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Data Networks

5

Businesses needed a solution that would successfullyaddress the following three problems:

Duplication of equipment and resources Implementation of effective communication Network management

Businesses realized that networking technology couldincreaseproductivity while savingmoney.

What are the components of a network ?

6

Main OfficeBranch Office

HomeOffice

MobileUsers

Internet

Devices in Data Networks

7

End-userdevicesDevices that provide services directly to the user.(computers,printers,scanners,etc.)

Network devicesDevices that connect the end-user devicestogether.(routers,switches,hubs, etc.)

Network Interface Card

8

A NIC card is a printed circuit board that providesnetwork communication capabilities to and from apersonalcomputer.

Also known as LAN adapter.

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Network Topology

9

Network TopologyDefines the structure of the network.

Network Topology Types

Physical TopologyActual layout of the wire or media.

Logical TopologyDefines how the media is accessed by the hostsfor sending data.

Physical and Logical Topology

10

Media Type Physical Topology Logical Topology

Ethernet Bus, Star, Point to Point Bus

FDDI Ring Ring

Token Ring Star Ring

Bus Topology

11

Uses a single backbone cable that is terminated at bothends.

All the hosts connect directly to this backbone.

Ring Topology

12

Connects one host to the next and the last host to the first.

This creates a physical ring of cable.

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Star Topology

13

Connects all cables to a central point of concentration.

Extended Star Topology

14

Links individual stars together by connecting the hubsand/or switches.

Mesh Topology

15

Implemented to provide as much protection as possiblefrom interruption of service.

Each host has its own connections to all other hosts.

Although the Internet has multiple paths to any onelocation, it does not adopt the full mesh topology.

LANs, MANs and WANs

16

One early solution was the creation of LAN standardswhich provided an open set of guidelines for creatingnetwork hardware and software, making equipmentfromdifferent companies compatible.

What was needed was a way for information to move

efficiently and quickly, not only within a company, butalso from one business to another.

The solution was the creation of metropolitan-area

networks (MANs) and wide-area networks (WANs).

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LANs

Operate within a limitedgeographic area

Allow multi-access to high

bandwidth media

Control the network privatelyunder local administration

Provide full-time connectivityto local services

Connect physically adjacentdevices

17

WANs

Operate within a largegeographic area

Allow access over serial

interfaces operating at low erspeeds

Provide full- time and part-time connectivity

Connect devices separated

over wide, even global areas

18

VPNs

19

A VPN is a private network that is constructed within a publ icnetwork infrastructure such as the global Internet. Using VPN, atel ecommuter can access the network of the companyheadquarters through the Internet by building a secure tunnel

between the telecommuters PC and a VPN router in theheadquarters.

Bandwidth

20

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Measuring Bandwidth

21

Introduction to Networks

1. Which of the fol lowing network characteristics is concerned about MTBF?

A. Cost

B. Security

C. Reliability

D. Availability

2. _____ _____ describe(s) users working from home.

A. SOHO

B. Branch office

C. Regional office

D. Corporate office

Network Topologies

3. A ___ _______ topology uses a single cable to connect all devices together.

A. Bus

B. Star

C. Point-to-point

D. Ring

4. __________ has both physical and logical ring topologies.

A. Ethernet

B. FDDI

C. Token Ring

D. Wireless

5. Ethernet __________ has/have both a physical and logical bus topology.

A. 10BaseT

B. 10Base2 and 10Base5

C. 10BaseT and 10Base2

D. 10BaseT, 10Base2, and 10Base5

22

Answers:

1. C. Mean time between failures (MTBF) is commo nly used to measure reliability

2. A. The term SOHO desc ribes users working from a home or small office

3. A. A bus topology uses a single cable to connect all devices together.

4. B. FDDI has both physical and logical ring structures.

5. B. Ethernet 10Base2 and 10Base5 have both physical and logical bus topologies

23 24

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Why do we need the OSI Model?

25

To address the problem of networks increasing in sizeand in number, the International Organization for

Standardization (ISO) researched many network schemesand recognized that there was a need to create anetwork model .

This would help network builders implement networksthat could communicate and work together

ISOtherefore, released the OSI reference model in 1984.

Dont Get Confused.

26

ISO - International Organization for Standardization

OSI - Open System Interconnection

*IOS - Internetwork Operating System

To avoid confusion, some people say InternationalStandard Organization.

*As of June 2010, the trademark of the term iOS nowbelongs to Apple.

The OSI Reference Model

27

7 Application

6 Presentation

5 Session

4 Transport

3 Network

2 Data Link

1 Physical

The OSI Model will be usedthroughout your entire

networking career!

Memorize it!

OSI Model

28

Data FlowLayers

Transport

Data-Link

Network

Physical

Application(Upper)Layers

Session

Presentation

Application

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Layer 7 - The Application Layer

29

7 Application

6 Presentation

5 Session

4 Transport

3 Network

2 Data Link

1 Physical

Deals with networkingapplications.

Examples:

EmailWeb browsers

PDU: User Data

Question: What is a PDU?

Layer 6 - The Presentation Layer

30

7 Application

6 Presentation

5 Session

4 Transport

3 Network

2 Data Link

1 Physical

Responsible for presenting thedata in the required format whichmay include:

Code FormattingEncryptionCompression

PDU: Formatted Data

Layer 5 - The Session Layer

31

7 Application

6 Presentation

5 Session

4 Transport

3 Network

2 Data Link

1 Physical

This layer establishes, manages,

and terminates sessions between twocommunicating hosts.

CreatesVirtualCircuit

Coordinates communicationbetween systems

Organize their communication byofferingthree different modes:

SimplexHalf DuplexFull Duplex

PDU: FormattedData

Half Duplex

It uses only one wire pair with a digital signal running in bothdirections on the wire.

uses the CSMA/CD protocol to help prevent collisions and topermit retransmitting if a col lision does occur.

If a hub i s attached to a swi tch, it must operate in half-duplexmode.

Half-duplex Ethernet (typically10BaseT) is only about 30 to 40percent efficient because a large 10BaseT network will usuallyonly give you 3 to 4Mbpsat most.

32

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Full Duplex

33

Full duplex, in twisted-pai r cabling, uses two pairs of wire for simultaneoustransmission andreception.

Layer 4 - The Transport Layer

34

7 Application

6 Presentation

5 Session

4 Transport

3 Network

2 Data Link

1 Physical

This layer breaks up the data fromthe sending host and thenreassembles it in the receiver.

It also is used to insure reliable datatransportacross the network.

Canbe reliable or unreliable

Sequencing, Acknowledgment,

Retransmission, Flow Control

PDU: Segments

Layer 4 : Transport Layer

35

Distinguishes betweenupper-layer applications

Establishes end-to-endconnectivity betweenapplications

Defines flow control

Provides reliable orunreliable services fordata transfer

Netwo

rk

IPXIP

Transport

SPXTCP UDP

TCP Segment Format

36

Source Port (16) Destination Port (16)

Sequence Number (32)

HeaderLength (4)

Acknowledgment Number (32)

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

Checksum (16) Urgent (16)

Options (0 or 32 if Any)

Data (Varies)

20Bytes

Bit 0 Bit 15 Bit 16 Bit 31

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Port Numbers

37

TCP

Port

Numbers

FTP

TransportLayer

TELNET

DNS

SNMP

TFTP

SMTP

UDP

ApplicationLayer

21 23 25 53 69 161

RIP

520

TCP Port Numbers

38

SourcePort

DestinationPort

Host A

1028 23

SP DP

Host ZTelnet Z

Destination port = 23.

Send packet to my

Telnet

application.

TCP Port Numbers

39

TCP Three-Way Handshake/Open Connection

40

Send SYN(seq= 100 ctl = SYN)

SYN Received

Send SYN, ACK(seq= 300 ack = 101 ctl = syn,ack)

Send ACK(seq= 101 ack = 301

ctl= ack)

Host A Host B

SYN Received

1

23

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Reliable Service

41

Synchronize

Acknowledge, Synchronize

Acknowledge

Data Transfer

(Send Segments)

Sender Receiver

Connection Established

Opening & Closing Connection

42

Windowing

Windowing in networki ng means the quantity of data segmentsthat a machine can transmit/send on the network withoutreceiving an acknowledgement.

Example:

There are two window sizesone set to 1 and one set to 3.

When youve configured a window size of 1, the sending

machine waits for an acknow ledgment for each data segment.

If youve configured a window size of 3, its all owed to transmit

three data segments before an acknowledgment is received.

43

TCP Simple Acknowledgment

Window Size = 1

44

Sender Receiver

Send 1Receive 1

Receive ACK 2Send ACK 2

Send 2Receive 2

Receive ACK 3Send ACK 3

Send 3Receive 3

Receive ACK 4 Send ACK 4

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Flow Control

49

SEQ 1024

SEQ 2048

SEQ 3072

AB

30723

User Datagram Protocol (UDP)

50

User Datagram Protocol (UDP) is the connectionless transportprotocol in the TCP/IP protocol stack.

UDP is a simple protocol that exchanges datagrams, withoutacknowledgments or guaranteed delivery. Error processing andretransmissionmust be handledby higher layer protocols.

Popular UDP protocols:

TFTP (Trivial File Transfer Protocol) SNMP (Simple Network Management Protocol) DHCP (Dynamic Host Control Protocol) DNS (Domain Name System)

UDP Segment Format

No sequence or acknowledgment fields

51

Source Port (16) Destination Port (16)

Length (16)

Data (if Any)

1Bit 0 Bit 15 Bit 16 Bit 31

Checksum (16)

8

Bytes

TCP vs UDP

52

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Layer 3 - The Network Layer

53

7 Application

6 Presentation

5 Session

4 Transport

3 Network

2 Data Link

1 Physical

Sometimes referred to as the

Cisco Layer.

Endto EndDelivery

Provide logical addressing for

bestpath determination

Internetwork Communication

Packet Filtering and Packetforwarding

PDU: Packets

Layer 3 : Network Layer

54

Defines logical sourceand destinationaddresses associatedwith a specific protocol

Defines paths throughnetwork

Network

IP, IPX

Data-Link

Physical

EIA/TIA-232

V.35

802.2

802.3

Layer 3 : (cont.)

55

DataSourceAddress

DestinationAddress

IP Header

172.15.1.1

NodeNetwork

LogicalAddress

Network Layer End-Station Packet

Route determination occurs at this layer, so a packet must include a sourceand destination address.

Network-layer addresses have two components:a network component for internetwork routing.

a node number for a device-specific address.

The example in the figure is an example of an IP packet and IP address.

Layer 3 (cont.)

56

11111111 11111111 00000000 00000000

10101100 00010000 01111010 11001100

BinaryMask

BinaryAddress

172.16.122.204 255.255.0.0

172 16 122 204

255

Address Mask

255 0 0

Network Host

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IP Datagram

57

Version(4)

Destination IP Address (32)

Options (0 or 32 i f Any)

Data (Varies if Any)

1Bit 0 Bit 15 Bit 16 Bit 31

HeaderLength (4)

Priority &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)

20Bytes

Protocol Field

Determines destination upper-layer protocol

58

TransportLayer

InternetLayer

TCP UDP

ProtocolNumbers

IP

176

Internet Control Message Protocol

59

Application

Transport

Internet

Data-Link

Physical

Destination

Unreachable

Echo (Ping)

Other

ICMP 1

Device On Layer 3 --- Router

60

Broadcast control

Multicast control

Optimal path determination

Traffic management

Logical addressing

Connects to WAN services

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Type of Transmission

Unicast

Multicast

Broadcast

61

Type of Transmission

62

Layer 2 - The Data Link Layer

Preamble DMAC SMAC Data length DATA FCS

63

7 Application

6 Presentation

5 Session

4 Transport

3 Network

2 Data Link

1 Physical

Performs Physical Addressing

This layer provides reliable transit ofdata across a physical link.

Combines bits into bytes andbytes into frames

MAC address

Error detection, not correction

LLC and MAC

PDU - Frames

The Ethernet FRAME

64

DataSMAC FCSLengthDMAC

Variable266 4

0000.0C xx.xxxx

VendorAssigned

OUI

MAC Layer802.3

*Preamble

Ethernet II uses

Type here

8

* synchronizes the sender and the receiver** in terms of bytes

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Layer 1 - The Physical Layer

65

7 Application

6 Presentation

5 Session

4 Transport

3 Network

2 Data Link

1 Physical

This is the physical mediathrough which the data,represented as electronic signals,is sent from the source host tothe destination host.

Move bits between devicesEncoding

PDU - Bits

Physical Layer

66

Defines

Media type

Connector type

Signaling type

802.3

Physical

802.3 is responsible for LANs based on the carrier sense multiple accesscollision detect (CSMA/CD) access methodology. Ethernet is an exampleof a CSMA/CD network.

Physical Layer: Ethernet/802.3

67

Hub

Hosts

Host

10Base2Thin Ethernet10Base5Thick Ethernet

10BaseT

Twisted Pair

Data Encapsulation

68

Transport

Data-Link

Physical

Network

Upper-Layer Data

Upper-Layer DataTCP Header

DataIP Header

DataLLC Header

0101110101001000010

DataMAC Header

Presentation

Application

Session

Segment

Packet

Bits

Frame

PDU

FCS

FCS

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Data Encapsulation

69

OSI Model Analogy

Application Layer - Source Host

70

After riding your new bicycle a few times inPhilippines, you decide that you want to give it to

a friend who lives in Houston.

OSI Model AnalogyPresentation Layer - Source Host

71

Make sure you have the proper directions todisassemble and reassemble the bicycle.

OSI Model AnalogySession Layer - Source Host

72

Call your friend and make sure you have hiscorrect address.

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OSI Model Analogy

Transport Layer - Source Host

73

Disassemble the bicycle and put different piecesin different boxes. The boxes are labeled

1 of 3, 2 of 3, and 3 of 3.

OSI Model Analogy

Network Layer - Source Host

74

Put your friend's complete mailing address (andyours) on each box.Since the packages are toobig for your mailbox (and since you dont have

enough stamps) you determine that you need togo to the post office.

OSI Model AnalogyData Link LayerSource Host

75

Phillipines post office takes possession of theboxes.

OSI Model AnalogyPhysical Layer - Media

76

The boxes are flown from Philippines to Texas.

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OSI Model Analogy

Data Link Layer - Destination

77

Texas post office receives your boxes.

OSI Model Analogy

Network Layer - Destination

78

Upon examining the destination address,Texas post office determines that yourboxes should be delivered to your written

home address.

OSI Model AnalogyTransport Layer - Destination

79

Your friend calls you and tells you he got all 3boxes and he is having another friend namedBOB reassemble the bicycle.

OSI Model AnalogySession Layer - Destination

80

Your friend hangs up because he is done talkingto you.

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OSI Model Analogy

Presentation Layer - Destination

81

BOB is finished and presents the bicycle to

your friend. Another way to say it is that your

friend is finally getting him present.

OSI Model Analogy

Application Layer - Destination

82

Your friend enjoys riding his new bicycle in

Texas.

Cisco Icons and Symbols

83

Devices associated in Each Layer

Layer Device Broadcast Domain Collision Domain

3 Router ? ?

2 Switch ? ?

1 Hub ? ?

84

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Broadcast Domain

Encompasses a group of devices receiving broadcastframes initiatingfrom any devicewithin the group.

Routers do not forward broadcast frames, broadcastsare not forwarded from one broadcast domain toanother.

85

Collision Domain

The network area in Ethernet over which collision offrames are expected to transpire.

extended by hubs and repeaters.

divided by switches, routers, or bridges

Q: Which is better, a network with 10 collision domains ora network with 1 collision domain?

Q2: a network with 3 broadcast domains or a network

with 10 broadcast domains?

86

Collision

The effect of two nodes sending transmissionssimultaneously in Ethernet.

When the electrical signals meet on the physicalmedia, the frames from each node collide and aredamaged.

Q: What is the role of communication?

87

Device Used At Layer 1

88

A B C D

Physical

All devices are in the same collision domain.

All devices are in the same broadcast domain.

Devices share the same bandwidth.

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Hubs & Collision Domains

89

More end stations means more

collisions.

CSMA/CD is used.

Devices On Layer 2 (Switches & Bridges)

90

Each segment has its own collision domain.

All segments are in the same broadcast domain.

Data-Link

OR1 2 3 1 24

Switches

91

Each segment is its

own collision domain.

Broadcasts areforwarded to allsegments.

Memory

Switch

Router

92

Routersare usedto connect networkstogether

Routepacketsof data from onenetwork to another

Cisco became the de facto standard of routers because of theirhigh-qualityrouter products

Routers, by default, break up a broadcastdomain

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Internetworking Devices

93

How They Operate

94

Hub Bridge Switch Router

Collision Domains:

1 4 4 4

Broadcast Domains:

1 1 1 4

Data Flow Through a Network

95

Network Structure & Hierarchy

96

DistributionLayer

Core Layer

AccessLayer

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97

Why Another Model?

98

Although the OSI reference model is universally recognized, thehistorical and technical open standard of the Internet is TransmissionControl Protocol / Internet Protocol (TCP/IP).

The TCP/IP reference model and the TCP/IP protocol stack make datacommunication possible between any two computers, anywhere inthe world, at nearly the speed of li ght.

The U.S. Department of Defense (DoD) created the TCP/IP referencemodel because it wanted a network that could surv ive any

conditions, even a nuclear war.

TCP/IP Protocol Stack

99

7

6

5

4

3

2

5

4

3

2

Application

Presentation

Session

Transport

Network

Data-Link

Physical1

Application

Transport

Internet

Data-Link

Physical1

Application Layer Overview

100

*Used by the Router

Application

Transport

Internet

Data-Link

Physical

File Transfer- TFTP*- FTP*- NFS

E-Mail- SMTP

Remote Login- Telnet*- rlogin*

Network Management- SNMP*

Name Management- DNS*

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Transport Layer Overview

101

Transmission ControlProtocol (TCP)

User DatagramProtocol (UDP)

Application

Transport

Internet

Data-Link

Physical

Connection-Oriented

Connectionless

Internet Layer Overview

102

In the OSI reference model, the network layer

corresponds to the TCP/IP Internet layer.

Internet Protocol (IP)

Internet Control MessageProtocol (ICMP)

Address ResolutionProtocol (ARP)

Reverse AddressResolution Protocol (RARP)

Application

Transport

Internet

Data-Link

Physical

Address Resolution Protocol

103

172.16.3.1

IP: 172.16.3.2Ethernet: 0800.0020.1111

172.16.3.2

IP: 172.16.3.2 = ???

I heard that broadcast.

The message is for me.

Here is my Ethernet

address.

I need the

Ethernet

address of

176.16.3.2.

Reverse ARP

104

Ethernet: 0800.0020.1111IP: 172.16.3.25

Ethernet: 0800.0020.1111 IP = ???

What is

my IP

address?

I heard that

broadcast.

Your IP

address is

172.16.3.25.

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IEEE 802 Standards

IEEE 802.1: Standards related to network management.

IEEE 802.2: General standard for the data li nk layer in the OSIReference Model. The IEEE divides this layer into two sublayers --

the logical link control (LLC) layer and the media access control(MAC) layer.

IEEE 802.3: Defines the MAC layer for bus networks that useCSMA/CD. This is the basis of the Ethernet standard.

IEEE 802.4: Defines the MAC layer for bus networks that use a

token-passing mechanism (token bus networks).

IEEE 802.5: Defines the MAC layer for token-ring networks.

IEEE 802.6: Standard for Metropoli tan Area Networks (MANs)105

106

107

Foundby XeroxPalo AltoResearchCenter(PARC) in 1975

Original designed as a 2.94 Mbps system to connect 100computers on a 1 km cable

Later, Xerox, Intel and DEC drew up a standard support 10MbpsEthernetII

Basis for the IEEEs 802.3 specification

Most widely usedLAN technology inthew orld

Origin of Ethernet

108

10BaseT 10 Mbps, baseband, overTwisted-pair cable

Running Ethernet over twisted-pairwiring as specified by IEEE 802.3

Configure in a star pattern

Twisting the wi res reduces EMI

Fiber Optic has no EMI

Unshielded twisted-pair

RJ-45 Plug and Socket

10 Mbps IEEE Standards - 10BaseT

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109

Unshielded Twisted Pair Cable (UTP)

most popularmaximum length 100 mprone to noise

Category 1

Category 2

Category 3

Category 4

Category 5

Category 6

Voice transmission of traditional telephone

For data up to 4 Mbps, 4 pairs full-duplex





Twisted Pair Cables

110

Shielded Twisted Pair Cable (UTP)

Used for backbone cabling, adds severallayers of protective layer used to counterthe effects of EMI

Maximum length = 25 m

Twisted Pair Cables

STANDARDS in TWISTED PAIR

Pin EIA-TIA 568A EIA-TIA 568B

1 WG WO

2 G O

3 WO WG

4 Bl Bl

5 WBl WBl

6 O G

7 WBr WBr

8 Br Br

111

112

Baseband Transmission Entire channel is used to transmit a single digital signalCompletebandwidth of the cable is used by a single signal The transmission distance is shorter The electrical interference is lower

Broadband Transmission Use analog signaling and a range of frequencies

Continuoussignals flow in the form of waves

Supportmultiple analog transmission(channels)

Modem Broadband

TransmissionNetwork

Card

Baseband

Transmission

Baseband VS Broadband

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113

Straight-through cable

114

Straight-through cable pinout

115

Crossover cable

116

Crossover cable

Pin 1 ---------------------------------- Pin 3

Pin 2 ---------------------------------- Pin 6

Pin 3 ---------------------------------- Pin 1

Pin 4 ---------------------------------- Pin 4

Pin 5 ---------------------------------- Pin 5

Pin 6 ---------------------------------- Pin 2

Pin 7 ---------------------------------- Pin 7

Pin 8 ---------------------------------- Pin 8

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117

Rollover cable

118

Rollover cable pinout

119

Straight-through or Crossover

Use straight-through cables for the foll owing cabling:

Switch to Router Switch to PC or server Hub to PC or server

Use crossover cables for the follow ing cabling:

Switch to switch Switch to hub Hub to hub Router to router

PC to PC

Router to PC

WJNGSYs

Straight-through or Crossover Principle: The Port Method

Port Devices

Few Ports PC, Router, Server, Printer

Many ports Switch, Hub

120

Same devices are CROSS,Different devices are STRAIGHT

Documents

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