Lecture10 - COP 5611 Operating Systems Spring 2010 Dan C....

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Click to edit Master subtitle style 5/13/10 Lecture 6 COP 5611 Operating Systems Spring 2010 Dan C. Marinescu Office: HEC 439 B Office hours: M-Wd 2:00-3:00 PM
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5/13/10 22 2 Lecture 10 n Reading Assignment: Chapter 7 from the online textbook n A progress report for the project is due on every Monday. n Last time: ¨ Network properties n Today: ¨ Layering ¨ Link layer ¨ Network layer n Next time ¨ Routing
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5/13/10 33 Networks encounter a v ast range of Data rates Propagation, transmission, queuing, and processing delays. Loads Numbers of users Networks traverse hostile envir onments Noise damages data Links stop working Best-effor t networks have Variable delays Variable transmission rates Discarded packets Duplicate packets Maximum packet length Reordered delivery 
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5/13/10 44 A B time X overloaded resend request, send request, receive response, send request, timer expires, set new timer receive response, X X set timer reset timer set timer reset timer forwarder discards request packet. request 1 response 1 request 2 request 2’ response 2’ Recovery of lost packets
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5/13/10 55 A B X overloaded forwarder send request, duplicate arrives at B B sends response 3’ timer expires, resend request, X receive response, set new timer set timer reset timer discards response 3 request 3 request 3’ response 3’ Duplicate requests
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5/13/10 66 A B packet containing response timer expires, resend send request, duplicate arrives at B B sends response 4’ receive response receive response, reset timer X duplicate gets delayed set timer request 4 response 4 request 4’ response 4’ Delays and recovery lead to duplicate response
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5/13/10 77 Layering n Simplify the design n Example- RPC
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5/13/10 88 result      FI RE  (#,  target action ) procedure   FIRE  ( nmiss where react ) Client stub Service stub proc:  FIRE args:   3 type:  integer value:  2 type:  string value:  “Lucifer” type:  procedure value:  EVADE Prepare request message. Send to service Receive request message. Call requested procedure. Prepare response message. Send to client. response: acknowledgment type:  string value:  “destroyed” request: Wait for response. return  result ... Client-server communication based on RPC
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5/13/10 99 Main program called procedure application protocol RPC client stub presentation protocol RPC service stub
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5/13/10 1010 Client network Service network transport protocol package package fire send_ receive_ (return) fire (return) Main program called procedure application protocol RPC client stub presentation protocol RPC service stub message message receive_ message send_ message
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5/13/10 Multiple protocols may be supported at each layer 1111 Layer One Layer Two Layer Three A B C D X Y Z J K L
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5/13/10 1212 Multiplexing and Demultiplexing
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5/13/10 Network layers for store and forward networks n Every module has three interfaces: ¨ To the layers above ¨ To the layers below ¨ To the peer layer on another system
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This note was uploaded on 05/12/2010 for the course CS COP5611 taught by Professor Dancristianmarinescu during the Spring '10 term at University of Central Florida.

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Lecture10 - COP 5611 Operating Systems Spring 2010 Dan C....

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