© 2009 Pearson Education, Inc. Publishing as Prentice Hall 1 Agenda Intro Review Syllabus and assignments Lecture Ch 1 and 2 Homework

© 2009 Pearson Education, Inc. Publishing as Prentice Hall 1

Agenda

• Intro

• Review Syllabus and assignments

• Lecture Ch 1 and 2

• Homework

© 2009 Pearson Education, Inc. Publishing as Prentice Hall

An Introductionto Networking

Chapter 1Updated January 2009

Raymond Panko’s

Business Data Networks and Telecommunications, 7th editionMay only be used by adopters of the book


History of Communications

• Why Study Data Communications?



1837 Invention of the telegraph by Samuel Morse

1876 Invention of the telephone by Alexander Graham Bell

1892 Canadian Government starts regulating telephone system

1910 US Gov begins to regulate telephone system (ICC)

1915 Transcontinental and transatlantic phone service begins

In 1934, the FCC established in the US to regulate interstate the telephone business.

1951 Direct-dialed long distance service begins

1962 Telstar satellite starts relaying international phone calls

1968 Carterfone decision allows use of non-Bell equipment

1970 MCI permitted to provide long distance services

1984 The Modified Final Judgment: AT&T broken up; long distance market deregulated

1996 US Telecom Act: local telecom markets deregulated



• 1968: Carterfone court decision allowing non-Bell customer premises equipment

• 1970: MCI wins court case; begins providing some long distance services

• 1984: Results of consent decree by US federal court:

– 1.Divestiture: AT&T was broken up into a long distance company (AT&T) & 7 Regional Bell Operating Companies (RBOCs).

– 2. Deregulation: the long distance (IXC) market became competitive. MCI & Sprint enter LD market (among others).

– (Note that local exchange service (LEC) markets remained an RBOC monopoly service).



• 1996: US Telecom Competition and Deregulation Act?

– Act replaces all current laws, FCC regulations, 1984 consent decree, and overrules state laws

– Main goal was opening local markets to competition. To date, though, local competition has been slow to take hold…

• Large IXCs were expected to move into the local markets, but this has not yet happened

• Likewise, RBOCs were expected to move into long distance markets, but they are prohibited from doing so before competition begins in local markets

• What are the current trends in Telecommunications?


Data Communications

• Data Communications

• Telecommunications


Datacom Basics

• Data Communications: the movement of computer information from one point to another by means of electrical or optical transmission systems (called networks).

• Telecommunications: broader term that includes the transmission of voice and video, as well as data, and may imply longer distances.

• Although once considered separate phenomenon, telecom & datacom are in the process of “converging” into a single “broadband” communications technology.

© 2009 Pearson Education, Inc. Publishing as Prentice Hall 1-9

1-1: Black Box View of Networks

• What Is a Network?

– Preliminary definition: A network is a communication system that allows application programs on different hosts to work together

Application 1Application 2

Host A

Host B

Network


Hosts

• Hosts

– Any computer attached to a network is called a host

– Including client PCs, servers, mobile phones, etc.

Host

Host

Host

Host

• Client/Server Applications


Networked Applications


Networked Applications

• What is the difference?

– Internet

– internet

– WWW

1-12


What are Networked Applications?

• Internet Applications that can only exist because of networking

• E-Mail

• The World Wide Web

• Facebook

• YouTube

• Etc.

1-13


Application Standards

• Application standards govern communication between application programs

– Allow products from different vendors cannot talk to one another

• For example, the Hypertext Transfer Protocol (HTTP) standardizes communication between any browser and any Web servers

– Different applications use different standards• E-mail uses the Simple Mail Transfer Protocol (SMTP)

and other standards• …


Application Standards

• Application standards govern communication between application programs

– Standards are also called protocols

• Many standards have “protocol” in their names

• Example: Hypertext Transfer Protocol

– HTTP is an open standard (not controlled by any vendor)• Open standards drive down product costs

– Vendor-controlled standards are called proprietary standards


1-2: Hypertext Transfer Protocol (HTTP)

Client HostWeb server

Web serverProgramBrowser

HTTPRequest Message

(Asks for File)

HTTPResponse Message

(Contains the Requested File)

• HTTP is a Client/Server Protocol– The client is the browser; it sends a request– The server is the Web server; it sends a response– Most application standards are client/server protocols

1


1-3: The ARPANET and the Internet

• ARPANET

– Some of the first networkedapplications were created forthe ARPANET

– Created by the DefenseAdvanced ResearchProjects Agency(DARPA) around 1970

• Served researchers doing business with DARPA

• Connected many sites around the United States



• Soon, Many Similar Networks Appeared

– CSNET in computer science

– BITNET in business and the social sciences

– Tower of Babel situation—no interconnection

– This was frustrating to users



• Next, DARPA Created the Internet in 1980 to Connect NetworksTogether

– Initially, commercial activitywas forbidden

– Became commercial in 1995

– Today, the Internet is almost entirely commercial

– Almost no government money flowing in to run the Internet


1-4: Traditional Internet Applications

• File Transfer Protocol (FTP)

• E-Mail

• The World Wide Web (WWW)

• E-Commerce– Buying and selling on the Internet


1-5: The Internet Versus the World Wide Web (and Other Applications)

World Wide Web

(Application)

E-Mail

(Application)

FTP

(Application)Other Applications

The Internet (Transmission System)

The Internet is a global transmission system. The WWW, e-mail, etc., are applications that run over the Internet global transmission system


1-6: Newer Internet Applications

• Instant Messaging (IM)

• Streaming Audio and Video– No need to wait until the entire file is

downloaded before beginning to see or hear it

• Voice over IP (VoIP)– Telephony over the Internet or other IP networks

• Peer-to-Peer (P2P) Applications– Growing processing power of PCs allows PCs to serve

other PCs directly

3


1-6: Newer Internet Applications

• Web 2.0

– A hazy term that focuses on using the Internet to facilitate communication among people

– Including the creation of communities

– In addition, the users themselves typically generate the content

– Blogs, wikis, podcasts

– Examples: community building sites such as MySpace and Facebook, video sharing sites such as YouTube, virtual worlds such as Second Life, and specific information sharing sites, such as craigslist


1-7: Corporate Network Applications

• Corporate Network Applications are Specific to Businesses

– Can consume far more corporate network resources than traditional and new Internet applications combined

• Transaction-Processing Applications

– Simple, high-volume repetitive clerical transaction applications

– Accounting, payroll, billing, manufacturing, etc.

– Not all corporate network applications are transaction-processing applications



• Enterprise Resource Planning (ERP) Applications

– Serve individual business functions while providing integration between functional modules

SalesSales

PurchasingPurchasing

ManufacturingManufacturing

ShippingShipping

WarehousingWarehousing

AccountingAccounting BillingBilling

Inter-FunctionTransaction





• Organizational Communication Applications

– E-mail, etc.

– Groupware• Integrate multiple types of communication, organize

communication for retrieval, and provide multiple ways to disseminate and retrieve information



• Converged Networks

– Voice and data traditionally have needed different networks

– Convergence: Moving voice/video and data networks to a single network

– Can save the corporation a great deal of money by only having a single network

– Many technical issues remain


1-8: File Service

File Server

1.User saves data file

to file server, which is backed up nightly

2

2.Later, user can

retrieve thedata file from

any other computer

3.Others can retrieve

the file and evenedit it if they aregiven permission


1-8: File Service

File Server

1.A program is Installed

on the file server;Less expensive

than installing it onmany individual PCs

2.A multiuser version

of the program is required

3

4.Note that the program is

executed on the client PC,not on the file server!

4.Note that the program is

executed on the client PC,not on the file server!

3.For execution,

a copy is downloadedfrom the file server


Quality of Service (QoS)


1-9: Network Quality of Service (QoS)

• Quality of Service (QoS)

– Indicators of network performance

– Speed, etc.

• Metrics

– Ways of measuring specific network quality-of-service variables

– The metric for speed is bits per second


1-10: Transmission Speed

• Measuring Transmission Speed

– Measured in bits per second (bps)

– In metric notation:

• Increasing factors of 1,000 …

– Not factors of 1,024

• Kilobits per second (kbps)-note the lowercase k

• Megabits per second (Mbps)

• Gigabits per second (Gbps)

• Terabits per second (Tbps)



• Measuring Transmission Speed– What is 23,000 bps in metric notation?

– What is 3,000,000,000 bps in metric notation?

– What is 15,100,000 bps in metric notation?

• Occasionally measured in bytes per second– If so, written as Bps, rather than bps

– Usually seen only in file downloads



• Writing Transmission Speeds in Proper Form

– The rule for writing speeds (and metric numbers in general) in proper form is that there should be 1 to 3 places before the decimal point

– 23.72 Mbps is correct (2 places before the decimal point)

– 2,300 Mbps has four places before the decimal point, so it should be rewritten as 2.3 Gbps (1 place)

– 0.5 Mbps has zero places to the left of the decimal point. It should be written as 500 kbps (3 places)

• Leading zeros do not count

3




– How to convert 1,200 Mbps to proper form, to 12.02 Gbps

Number Suffix

12,020 Mbps

Must divide number by 1,000

So must multiply suffix by 1,000

12,020 12.02 Mbps Gbps




– How to convert .2346 Mbps to proper form, to 234.6 kbps

Number Suffix

0.2346 Mbps

Multiply by 1,000 Divide by 1,000

0.2346 234.6 Mbps kbps




– How should you write the following in proper form?

• 549.73 kbps

• 0.47 Gbps

• 11,200 Mbps

• .0021 Gbps



• Rated Speed

– The speed in bits per second that you should get (advertised or specified in the standard)

• Throughput– The speed you actually get

– Almost always lower than the rated speed

• On Shared Transmission Lines– Aggregate throughput—total throughput for all users

– Individual throughput—the individual user’s share of the aggregate throughput


1-11: Cost

• Systems Development Life Cycle Costs

– Hardware: Full price: advertised base price plus necessary options

– Software: Full price: advertised base price plus necessary options

– Labor costs: Networking staff and user costs

– Outsourcing development costs

– Total development investment


1-11: Cost

• Systems Life Cycle (SLC) Costs

– System development life cycle (SDLC) versus system life cycle (SLC)

• SLC has ongoing costs after development

– Total cost of ownership (TCO)

• Total cost over entire life cycle

• SLC includes carrier costs– Carrier pricing is complex and difficult to analyze– Must deal with leases, which lock the firm in for months or

years

1


1-13: Other Quality-of-Service Metrics

• We Have Already Seen Speed and Cost

• Availability

– The percentage of time a network is available for use

– “Our availability last year was 99.9%”

• Downtime is the amount of time a network is unavailable

– Measured in minutes, hours, etc.

– “In July, we had five minutes of downtime.”



• Error Rates

– Packet error rate: the percentage of packets lost or damaged

– Bit error rate: the percentage of bits lost or damaged



• Latency and Jitter

– Latency

• Delivery delay, measured in milliseconds– For instance, 250 ms is a quarter of a second

• Bad for real-time applications– Voice and video– Network control messages



• Latency and Jitter

– Jitter• Variation in latency between successive packets• Makes voice sound jittery

Figure 1-14



• Service Level Agreements

– Customers want guarantees for performance

– Provider pays penalties if the network does not meet its service metrics guarantees

– Often specified on a percentage basis• At least 100 Mbps 99.5% of the time• To guarantee this speed 100% of the time would be

impossible, and even 99.99% would be far more expensive




– Latency SLAs

• Would an SLA specify a lowest latency or a highest latency?

• Ask yourself, “Which is worse: large latency or small latency?”

• The answer: Large latency is worse

• So specify a maximum latency

• No more than 100 ms 99% of the time




– What would an SLA guarantee for availability?

– What would an SLA guarantee for error rates?


1-15: Network Security

• Security

– Security attacks can be extremely expensive

– Companies need to install defenses against attacks

– Chapter 9 discusses network security in depth


Switched Networks


Figure 1-16: Ethernet Switch Operation

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

In switched networks,Messages are called frames

Host A1-… wishes to senda frame to Host C3

The frame must passThrough the switch

In switched networks,Messages are called frames

Host A1-… wishes to senda frame to Host C3

The frame must passThrough the switch

Switch connectors arecalled ports

Switch connectors arecalled ports



UTP

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…

Host A1-… sends theframe to the switch

Host A1-… sends theframe to the switch



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

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…

The switch reads the destinationaddress in the frame.

It looks up the address (C3-…)in the switching table.

It reads the port number (15)

The switch reads the destinationaddress in the frame.

It looks up the address (C3-…)in the switching table.

It reads the port number (15)



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

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…

The switch sends theframe out Port 15,

to the destination host.

The switch sends theframe out Port 15,

to the destination host.


1-17: Switched Network in a Multistory Building

On each floor, hostsconnect to a workgroup switch via wire or wireless transmission

A core switch connectsthe workgroup switches to each other


1-17: Switched Network in a Multistory Building

Router Core Switch

Workgroup Switch 2

Workgroup Switch 1

Wall Jack

ToWAN

Wall Jack

Server

Client

Frames from the client to the server go through Workgroup Switch 2, through the Core Switch, through Workgroup Switch 1, and then to the server

3


Figure 1-18: Four-Pair Unshielded Twisted Pair (UTP) Copper Wiring


1-19: Packet Switching and Multiplexing

In packet switching, the sending host breakseach message into many smaller packets

Sends these packets out one at a time

Packets are routed to the destination host

In packet switching, the sending host breakseach message into many smaller packets

Sends these packets out one at a time

Packets are routed to the destination host


1-19: Packet Switching and Multiplexing

Multiplexing reduces cost. Each conversation only has to payfor its share of the trunk lines it uses

Multiplexing reduces cost. Each conversation only has to payfor its share of the trunk lines it uses


Routed Networks(Internets)


1-20: Routed Networks

• The 1980s: A Switched Tower of Babel

– At first, there were only switched networks

– Soon, there were many incompatible switched networks

– Users on different switched networks could not communicate with each other

SWSW SWSW

SWSW

SWSW

SWSW

SWSW

Switched Network 1 Switched Network 2



• Routers and Routed Networks

– Routers were created connect different switched networks together

– Routed networks are also called internets

SWSW SWSW

SWSW

SWSW

SWSW

SWSW


RouterRouter RouterRouter

Routed Network (Internet)



• Routers and Routed Networks– Routers are more complex (and expensive) than

switches• Designed to work no matter how complex the internet• Require more hands-on administration than switches

SWSW SWSW

SWSW

SWSW

SWSW

SWSW


RouterRouter RouterRouter

Routed Network (Internet)



• So Hosts on an Internet Have Two Addresses

• Example

– The author’s computer has the Ethernet addressAF-23-B9-C8-4E-38

• This is its address on its Ethernet switched network

– The author’s computer also has the IP address 128.171.17.13

• This is its globally unique IP address



• Packets and Frames

– Packets are called frames in switched networks

– Packets are called packets in routed networks

– A packet is carried in a frame within each switched network

PacketPacket

Frame


Routers, Frames, and Packets

• A frame arrives at a router– The frame contains a packet

• The router takes the packet out of the frame– The router puts the packet into a new frame appropriate

for the next network and sends it out– The packet continues; the frame does not

RouterRouterPacketPacket

Frame 1

PacketPacket

Frame 2

PacketPacket

Network 2 Network 2


1-21: Routed Network (Internet)

2. Packet travels through three switched networks

2

1. When a packet is sent, the packet travels all the way from the source host to the destination host

3. The packet travels in three frames—one ineach switched network


1-21: Routed Network (Internet)

• In this example, the internet has three networks

– When a packet is sent,

– That one packet goes all the way from the source host to the destination host

– The packet travels in three different frames along the way, one in each network

– A frame only travels through a single network


1-22: The Global Internet1.

User PCHost

Computer

1.Web server

HostComputer

4

Router

2.User PC’s

Internet ServiceProvider

ISP

AccessLine

3.Web server’s

Internet ServiceProvider

ISP

AccessLine

4.Internet Backbone

(Multiple ISP Carriers)

ISP

ISP

5.NAPs = Network Access

PointsConnect ISPs

NAPNAPNAPNAP

NAPNAP


1-22: The Global Internet

• How is the Internet Financed?

– Through ISP subscriber payments• Residences typically pay $10 to $100 per month• Business typically pay thousands or tens of thousands

of dollars per month

– Like the telephone network• The telephone network is supported by customer

payments to telephone carriers

– Almost no government money involved


1-22: The Internet

• The TCP/IP Standards

– The set of protocols that governs the Internet

– Standards for both applications and packet delivery

– Created by the Internet Engineering Task Force (IETF)


1-23: Domain Name System (DNS)

• Domain Name System (DNS)

– IP addresses are official addresses on the Internet and other internets

– Hosts can also have host names (e.g., cnn.com)

• Not official—like nicknames

– If you only know the host name of a host that you want to reach, your computer must learn its IP address

• DNS servers tell our computer the IP address of a target host whose name you know

– Like looking up someone’s name in a telephone directory

72


LANs and WANs


1-25: LANs and WANs (Study Figure)

Category Local Area Networks Wide Area Networks

Abbreviation LAN WAN

Distance Span Customer premises (apartment, office, building, campus, etc.)

Between sites within a corporation or between different corporations

Wide AreaNetwork

BuildingLAN Home

LAN

CampusLAN


1-25: LANs and WANs


Can use switched network technology?

Yes Yes

Can use routed network technology?

Yes, especially in large LANs

Yes, in fact, that is what the Internet is

Many students are surprised that LANs can be routedand that WANs can be switched

Many students are surprised that LANs can be routedand that WANs can be switched


1-25: LANs and WANs


Implementation Do it yourself Must use a carrier with rights of way

Ability to choose technologies

High Low

Need to manage technologies

High Low


1-25: LANs and WANs


Cost per bit transmitted Low High with arbitrary Changes unrelated to costs

Therefore, typical transmission speed

Usually 100 Mbps to 10 Gbps

About 256 kbps to 50 Mbps

In economics, you learned that when unit price goes up, people will purchase less of the product

Because WANs cost much more per bit, companies learn to live with fewer bits per second


Network Management


1-26: Network Management

• Strategic Network Management

– SDLC – Initial design, procurement• What factors drive initial design decisions• Legacy – transitions• Expansion

• Ongoing Management

– After the SDLC ends - The most important (and expensive) part of the systems life cycle

– Operations, administration, maintenance, and provisioning - OAM&P


Simple Network Management Protocol (SNMP)


1-29: Simple Network Management Protocol (SNMP)

Network ManagementSoftware (Manager)

ManagedDevice

ManagedDevice

The manager manages multiplemanaged devices from a

central location

Collects information abouteach managed device

Can sometimes reconfiguremanaged devices remotely


Figure 10-13: Simple Network Management Protocol (SNMP)


ManagedDevice

NetworkManagement

Agent (Agent),Objects

Manager talks to a network management agent on each managed device—not to themanaged device directly


Manager collects data abouteach device; stores the data

in a ManagementInformation Base (MIB)


ManagementInformationBase (MIB)


Data

Data




Simple NetworkManagement Protocol (SNMP)

MessagesManaged Device

1.Command (Get, Set, etc.)

2.Response

3.Trap (Alarm) Initiated by

a Managed Device


Key Points

• Perspective– Definition of a network– Networked applications– Quality of Service

• Network Technology– Switched versus routed networks (internets)– The global Internet– LANs versus WANs

• Network Management


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© 2009 Pearson Education, Inc. Publishing as Prentice Hall 1 Agenda Intro Review Syllabus and assignments Lecture Ch 1 and 2 Homework