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COP 5611 Operating Systems Spring 2010

COP 5611 Operating Systems Spring 2010. Dan C. Marinescu Office: HEC 439 B Office hours: M-Wd 2:00-3:00 PM. Lecture 9. Reading Assignment: Chapter 7 from the online textbook HW1 due today. Remember: A progress report for the project is due on every Monday till week 12.

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COP 5611 Operating Systems Spring 2010

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  1. COP 5611 Operating Systems Spring 2010 Dan C. Marinescu Office: HEC 439 B Office hours: M-Wd 2:00-3:00 PM

  2. Lecture 9 Reading Assignment: Chapter 7 from the online textbook HW1 due today. Remember: A progress report for the project is due on every Monday till week 12. Last time: Thread coordination and scheduling Multi-level memories I/O bottleneck Today: Network properties Layering Data link layer Next time Network layer 2 2 2 2 2

  3. Properties of Networks • Physical limitations: • Speed of light  finite communication latency • Hostile environments • Limited channel capacity  limited bandwidth • Channels are shared - multiplexed • Why: • Support any-to-any communication • Share costs • How • Isochronous multiplexing – scheduled access • TDM • FDM • Asynchronous multiplexing

  4. Communication channels are multiplexed

  5. Data flow on an isochronous link

  6. A data communication network

  7. Asynchronously multiplexed link

  8. Communication • Continuous versus bursty • The old phone network versus data networks • Human versus computer communication • Connection-oriented versus connectionless communication • Packet-forwarding networks • Routing problem • Delays

  9. Packet forwarding (store and forward) networks

  10. Problems in packet forwarding networks • Delay • Propagation delay • Transmission delay • Processing delay • Queuing delay • Resources are finite and a worst case design is not feasible  heavy tail distributions of resource needs • Buffer overflow and discarded packets • Adaptive rate modulated by information regarding network congestion • Timers and packet retransmission • Duplicate packets

  11. Queuing delays versus utilization.

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