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Introduction1-1 Chapter 1 Computer Networks and the Internet Computer Networking: A Top Down Approach Featuring the Internet, 2 nd edition. Jim Kurose, Keith Ross Addison-Wesley, July 2002. A note on the use of these ppt slides: Were making these slides freely available to all (faculty, students, readers). Theyre in powerpoint form so you can add, modify, and delete slides (including this one) and slide content to suit your needs. They obviously represent a lot of work on our part. In return for use, we only ask the following: If you use these slides (e.g., in a class) in substantially unaltered form, that you mention their source (after all, wed like people to use our book!) If you post any slides in substantially unaltered form on a www site, that you note that they are adapted from (or perhaps identical to) our slides, and note our copyright of this material. This slide show has been modified by Merrie Bergmann 1/26/03 Thanks and enjoy! JFK/KWR All material copyright 1996-2002 J.F Kurose and K.W. Ross, All Rights Reserved Slide 2 Introduction1-2 Whats the Internet: nuts and bolts view millions of connected computing devices: hosts, end-systems m PCs, workstations, servers m PDAs, phones, toasters running network apps communication links m fiber, copper, radio, satellite m transmission rate = bandwidth routers: forward packets (chunks of data) local ISP company network regional ISP router workstation server mobile Slide 3 Introduction1-3 Slide 4 Introduction1-4 Cool internet appliances Web-enabled toaster+weather forecaster Slide 5 Introduction1-5 Whats the Internet: nuts and bolts view protocols control sending, receiving of msgs m e.g., TCP, IP, HTTP, FTP, PPP Internet: network of networks m loosely hierarchical Internet standards m RFC: Request for comments m IETF: Internet Engineering Task Force (www.ietf.org) local ISP company network regional ISP router workstation server mobile Slide 6 Introduction1-6 Whats a protocol? a human protocol and a computer network protocol: Hi Got the time? 2:00 TCP connection req TCP connection response Get http://www.awl.com/kurose-ross time Slide 7 Introduction1-7 Whats the Internet: a service view communication infrastructure enables distributed applications: m Web, email, games, e- commerce, database, voting, file (MP3) sharing communication services provided to apps: m connectionless m connection-oriented m Loosely speaking, the connection-oriented service guarantees that data transmitted from a sender to a receiver will eventually be delivered to the receiver in order and in its entirety. (p.5) m Currently, no time delay guarantees! Slide 8 Introduction1-8 A closer look at network structure: network edge: applications and hosts network core: m routers m network of networks access networks, physical media: communication links Slide 9 Introduction1-9 The network edge:End systems, clients, and servers end systems (hosts): m run (distributed) application programs m e.g. Web, email m at edge of network client/server model m client host requests, receives service from always-on server m e.g. Web browser/server; email client/server peer-peer model: m minimal (or no) use of dedicated servers m e.g. Napster, Gnutella, KaZaA Slide 10 Introduction1-10 Network edge: connection-oriented service Goal: data transfer between end systems handshaking: setup (prepare for) data transfer ahead of time m Hello, hello back human protocol m set up state in two communicating hosts TCP - Transmission Control Protocol m Internets connection- oriented service TCP service [RFC 793] reliable, in-order byte- stream data transfer m loss: acknowledgements and retransmissions flow control: m sender wont overwhelm receiver congestion control: m senders slow down sending rate when network congested Slide 11 Introduction1-11 Network edge: connectionless service Goal: data transfer between end systems m same as before! UDP - User Datagram Protocol [RFC 768]: Internets connectionless service m unreliable data transfer m no flow control m no congestion control Apps using TCP: HTTP (Web), FTP (file transfer), Telnet (remote login), SMTP (email) Apps using UDP: streaming media, teleconferencing, DNS, Internet telephony Slide 12 Introduction1-12 The Network Core mesh of interconnected routers the fundamental question: how is data transferred through net? m circuit switching: dedicated circuit per call: telephone net m packet-switching: data sent thru net in discrete chunks Slide 13 Introduction1-13 Network Core: Circuit Switching End-end resources reserved for call link bandwidth dedicated resources: no sharing circuit-like (guaranteed) performance call setup required Slide 14 Introduction1-14 Network Core: Circuit Switching network resources (e.g., bandwidth) divided into pieces pieces allocated to calls resource piece idle if not used by owning call (no sharing) dividing link bandwidth into pieces m frequency division m time division Slide 15 Introduction1-15 Circuit Switching: FDM and TDM FDM frequency time TDM frequency time 4 users Example: