Computer Science: Networking and the Internet (2015) PDF

Chapter 4: Networking and the Internet © 2015 Pearson Education Limited 2015  Chapter 4: Networking and the Internet 4.1 Network Fundamentals 4.2 The Internet 4.3 The World Wide Web 4.4 Internet Protocols 4.5 Security © 2015 Pearson Educatio...

Chapter 4: Networking and the Internet © 2015 Pearson Education Limited 2015  Chapter 4: Networking and the Internet 4.1 Network Fundamentals 4.2 The Internet 4.3 The World Wide Web 4.4 Internet Protocols 4.5 Security © 2015 Pearson Education Limited 2015. 4-2  Computer Network An infrastructure of autonomous computers connected each other. If a computer can forcibly start or stop another, it cannot be said that these computers are autonomous. © 2015 Pearson Education Limited 2015. 4-3  Network Classifications Scope – Personal area network (PAN) – Local area network (LAN) – Metropolitan area (MAN) – Wide area network (WAN) Ownership – Closed versus open Topology (configuration) – Bus (Ethernet) – Star (Wired/Wireless; Networks with central active devices, HUB/Switch/Access Point) © 2015 Pearson Education Limited 2015. 4-4  Figure 4.1 Network topologies © 2015 Pearson Education Limited 2015. 4-5  Figure 4.1 Network topologies (continued) © 2015 Pearson Education Limited 2015. 4-6  Protocols CSMA/CD (Not used in modern networks) – Carrier Sense Multiple Access/Collision Detection – Used in Ethernet – Silent bus provides right to introduce new message CSMA/CA – Carrier Sense Multiple Acces/Collision Avoidence – Used in WiFi – Hidden terminal problem © 2015 Pearson Education Limited 2015. 4-7  Please DO NOT answer like this!!! © 2015 Pearson Education Limited 2015. 0-8  Figure 4.2 Communication over a bus network © 2015 Pearson Education Limited 2015. 4-9  Figure 4.3 The hidden terminal problem © 2015 Pearson Education Limited 2015. 4-10  Connecting Networks Repeater: Extends a network Bridge: Connects two compatible networks Switch: Connects several compatible networks Router: Connects two incompatible networks Network of networks: internet (INTERconnected NETworks) Internet is formed with routers © 2015 Pearson Education Limited 2015. 4-11  Figure 4.4 Building a large bus network from smaller ones © 2015 Pearson Education Limited 2015. 4-12  Figure 4.5 Routers connecting two WiFi networks and an Ethernet network to form an internet © 2015 Pearson Education Limited 2015. 4-13  Inter-process Communication Client-server – One server, many clients – Server must execute continuously – Client initiates communication Peer-to-peer (P2P) – Two processes communicating as equals – Peer processes can be short-lived © 2015 Pearson Education Limited 2015. 4-14  Figure 4.6 The client/server model compared to the peer-to-peer model © 2015 Pearson Education Limited 2015. 4-15  Distributed Systems Systems with parts that run on different computers – Cluster computing – Grid computing – Cloud computing Amazon’s Elastic Compute Cloud Google Drive © 2015 Pearson Education Limited 2015. 4-16  Behavior of a Distributed System A distributed system, the system which many computers are connected to, is visible as only one system to the user. User does not know how many processors that system have. All processors are visible as one virtual processor. Distributed system is a software system built on a computer network. © 2015 Pearson Education Limited 2015. 4-17  The Internet The Internet: An internet that spans the world; – Original goal was to develop a means of connecting networks that would not be disrupted by local disasters – Today a commercial undertaking that links a worldwide combination of PANs, LANs, MANs, and WANs involving billions of computers © 2015 Pearson Education Limited 2015. 4-18  Internet Architecture Internet Service Provider (ISP) – Tier-1 – Tier-2 Access or Tier-3 ISP: Provides connectivity to the Internet – Hot spot (wireless) – Telephone lines – Cable/Satellite systems DSL – Fiber optics © 2015 Pearson Education Limited 2015. 4-19  Figure 4.7 Internet Composition © 2015 Pearson Education Limited 2015. 4-20  Basic Components of an ISP Firewall Router Modem Web Server DNS Server E-mail Server AAA Server © 2015 Pearson Education Limited 2015. 0-21  Internet Addressing IP address: pattern of 32 or 128 bits often represented in dotted decimal notation Mnemonic address: – Domain names – Top-Level Domains Domain name system (DNS) – Name servers – DNS lookup © 2015 Pearson Education Limited 2015. 4-22  IPv4 Address Classes © 2015 Pearson Education Limited 2015. 4-23  Dotted Decimal Notation (DDN) Binary notation is not easy to be understood. IP addresses can be defined in decimal values. It is called “Dotted Decimal Notation (DDN)” DDN is a syntactic form DDN is used to express 32-bit binary values © 2015 Pearson Education Limited 2015. 24 4-24  Boundaries of IPv4 Address Classes DDN represents each octet in decimal and uses a dot to separate octets. Dotted decimal addresses range from 0.0.0.0 to 255.255.255.255 Class From To A 0.0.0.0 127.255.255.255 B 128.0.0.0 191.255.255.255 C 192.0.0.0 223.255.255.255 D 224.0.0.0 239.255.255.255 E 240.0.0.0 255.255.255.255 © 2015 Pearson Education Limited 2015. 4-25  New Dimension: IPv6 128 bit – 296 times the size of IPv4 address space – 340,282,366,920,938,463,463,374,607,431,768,211,456 – 665,570,793,348,866,943,898,599 addresses/m2 (earth surface) Representation of addresses – Hexadecimal form 69DC:8864:FFFF:FFFF:0:1280:8C0A:FFFF – Zero compression: FF0C:0:0:0:0:0:0:B1 becomes FF0C::B1 – IPv4 embedded: 0:0:0:0:0:0:10.0.101.7 © 2015 Pearson Education Limited 2015. 4-26  Internet Corporation for Assigned Names & Numbers (ICANN) ICANN allocates IP addresses to ISPs via regional internet registries. ISPs assign those addresses within their regions. ICANN oversees the registration of domains and domain names. There are five regional internet registries. © 2015 Pearson Education Limited 2015. 4-27  Early Internet Applications Network News Transfer Protocol (NNTP) File Transfer Protocol (FTP) Telnet and Secure Shell (SSH) Hypertext Transfer Protocol (HTTP) Electronic Mail (email) – Domain mail server collects incoming mail and transmits outgoing mail – Mail server delivers collected incoming mail to clients via POP3 or IMAP © 2015 Pearson Education Limited 2015. 4-28  Classic e-Mail System © 2015 Pearson Education Limited 2015. 0-29  Basic Terms for Mail Systems Simple Mail Transport Protocol Multipurpose Internet Mail Extensions Post Office Protocol Internet Mail Access Protocol © 2015 Pearson Education Limited 2015. 0-30  Sample SMTP Mail Conversation 220 mail.tardis.edu SMTP Sendmail Gallifrey-1.0; Fri, 23 Aug 2413 14:34:10 HELO mail.skaro.gov 250 mail.tardis.edu Hello mail.skaro.gov, pleased to meet you MAIL From: [email protected] 250 2.1.0 [email protected]... Sender ok RCPT To: [email protected] 250 2.1.5 [email protected]... Recipient ok DATA 354 Enter mail, end with "." on a line by itself Subject: Extermination. EXTERMINATE! Regards, Dalek. 250 2.0.0 r7NJYAEl028071 Message accepted for delivery QUIT 221 2.0.0 mail.tardis.edu closing connection © 2015 Pearson Education Limited 2015. 4-31  More Recent Applications Voice Over IP (VoIP) Internet Multimedia Streaming – N-unicast – Multicast – On-demand streaming – Content delivery networks (CDNs) © 2015 Pearson Education Limited 2015. 4-32  World Wide Web Hypertext combines internet technology with concept of linked-documents – Embeds hyperlinks to other documents Browsers present materials to the user Webservers provide access to documents Documents are identified by URLs and transferred using HTTP © 2015 Pearson Education Limited 2015. 4-33  Figure 4.8 A typical URL (Uniform Resource Locater) © 2015 Pearson Education Limited 2015. 4-34  Hypertext Markup Language (HTML) 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 © 2015 Pearson Education Limited 2015. 4-35  Figure 4.9 A simple webpage © 2015 Pearson Education Limited 2015. 4-36  Figure 4.9 A simple webpage (continued) © 2015 Pearson Education Limited 2015. 4-37  Figure 4.10 An enhanced simple webpage © 2015 Pearson Education Limited 2015. 4-38  Figure 4.10 An enhanced simple Web page (continued) © 2015 Pearson Education Limited 2015. 4-39  Extensible Markup Language (XML) XML: A language for constructing markup languages similar to HTML – A descendant of SGML (Standard Generalized Markup Language) – Opens door to a World Wide Semantic Web © 2015 Pearson Education Limited 2015. 4-40  Using XML C minor 2/4 < rest> egth egth G, egth G, egth G hlf E © 2015 Pearson Education Limited 2015. 4-41  Figure 4.11 The first two bars of Beethoven’s Fifth Symphony © 2015 Pearson Education Limited 2015. 4-42  Client Side Versus Server Side Client-side activities – Javascript – Macromedia Flash (Outdated) Server-side activities – Common Gateway Interface (CGI) – Servlets – JavaServer Pages (JSP) / Active Server Pages (ASP) – PHP © 2015 Pearson Education Limited 2015. 4-43  Figure 4.12 Package-shipping example © 2015 Pearson Education Limited 2015. 4-44  Networking Problem Communication problem is divided into subpieces. Separate protocol is designed for each piece. It is easier to design, analyze, implement and test a protocol. Each protocol should handle part of the communication problem. © 2015 Pearson Education Limited 2015. 4-45  Standardization: ISO 7 Layer Reference Model © 2015 Pearson Education Limited 2015. 4-46  Protocol for Internet: TCP/IP Protocol Suite Transmission Control Protocol / Internet Protocol – Protocol developed for use on internet – Researchers who developed TCP/IP also developed the internet architecture. © 2015 Pearson Education Limited 2015. 4-47  Internet Software Layers Application: Constructs message with address Transport: Chops message into packets Network: Handles routing through the Internet Link (Data Link): Handles actual transmission of packets © 2015 Pearson Education Limited 2015. 4-48  Figure 4.13 The Internet software layers © 2015 Pearson Education Limited 2015. 4-49  Sample Network © 2015 Pearson Education Limited 2015. 0-50  Figure 4.14 Following a message through the Internet (Sample Net) © 2015 Pearson Education Limited 2015. 4-51  TCP/IP Protocol Suite Components Transport Layer – Transmission Control Protocol (TCP) – User Datagram Protocol (UDP) Network (Internet) Layer – Internet Protocol (IP) IPv4 IPv6 © 2015 Pearson Education Limited 2015. 4-52  Figure 4.15 Choosing between TCP and UDP © 2015 Pearson Education Limited 2015. 4-53  Common terms used for messages Packet: Data at Internet Layer and above Frame: Data at Network Interface Layer Datagram: Data between routers Port Number: Numbers assigned to each protocol © 2015 Pearson Education Limited 2015. 0-54  Security Attacks – Malware (viruses, worms, Trojan horses, spyware, phishing software) – Denial of service (DoS) – Spam Protection – Firewalls – Spam filters – Proxy Servers – Antivirus software © 2015 Pearson Education Limited 2015. 4-55  Encryption HTTPS and SSL Public-key Encryption – Public key: Used to encrypt messages – Private key: Used to decrypt messages Certificates and Digital Signatures – Certificate authorities © 2015 Pearson Education Limited 2015. 4-56  Figure 4.16 Public-key encryption © 2015 Pearson Education Limited 2015. 4-57  End of Chapter © 2015 Pearson Education Limited 2015