414Lecture3preview

414Lecture3preview - Lecture 3 Application Layer...

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Lecture 3 Application Layer Application Layer Principles, The Web and HTTP, Cookies, Web Caching ECSE 414 – Fall 2010
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2010 Michael Rabbat Last Lecture Circuit-switching vs. packet-switching Delay Processing delay Queueing delay Transmission delay Propagation delay Loss Packets are dropped when the queue fills completely Throughput Rate (bits/sec) of transfer from sender to receiver Bottleneck link constrains end-to-end throughput ECSE 414, Lecture 3 2
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2010 Michael Rabbat ECSE 414, Lecture 3 3 Review Question Suppose N packets arrive simultaneously to a link No packets are currently in the queue Each packet is of length L bits The link has a transmission rate of R bits per second The link is 150km long (assume 2x10 8 meters/sec prop. speed) What is the average queuing delay for the N packets? 1 2 3 4
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2010 Michael Rabbat ECSE 414, Lecture 3 5 Topics for Today Application Layer Principles The Web HTTP Persistent and non-persistent connections, pipelining Web caching Cookies
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2010 Michael Rabbat ECSE 414, Lecture 3 6 What’s a Protocol? Textbook Example 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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2010 Michael Rabbat ECSE 414, Lecture 3 7 Protocol: Textbook Example a human protocol and a computer network protocol: Q: Other human protocols? Hi Hi Got the time? 2:00 TCP connection request TCP connection response Get http://www.google.com <file> time
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2010 Michael Rabbat ECSE 414, Lecture 3 8 Addressing Host has a 32-bit Internet Protocol (IP) address End hosts may have multiple processes running To receive messages, each process must have an identifier Identifier is both IP address and port number Example: HTTP servers run on port 80 http://www.google.com Maps to IP address 64.233.167.99 (more later…) Maps to port 80 We sometimes write 64.233.167.99:80
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2010 Michael Rabbat ECSE 414, Lecture 3 9 Protocol Layering and Data Each layer takes data from above adds header information to create new data unit passes new data unit to layer below application transport network link physical application transport network link physical source destination M M M M H t H t H n H t H n H l M M M M H t H t H n H t H n H l message segment datagram frame
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2010 Michael Rabbat ECSE 414, Lecture 3 10 Layered Design Principles Protocols, services HTTP, Email, Skype, BitTorrent Reliable data transfer Congestion/flow control TCP, UDP Routing, multicast IP, OSPF, BGP Switching, multiple access Ethernet, 802.11, GSM, CDMA Digital transmission Error correction BPSK, QPSK, parity check
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414Lecture3preview - Lecture 3 Application Layer...

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