24-WirelessMcastScheduling - Networking Acronym...

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1 Networking Acronym Smorgasbord: 802.11, DVMRP, CBT, WFQ EE122 Fall 2011 Scott Shenker http://inst.eecs.berkeley.edu/~ee122/ Materials with thanks to Jennifer Rexford, Ion Stoica, Vern Paxson and other colleagues at Princeton and UC Berkeley
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Announcements • Congratulations: You all got 100% on HW4 – Worksheet will provide practice • This is last week of sections – See posting about additional office hours next week • Next week will have office hours during class times – Will work through problems on work sheet Be there or be square…. • Wednesday’s Review: will figure something out…. 2
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Today’s Lecture: Dim Sum of Design • Wireless review • Multicast • Packet Scheduling • Peer-to-peer 3
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4 Wireless Review
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History • MACA proposal: basis for RTS/CTS in lecture – Contention is at receiver, but CS detects sender! – Replace carrier sense with RTS/CTS • MACAW paper: extended and altered approach – Implications of data ACKing – Introducing DS in exchange: RTS-CTS-DS-Data-ACK o Shut up when hear DS or CTS – Other clever but unused extensions for fairness, etc. • 802.11: uses carrier sense and RTS/CTS – RTS/CTS often turned off, just use carrier sense – When RTS/CTS turned on, shut up when hear either – RTS/CTS augments carrier sense 5
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What Will Be on the Final? • General awareness of wireless (lecture) • Reasoning about a given protocol – If we used the following algorithm, what would happen? • You are not expected to know which algorithm to use; we will tell you explicitly. 6
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7 Multicast
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Motivating Example: Internet Radio • Internet concert – More than 100,000 simultaneous online listeners – Could we do this with parallel unicast streams? • Bandwidth usage – If each stream was 1Mbps, concert requires > 100Gbps • Coordination – Hard to keep track of each listener as they come and go • Multicast addresses both problems…. 8
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9 Unicast approach does not scale… Backbone ISP Broadcast Center
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10 Instead build data replication trees Backbone ISP Broadcast Center •Copy data at routers •At most one copy of a data packet per link •LANs implement link layer multicast by broadcasting •Routers keep track of groups in real-time •Routers compute trees and forward packets along them
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Multicast Service Model • Receivers join multicast group identified by a multicast address G • Sender(s) send data to address G • Network routes data to each of the receivers Note: multicast is both a delivery and a rendezvous mechanism – Senders don’t know list of receivers – For many purposes, the latter is more important than the former S R 0 R 1 . . . [G, data]
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This note was uploaded on 01/09/2012 for the course ELECTRICAL 122 taught by Professor Shenker during the Spring '11 term at University of California, Berkeley.

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24-WirelessMcastScheduling - Networking Acronym...

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