Lecture02 - Thursday, April 3 Lab #1 is due tonight before...

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Thursday, April 3 Lab #1 is due tonight before midnight Spoof emails received so far have been acknowledged Questions? Homework #1 is assigned Hardcopy due Thursday, April 10 • (beginning of class) One copy of the textbook is on 2-hour reserve in Valley Library • Call number: VR209
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Proposed sessions for Lab #2 M 12:00 – 1:50, 4:00 – 5:50 T 9:00 – 10:50, 2:00 – 3:50 W 9:00 – 10:50, 1:00 – 2:50 R 2:00 – 3:50, 4:00 – 5:50 F 2:00 – 3:50 Anyone who can’t attend one of these sessions every other week?
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Today’s topics Overview of Networking: Network protocols, service models Network edge ("fringe", "border") end systems, links Network core circuit switching, packet switching, network structure Access networks and physical media Internet structure Note: Many of the lecture slides are based on presentations that accompany Computer Networking: A Top Down Approach, 4 th edition, by Jim Kurose & Keith Ross, Addison-Wesley, July 2007.
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What’s a protocol? human protocols: “what’s the time?” “I have a question” introductions … specific msgs sent … specific actions taken when msgs received, or other events network protocols: machines rather than humans all communication activity in Internet governed by protocols protocols define format, order of msgs sent and received among network entities, and actions taken on msg transmission, receipt
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What’s a protocol? a human protocol and a computer network protocol: Hi Hi Got the time? 2:00 TCP connection request TCP connection response Get http://web.engr.oregonstate.edu/~paulson/ <file> time
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A closer look at network structure: network edge: applications and hosts network core: routers network of networks physical media: communication links
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The network edge : service models end systems (hosts): run application programs e.g. Web, email at “edge of network” client/server model client host requests/receives service from a server that is “always on” e.g. Web browser/server; email client/server peer-to-peer model: minimal (or no) use of dedicated servers e.g. Skype, BitTorrent, KaZaA
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The network edge : connection-oriented service Goal : data transfer between end systems TCP service [RFC 793] TCP - Transmission Control Protocol • Internet’s connection-oriented service handshake: prepare for transfer • Hello, hello back (human protocol) • set up “state” in two communicating hosts reliable, in-order, byte-stream data transfer acknowledgements and retransmissions flow control: sender won’t overwhelm receiver congestion control: • senders “slow down sending rate” when network is congested
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The network edge : connectionless service Goal : data transfer between end systems same as connection-oriented UDP service [RFC 768]: UDP – User Data Protocol
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This note was uploaded on 06/28/2009 for the course CS 372 taught by Professor Leviet during the Fall '07 term at Oregon State.

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Lecture02 - Thursday, April 3 Lab #1 is due tonight before...

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