Computer Communication - an introduction. Maria Kihl

Transcription

1 Computer Communication - an introduction Maria Kihl

2 Reading directives Forouzan 4th ed.: Chapter 1, Introductions of Chapters 26 and 27. Forouzan 5th ed: Chapter 1, 25.1, Introductions of Kihl: Kapitel 1, 8.8 2

3 Internet from your perspective

4 Internet from my perspective 4

5 Data communication After torches and smoke signals, the optical telegraph was invented in the 18th century. 5

6 Data communication Optical telegraphs evolved into electrical telegraphs, which quickly increased the available data communication speed and distance. 6

7 Telephone networks The need for telephone networks became obvious in the late 19th century... 7

8 Telephone networks The telephone networks were built on the idea of circuit switching. 8

9 Basics of circuit switching 9

10 Packet switched networks Several people proposed the idea of packet switched networks in the early 1960s. Source: 10

11 Basics of packet switching Source: 11

12 ARPAnet was developed in 1968 Robert Taylor at ARPA (later DARPA) had three terminals for connecting with different sites: For each of these three terminals, I had three different sets of user commands. So if I was talking online with someone at S.D.C. and I wanted to talk to someone I knew at Berkeley or M.I.T. about this, I had to get up from the S.D.C. terminal, go over and log into the other terminal and get in touch with them. I said, oh, man, it's obvious what to do: If you have these three terminals, there ought to be one terminal that goes anywhere you want to go where you have interactive computing. That idea is the ARPAnet. Source: 12

13 ARPAnet Four Interactive Message Processors (IMP) at four universities connected with leased lines of 50 kbps. The IMPs could store and forward messages. The picture shows Leonard Kleinrock with the first IMP at UCLA. Source: 13

14 Protocols To form a computer network, there must be standardized rules for the communication and host identification, which is called protocols. ARPAnet used a network protocol called the 1822 protocol. It defined how IMPs could communicate and forward messages. Also, each host computer had a numeric address. Also, the Network Control Protocol (NCP) enabled several applications on the same host. 14

15 ARPAnet evolution 15

16 Client/Server paradigm Basically all early applications were based on the client/server paradigm. Reply Request 16

17 Telnet Telnet was invented in 1969, and provided access to a remote terminal. Terminal driver TELNET, klient TELNET, server Pseudoterminal driver Local computer Network Applications 17

18 Ray Tomlinson sent the first in 1971 between two computers in the same room. To separate a specific user on a host computer, he used sign, which was unused on the keyboard. 18

19 Today, basically works the same way: Source: 19

20 File Transfer Protocol (FTP) Another original application was FTP, which was devloped in 1971, and that enabled file transfer between two host computers. Source: 20

21 Internet protocol In 1973, Robert E. Kahn and Vincent Cerf at DARPA developed the ideas of an internetwork protocol that made it possible for hosts on different networks to communicate with each other. The ideas were defined as the Transmission Control Protocol (TCP) protocol in 1974, where the term Internet was introduced. Later, some parts of the TCP protocol were moved to the Internet protocol (IP), creating the TCP/IP protocol suite. 21

22 Basic idea of Kahn and Cerf s internetworking Host identification (Addresses) Forwarding of messages between networks (routing) End-to-end reliability (error and flow control) Network Network Network 22

23 Internet was born The Internet protocol suite was formalized in Jan , all networks connected to the Internet had to use the TCP/IP protocol suite. 23

24 1991: World Wide Web (WWW) : Tim Berners-Lee and his group at CERN worked on the ideas of information presentation and sharing. 1990: HyperText Transfer Protocol (HTTP), HyperText Markup Language (HTML), a web browser, and server software were presented at CERN. 1991: WWW goes public 1993: Mosaic, the first public web browser was presented. Source: 24

25 First web site: The first web site is still working. WWW is based on a simple client/server protocol HTTP, where clients send requests for pages to the web server. 25

26 1991: The Trojan Coffee room pot The people working at the Computer Laboratory at the University of Cambridge implemented the first real-time Internet video application for their coffee pot. The application server sent real-time images of the coffee pot to the clients. Source: 26

27 The rest is almost not history 1994: Pizza Hut started first online webshop 1997: AOL instant messanger 1997: Sixdegrees.com (first modern social network) 1997: Google.com 1999: Napster 2001: BitTorrent 2003: Skype 2005: YouTube 2005: Facebook.com 2008: Spotify 27

28 Peer-to-peer paradigm Several of the modern Internet applications are based on the Peer-to-peer (P2P) paradigm. 28

29 Example: Skype Source: 29

30 Me: Maria Kihl, Associate Professor at Dept. of Electrical and Information technology MSc in Computer Science and Engineering (D88) PhD in Communication Systems, 1999 Research leader for several projects with focus on Performance of Content-based Internet applications and architectures. Strong academic collaboration with Dept. of Automatic Control and Acreo AB Industry collaborations with Ericsson, TeliaSonera, TV4, SVT, Spotify, Procera Networks, etc. 30

31 Evolution of Internet usage (traffic volumes) seen from the users 2007: 2011: J. Li, A. Aurelius, V. Nordell, M. Du, Å. Arvidsson, M. Kihl: A five year perspective of traffic pattern evolution in a residential broadband access network Future Network & Mobile Summit

32 Content distribution architectures Media content is stored in back-end server clusters (cloud) and then distributed to clients when requested. Internet Content Clients 32

33 Example:Live sport channel at TV4 Production Transmissi on control IP multicast network Encoding Encryption Ingest servers Origin servers (http) Speakers Ingest servers (http) Content Distribution Network (CDN) Cache servers (http) National ISP Access network Modem PC / CE device (TV / bluray) 33

34 Performance challenges Client/server archictures are usually deployed: Standardized protocols as HTTP are used. Control of the material. Client/server archtectures cause performance problems: Heavy traffic loads on network infrastructure (unicast transmission). Delays due to centralized data centers and overloaded access networks. 34

35 One solution: P2P and caches (Spotify) Source: 35

36 Impact of using caches and P2P (Spotify) Source: 36

37 Internet from your perspective

38 Internet from my perspective 38

39 Course objectives Introduction to computer communication and networking, with focus on the Internet. Digital communication Network access Internet protocols Routing Mobile networks Hands-on experience in two laboratory sessions. 39

40 Course content? 10 lectures 6 problem solving classes 2 mandatory laboratory sessions One volontary midterm exam Final exam: 23/10 40

41 Course material Main textbook: Data Communications and Networking 4th ed. by B.A. Forouzan. Alternative textbook (in Swedish) Datakommunikation en inledande översikt by M. Kihl. This book is used together with the extra matreial by J.A. Andersson sold at KFS. Material for the problem solving classes and laboratory sessions sold at KFS. 41

42 Lectures Mondays 10-12, Aulan Wednesday 8-10, E:A 10 lectures, please look at the schedule for exact dates! 42

43 Problem solving classes 6 groups: Monday 15-17, E:1409 Tuesday 10-12, E:1409 Tuesday 15-17, E:3319 Thursday 8-10, E:1409 Thursday 13-15, E:1409 Thursday 15-17, E:3318 The problem solving classes start next week. 43

44 Laboratory sessions Two mandatory laboratory sessions: Week 4-5: Point to Point Protocol (PPP) Week 6-7: Networking You need to sign up for each laboratory session on the web. Before the lab you need to do the preparations. You need to pass a written test! 44

45 Midterm exam There is one voluntary midterm exam Monday 1/10 in Aulan. The midterm exam is worth max 20 credits that can be used for the final exam. Content: Lectures 1-6 Problem solving classes

46 Final exam The final exam is given 23/10 at in Victoria stadium. The final exam is worth 100 credits, 50 credits are needed to pass the exam. 46

47 International student? The lectures will be given in Swedish. All material is in English. Also, Q&A sessions may be organized if needed. If you need any help, please Maria Kihl, 47

48 Previous knowledge? Read through the old exam Classify yourself as between 1-5 where 1 = knows very little 5 = knows a lot Write down your classification on the piece of paper and hand in. 48