Chapter 7 Computer Networks, the Internet, and the World Wide Web Introduction to Networks

Chapter 7Chapter 7

Computer Networks, the Computer Networks, the Internet, and the World Wide Internet, and the World Wide

WebWeb

Introduction to Networks

Invitation to Computer Science, 5th Edition 22

Basic Networking Concepts

• Computer network – Set of independent computer systems connected by

telecommunication links

• Individual computers on the network – Referred to as nodes, hosts, or end systems

Communication Links

• In early days of networking:– Most common way to transmit data was via

switched, dial-up telephone lines

• Voice-oriented dial-up telephone network – Originally a totally analog medium

• Modem– Modulates, or alters, a standard analog signal called

a carrier so that it encodes binary information

Figure 7.1 Two Forms of Information Representation

Figure 7.2 Modulation of a Carrier to Encode Binary Information

Communication Links (continued)

• Broadband – Has rapidly been replacing modems and analog

phone lines for data communications

• Digital subscriber line – Provided by either your local telephone company or

someone certified to act as their intermediary

• Asymmetric digital subscriber– Does not have the same transmission speed in the

download direction as in the upload direction

• Cable modem– Makes use of links that deliver cable TV signals into

your home– Offered by cable TV providers

• Ethernet – Designed to operate at 10 Mbps using coaxial cable

• Fast Ethernet– Transmits at 100 Mbps across coaxial cable, fiber-

optic cable, or regular twisted-pair copper wire

• Gigabit networking– Transmission lines that support speeds in excess of

1 billion bits per second (Gbps)

• Ten-gigabit Ethernet standard– Version of Ethernet with data rate of 10 billion bits

per second– Adopted by IEEE in 2003

• Wireless data communication– Uses radio, microwave, and infrared signals

Figure 7.3 Transmission Time of anImage at Different Transmission Speeds

• Wireless local access network– User transmits from his or her computer to a local

wireless base station

• Wi-Fi (Wireless Fidelity)– Used to connect a computer to the Internet when it is

within range of a wireless base station

• Metropolitan Wireless Local Access Network– Routers provide convenient, low cost wireless

Internet access to all residents

• Bluetooth– Often used to support communication between

wireless computer peripherals

• Wireless wide area access network– Computer transmits messages to a remote base

station provided by a telecommunications company

• 3G– Offers voice services as well as data communication

at rates of 0.5 to 2.4 Mbps– Now 4G (up to 10 times faster than 3G)

Local Area Networks

• Local area network (LAN)– Connects hardware devices such as computers,

printers, and storage devices that are all in close proximity

• Bus topology– All nodes are connected to a single shared

communication line

• Ring topology – Connects the network nodes in a circular fashion

Figure 7.4 Some Common LAN Topologies

Local Area Networks (continued)

• Shared cable– A wire is strung around and through a building– Users tap into the cable at its nearest point using a

transceiver

• Repeater – Device that simply amplifies and forwards a signal

• Bridge (switch)– “Smarter” device that has knowledge about the

nodes located on each separate network

Figure 7.5 An Ethernet LAN Implemented Using Shared Cables

Local Area Networks (continued)

• Switch – Located in a room called a wiring closet– Contains a number of ports, with a wire leading from

each port to an Ethernet interface

Figure 7.6 An Ethernet LAN Implemented Using a Switch

Wide Area Networks

• Wide area network (WAN) – Connects devices that are not in close proximity but

rather are across town, across the country, or across the ocean

• Most WANs – Use a store-and-forward, packet-switched

technology to deliver messages

• Packet– Information block with a fixed maximum size that is

transmitted through the network as a single unit

Figure 7.7 Typical Structure of a Wide Area Network

Overall Structure of the Internet

• Individual networks are interconnected via a device called a router

• Internet Service Provider (ISP)– Business whose purpose is to provide access from a

private network to the Internet – Hierarchical, interconnecting to each other in

multiple layers, or tiers, that provide ever-expanding geographic coverage

Figure 7.8(a) Structure of a Typical Company Network

Figure 7.8(b) Structure of a Network Using an ISP

Figure 7.8(c) Hierarchy of Internet Service Providers

Overall Structure of the Internet (continued)

• International ISP– Also called tier-1 network or an Internet backbone– Provides global coverage

• Internet – Huge interconnected “network of networks” that

includes nodes, LANs, WANs, bridges, routers, and multiple levels of ISPs

Communication Protocols

• Protocol – Mutually agreed upon set of rules, conventions, and

agreements for the efficient and orderly exchange of information

• Internet Society– Nonprofit, nongovernmental, professional society

composed of more than 100 worldwide organizations

• Internet protocol hierarchy– Also called a protocol stack– Has five layers

Figure 7.10 The Five-Layer TCP/IP Internet Protocol Hierarchy

Physical Layer

• Physical layer protocols – Govern the exchange of binary digits across a

physical communication channel

• Goal of the physical layer – To create a “bit pipe” between two computers

Figure 7.11 The Concept of a Bit Pipe

Data Link Layer

• Error detection and correction problem– How do we detect when errors occur, and how do we

correct them?

• Framing problem– Identifying the start and end of a message

• Data link protocols– Address and solve error handling and framing

• Medium access control protocols – Determine how to arbitrate ownership of a shared line

when multiple nodes want to send messages at the same time

Figure 7.12 The Medium Access Control Protocols in Ethernet

Data Link Layer (continued)

• Collision– Two or more messages transmitted at exactly the

same time– Common occurrence in contention-based networks

like Ethernet

• Layer 2b logical link control protocols – Ensure that message traveling across this channel

from source to destination arrives correctly

• ARQ algorithm– Basis for all data link control protocols in current use

Network Layer

• Network layer protocols – Deliver message from the site where it was created

to its ultimate destination

• Responsibilities of the network layer – Creating a universal addressing scheme for all

network nodes– Delivering messages between any two nodes in the

network

Figure 7.13 A Message Packet Sent by the Data Link Protocols

Network Layer (continued)

• Nodes identify each other using a 32-bit IP address

• Domain Name System (DNS) – Converts from a symbolic host name such as

macalester.edu to its 32-bit IP address 141.140.1.5

• Local name server – Checks to see if it has data record containing a

specific IP address

Network Layer (continued)

• Routing– Process of selecting one specific path

• Shortest path– Path via which message can travel the fastest

Transport Layer

• Transport layer protocols– Assigns port numbers to programs – Remembers which program goes with which port

• Well-known port numbers– Used by all important applications on the Internet

Figure 7.14 Relationship between IP Addresses and Port Numbers

Application Layer

• Application layer protocols– Rules for implementing end-user services provided

by a network• Uniform Resource Locator (URL)

– protocol://host address/page• HTTP request message

– Sent on the TCP connection from the client to the server, specifying the name of a Web page

• HTTP response message– Returned from the server to the client along the

same TCP connection

Figure 7.16 Some Popular Application Protocols on the Internet

Figure 7.17 Behavior of the HTTP Application-Level Protocol

Network Services and Benefits

• Electronic mail (e-mail) – Single most popular application of networks for the

last 30 years

• Bulletin boards– Shared public file where anyone can post messages

and everyone is free to read the postings of others

• Social networks– Systems that create communities of users who

share common interests

Network Services and Benefits (continued)

• Resource sharing– Ability to share physical and logical resources

• Client-server computing– Some nodes provide services, while the remaining

nodes are users of those services

• Information sharing – A network is an excellent way to access scientific,

medical, legal, and commercial data files

Figure 7.18 The Client-Server Model of Computing

Network Services and Benefits (continued)

• Information utility (data warehouse)– Nodes contain massive amounts of information that

can be electronically searched for specific facts

• Collaborative software (groupware)– Facilitates the efforts of individuals connected by a

network and working on a single shared project

• Electronic commerce (e-commerce) – Use of computers and networking to support the

paperless exchange of goods, information, and services

A Brief History of the Internet and the World Wide Web

• ARPA– Small research office of the Department of Defense

charged with developing technology that could be of use to the U.S. military

• ARPANET – Formally demonstrated to scientific community at an

international conference in 1972

• Internetworking– Any WAN is free to do whatever it wants internally

A Brief History of the Internet and the World Wide Web (continued)

• Robert Kahn and his colleagues needed to create: – A standardized way for a node in one WAN to

identify a node located in a different WAN– A universally recognized message format for

exchanging information across WAN boundaries

• Telnet – Allows users to log on remotely to another computer

and use it as though it were their own local machine

Figure 7.19 A Network of Networks

A Brief History of the Internet and the World Wide Web (continued)

• FTP (file transfer protocol)– Provides a way to move files around the network

quickly and easily

• NSFNet– Used TCP/IP technology identical to the ARPANET– Interconnected six NSF supercomputer centers with

dozens of new regional networks set up by the NSF

• Internet service providers – Offered Internet access once provided by ARPANET

and NSFNet

Figure 7.20 State of Networking in the Late 1980s

The World Wide Web

• Tim Berners-Lee– Researcher at CERN– First developed the idea for a hypertext-based

information distribution system in 1989

• Hypertext– Collection of documents interconnected by pointers,

called links

• Uniform Resource Locator– Worldwide identification of a Web page located on a

specific host computer on the Internet

The World Wide Web (continued)

• World Wide Web– Completed and made available to all researchers at

CERN in May 1991

• Mosaic– Web browser developed in late 1993 and made

available to the general public

Figure 7.21 Hypertext Documents

Summary

• Computer network– Set of independent computer systems connected by

telecommunication links

• Options for transmitting data on a network– Dial-up telephone lines, DSL, cable modem,

Ethernet, Fast Ethernet

• Types of networks– Local area network (LAN) and wide area network

Summary (continued)

• The Internet– Huge interconnected "network of networks"

• TCP/IP – Internet protocol hierarchy, composed of five layers:

physical, data link, network, transport, and application

• World Wide Web – An information system based on the concept of

hypertext

Chapter 7 Computer Networks, the Internet, and the World Wide Web Introduction to Networks

Documents

Communications, Networks, the Internet, and the World Wide Web

Chapter 2 Communications, Networks, the Internet, and the World Wide Web

Internet of Things (IoT): A Vision, Architectural Elements, and ...gridbus.cs.mu.oz.au/papers/Internet-of-Things-Vision...wireless sensor networks (WSN) and find wide application in

Wide Area Networks Eric Cozzi eric (at) cozzi (dot) us The Internet and the World Wide Web

The Internet and World Wide Webspp2k/1150/008/concepts/L02.pdf · The World Wide Web •Not exactly the same as the Internet –Internet is a system of interconnected computer networks

Wide Area Networks What is a WAN Types of Networks Global and Regional Networks Metropolitan Area Networks WANS Internet and WWW Types of connections used

Securing Generic Routing Encapsulation With Internet Protocol Security (IPSec) For Institutional Wide Area Networks

An Internet-Wide View of Internet-Wide Scanning

Computer Networks with Internet Technology William Stallings Chapter 13 Wide Area Networks

The Internet. The Internet, also called the Net, is a world-wide collection of networks that links millions of businesses, government agencies, educational

Analysis of Country-wide Internet Outages Caused …...C.2.5 [Local and Wide-Area Networks]: Internet General Terms Measurement, Security Permission to make digital or hard copies

1 Wide Area Networks and Internet CT1403 Lecture-8: Internet Network Layer (Part-3) By : Najla Al-Nabhan

Introduction to Web Application Development, for CS437/637Introduction: Internet vs. World Wide Web • Internet is an interconnected network of thousands of networks and millions

The Internet and The World Wide Web - William & Mary · The Internet and The World Wide Web ... computer networks that use the Internet protocol suite ... A collection of data sent

1 Low Power Wide Area Networks (LPWANs) for Internet of ... · arXiv:1611.07449v1 [cs.NI] 2 Nov 2016 1 Low Power Wide Area Networks (LPWANs) for Internet of Things (IoT) Applications:

Internet Overview · 2016. 3. 9. · What is the Internet? An internet is a set of computer networks that are connected to each other (e.g. intranet). The Internet is a world-wide

Internet of Place - University of Brightonarts.brighton.ac.uk/.../InternetofPlaceFeb2016.pdf · networks of first the internet and then the world wide web (www). The virtual nature

The Internet. What is the Internet? The Internet is a network of networks. It gives users access to a wide variety of information from millions of

THE INTERNET AND THE WORLD WIDE WEB · THE INTERNET AND THE WORLD WIDE WEB 1 . What is the internet? ! A collection of computer networks that use a protocol to exchange data ! Is

Chapter 7 Computer Networks, the Internet, and the World Wide Web