Copyright © 2008 Pearson Education, Inc. Publishing as Pearson Addison-Wesley Chapter 4: Networking and the Internet Computer Science: An Overview Tenth 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

Copyright © 2008 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 4-3 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)

Copyright © 2008 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 4-4 Figure 4.1 Network topologies Access point (Server)

Copyright © 2008 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 4-5 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

Copyright © 2008 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 4-6 Figure 4.2 Communication over a bus network

Copyright © 2008 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 4-7 Figure 4.3 The hidden terminal problem

Copyright © 2008 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 4-8 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

Copyright © 2008 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 4-9 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

Copyright © 2008 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 4-10 Figure 4.4 Building a large bus network from smaller ones

Copyright © 2008 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 4-11 Figure 4.5 Routers connecting two WiFi networks and an Ethernet network to form an internet Wi Fi = Wireless Fidelity

Copyright © 2008 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 4-12 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

Copyright © 2008 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 4-13 Figure 4.6 The client/server model compared to the peer-to-peer model

Copyright © 2008 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 4-14 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

Copyright © 2008 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 4-15 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.

Copyright © 2008 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 4-16 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

Copyright © 2008 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 4-17 Figure 4.7 Internet Composition End systems= hosts

Copyright © 2008 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 4-18 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 – =

Copyright © 2008 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 4-19 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

Copyright © 2008 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 4-20 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.

Copyright © 2008 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 4-21 Traditional Internet Applications Electronic Mail ( ) –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)

Copyright © 2008 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 4-22 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

Copyright © 2008 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 4-23 More Recent Applications Voice Over IP (VoIP)  peer to peer  Skype 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)

Copyright © 2008 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 4-24 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

Copyright © 2008 Pearson Education, Inc. Publishing as Pearson Addison-Wesley World Wide Web 4-25 The Web contains the information. The Internet transports information to and from users.

Copyright © 2008 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 4-26 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

Copyright © 2008 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 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) 4-27

Copyright © 2008 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 4-28 Figure 4.8 A typical URL The identification of an Internet resource’s type and location is performed through its Uniform Resource Locator (URL).

Copyright © 2008 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 4-29 Hypertext Document Format Encoded as text file Contains tags to communicate with browser –Appearance to start a level one heading to start a new paragraph –Links to other documents and content –Insert images

Copyright © 2008 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 4-30 Figure 4.9 A simple Web page

Copyright © 2008 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 4-31 Figure 4.9 A simple Web page (continued)

Copyright © 2008 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 4-32 Figure 4.10 An enhanced simple Web page

Copyright © 2008 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 4-33 Figure 4.10 An enhanced simple Web page (continued)

Copyright © 2008 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 4-34 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

Copyright © 2008 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 4-35 Using XML : EXAMPLE Tove Jani Reminder Don't forget me this weekend!

Copyright © 2008 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 4-36 Using XML: EXAMPLE Computer Parts Motherboard ASUS P3B-F Sound Card Creative Labs Sound Blaster Live 80.00

Copyright © 2008 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 4-37 Client Side & Server Side Activities Client-side activities –Examples: java applets, javascript, Macromedia Flash

Copyright © 2008 Pearson Education, Inc. Publishing as Pearson Addison-Wesley 4-38 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