Session 1. Introduction to Computer Communications and Networking. Communication Network. A communication network consists of a set

Transcription

1 Session 1 Introduction to Computer Communications and Networking Communication Network A communication network consists of a set of equipment and facilities that provides a service. Same as any utility network (water, electricity, gas, etc.) The service is the transfer of information between users located at various geographical points. The equipment is electronic equipment.

2 Examples of Communication Networks Some examples of communication networks: Uses of Computer Networks Business Applications Home Applications Mobile Users Social Issues All about Communication

3 Business Applications of Networks A network with two clients and one server. The old terminal-oriented networks used to work following the client-server model. Business Applications of Networks (2) The client-server model involves requests and replies.

4 Computer Networks Applications Access to remote information Person-to-person communication Interactive entertainment Electronic commerce (e-commerce) Mobile commerce (m-commerce) Social networking Home Network Applications (2) In peer-to-peer system there are no fixed clients and servers. Current computer networks can work on peer-to-peer or client-server

5 Home Network Applications (3) Some forms of e-commerce. We rename it as m-commerce, if we can do the same from a mobile phone or PDA Mobile Network Users Combinations of wireless networks and mobile computing. The current trend is everything wireless and mobile.

6 Network Hardware Local Area Networks Metropolitan Area Networks Wide Area Networks Wireless Networks Home Networks Personal Networks Internetworks Types of Networks Types of networks based on transmission technology: Broadcast Networks: a single communication channel is shared by all devices in a network. (e.g., the public WLAN in the campus or in the shopping mall) Point-to-point Networks: consist of many connections between individual pairs of devices. (e.g., the Internet)

7 Type of Networks Classification of interconnected processors by scale. Local Area Networks Two broadcast networks (a) Bus (b) Ring

8 Metropolitan Area Networks A metropolitan area network based on cable TV. Wide Area Networks Relation between hosts on LANs and the subnet. The subnet consist of two different components: Transmission lines: they move bits between machines and can be made from copper wire, optical fiber or radio links. Switching elements: they are specialized computers that connect several transmission lines. When data arrive to an incoming line it must choose an outgoing line and forward the data. They are know as routers.

9 Wide Area Networks (2) Most WANs contains numerous transmission lines and hence several routers are required to build the network. WANs usually work according to the store-and-forward principle, thus, they are called packet-switched networks too. Wide Area Networks (3) A stream of packets from sender to receiver.

10 Wireless Networks Categories of wireless networks: System interconnection Wireless LANs Wireless WANs Wireless Networks (2) (a) Bluetooth configuration (i.e., personal area network) (b) Wireless LAN

11 Wireless LANs (3) (a) Wireless networking with a base station (DCF vs PDF). (b) Ad hoc networking. Wireless Networks (4) Diversos tecnologías y estándares inalámbricos.. Nuevas terminales móviles.. 22

12 Home Network Categories Computers (desktop PC, PDA, shared peripherals) Entertainment (TV, DVD, VCR, camera, stereo, MP3) Telecomm (telephone, cell phone, intercom, fax) Appliances (microwave, fridge, clock, furnace, airco) Telemetry (utility meter, burglar alarm, babycam). Industrial (networks of PLCs) Vehicles (car-to-car, car-to-network, ITS) Network Software Protocol Hierarchies Design Issues for the Layers Connection-Oriented and Connectionless Services The Relationship of Services to Protocols

13 Network Software Protocol Hierarchies Layers, protocols, and interfaces. Protocol Hierarchies (2) Location A Location B I like J'aime Message Philosopher rabbits bien les lapins 3 3 Information L: Dutch for the remote Translator L: Dutch Ik vind translator Ik vind 2 konijnen konijnen leuk leuk 2 Information Fax #--- for the remote Fax #--- L: Dutch secretary Secretary L: Dutch 1 Ik vind Ik vind 1 konijnen leuk konijnen leuk The philosopher-translator-secretary architecture.

14 Protocol Hierarchies (3) Example information flow supporting virtual communication in layer 5. Design Issues for the Layers Addressing MAC address (L2)/IP address (L3) Error Control Error detection/error correction Flow Control Prevent a Tx from overrunning a Rx s buffer Multiplexing I l h i l i b lti l l +1 Involves sharing layer n service by multiple layer n+1 users Routing Finding a path for each destination within the network

15 Services to Protocols Relationship The relationship between a service and a protocol. Reference Models The OSI Reference Model The TCP/IP Reference Model A Comparison of OSI and TCP/IP A Critique of the OSI Model and Protocols A Critique of the TCP/IP Reference Model

16 Reference Models The OSI reference model. Reference Models (2) The TCP/IP reference model.

17 Reference Models (3) Protocols and networks in the TCP/IP model initially. Comparing OSI and TCP/IP Models Concepts central to the OSI model Services Interfaces Protocols

18 A Critique of the OSI Model and Protocols Why OSI did not take over the world Bad timing Bad technology Bad implementations Bad politics Bad Timing The apocalypse of the two elephants.

19 A Critique of the TCP/IP Reference Model Problems: Service, interface, and protocol not distinguished Not a general model Host-to-network layer not really a layer No mention of physical and data link layers Minor protocols deeply entrenched, hard to replace Hybrid Model IETF Suite of Protocols TCP/IP IMS IP Multimedia Subsystem IEEE 802 3GPP/3GPP2 The hybrid reference model to be used in this course. IETF Internet Engineering Task Force IP/TCP Internet Protocol/Transsmission Control Protocol IEEE Institute of Electrical and Electronic Engineering 3GPP/2 3G Partnership Project

20 International Telecommunications Union (ITU) Main sectors Radiocommunications Telecommunications Standardization Development Classes of Members National governments Sector members Associate members Regulatory agencies IEEE 802 Standards The 802 working groups. The important ones are marked with *. The ones marked with are hibernating. The one marked with gave up.

21 The ARPANET (a) Structure of the telephone system. (b) US Army proposed distributed switching system. The ARPANET (2) 1969 La red militar ARPANET entra en operación. Desarrollada por la Advanced Research Projects Agency (ARPA) del Departamento de Defensa de los Estados Unidos de Norteamérica. Red operando con la tecnología de conmutación de paquetes desarrollada por el Dr. Leonard Kleinrock del MIT. El Dr. Leonard Kleinrock con el primer IMP (Interface Message Processor). Aunque financiado por el ejercito, ARPANET se desarrollo en las universidades. Primeras dos universidades conectadas: University of California Los Angeles (UCLA) Stanford

22 The ARPANET (3) The original ARPANET design. The ARPANET (3) Growth of the ARPANET (a) December (b) July (c) March (d) April (e) September 1972.

23 NSFNET The NSFNET backbone in Internet Usage Traditional applications ( ) News Remote login File transfer

24 Architecture of the Internet Overview of the Internet. Internet Today Picture of Internet January 15, Source:

25 Internet Usage Today Current applications ( ) News Remote login File transfer HTTP Web Instant Messaging (text, voice, video) Everything over IP (VoIP, IPTV, etc.) Internet Usage Today Current applications ( ) P2P file sharing Streaming video Multi-user network games Internet Telephony and Video Telephony Real-Time video conference Massive parallel computing Grid computing

26 Connection-Oriented and Connectionless Services Six different types of service.

27 RFC Request for Comments (document in progress from IETF)

28 Readings: Chapter 1 Introduction of Computer Networks from A. Tanenbaum. Chapter 1 Communication Networks and Services and Chapter 2 Applications and Layered Architectures of Communication Networks from A. Leon-Garcia.