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Feb. 4., 2002. Kåre J. KristoffersenNetworks and Protocols - Introduction1 Networks and Protocols - What is really going on when we send emails and surf.

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Presentation on theme: "Feb. 4., 2002. Kåre J. KristoffersenNetworks and Protocols - Introduction1 Networks and Protocols - What is really going on when we send emails and surf."— Presentation transcript:

1 Feb. 4., Kåre J. KristoffersenNetworks and Protocols - Introduction1 Networks and Protocols - What is really going on when we send s and surf the web?

2 Feb. 4., Kåre J. KristoffersenNetworks and Protocols - Introduction2 The Book: Computer Networking A Top-Down Approach Featuring the Internet, by James F. Kurose og Keith W. Ross, Addison-Wesley Longman, Inc., se Kan købes på IT-Højskolen d. 6. – 7. Feb 2002 i lokale 1.05 fra til Pris: Kr. 645,-

3 Feb. 4., Kåre J. KristoffersenNetworks and Protocols - Introduction3 Excercises and Instructors Rooms: 3.15 and 3.16, Glentevej 67. Monday Afternoon (13:00 – 15:30): Anders Ejlev, Monday Evening (19:00 – 21:30): Sune Kloppenborg Jeppesen,

4 Feb. 4., Kåre J. KristoffersenNetworks and Protocols - Introduction4 Examination – June min individual oral examn without preparation, judged using the, Dansih 13-scale, external censor. It is allowed to bring a disposition (one sheet of A4 paper for each question) The book will be available at the exam.

5 Feb. 4., Kåre J. KristoffersenNetworks and Protocols - Introduction5 Outline feb What is the internet? 2.What is a Protocol? 3.Connection-Oriented service. 4.Connectionless service. 5.Multiplexing. 6.Message switching (demo). 7.Packet switching (demo). 8.Routing. 9.Access Networks. 10.Delay and Packet loss i a network. 11.Protocol Layering. 12.Course overview.

6 Feb. 4., Kåre J. KristoffersenNetworks and Protocols - Introduction6 Some Internet Applications Streaming multimedia www File transfer Internet telephony

7 Feb. 4., Kåre J. KristoffersenNetworks and Protocols - Introduction7 Some pieces of the Internet

8 Feb. 4., Kåre J. KristoffersenNetworks and Protocols - Introduction8 A service description The Internet: Allows distributed applications running on it’s end systems to exchange data with each other. Provides a connection-oriented and a connectionless service. Makes no promises about time of delivery.

9 Feb. 4., Kåre J. KristoffersenNetworks and Protocols - Introduction9 What is a protocol? A human protocol and a computer network protocol.

10 Feb. 4., Kåre J. KristoffersenNetworks and Protocols - Introduction10 Definition (protocol): A protocol defines the format and the order of messages exchanged between two or more communicating entities, as well as the actions taken on the transmission and/or receipt of a message or other event.

11 Feb. 4., Kåre J. KristoffersenNetworks and Protocols - Introduction11 End systems, Clients and Servers

12 Feb. 4., Kåre J. KristoffersenNetworks and Protocols - Introduction12 Connection-Oriented Service 1.Initial handshake. 2.Reliable data transfer, using acknowledgements. 3.Flow Control. 4.Congestion Control. Note: The Transmission Control Protocol (TCP) implements a connection- oriented service. Used by: , www, FTP, Telnet.

13 Feb. 4., Kåre J. KristoffersenNetworks and Protocols - Introduction13 Connectionless Service 1.No Initial handshake. 2.Unreliable data transfer. 3.No Flow Control. 4.No Congestion Control. Used by: audio on demand, intertenet telephony, … Note: The User Datagram Protocol (UDP) implements a connectionless service.

14 Feb. 4., Kåre J. KristoffersenNetworks and Protocols - Introduction14 The Network Core

15 Feb. 4., Kåre J. KristoffersenNetworks and Protocols - Introduction15 How to share a communication link? 1.In Curcuit switching (e.g. ordinary telephone) a curcuit is reserved for the duration of the session. 2.In Packet switching (e.g. internet) the ressource is used on demand. Note: Sharing is called Multiplexing.

16 Feb. 4., Kåre J. KristoffersenNetworks and Protocols - Introduction16 Multiplexing (FDM) Frequency-division multiplexing (FDM): Each Connection gets 4 KHz of the total frequency spectrum.

17 Feb. 4., Kåre J. KristoffersenNetworks and Protocols - Introduction17 Multiplexing (TDM) Time-division Multiplexing: Each connection get one slot in each Frame. Frame

18 Feb. 4., Kåre J. KristoffersenNetworks and Protocols - Introduction18 Multiplexing for Packetswitching.

19 Feb. 4., Kåre J. KristoffersenNetworks and Protocols - Introduction19 Message Switching

20 Feb. 4., Kåre J. KristoffersenNetworks and Protocols - Introduction20 Packet switching

21 Feb. 4., Kåre J. KristoffersenNetworks and Protocols - Introduction21 Example: Message Switching

22 Feb. 4., Kåre J. KristoffersenNetworks and Protocols - Introduction22 Example: Packet Switching

23 Feb. 4., Kåre J. KristoffersenNetworks and Protocols - Introduction23 Demo: Packet Switching Run the JAVA Applet on:

24 Feb. 4., Kåre J. KristoffersenNetworks and Protocols - Introduction24 Break Table Tennis Table soccer

25 Feb. 4., Kåre J. KristoffersenNetworks and Protocols - Introduction25 Routing: Virtual Curcuit Networks Incoming InterfaceIncoming VC#Outgoing InterfaceOutgoing VC# ………… VC number translation table for PS1:

26 Feb. 4., Kåre J. KristoffersenNetworks and Protocols - Introduction26 Routing: Datagram Networks Tom Jones(name) Walnut Street 421 (street) Philadelphia(city) Pennsylvania (state) USA(country) Using: Hierarchical adresse, e.g:

27 Feb. 4., Kåre J. KristoffersenNetworks and Protocols - Introduction27 Access Networks and Physical Media Residental access networks Institutional access networks Mobile access networks

28 Feb. 4., Kåre J. KristoffersenNetworks and Protocols - Introduction28 Residental Access Networks Modem (telephone line, e.g. 56 kbps) ISDN, 128 kbps ADSL, up to 8Mbps using frequency Multiplexing - A high speed downstream channel 50 kHz – 1 MHz - A medium-speed upstream channel 4 kHz – 50 kHz - Ordinary telephone 0 – 4 kHz.

29 Feb. 4., Kåre J. KristoffersenNetworks and Protocols - Introduction29 HFC: Hybrid Fiber coaxial cable Note: Cable modem needed! Note: HFC is a shared broadcast medium.

30 Feb. 4., Kåre J. KristoffersenNetworks and Protocols - Introduction30 Company Access Networks A Local Area Network (LAN) is used to connect end systems to an edge router. Ethernet: A shared medium using twisted-pair copper wire or coaxial cable.

31 Feb. 4., Kåre J. KristoffersenNetworks and Protocols - Introduction31 Mobile Access AP = Access Point.

32 Feb. 4., Kåre J. KristoffersenNetworks and Protocols - Introduction32 Delay and packet-loss Delay through router A: - nodal processing delay+ - Queuing delay + - Transmission delay+ - Propagation delay

33 Feb. 4., Kåre J. KristoffersenNetworks and Protocols - Introduction33 Traffic intensity Packet size: L bits Transmission Rate: R bits/second Average packet arrival: a packets / second Traffic intensity: La/R Hopefully: Traffic intensity < 1 If Traffic Intensity > 1 then queue will overflow and packets are lost.

34 Feb. 4., Kåre J. KristoffersenNetworks and Protocols - Introduction34 Average Queuing Delay (Traffic Intensity)

35 Feb. 4., Kåre J. KristoffersenNetworks and Protocols - Introduction35 Protocol Layering PDU = Protocol Data Unit.

36 Feb. 4., Kåre J. KristoffersenNetworks and Protocols - Introduction36 Internet Protocol stack

37 Feb. 4., Kåre J. KristoffersenNetworks and Protocols - Introduction37 Moving data in a network

38 Feb. 4., Kåre J. KristoffersenNetworks and Protocols - Introduction38 Course overview Introduction (today) Application Layer Transport Layer Network Layer Link Layer + Physical Layer Multimedia Networking Security – Encryption Network Management


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