1	Chapter Eleven The Internet CS 320 Data Communications
2	After reading this chapter, you should be able to: Discuss the responsibilities of the Internet Protocol (IP) and how IP can be used to create a connection between networks Discuss the responsibilities of the Transmission Control Protocol (TCP) and how it can be used to create a reliable, end-to-end network connection Identify the relationships between TCP/IP and the protocols ICMP, UDP, ARP, DHCP, NAT, and tunneling protocols
3	After reading this chapter, you should be able to (continued): Cite the basic features of HTML, dynamic HTML, and XML, and describe how these three languages differ from one another Describe the responsibility of the Domain Name System and how it converts a URL into a dotted decimal IP address Describe the major Internet applications and services
4	After reading this chapter, you should be able to (continued): Discuss the business advantages of the World Wide Web Recognize that the Internet is constantly evolving and that IPv6 and Internet2 demonstrate that evolution
5	Introduction Today’s present Internet is vast collection of thousands of networks and their attached devices The Internet began as ARPANET during the 1960s One high-speed backbone connected several university, government, and research sites Backbone was capable of supporting 56 kbps transmission speeds and eventually became financed by the National Science Foundation (NSF)
6	Introduction (continued)
7	Old Major ISP Maps
8	Internet Map by ISP
9	Internet Map 2005
10	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) Dynamic Host Configuration Protocol (DHCP) Network Address Translation (NAT)
11	Internet Protocols (continued) Recall that the Internet with all its protocols follows the TCP/IP protocol suite (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 network access (or data link) layer
12	Internet Protocols (continued)
13	The Internet Protocol (IP) IP prepares a packet 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
14	The Internet Protocol (IP) (continued)
15	The Internet Protocol (IP) (continued) Using IP, a router: Makes routing decisions based on the destination address May have to fragment the datagram into smaller datagrams (rare today) using Fragment Offset May determine that current datagram has been hopping around the network too long and delete it (Time to Live)
16	The Internet Protocol (IP) (continued)
17	Types of Internet Packets
18	The Transmission Control Protocol (TCP) TCP layer creates connection between sender and receiver using port numbers The port number identifies a particular application on a particular device (IP address) TCP can multiplex multiple connections (using port numbers) over a single IP line
19	The Transmission Control Protocol (TCP) (continued) 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
20	The Transmission Control Protocol (TCP) (continued)
21	Internet Control Message Protocol (ICMP) ICMP Used by routers and nodes Performs 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
22	User Datagram Protocol (UDP) A transport layer protocol used in place of TCP Where TCP supports a connection-oriented application, UDP is used with connectionless applications UDP also encapsulates a header onto an application packet but the header is much simpler than TCP
23	Address Resolution Protocol (ARP) When an IP packet has traversed the Internet and encounters the destination LAN, how does the packet find the destination workstation? Even though destination workstation may have an IP address, a LAN does not use IP addresses to deliver frames A LAN uses MAC layer address ARP translates IP address into MAC layer address so frame can be delivered to proper workstation
24	Dynamic Host Configuration Protocol (DHCP) An IP address can be assigned to a workstation permanently (static assignment) or dynamically Dynamic IP address assignment is a more efficient use of scarce IP addresses When DHCP client issues an IP request, DHCP server looks in its static table If no entry exists, server selects an IP address from available pool
25	Dynamic Host Configuration Protocol (DHCP) (continued) The address assigned by DHCP server is temporary Part of agreement includes specific period of time If no time period specified, the default is one hour DHCP clients may negotiate for a renewal before the time period expires
26	Network Address Translation (NAT) NAT lets router represent entire local area network to Internet as single IP address Thus, all traffic leaving LAN appears as originating from global IP address All traffic coming into this LAN uses this global IP address This security feature allows a LAN to hide all the workstation IP addresses from the Internet
27	Network Address Translation (NAT) (continued) Since the outside world cannot see into LAN, you do not need to use registered IP addresses on inside LAN We can use the following blocks of addresses for private use: 10.0.0.0 – 10.255.255.255 172.16.0.0 – 172.31.255.255 192.168.0.0 – 192.168.255.255
28	Network Address Translation (NAT) (continued) When a user on inside sends packet to outside, the NAT interface changes the user’s inside address to global IP address This change is stored in a cache When the response comes back, the NAT looks in cache and switches the addresses back If not the packet is dropped Unless NAT has a service table of fixed IP address mappings This service table allows packets to originate from the outside
29	Tunneling Protocols and Virtual Private Networks (VPNs) The Internet is not normally a secure system If person wants to use Internet to access corporate computer system, how can a secure connection be created? One possible technique is by creating a virtual private network (VPN) VPN creates a secure connection through the Internet by using a tunneling protocol
30	The World Wide Web The World Wide Web (WWW) – immense collection of web pages and other resources that can be downloaded across the Internet and displayed on a workstation via a web browser and is the most popular service on the Internet Basic web pages are created with the Hypertext Markup Language (HTML) Hypertext Transport Protocol (HTTP) is protocol to transfer a web page
31	Locating a Document on the Internet Every document on the Internet has a unique Uniform Resource Locator (URL) All URLs consist of four parts: Service type Host or domain name Directory or subdirectory information Filename
32	Locating a Document on the Internet (continued)
33	Locating a Document on the Internet (continued) When a user, running a Web browser, enters a URL, how is URL translated into an IP address? Domain Name System (DNS) – large, distributed database of URLs and IP addresses The first operation performed by DNS is to query a local database for URL/IP address information If local server does not recognize address, the server at next level will be queried Eventually root server for URL/IP addresses will be queried If root server has answer, results are returned If root server recognizes domain name but not extension in front of domain name, root server will query server at domain name’s location When domain’s server returns results, they are passed back through chain of servers (and their caches)
34	IP Addresses All devices connected to Internet have 32-bit IP address associated with them Think of the IP address as a logical address (possibly temporary), while the 48-bit address on every NIC is the physical, or permanent address Computers, networks and routers use the 32-bit binary address, but a more readable form is the dotted decimal notation
35	IP Addresses (continued) For example, the 32-bit binary address 10000000 10011100 00001110 00000111 translates to 128.156.14.7 in dotted decimal notation
36	IP Addresses (continued) When IP addresses were originally created, they were called classful addresses That is, each IP address fell into particular class A particular class address has a unique network address size and a unique host address size There are basically five types of IP addresses: Classes A, B, C, D and E
37	IP Addresses (continued)
38	IP Addresses (continued) When you examine the first decimal value in the dotted decimal notation: All Class A addresses are in the range 0 - 127 All Class B addresses are in the range 128 - 191 All Class C addresses are in the range 192 - 223
39	IP Addresses (continued) Today, IP addresses are considered classless addresses With classless addressing, companies (users) do not apply for particular class of addresses Instead, company will get its IP addresses from an Internet service provider (ISP) Most ISPs have already applied for a large number of IP addresses and are willing to lease those addresses to companies
40	IP Addresses (continued) Example – instead of applying for two Class C addresses, a company could contact an ISP, which would lease 500 IP addresses to the company The addresses are not identified by any class – they are simply a contiguous block of IP addresses Classless addressing has led to a much more efficient allocation of the IP address space A company can lease only as many addresses as it needs
41	IP Addresses (continued) IP subnet masking Sometimes you have a large number of IP addresses to manage By using subnet masking, you can break the host ID portion of the address into a subnet ID and host ID Example – subnet mask 255.255.255.0 applied to a class B address will break the host ID (normally 16 bits) into an 8-bit subnet ID and an 8-bit host ID
42	Creating Web Pages As mentioned earlier, HTML is basic language used to create Web pages 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
43	Creating Web Pages (continued)
44	Creating Web Pages (continued)
45	Creating Web Pages (continued) 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 Syntax of XML is fairly similar to HTML You can define your own tags, such as <CUSTOMER> which have their own, unique properties
46	Internet Services The Internet provides many types of services, including several very common ones: Electronic mail (e-mail) File transfer protocol (FTP) Remote login (Telnet) Internet telephony Listservs Usenet Streaming audio and video Instant Messaging
47	Electronic Mail (e-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 Post Office Protocol version 3 (POP3) and Internet Message Access Protocol (IMAP) are used to hold and later retrieve e-mail messages
48	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 are: Through a browser Using a canned FTP program Issuing FTP commands at a text-based command prompt
49	Remote Login (Telnet) Allows a user to remotely log in to a distant computer site User usually needs a login and password to access a remote computer site User saves money on long-distance telephone charges
50	Voice Over IP The transfer of voice signals using a packet-switched network and the IP protocol Voice over IP (VoIP) can be internal to a company (private VoIP) 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
51	Voice Over IP (continued) Three basic ways to make a telephone call using VoIP: PC to PC using sound cards and headsets (or speakers and microphone) PC to telephone (need a gateway to convert IP addresses to telephone numbers) Telephone to telephone (need gateways)
52	Voice Over IP (continued) Three functions necessary to support VoIP: Voice must be digitized (PCM, 64 kbps, fairly standard) 64 kbps voice must be compressed Once the voice is compressed, the data must be transmitted
53	Voice Over IP (continued) How can we transport compressed voice? H.323 Created in 1996 by ITU-T Actually, H.323 created for a wide range of applications both audio and video, and not for TCP/IP networks Session Initiation Protocol (SIP) Created by IETF specifically for supporting the transfer of voice over the Internet Many feel SIP will surpass H.323
54	Voice Over IP (continued) ENUM A protocol that supports VoIP Converts telephone numbers to fully qualified domain name addresses Example – telephone number (312) 555-1212 will be converted to 2.1.2.1.5.5.5.2.1.3.1.e164.arpa
55	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
56	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
57	Instant Messaging Allows a user to see if people are currently logged in on the network and to send short messages in real time Consumes less resources than e-mail, and faster Numerous Internet service providers such as America Online, Yahoo!, and Microsoft MSN offer instant messaging
58	The Internet and Business E-Commerce – the buying and selling of goods and services via the Internet Many agree that e-commerce consists of four major areas: E-retailing Electronic data interchange (EDI) Micro-marketing Internet security
59	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
60	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
61	The Future of the Internet Various Internet committees are constantly working on new and improved protocols Examples include: Internet Printing Protocol Internet fax Extensions to FTP Common Name Resolution Protocol WWW Distributed Authoring and Versioning
62	IPv6 The next version of the Internet Protocol Main features include: Simpler header 128-bit IP addresses Priority levels and quality of service parameters No fragmentation
63	IPv6 (continued)
64	Internet2 A new form of the Internet is being developed by a number of businesses and universities Internet2 will support very high-speed data streams Applications might include: Digital library services Tele-immersion Virtual laboratories
65	The Internet In Action: A Company Creates a VPN A fictitious company wants to allow 3500 of its workers to work from home If all 3500 users used a dial-in service, the telephone costs would be very high
66	The Internet In Action: A Company Creates a VPN (continued)
67	The Internet In Action: A Company Creates a VPN (continued) Instead, the company will require each user to access the Internet via their local Internet service provider This local access will help keep telephone costs low Then, once on Internet, company will provide software to support virtual private networks The virtual private networks will create secure connections from the users’ homes into the corporate computer system
68	The Internet In Action: A Company Creates a VPN (continued)
69	Corporate VPN’s
70	Why Use a VPN?
71	Types of VPN’s
72	VPN Security
73	Firewalls
74	Encryption
75	IPSEC
76	How IPSEC Works
77	Tunneling
78	Remote Access Tunneling
79	P2P Tunneling
80	Making Connection
81	Establishing Connection
82	Summary To support Internet, many protocols, such as IP, TCP, ICMP, UDP, ARP, DHCP, and NAT, are necessary Tunneling protocols allow a company to create virtual private network connections into a corporate computing system World Wide Web is vast collection of electronic documents containing text and images that can be accessed by simply clicking link within browser’s Web page To locate document on Internet, you usually refer to its Uniform Resource Locator (URL)
83	Summary (continued) Internet consists of many commonly used network applications E-commerce is the buying and selling of goods and services electronically Cookies store state information on user’s hard drive and provide a way for Web sites to track a user’s Web-browsing patterns and preferences
84	Summary (continued) Intranet is in-house Internet with Web-like services that are available only to a company’s employees or to customers and suppliers through an extranet Internet continues to evolve, with new Internet Protocol version 6 as well as a completely new, higher-speed Internet2