Three-Way Handshake/OpenConnection

TCP Three-Way Handshake/OpenConnection

Host A Host B

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Send SYN(seq = 100 ctl = SYN)

SYN Received

1

Send SYN, ACK

(seq = 300 ack = 101

2

SYN Receivedctl = syn,ack)

Established

(seq = 101 ack = 3013

ctl = ack)

TCP Simple AcknowledgmentTCP Simple Acknowledgment

Sender Receiver

Send 1

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Window Size = 1

Send 1Receive 1

Receive ACK 2 Send ACK 2

Send 2Receive 2

Receive ACK 3Send ACK 3

Send 3

Receive 3

Receive ACK 4 Send ACK 4

TCP Sequence andAcknowledgment Numbers

TCP Sequence andAcknowledgment Numbers

Source

Port

Source

PortDestination

Port

Destination

PortSequence

Sequence

Acknowledgment

Acknowledgment

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PortPort PortPort

10281028 2323

Source Dest.

111111

Seq.

22

Ack.

10281028 2323

Source Dest.

101010

Seq.

11

Ack.

102810282323

Source Dest.

111111

Seq.

11

Ack.

.

I just

sent number

10I just got number

10, now I need

number 11.

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UDP (User Datagram Protocol)UDP (User Datagram Protocol)

A connectionless and unacknowledged protocol.

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UDP is also responsible for transmittingmessages.

But no checking for segment delivery is provided.

UDP depends on upper layer protocol forreliability.

TCP and UDP uses Port no. to listen to aparticular services.

UDP Segment FormatUDP Segment Format

1


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Source Port (16) Destination Port (16)

No sequence or acknowledgment fields

Length (16)

8

BytesChecksum (16)

Data (if Any)

UDP Segment FormatUDP Segment Format

Source port Number of the calling port

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p g p

Destination Port Number of the called port Length Number of bytes, including header and data

Checksum Calculated checksum of the header and data

fields

Data Upper layer protocol data

Application Layer OverviewApplication Layer Overview

File Transfer

- TFTP*

File Transfer

- TFTP*

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*Used by the Router

Application

Transport

Internet

Data-Link

Physical

TFTP

- FTP*

- NFSE-Mail

- SMTP

Remote Login

- Telnet*- rlogin*

Network Management

- SNMP*

Name Management

- DNS*

TFTP

- FTP*

- NFSE-Mail

- SMTP

Remote Login

- Telnet*

- rlogin*

Network Management

- SNMP*

Name Management

- DNS*

TelnetTelnet

Telnet is used for Terminal Emulation.

It ll i tti t hi t

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It allows a user sitting on a remote machine to

access the resources of another machine.

It allows you to transfer files from one machine to another.

It also allows access to both directories and files.

It uses TCP for data transfer and hence slow but reliable.

Simple Network ManagementProtocol

Simple Network ManagementProtocol

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SNMP enable a central management ofNetwork.

Using SNMP an administrator can watch theentire network.

SNMP works with TCP/IP.

IT uses UDP for transportation of the data.

DNS (Domain Name Service)DNS (Domain Name Service)

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DNS resolves FQDNs with IP address.

DNS allows you to use a domain name tospecify and IP address.

It maintains a database for IP address andHostnames.

On every query it checks this database andresolves the IP.

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WAN Basics

What Is a WAN?What Is a WAN?

A network that serves users across a broadgeographic area

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geographic area

Often uses transmission devices providedby public carriers (Pacific Bell, AT&T, etc.)

This service is commonly referred to as plain old telephone service (POTS)

WANs function at the lower three layers of

the OSI reference modelPhysical layer, data link layer, and network

layer

WAN OverviewWAN Overview

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Service

Provider

WANs connect sites

Connection requirements vary depending

on user requirements and cost

What is a WAN?

A WAN is a data communications network that covers a relatively broad geographicarea and often uses transmission facilities provided by common carriers, such as

telephone companies. WAN technologies function at the lower three layers of the OSI

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p p g y

reference model: the physical layer, the data link layer, and the network layer.

Serial Implementation ofDTE versus DCE

Serial Implementation ofDTE versus DCE

Data Terminal Equipment

End of the users device

on the WAN link

Data Communications Equipment End of the WAN providers

side of the communication facility

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o t e side of the communication facility

DCE is responsible for clocking

DCEDTE

Modem

CSU/DSU

SS SS

SSSS

SSSS

DTE DTEDCE DCE

WAN Terminating EquipmentWAN Terminating Equipment

EIA/TIA-232

V.35WAN Provider

(Carrier) Network

Physical Cable Types

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Modem

Data Terminal Equipment

DTE

Data Circuit-Terminating Equipment

The Service ProvidersThe Service Providers

EquipmentEquipment

DCE

V.35

X.21HSSITo Corporate

Network

The CustomerThe Customerss

EquipmentEquipment

(Carrier) Network

Usually on theCustomers

Premises

Router

Serial TransmissionSerial Transmission

WAN Serial connectors use serialtransmission

Serial transmission uses one bit at time

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Serial transmission uses one bit at time

over a single channel.Parallel transmission can use 8 bits at

a time, but all WANs use serial

transmission. Cisco Routers use a proprietary 60 pin

serial connector.

Connector at the other end of the cablewill depend on your service provider orend device requirements.

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LAN/WAN DevicesLAN/WAN Devices

1999, Cisco Systems, Inc.

LAN/WAN DevicesLAN/WAN Devices

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Hubs

Bridges

Switches

Routers

HubHub

Device that serves as the center of aDevice that serves as the center of a

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Device that serves as the center of aDevice that serves as the center of a

star topology network, sometimesstar topology network, sometimes

referred to as areferred to as a multiport repeatermultiport repeater,, nono

forwarding intelligenceforwarding intelligence

HubsHubs

123123 126126

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124124

125125

127127

128128

Hub

Data

Data

Data

Data

Amplifies signals

Propagates signals through the network Does not f ilter data packets based on destination

No path determination or switching

Used as network concentration point

Hubs Operate at Physical layerHubs Operate at Physical layer

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A B C D

Physical

All devices in the same collision domain

All devices in the same broadcast domain

Devices share the same bandwidth

Hubs: One Collision DomainHubs: One Collision Domain

M d t ti

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More end stations means

more collisions

CSMA/CD is used

BridgeBridge

Device that connects and passes packetsDevice that connects and passes packets

between two network segmentsbetween two network segments

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between two network segments.between two network segments.

More intelligent than hubMore intelligent than hubanalyzesanalyzes

incoming packets and forwards (or filters)incoming packets and forwards (or filters)

them based on addressing information.them based on addressing information.

Bridge ExampleBridge Example

Bridge

123123

124124

126126

12

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Segment 1 Segment 2

125125

127127

128128

Corporate Intranet

Hub Hub

More intelligent than a hubcan analyze incoming packetsand forward (or fi lter) them based on addressing information

Collects and passes packets between two network segments

Maintains address tables

SwitchesSwitches

UseUse bridging technologybridging technology totoforward traffic between ports.forward traffic between ports.

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pp

Provide fullProvide full dedicateddedicated datadatatransmission rate between twotransmission rate between two

stations that are directly connectedstations that are directly connectedto the switch ports.to the switch ports.

Build and maintainBuild and maintain addressaddress

tablestables called contentcalled content --addressableaddressablememory (CAM).memory (CAM).

Switching Dedicated MediaSwitching Dedicated Media

10-MbpsUTP Cable

Dedicated

Workstation

3131

Switch 3434

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Corporate Intranet

3232

33 3636

100 Mbps 100 Mbps

Uses bridging technology to forward traffic (i.e.

maintains address tables, and can fil ter) Provides full dedicated transmission rate between

stations that are connected to switch ports

Used in both local-area and in wide-area networking

All types availableEthernet, Token Ring, ATM

3535

Switches and Bridges Operate atData Link Layer

Switches and Bridges Operate atData Link Layer

Data Link

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Each segment has its own collision domain

All segments are in the same broadcast domain

OR1 2 3 1 24

SwitchesSwitches

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Each segment has its owncollision domain

Broadcasts are forwardedto all segments

Memory

Switch

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Network Layer Functions (cont.)Network Layer Functions (cont.)

1.0 4.0

1.3 4.32.22.1

4.11.1

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Routing TableNET INT Metric

12

4

S0S0

E0

10

0

1.3

E0

4.3

S0 E0S0 4.21.2

Routing TableNET INT Metric

12

4

E0S0

S0

00

1

Logical addressing allows for hierarchical network

Configuration required

Uses configured information to identify paths to networks

Routers: Operate at theNetwork Layer

Routers: Operate at theNetwork Layer

Broadcast control

Multicast control

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Optimal pathdetermination

Traffic management Logical addressing

Connects to WANservices

Using Routers to Provide RemoteAccess

Using Routers to Provide RemoteAccess

Telecommuter

Modem or ISDN TA

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Internet

Branch Office

Mobile User

Main Office

Network Device DomainsNetwork Device Domains

Hub Bridge Switch Router

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Collision Domains:

1 4 4 4

Broadcast Domains:

1 1 1 4

Documents

( BASICS).pdf