Chapter 4: Networking and the Internet

Copyright © 2008 Pearson Education, Inc. Publishing as Pearson Addison-Wesley

Chapter 4:Networking and the Internet

Computer Science: An OverviewTenth Edition

by J. Glenn Brookshear

Copyright © 2008 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 4-2

Chapter 4: Networking and the Internet

• 4.1 Network Fundamentals• 4.2 The Internet• 4.3 The World Wide Web


Network Classifications

• Scope– Local area network (LAN)– Metropolitan area (MAN)– Wide area network (WAN)

• Ownership– Closed versus open Internet is an open network

• Topology (configuration-physical layout of network)– Bus (Ethernet)– Star (Wireless networks with central Access

Point)


Figure 4.1 Network topologies

Access point (Server)


Protocols• The set of rules by which activities are conducted

• Example: Protocols which controls rights to transmit messages

– CSMA/CD (Carrier Sense, Multiple Access with Collision Detection)

• Used in Ethernet• Silent bus provides right to introduce new message

– CSMA/CA (Carrier Sense, Multiple Access with Collision Avoidance)

• Used in WiFi• Hidden terminal problem


Figure 4.2 Communication over a bus network


Figure 4.3 The hidden terminal problem


Connecting Networks

• Repeater– Extends a network– Simply transmits messages with some form of

amplification

• Bridge: – Connects two compatible networks– Transmits message ony when that message is

destined for a computer on the other side


Connecting Networks

• Switch: – A bridge with multiple connections

– Connect several compatible networks

– Minimizes traffic load

• Repeater, bridge and switch are used to construct a single large network (same protocol)

• Router: Connects two incompatible networks resulting in a network of networks called an internet


Figure 4.4 Building a large bus network from smaller ones


Figure 4.5 Routers connecting two WiFi networks and an Ethernet network to form an internet

Wi Fi = Wireless Fidelity


Inter-process Communication• The communication between computers

within a network • Methods of process communication

– Client-server model• One server, many clients• Server must execute continuously• Client initiates communication

– Peer-to-peer (P2P) model• Two processes communicating as equals• Peer processes can be short-lived


Figure 4.6 The client/server model compared to the peer-to-peer model


Distributed Systems

• Systems with parts that run on different computers

• eg. global information retrieval systems, companywide accounting and inventory systems, computer games.

• Infrastructure can be provided by standardized toolkits• Example: Enterprise Java Beans from Sun Microsystems• Example: .NET framework from Microsoft


The Internet

• The Internet: An internet that spans the world (a worldwide collection of connected networks )

– Original goal was to develop a means of connecting networks that would not be disrupted by local disasters (early 1960s).

– Today it has shifted from an academic research project to a commercial undertaking.


Internet Architecture

• Internet Service Provider (ISP): Organization which constructs and maintains internet.

– Tier-1 : Consist high-speed, high capacity, international WANs (The backbone of Internet)

– Tier-2 : More regional ISPs

– Access ISP: Provides connectivity to the Internet• Traditional telephone (dial up connection)• Cable connections• DSL• Wireless


Figure 4.7 Internet Composition

End systems= hosts


Internet Addressing

• IP (Internet Protocol) address:

– The unique address of a computer in internet

– Pattern of 32 or 128 bits often represented in dotted decimal notation

– 17.12.25 = 00010001 00001100 00011001


Internet Addressing

• Mnemonic address:– Domain names– Top-Level Domains (edu, com, gov, org etc.)– Country-codeTop-Level Domains (tr, au, ca, etc.)

• Domain name system (DNS)– Name server : Translates mnemonic names to IP

address– DNS lookup : The process of translation


Internet Corporation for Assigned Names & Numbers (ICANN)

• Allocates IP addresses to ISPs who then assign those addresses within their regions.

• Oversees the registration of domains and domain names.


Traditional Internet Applications

• Electronic Mail (email)

– Domain mail server collects incoming mail and transmits outing mail

– SMTP: The protocol used to transfer between mail servers as well as to send a new message from it’s author’s local machine to author’s mail server (transfers ASCII text messages MIME: non ASCII)

– Mail server delivers collected incoming mail to clients via POP3(Post Office Protocol Version 3) or IMAP (Internet Mail Access Protocol)


Traditional Internet Applications

• File Transfer Protocol (FTP)

• Telnet : A distant user may contact the telnet server and gain access to the applications and utilities on the computer that a local user has)

• SSH : Secured Shell = Secured Telnet


More Recent Applications

• Voice Over IP (VoIP) peer to peerSkype

• Internet Radio– Unicast (One sender sending messages to

one receiver)– N-unicast (A single sender involved with

multiple unicasts)– Multicast (A single sender with multiple clients)


World Wide Web

• The World Wide Web, also known as the Web or WWW:

– Contains billions of documents– Is a portion of the Internet– Uses the Internet as a means to transport

information– Is a separate entity from the Internet


World Wide Web

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• The Web contains the information.

• The Internet transports information to and from users.


World Wide Web

• Hypertext : Text file which contains tags to communicate with browser and which contains links to other documents

• Hyperlinks or links are words and images that bring other documents into view when clicked

• HTTP: Hyper Text Transfer Protocol


World Wide Web

• A Web page is a document that may include text, graphics, sound, animation, and video.

• A Web site is a collection of Web pages.

• A Web browser is a program that displays Web pages and linked items (gets documents from Web server)

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Figure 4.8 A typical URLThe identification of an Internet resource’s type and location is performed through its Uniform Resource Locator (URL).


Hypertext Document Format

• Encoded as text file• Contains tags to communicate with browser

– Appearance • <h1> to start a level one heading• <p> to start a new paragraph

– Links to other documents and content• <a href = . . . >

– Insert images• <img src = . . . >


Figure 4.9 A simple Web page


Figure 4.9 A simple Web page (continued)


Figure 4.10 An enhanced simple Web page


Figure 4.10 An enhanced simple Web page (continued)


Extensible Markup Language (XML)

• XML: A language for constructing markup languages similar to HTML

– A descendant of SGML– Opens door to a World Wide Semantic Web


Using XML : EXAMPLE

<?xml version="1.0"?>

<note>

<to>Tove</to>

<from>Jani</from>

<heading>Reminder</heading>

<body>Don't forget me this weekend!</body>

</note>


Using XML: EXAMPLE<PARTS>

<TITLE>Computer Parts</TITLE>

<PART>

<ITEM>Motherboard</ITEM>

<MANUFACTURER>ASUS</MANUFACTURER>

<MODEL>P3B-F</MODEL>

<COST> 123.00</COST>

</PART>

<PART>

<ITEM>Sound Card</ITEM>

<MANUFACTURER>Creative Labs</MANUFACTURER>

<MODEL>Sound Blaster Live</MODEL>

<COST> 80.00</COST>

</PART>

</PARTS>


Client Side & Server Side Activities

• Client-side activities

– Examples: java applets, javascript, Macromedia Flash


Client Side & Server Side Activities

• Server-side activities– Common Gateway Interface (CGI) : A set of

standards by which clients could request execution of programs stored in server

– Servlets: Java programs (class) that generate web content dynamically depending on the content of a request from a client

– PHP (Hypertext Processor ) A widely used, general-purpose scripting language that was originally designed for web development to produce dynamic web pages

Documents

Chapter 4: Networking and the Internet