Introduction

Chapter 1

Panko’sBusiness Data Networks and Telecommunications, 5th editionCopyright 2005 Prentice-Hall

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Learning Objectives

By the end of this session, you should be able to

List the eight elements of networks.

Explain the major types of networks in businesses: LANs, WANs, internets, intranets, and extranets.

Discuss major concerns for network managers: staffing, network architecture, standards, security, wireless networking, efficiency, and quality of service (QoS).

Explain the elements and operation of a small home PC network using a LAN

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Definition

A NETWORK is a system of hardware software and transmission components that allow applications to on different stations within the system communicate with each other

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AccessLine

Figure 1-2: Elements of a Network

ApplicationApplication

ServerStation

TrunkLine

TrunkLine

Switch

Switch

Switch

Switch

OutsideWorld

ClientStation

Mobile ClientStation

Mobile ClientStation

Message (Frame)

Router

Networks connect stations: clients (fixed and mobile) and serversNetworks connect applications on different stations.Applications are all users care about

Stations (and routers) usually communicateby sending messages called frames

The path a frame takes is called its data link

Switches move frames to or closer to the destination stationSwitches handle a packet sequentiallyRouters connect networks to the outside world. Treated just like stations

Access lines connect stations to switchesTrunk lines connect switches to switches (and routers)

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Figures 1-6 and 1-7: Workgroup and Core Switches

Small Switches(Stacked):

Workgroup SwitchesTo Link Stations

To Network Central Core Switch

19 inches (48 cm) wide19 inches (48 cm) wide

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Figure 1-3: Multiplexing in a Packet-Switched Network

ClientStation A

Mobile ClientStation B

Router D

ServerStation C

Trunk linemultiplexes themessages of

differentconversations

AC

ACAC

AC

ACAC

BD

BD

BD

BD

AccessLine

Trunk Line

This reducestrunk line

costs throughcost sharing

by users

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Figure 1-2: Elements of a Network (Recap)

Applications (the only element that users care about) Stations

Clients Servers

Switches Routers Transmission Lines

Trunk lines Access Lines

Messages (Frames)

Never talk about anInnovation “reducing cost,”

“increasing speed,” etc.without specifyingwhich element ischeaper or faster.

For example, multiplexingonly reduces the cost of

trunk lines; othercosts are not decreased

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LANs and WANs

LANs transmit data within corporate sites

WANs transmit data between corporate sites

Each LAN or WAN is a single network

WAN

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Figure 1-5: Local Area Network (LAN) in a Large Building

Multi-floorOffice Building

The bank has multipleLANs—one at each site

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Figure 1-5: Local Area Network (LAN) in a Large Building, Continued

Router Core Switch

Workgroup Switch

Workgroup Switch

Wall Jack

ToWAN

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LAN WAN LAN

Internets

Most firms have multiple LANs and WANs. They must create internets

An internet is a collection of networks connected by routers so that any application on any host on any single network can communicate with any application on any other host on any other network in the internet.

ApplicationApplication

Router Router

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Figure 1-8: Internet with Three Networks

Host B

Host A

Network XNetwork Y

Network Z

R1

R2

Route A-B

Packet

A packet goes all theway across the internet;

It’s path is its route

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Figure 1-8: Internet with Three Networks, Continued

Messages in single networks (LANs or WANs) are called frames

Message in internets are called packets Travel from the source host to the destination host

across the entire internet

Within a single network, the packet is encapsulated in (carried in) the network’s frame

Packet

Frame

Truck(frame)

Package(Packet)

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Figure 1-8: Internet with Three Networks, Continued

Host A

Mobile ClientHost

ServerHost

Switch

SwitchX2

SwitchX1

Switch

Data LinkA-R1

Router R1

Packet

Frame X

Network X

RouteA-B

Details inNetwork X

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Figure 1-8: Internet with Three Networks, Continued

Router R1

Router R2

Packet

Frame Y

ToNetwork X

ToNetwork Z

Network Y

Data LinkR1-R2

RouteA-B

Details inNetwork Y

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Figure 1-8: Internet with Three Networks, Continued

Host B

Mobile ClientHosts

SwitchZ1

Switch

SwitchZ2

Switch

Packet

Frame Z

Network Z

Router R2

Router

Data LinkR2-B

Details inNetwork Z

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Figure 1-8: Internet with Three Networks, Continued

In this internet with three networks, in a transmission, There is one packet There are three frames (one in each network)

If a packet in an internet must pass through N networks, How many packets will be sent? How many frames must carry the packet?

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Figure 1-8: Internet with Three Networks, Continued

Lower-case internet is any internet

Upper-case Internet is the global Internet

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Figure 1-11: The Internet

InternetServiceProvider

For User PC

Internet ServiceProvider

For Webserver

ISP 1 ISP 4

User PC Webserver

NAP = Network Access Point

Router

NAPNAP

NAPISP 2

ISP 3

The Internet Backbone(Multiple Carriers)

AccessLine

AccessLine

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Figures 1-9 and 1-10: Routers

Small RoutersStacked

For Branch Offices

Large Routersfor Large Sites and ISPs

19 inches (48 cm) wide19 inches (48 cm) wide

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Figure 1-12: The Internet, internets, Intranets, and Extranets

internets versus the Internet

Intranets Internal internet for use within an organization Based on the TCP/IP standards created for the

Internet

Extranets Connect multiple firms

Only some computers from each firm are on the extranet

Use TCP/IP standards

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Recap

Switches versus Routers Switches move frames through single networks

(LANs or WANs)

Routers move packets through internets

Messages Messages in single networks are called frames

Messages in internets are called packets

Packets are encapsulated within frames

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End Day 1

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Day 2

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Review

List the 8 common elements of a network Explain difference between a message and a packet Explain difference between switch and router Difference between trunk and access lines Given an internet, indicate number of frames,

packets, networks traversed for message from A to B

Different types of addresses

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Figure 1-23: Logical Functions of the Access Router

DHCPServer

Function

Router Function

NATFunction

Switch Function

Access Router

CableModem

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Figure 1-24: Ethernet Switch Operation

Switching TablePort Host 10 A1-44-D5-1F-AA-4C13 B2-CD-13-5B-E4-6515 C3-2D-55-3B-A9-4F16 D4-47-55-C4-B6-9F

UTP

UTPUTPUTP

Ethernet Switch

A1-44-D5-1F-AA-4C B2-CD-13-5B-E4-65

D4-47-55-C4-B6-9F

C3-2D-55-3B-A9-4F

Frame To C3…Frame To C3…

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Figure 1-25: Frames and Packets

InternalRouter

Packet inDOCISFrame

Access Router

CableModem

Packet inEthernet Frame

A1-BD-33-6E-C7-BBIP address = 192.168.0.3

PC in Emily’s Room

B2-CD-13-5B-E4-65IP address = 192.168.0.2

PC in Study

Packet is alwayscarried (encapsulated)

in a frame

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Figure 1-26: Dynamic Host Configuration Protocol (DHCP)

Access Router

CableModem

A1-BD-33-6E-C7-BBPC in Emily’s Room

B2-CD-13-5B-E4-65PC in Study

ISPDHCPServer

1.IP Address =60.47.112.6

A DHCP Serverprovides User PCs witha temporary IP Address

each time the userconnects to the Internet

The ISP onlyGives each home aSingle IP address

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Figure 1-26: Dynamic Host Configuration Protocol (DHCP), Continued

InternalDHCPServer

Access Router

CableModem

A1-BD-33-6E-C7-BBIP address = 192.168.0.3

PC in Emily’s Room

B2-CD-13-5B-E4-65IP address = 192.168.0.2

PC in Study

ISPDHCPServer

1.IP Address =60.47.112.6

2. IP Address =192.168.0.2

2. IP Address =192.168.0.3

The access router’sInternal DHCP server

Gives private IPAddresses to each PC

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Figure 1-27: Network Address Translation (NAT)

Access Router

CableModem

WebserverIP address=123.7.86.285

1. Packet from192.168.0.2

InternalNAT

Module

PC in Study192.168.0.2

2. Packet from60.47.112.6

The access router’s NATmodule translates between the

private IP addresses andthe single ISP-given IP address

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Figure 1-27: Network Address Translation (NAT), Continued

Access Router

CableModem

WebserverIP address=123.7.86.285

4. Packet to192.168.0.2

InternalNAT

Module

PC in Study192.168.0.2

3.Packet

to60.47.112.6

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Figure 1-28: The Domain Name System (DNS), Continued

Host Name IP Address … …… …Voyager.cba.hawaii.edu 128.171.17.13… …

DNS Table

DNSHost

OriginatingHost’s DNS

Resolver

DNS Request Message“The host name is Voyager.cba.hawaii.edu”

DNS Response Message“The IP address is 128.171.17.13”

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Figure 1-29: Converting Binary IP Addresses to Dotted Decimal Notation

BinaryIP Address 01111111101010110001000100001101

8-Bit Segments

01111111 10101011 00010001 00001101

Convert Segmentsto Decimal

127 171 17 13

Dotted Decimal Notation

127.171.17.13

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Elements of a Network

ClientStation

Mobile ClientStation

ApplicationApplication

ServerStation

Router

Mobile ClientStation

AccessLine

TrunkLine

Switch

Switch

Switch

Switch

TrunkLine

OutsideWorld

Message (Frame)

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Figure 1-22: Home Network Access Router

Switch PortsUTP Cords

Run to Stations

WAN PortUTP CordRuns to

Cable Modem

About 4 inches (10 cm) Wide

PowerJack forExternalPower

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Figure 1-19: Network Interface Cards (NICs) (Photo)

Internal NIC. Installed inside systems unit. Plugged into expansion slot on the mother board.

PC Card NIC. Installed in PC Card slot in notebook and some PDAs.

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Internal NIC

RJ-45Jack

PCI Connector Pins

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Computer Mother Board

Mother BoardPCI Slots

for Expansion Boards(NICs, etc.)

Slots for RAM

Slot forMicroprocessor

(Pentium 4)

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Mother Board and Expansion Boards

ConnectorExpansion Board

(NIC)Expansion

Slots

Mother Board

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Figure 1-20: Unshielded Twisted Pair (UTP) Cord With RJ-45 Connector (Photo)

8-Pin RJ-45 Connector

4-Pair Unshielded Twisted Pair (UTP)

Industry Standard Pen

UTP Cord

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Figure 1-21: UTP Cord RJ-45 Connector and Jack

RJ-45 JackOn a Wall

On a Switchor

On a NIC

RJ-45Connector

UTP Cord---

About as thickas a pencil

---Rugged and

Flexible

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Figure 1-13: Major Network Technical Concerns

Architecture

Standards

Security

Efficiency

Wireless Communication

QoS

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Figure 1-13: Major Network Technical Concerns

Network Architecture A broad plan for how the firm will connect all of its computers

within buildings (local area networks), between sites (wide area networks), and to the Internet

New systems must fit the rules of the architecture

Scalability – ability to accommodate growth efficiently

Undisciplined growth in the past No overall plan

Legacy networks

Use obsolete technologies that do not fit the long-term architecture

Too expensive to replace quickly; must live with many for awhile

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Figure 1-13: Major Network Technical Concerns, Continued

Standards Standards govern message interactions between pairs of

entities (Figure 1-14) For example, HTTP request and response messages for WWW

access

Standards create competition This reduces costs

It also stimulates the development of new features

Protects the business if the main vendors go out of business

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Figure 1-13: Major Network Technical Concerns, Continued

Security

A Major ProblemMany attacks

Growing trend toward criminal attackers

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Figure 1-15: Firewalls

Log File

LegitimateHost

Attacker

LegitimatePacket

BorderFirewall

HardenedServer

Allowed Legitimate Packet

HardenedClient PC

InternalCorporateNetwork

Border firewallshould pass

legitimate packets

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Figure 1-15: Firewalls, Continued

Log File

LegitimateHost

AttackerAttack PacketBorderFirewall

DeniedAttackPacket

Network ManagementConsole

HardenedServer

HardenedClient PC

InternalCorporateNetwork

Border firewallshould deny (drop)

and logattack packets

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Figure 1-13: Major Network Technical Concerns, Continued

Security Virtual Private Networks (VPNs) (Figure 1-16)

Provide communication over the Internet with added security

Cryptographic protection for confidentiality (eavesdroppers cannot read)

Cryptographic authentication (confirms sender’s identity)

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Figure 1-16: Virtual Private Networks (VPNs)

VPNGateway

InternalServer

CorporateSite A

CorporateSite B

VPNGateway

RemoteClient PC 2

Site-to-Site VPNUsing Gateway

Internet

Host-to-HostVPN

Remote AccessVPN UsingGateway

ClientPC 1

Remote Client PC 3

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Figure 1-13: Major Network Management Concerns, Continued

Wireless Communication

To improve mobility

Drive-by hackers can eavesdrop on internal communication

Drive-by hackers can break into the network bypassing firewalls Drive-By Hacker

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Figure 1-13: Major Network Technical Concerns, Continued

Quality of Service (QoS) Numerical objectives for performance Transmission speed in bits per second (bps)

A bit is a single one or zero NOT bytes per second

Increase by factors of 1000, not 1024 kilobits per second (kbps)—lower-case k Megabits per second (Mbps) Gigabits per second (Gbps) Terabits per second (Tbps)

QoS

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Figure 1-13: Major Network Technical Concerns, Continued

Quality of Service For Transmission Speed, have 1 to 3 places

BEFORE the decimal point. Example

.5 Mbps is wrong 500 kbps is correct

Example 2,300 Mbps is wrong 2.3 Gbps is correct

Example 473.2 Mbps is correct

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Figure 1-13: Major Network Technical Concerns, Continued

Quality of Service

Typical transmission speeds in most firms:

LANs: 100 Mbps to each desktop

WANs: most site-to-site links only are 56 kbps to a few megabits per second because long-distance transmission is very expensive and so must be used more sparingly

LANs:100 Mbps

WANs:56 kbpsto a fewMbps

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Figure 1-13: Major Network Technical Concerns, Continued

Quality of Service

Congestion, Throughput, Latency, and Response Time

Congestion: when there is too much traffic for the network’s capacity

Throughput: The speed users actually see (often much less than rated speed)

Individual throughput is less than total throughput on shared-speed links

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Figure 1-13: Major Network Technical Concerns, Continued

Quality of Service Congestion, Throughput,

Latency, and Response TimeLatency: delay (usually

measured in milliseconds or ms)

Within corporations, latency is typically under 60 ms 90% of the time

On the Internet, typically 30 ms to 150 ms

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Figure 1-13: Major Network Technical Concerns, Continued

Quality of Service Congestion, Throughput, Latency, and Response

TimeResponse Time

The time to get a response after a user issues a command

A quarter second or less is good

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Figure 1-13: Major Network Technical Concerns, Continued

Availability Availability is the percentage of

time a network can be used

Downtime: when the user cannot use the network

Want 24x7 availability

Telephone network gives 99.999% availability

Typical networks reach 98% today

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Figure 1-13: Major Network Technical Concerns, Continued

Error Rate

Measured as the percentage of messages damaged or lost

Substantial error rates can disrupt applications

Substantial error rates generate more network traffic because of retransmissions