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Communications Networks: Fundamental Concepts and Key Architectures Leon-Garcia and Widjaja University of Toronto.

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Presentation on theme: "Communications Networks: Fundamental Concepts and Key Architectures Leon-Garcia and Widjaja University of Toronto."— Presentation transcript:

1 Communications Networks: Fundamental Concepts and Key Architectures Leon-Garcia and Widjaja University of Toronto

2 Outline of Course C1 Networks and Services Survey –Appendix A1 Queues –Online tutorial Probability C2 Applications and Layered Architectures –(Skip 2.4 Berkeley API) C3 Digital Transmission Fundamentals C4 Transmission Systems –(Skip 4.4, 4.6, 4.7 on telephone details)

3 Course Outline Continued C5 Peer-Peer Protocols (C6 skip LANs) covered in CS487 C7 Packet Switching Nets C8 TCP/IP –(Skip 8.8)

4 C1 Intro to Nets 1.1 Networks and Services 1.2 Approaches to Network Design 1.3 Internet and Packet Switching 1.4 Factors in Network Evolution

5 1.1 Networks and Services Definition of network TV Broadcasting Telephone Service PSTN POTS Cellular Phones Web Video on Demand

6 1.2 Approaches to Network Design Network Functions and Topology –Terminals –Connectivity –Switches –Access Network –Multiplexers –LANS, Metropolitan net, WANs –Topologies –Addressing (Flat vs. Hierarchical) –Traffic Control –Network Management

7 Network (a) A switch provides the network to a cluster of users (b) A multiplexer connects two access networks Access network Figure 1.7

8 Message, Packet and Circuit Switching –Telegraph Network (Message) –Internet (Packet) –Telephone Network (Circuit) Table 1.1 Not Functions but rather dimensions of classifying nets


10 Telegraph Sam F. B. Morse Baltimore to DC 1837 Binary representation Relay Hardware, Relay, MD Message Switching Multiplexing Edison, Bell Teletype Networks

11 Telephone Alexander Graham Bell 1876 Boston Circuit Switching Hierarchy Analog Transmission Grafting of Digital Traffic Huge Investment, particularly local drops (last mile)

12 (a) A switch in the form of an operator with a patch cord panel (not shown) (b) Cords interconnect user sockets providing end-to-end connection Figure 1.10

13 Tandem CO Toll CO Tandem Figure 1.11 Fig Part of the Hierarchy for Telephone Switching

14 The caller picks up the phone triggering the flow of current in wires that connect to the telephone office. The current is detected and a dial tone is transmitted by the telephone office to indicate that it is ready to receive the destination number. The caller sends this number by pushing the keys on the telephone set. Each key generates a pair of tones that specify a number. (In the older phone sets the user dials a number which in turn generates a corresponding number of pulses.) The equipment in the telephone office then uses the telephone network to attempt a connection. If the destination telephone busy, then a busy tone is returned to the caller. If the destination telephone is idle, then ringing signals are sent to both the originating and destination telephones. The ringing signals are discontinued when the destination phone is picked up and communication can then proceed. Either of the users terminate the call by putting down a receiver. Telephone Office 1. Telephone Office 2. Telephone Office Telephone Office Telephone Office Telephone Office Figure 1.1 Telephone call set up

15 Internet Packet Switching Taste of History SAGE, SABRE, ARPANET Terminal Oriented Nets Multiplexers LANs flat addressing Ethernets WAN Routers TCP/IP Protocol Suite

16 ( C TT C T T T Modem Pool PSTN Modem T T = terminal Figure 1.12 (a) Time-Shared Computers & Cables for Input Devices (b) Dial In

17 C TTTT Response from terminal Poll to terminal Figure 1.13 Sharing a multidrop line

18 (a) transceivers Figure 1.17 Ethernet Local Area Network (LAN) Original bus version Current star version


20 G G G G G net 1 net 2 net 3 net 4 net 5 G = gateway G Figure 1.18 An internetwork, not the Internet, necessarily

21 The user clicks on a link to indicate which document is to be retrieved. The browser must determine the address that contains the document. It does this by sending a query to its local name server. Once the address is known the browser establishes a connection to the specified machine, usually a TCP connection. In order for the connection to be successful, the specified machine must be ready to accept TCP connections. The browser runs a client version of HTTP, which issues a request specifying both the name of the document and the possible document formats it can handle. The machine that contains the requested document runs a server version of HTTP. It reacts to the HTTP request by sending an HTTP response which contains the desired document in the appropriate format. The TCP connection is then closed and the user may view the document Figure 1.4 Retrieving a Web page over the Internet

22 1.3 Key Factors in Network Evolution Rapid Improvement of Communications and Computer Performance – Rapid Technology Push Market Pull Regulation Standards

23 Transmission capacity (bits/second) Printing telegraph Baudot multiplex T-1 carrier T-4 carrier SONET OC-48 DWDM Figure 1.9 Evolution of network capacity

24 Technology Regulation Market Standards Figure 1.19 Factors involved in success of a new service

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