42.444 Telecommunications: A Management Perspective

1. 42.444 Telecommunications: A Management Perspective The Internet: Addressing and Services Lecture 4 (Chapters 5) Dr Gerald Grant

2. Introduction • Internet is having a dramatic impact on the way we live our lives. • It is growing exponentially • Over 93 million hosts (Network Wizards Survey July 2000) Dr Gerald Grant

3. Internet Hosts (2000) Dr Gerald Grant

4. The Internet • Evolved from the ARPANET (1969) • The first operational packet-switching network which is different from traditional circuit (voice) and message (telegraph, telex) switching • Special properties • Transmitted data unit, the packet, is limited in length • When packets are passed from switch to switch they are stored in high-speed random access memory (RAM) • Advantages: • Delay is much shorter • Data can be transmitted at different rates • Offers adaptive routing Dr Gerald Grant

5. The Internet • Applications developed for the ARPANET • TELNET : provide a lingua franca for remote computer terminals • FTP : allowed the transparent transfer of files from one computer to the other over the network • Electronic mail • Tactical radio communication (packet radio) • Satellite communication (SATNET) • TCP/IP Dr Gerald Grant

6. The Internet National Science Foundation’ Role Acceptable use policies: • NSF backbone was originally limited to research, educational, and government use Internet Interconnection Points • Commercial information interchange (CIX) • US government privatized the national backbone in 1995 - internet was opened to virtually unlimited commercial activity • .com greater than .edu since then. Dr Gerald Grant

7. The Internet The world wide web • WWW prototype was developed at CERN (the European Laboratory for Particle Physics) by Tim Berners-Lee • First graphic oriented browser, Mosaic, developed at the NCSA center at the U. of Illinois. (Mark Andreason) • The web is a system consisting of an internationally distributed collection of multimedia files supported by clients and servers • Hyperlink : transfer from one file to the next • Hypertext Markup Language (HTML) : control the browser display layout • Hypertext Transfer Protocol (HTTP) : a communications protocol for use in TCP/IP networks for fetching the files from the appropriate servers as specified by the hyperlinks Dr Gerald Grant

8. The Internet Today • Connection alternatives: ISDN, ADSL, and cable modem • Connection alternatives for organizations: ISDN, T-1 circuit, T-3 circuit, Gigabit circuit • Electronic data interchange • Virtual private networks (VPN) • Security concern for online transaction • User privacy concerns Dr Gerald Grant

9. Internet Addressing IP header - 32 bit global internet address e.g. 192.228.17.57 Network classes • The address is coded to allow a variable allocation of bits to specify network and host • Three principal network classes • Class A : Few networks, each with many hosts (1-126) • 126 network numbers, 16.7 million hosts • Class B : Medium number of networks, each with a medium number of hosts (128-191) • 16, 384 networks, 16,536 hosts • Class C : Many networks, each with a few hosts (192-223) • 2.1 million networks, 256 hosts Dr Gerald Grant

10. Subnets • Single network number is assigned to all LANs • simplifies addressing and routing to the site • To allow routers on site to function properly each LAN on the site is assigned a subnet number • host portion of IP address partitioned into subnet number and host number • Local routers route on basis of subnet number • Subnet mask used to convert IP address into subnet number and host number Dr Gerald Grant

11. Example of Subnetworking Dr Gerald Grant

12. Internet Addressing Domain Name System • Internet Names and Addresses: • the 32-bit IP address, consisting of a network number and a host number, provides a way of uniquely identifying devices attached to the Internet • Two problems of this approach: • Routers devise a path through the Internet on the basis of the network number. Management of network tables cumbersome • The number scheme is effective for computer processing but is not convenient for users Dr Gerald Grant

13. Internet Addressing Domain • refers to a group of networks that are under the administrative control of a single entity, such as a company or government agency • a given domain may consist of a number of subordinate domains • names are assigned to domains and reflect the hierarchical organization • .ca domain for Canada • carleton.ca - Carleton University • business.carleton.ca - School of Business Dr Gerald Grant

14. Internet Governance • The Internet Corporation for Assigned Names and Numbers (ICANN) • “a technical coordination body for the Internet. Created in October 1998 by a broad coalition of the Internet's business, technical, academic, and user communities, ICANN is assuming responsibility for a set of technical functions previously performed under U.S. government contract by IANA and other groups.” • Canadian Internet Registration Authority (CIRA) • manages .ca domain • Began operation December 1, 2000 Dr Gerald Grant

15. New Top-level Domain Names • TLDPurpose • .aeroAir-transport industry • .bizBusinesses • .coopNon-profit cooperatives • .infoUnrestricted use • .museumMuseums • .nameFor registration by individuals • .proAccountants, lawyers, and physicians Dr Gerald Grant

16. Internet Addressing The DNS Database • The domain name system (DNS) is based on a hierarchical database containing records that include the name, IP address, and other information about hosts • Key features: • Variable-depth hierarchy • Distributed database • Distribution controlled by the database Dr Gerald Grant

17. DNS Operation • DNS lookup follows steps: • User program request IP address for domain • Resolver module in local host or ISP queries local name server • Name server checks local database and cache; if present, returns IP addressotherwise queries other nearby name servers • User program is given IP address or error message Dr Gerald Grant

18. Quality of Service • Best-effort scheme: A network or internet delivery technique that treats all packets equally. All packets are forwarded on a first-come-first-served basis. • Quality of service: A set of parameters that describe the quality of a specific stream of data Dr Gerald Grant

19. Quality of Service Internet Traffic • Two categories: • Elastic: • traditional type of traffic supported on TCP/IP based internet. The traffic can adjust, over wide ranges, to changes in delay and throughput across an internet and still meet the needs of its applications • applications: file transfer, electronic mail, remote logon, network management, and Web access Dr Gerald Grant

20. Quality of Service Internet Traffic • Two categories: • Inelastic: • does not easily adapt to changes in delay and throughput across an internet e.g. voice and video. • requirements: • throughput - minimum value required • delay - some applications are very sensitive • delay variation - larger allowable delay, longer real delay • packet loss -application vary in the amount of loss that can be sustained Dr Gerald Grant

21. Quality of Service The IPv4 Type of Service (TOS) Field • TOS Subfield • set by the source system to indicate the type or quality of service that should be provided for the datagram • three ways that the router can respond to the TOS value: • route selection • network service • queuing discipline Dr Gerald Grant

22. Quality of Service • Precedence Subfield • Set to indicate urgency or priority given to datagram • The precedence indicator ranges from the highest level of network control to the lowest level of routine • The network control level is intended for use only within a single network • The internetwork control level is intended for router-based control messages • Queue Service • Congestion Control Dr Gerald Grant