CE80N Introduction to Networks & The Internet

1. CE80NIntroduction to Networks&The Internet Dr. Chane L. Fullmer UCSC Winter 2002

2. Class Details • Web Search Assignment due today. • Midterm on Thursday. • Up to 50 questions.. (multiple choice) • Taken from book, lectures and glossary • Section times.. Wed 7:30PM • Web page submission: • Email to venkat@cse.ucsc.edu • Subject: cmpe080n-assgn4 CE80N -- Lecture #8

3. Grading Schedule CE80N -- Lecture #8

4. Today’s Reading • Chapter 17 – • Clients + Servers = Distributed Computing • Chapter 18 – • Names For Computers CE80N -- Lecture #8

6. Master/Slave Networking • Early computers were large and expensive. • One computer per company • Controlling I/O devices at remote sites. • Master-Slave networking. CE80N -- Lecture #8

7. Small Computer Use Networks To Interact • Personal computers had processing power and acted independently. • Resulting in: • Peer-to-peer networking • Distributed computing CE80N -- Lecture #8

8. Peer-to-Peer Networking • Peer-to-Peer networking permit communication among computers in which all computers are equal. CE80N -- Lecture #8

9. Distributed Computing • Distributed computing is any interaction that involves two or more computers communicating over a network. CE80N -- Lecture #8

10. Distributed Computing On The Internet • The Internet offers an amazing diversity of services. • Sending messages • Retrieving files • Printing documents • Also, diversity of styles of interaction. • Interacting with humans • Interacting with a computer program CE80N -- Lecture #8

11. Client-Server Computing • Despite the diversity of services and differences in their use, all are client-server. CE80N -- Lecture #8

12. Three Basic Facts • Programs communicate. • TCP/IP does not create or run application programs. • Computers can run multiple programs. CE80N -- Lecture #8

13. Programs Are Clients Or Servers • Any program that offers a service is a server; any program that contacts a service is a client. CE80N -- Lecture #8

14. A Server Must Always Run • A server program must always be ready to receive requests. • Server software starts and runs automatically. CE80N -- Lecture #8

17. People Prefer Names To Numbers • Names are preferred for computers instead of IP addresses. • This is possible by: • Allowing users to name their machine • Allowing users to enter alphabetic name for their IP address • Providing a service that translates an alphabetic name to a numeric address CE80N -- Lecture #8

18. Naming A Computer Can Be Difficult Or Fun • A name creates a sense of personality. • Can reflect the role of the computer • Mail • Smtp • Can reflect the name of the owner • John • Can reflect a naming scheme (aka “naming convention”) • I.e., chemical gases • Hydrogen, Helium, Argon, …. CE80N -- Lecture #8

19. Figure 18.1 The fifty most common names assigned to computers on the Internet in 2000.

20. Computer Names Must Be Unique • Each computer on the Internet must have a unique name. • The Internet uses a familiar idea. • Extends name by adding strings • Appends a suffix to the name • Qualifies each name by giving the type of organization CE80N -- Lecture #8

21. Names With Many Parts • The Internet naming scheme allows names to contain multiple parts. • Permits organizations to add additional parts such as: • Groups • Departments • Locations • www.cc.purdue.edu • www.soe.ucsc.edu CE80N -- Lecture #8

22. Domain Names Outside The US • Most countries append a two-letter code to the domain name. • Allows for alternative schemes • jp = Japan • uk = United Kingdom • Recognized internationally CE80N -- Lecture #8

23. Translating A Name To An Equivalent IP Address • Internet communication software must use IP addresses to send and receive datagrams. • Translates names to IP addresses automatically • Called the Domain Name System (DNS) CE80N -- Lecture #8

24. Computer Name Lookup Is Automatic Figure 18.2 To communicate with a remote computer, an application program asks a local domain name server for the remote computer’s IP address If the local domain name does not know the answer, it contacts a remote domain server automatically. Numbers on the arrows tell the order of the four step taken. CE80N -- Lecture #8

25. IP Addresses And Domain Names Are Unrelated • Domain names resemble IP addresses. • Can be deceiving • Look similar • An IP address is a 32 bit number divided into 4 parts. • A domain name may contain multiple parts. CE80N -- Lecture #8

26. Software Network Tools • Nslookup: • Converts name  IP address • > nslookup mit.edu • > nslookup 18.7.21.69 • Traceroute (tracert in windows) • Traces path between hosts • Displays delay along path • > tracert mit.edu • > tracert 18.7.21.69 CE80N -- Lecture #8

27. Summary • Distributed Computing Paradigm (Client-Server) • Programs communicate • TCP/IP does not create/run programs • Computers can run multiple programs • Clients contact servers • Servers always run 24/7… CE80N -- Lecture #8

28. Summary • Computer naming … • Must be unique across the Internet • Name prefix added to domain suffix • Domain Name System (DNS) provides translations between names and IP address • Names are similar in style, but not directly related to IP address CE80N -- Lecture #8

29. Glossary • Client • A program that uses the Internet to contact a remote server • Client-Server Computing • The interaction between two programs when they communicate across a network CE80N -- Lecture #8

30. Glossary • Distributed Computing • Computations involving more than one computer • Peer-to-Peer Networking • Any network system in which all computers are equal • Server • A program that offers a service CE80N -- Lecture #8

31. Glossary • Domain Name • The name assigned to a computer on the Internet. A single computer’s name can contain several strings separated by periods. • Domain Name System • (DNS) The Internet service used to look up a computer’s name and find the computer’s IP address. CE80N -- Lecture #8

33. Midterm Review

34. The Telephone Network • Telephone analogy used for Internet development • 1876: Alexander Graham Bell obtains patent for the telephone • 1927: Commercial telephone service by radio between New York and London opens for the first time • Provides Universal Service • Ubiquitous • Designed for voice transmission CE80N -- Lecture #8

35. Digital to Analog • Analog is easy, but prone to distortion • Digital is distortion free, but lossey • Computers use binary numbers to encode digital information • ASCII encodes characters • Sampling.. • Nyquist theorem • Quantization • Introduces lossiness (quantization error) CE80N -- Lecture #8

36. Digital Telephone Network • Circuit switched • circuit is limited to 64 kbps • wasteful when idle • unsuitable for multimedia services • Telephone network is now digital • Multiplexed – TDMA • DS0, DS1 = 24 DS0, DS2 = 4 DS1….. CE80N -- Lecture #8

37. Introduction to Networks • Modulation of signals • Modulator/Demodulator -- Modem • Encoding of data to binary • ASCII • Error detection • Parity, checksum • LAN Technology • Easy, cheap, reliable CE80N -- Lecture #8

38. The Early Years • The Internet began as an ARPA research project. • The TCP/IP protocol software was developed to make the Internet operational. • The Internet is an Open System, with the technology freely available to all. • The Internet documentation is available on-line in the form of reports known as RFCs. CE80N -- Lecture #8

39. The Early Years • BSD UNIX distributed TCP/IP suite freely to universities in the early 80s • 1982 US Military adopted TCP/IP as primary communication standard • Exponential growth from its inception • IAB formed to coordinate development • IETF - major technical development body • Working groups CE80N -- Lecture #8

40. The Early Years • 1988 – NSFNET Backbone • 1992 – Privatization (ANSNET) • Exponential growth from its inception • Half of the users today have been there less than one year…… • IP Address 32 bit limitation CE80N -- Lecture #8

41. The Global Internet • Email was the first killer app. • EBONE brought Europe to the Internet • 1997 – Every continent is connected • 1998 – Every populated country is connected • The Internet is the new infrastructure • TCP/IP is the key to how the Internet works. CE80N -- Lecture #8

42. How Does the Network Work? • Circuit Switching • Reserves resources • Packet Switching • Shares resources • Increased overhead – headers • Packets are labeled with destination info • Efficient – resources used as needed • Unreliable – packets can be dropped CE80N -- Lecture #8

43. How Does the Network Work? • Packet Switching • Store and Forward • Packets move one hop at a time • Decisions are made at each hop • Delay .. • Processing delay • Queueing delay • Transmission delay • Propagation delay CE80N -- Lecture #8

44. How Does the Network Work? • A router is used to interconnect networks • LANs to LANs or LANs to WANs • Routers forward packets from one network to another • Process is called Routing • Routers are the building blocks of the Internet CE80N -- Lecture #8

45. How Does the Network Work? • ISPs provide the connection service to access the Internet • “The Last Mile” • Dialup • ADSL • Cable modem • Wireless • Also may provide email, web space or other services CE80N -- Lecture #8

46. IP & Routing • Protocols and protocol stack • Internet stack, OSI stack • Layering model • IP addressing • Class-based vs. CDIR • IP forwarding • Routing • Link State • Distance Vector CE80N -- Lecture #8

47. Principles behind transport layer services: multiplexing/demultiplexing reliable data transfer flow control, congestion control Instantiation and implementation in the Internet UDP, unreliable delivery TCP, reliable with control Transport Layer CE80N -- Lecture #8

48. See you Thursday! CE80N -- Lecture #8