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Chapter 11 The Internet

Chapter 11 The Internet

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Chapter 11 The Internet

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  1. Data Communications and Computer Networks: A Business User’s Approach Chapter 11 The Internet

  2. This time Move up the OSI hierarchy • Internet • Apps • Protocols • XXXP

  3. The Internet Model

  4. Introduction Today’s present Internet is a vast collection of thousands of networks and their attached devices. The Internet began as the Arpanet during the 1960s. One high-speed backbone connected several university, government, and research sites. The backbone was capable of supporting 56 Kbps transmission speeds and eventually became financed by the National Science Foundation (NSF).

  5. Old NSFnet backbone & connecting midlevel and campus networks

  6. Brief History of the Internet (1) • 1964 - Packet switching network paper by Rand Corporation • 1969 - The DOD Advanced Research Projects Agency creates an experimental network called ARPANET • 1972 - Email programs sent • 1980s - ARPANET splits into two networks: ARPANET and MILNET • 1984 - Arpanet shut down and Internet resulted • 1987 - NSFnet Network service Center (NNSC)

  7. Brief History of the Internet (2) • 1993 -InterNIC formed replaced NNSC • 1993 - CERN releases the World Wide Web (WWW), developed by Tim Berners-Lee • 1993-1994 - The graphical web browsers Mosaic and Netscape Navigator are introduced • 1995 - NSF quits all support and backbone, and the Internet became commercially supported • 1996-present -Internet access increases rapidly among home, education and business users

  8. Brief History of the Internet (3) • Internet Growth in Nodes • 1969 - only 4 • 1983 - approximately 500 • 1989 - approximately 80,000 • 1997 - over 16 million • Now - over 370 million

  9. Internet Growth • http://www.netsizer.com/ • Hosts vs nodes Hosts – users connected to the internet 130 M (2001) • Nodes are all connected devices

  10. Internet Services • The Internet provides many types of services, including several very common ones: • File transfer protocol (FTP) • Remote login (Telnet) • Internet telephony • Electronic mail • World Wide Web • Streaming Video and Audio

  11. File Transfer Protocol (FTP) Used to transfer files across the Internet. User can upload or download a file. The URL for an FTP site begins with ftp://… The three most common ways to access an FTP site is: 1. Through a browser 2. Using a canned FTP program 3. Issuing FTP commands at a text-based command prompt.

  12. Remote Login (Telnet) Allows a user to remotely login to a distant computer site. User usually needs a login and password to remove computer site. User saves money on long distance telephone charges.

  13. Internet Telephony The transfer of voice signals using a packet switched network and the IP protocol. Also known as packet voice, voice over packet, voice over the Internet, and voice over Internet Protocol (VoIP). VoIP can be internal to a company or can be external using the Internet. VoIP consumes many resources and may not always work well, but can be cost effective in certain situations.

  14. Internet Telephony (VoIP) Three basic ways to make a telephone call using VoIP: 1. PC to PC using sound cards and headsets (or speakers and microphone) 2. PC to telephone (need a gateway to convert IP addresses to telephone numbers) 3. Telephone to telephone (need gateways)

  15. Internet Telephony (VoIP) Three functions necessary to support voice over IP: 1. Voice must be digitized (PCM, 64 Kbps, fairly standard) 2. 64 Kbps voice must be compressed (many standards here - ITU-T G.729A, used by AT&T, Lucent, others; G.723.1, used by Microsoft and Intel) 3. Once the voice is compressed, the data must be transmitted. Many different ways to do this.

  16. Internet Telephony (VoIP) How can we transport compressed voice? Streaming audio, such as Real Time Streaming Protocol (RTSP) and Microsoft’s Active Streaming Format (ASF) Resource Reservation Protocol (RSVP) - carries a specific QoS through the network, reserving bandwidth at every node. Operates at the transport layer. Internet Stream Protocol version 2 (ST2) - an experimental resource reservation protocol that operates at same layer as IP

  17. Electronic Mail • E-mail programs can create, send, receive, and store e-mails, as well as reply to, forward, and attach non-text files. • Multipurpose Internet Mail Extension (MIME) is used to send e-mail attachments. • Simple Mail Transfer Protocol (SMTP) is used to transmit e-mail messages. (uses port TCP port 25) • Email daemon always waiting to perform its function • Post Office Protocol version 3 (POP3) and Internet Message Access Protocol (IMAP) are used to hold and later retrieve e-mail messages.

  18. eMail Consists of 2 parts: User Agent: Allows users to create, edit, store and forward programs Message Transfer Agent: Prepares and transfers email message

  19. Electronic Mail Holders Post Office Protocol version 3 (POP3) and Internet Message Access Protocol (IMAP) are used to hold and later retrieve e-mail messages. POP allows you to save messages in your email box IMAP allows you to only view message heading and not download everything. Also permits mailboxs, search, etc.

  20. Listservs A popular software program used to create and manage Internet mailing lists. When an individual sends an e-mail to a listserv, the listserv sends a copy of the message to all listserv members. Listservs can be useful business tools for individuals trying to follow a particular area of study.

  21. Usenet A voluntary set of rules for passing messages and maintaining newsgroups. A newsgroup is the Internet equivalent of an electronic bulletin board system. Thousands of Usenet groups exist on virtually any topic.

  22. Streaming Audio and Video The continuous download of a compressed audio or video file, which can be heard or viewed on the user’s workstation. Real-time Protocol (RTP) and Real Time Streaming Protocol (RTSP) support streaming audio and video. Streaming audio and video consume a large amount of network resources.

  23. World Wide Web The World Wide Web (WWW) is a immense collection of web pages and other resources that can be downloaded across the Internet and displayed on a workstation via a web browser. Browser is the user agent. The most popular service on the Internet. Basic web pages are created with the HyperText Markup Language (HTML).

  24. World Wide Web While HTML is the language to display a web page, HyperText Transport Protocol (HTTP) is the protocol to transfer a web page. Many extensions to HTML have been created. Dynamic HTML is a very popular extension to HTML. Common examples of dynamic HTML include mouse-over techniques, live positioning of elements (layers), data binding, and cascading style sheets.

  25. World Wide Web – XML Extensible Markup Language (XML) is a description for how to create a document - both the definition of the document and the contents of the document. The syntax of XML is fairly similar to HTML. You can define your own tags, such as <CUSTOMER> which have their own, unique properties.

  26. e-Commerce and e-government The buying and selling of goods and services via the internet. Government transitions via the internet. e-commerce major areas: 1. e-retailing 2. Electronic Data Interchange (EDI) 3. Micro-marketing 4. Electronic security 5. Web services

  27. Security of Data Privacy of Data Business Policies Transaction Processing Integrity

  28. Security of Data • How secure is the data maintained by the business? • Personal/business entity data • data stored by a web site that is used by a trading partner to make transaction decision • How secure is the data as it is transmitted to and from this business?

  29. Business Policies • What are the business policies and practices of this business? • billing and payment policies • shipping policy • return policy • tax collection • additional policy information

  30. Transaction Processing Integrity • What procedures are in place to ensure that the transactions are handled as disclosed? • How does the company ensure that is does not lose orders placed? • How does the company ensure that it accurately processes bills and account information? • What controls exist to ensure that the company accurately posts payment in a timely fashion? • Does the company have controls in place to ensure that it ships the right inventory items and quantities?

  31. Privacy of Data • What is the privacy policy of the business? • What information does it keep? • How will the information collected be used by the business? • Will this business share or sell customer data without the customer’s permission or knowledge? • What ensures that the company’s privacy policies are observed and practiced on a continuous basis?

  32. Security Assurance Systems ensure that... • The transacting parties are authenticated - who they claim to be - a security issue • that electronic data are protected from unauthorized disclosure - a security issue

  33. Electronic Data Interchange... • is the electronic exchange of business documents between trading partners using a standardized format. • Traditional EDI • High start-up costs • Used primarily by large firms • Generally, even large firms could only connect with 20% of their trading partners

  34. Cookies and State Information A cookie is data created by a web server that is stored on the hard drive of a user’s workstation. This state information is used to track a user’s activity and to predict future needs. Information on previous viewing habits stored in a cookie can also be used by other web sites to provide customized content. Many consider cookies to be an invasion of privacy. www.cookiecentral.com

  35. Cookie Control Delete cookies after inserted Accept no or restricted cookies Change permissions www.cookiecentral.com

  36. Intranets and Extranets An intranet is a TCP/IP network inside a company that allow employees to access the company’s information resources through an Internet-like interface. When an intranet is extended outside the corporate walls to include suppliers, customers, or other external agents, the intranet becomes an extranet.

  37. Internet Protocols • To support the Internet and all its services, many protocols are necessary. • Some of the protocols that we will look at: • Internet Protocol (IP) • Transmission Control Protocol (TCP) • Address Resolution Protocol (ARP) • Domain Name System (DNS)

  38. Internet Protocols Recall that the Internet with all its protocols follows the Internet model. An application, such as e-mail, resides at the highest layer. A transport protocol, such as TCP, resides at the transport layer. The Internet Protocol (IP) resides at the Internet or network layer. A particular media and its framing resides at the interface layer.

  39. The Internet Model

  40. Network Layer • Responsible for creating maintaining and ending network connections. • Transfers a data packet from node to node within the network. • Message routing • Billing • Accounting

  41. Transport Layer • Provides an end-to-end, error-free network connection. • Makes sure the data arrives at the destination exactly as it left the source. • Makes sure all information is accounted for: • Missing information • Duplicated information

  42. The Internet Protocol (IP) IP prepares a packet called a datagram for transmission across the Internet. The IP header is encapsulated onto a transport data packet. The IP packet is then passed to the next layer where further network information is encapsulated onto it.

  43. Progression of a datagram packet from one network to another

  44. The Internet Protocol (IP) Using IP, a subnet router: Makes routing decision based on the destination address. May have to fragment the datagram into smaller datagrams (very rare) using Fragment Offset. May determine that the current datagram has been hopping around the network too long and delete it TTL (Time to Live).

  45. Format of the IP Datagram

  46. The Transmission Control Protocol (TCP) • The TCP layer creates a connection between sender and receiver using port numbers. • The port number identifies a particular application on a particular device (IP address). • ftp: 20 • smtp: 25 • http: 80 • TCP can multiplex multiple connections (using port numbers) over a single IP line.

  47. The Transmission Control Protocol (TCP) The TCP layer can ensure that the receiver is not overrun with data (end-to-end flow control) using the Window field. TCP can perform end-to-end error correction (Checksum). TCP allows for the sending of high priority data (Urgent Pointer).

  48. Fields of the TCP Header

  49. Internet Control Message Protocol (ICMP) ICMP, which is used by routers and nodes, performs the error reporting for the Internet Protocol. ICMP reports errors such as invalid IP address, invalid port address, and the packet has hopped too many times.

  50. Ping (Packet Internet Groper) ping command