Lecture12 - 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 12 n Reading Assignment: Chapters 8 from the online textbook n Homework 3 due on March 3 n Midterm: Wednesday March 17, the first week after Spring Break n Last time: ¨ More about layering and broadcast channels ¨ Network layer n Today: ¨ End-to-end-layer ¨ Resource Management - Congestion n Next time ¨ Faults, Failures and Fault-Tolerant Design ¨ Measures of Reliability and Failure Tolerance ¨ Tolerating active Faults
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5/13/10 Requirements for routing algorithms n Routing algorithms should be dynamic and deal with: ¨ Topological changes: links go down and new links are added ¨ Congestion n Run asynchronously n Converge rapidly n Avoid oscillatory behavior n Ensure that no packet bounces around forever: add a hop count in the network header 33
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5/13/10 Flat versus hierarchical addressing schemes n The scheme we discussed so far based on flat addresses have disadvantages: ¨ Each attachment point must have a unique address and the number of attachment points is equal to the number of systems connected to the network ¨ The number of path vectors increases linearly with the size of the network. n Hierarchical addressing: e.g., two levels ¨ Region ¨ Address of the station/node within the region 44
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5/13/10 to link R1.A 1 forwarding table in R1.B R1.B R1.C end-layer 2 to link R1 local R2 R3 R4 1 1 3 region forwarding local forwarding region R1 region R2 region R3 region R4 R1.B R3.C R1.C 1 3 2 R1.A R1.D 3 R1.D section section Hierarchical addressing with two levels
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5/13/10 Advantages and disadvantages of hierarchical addressing n Reduces the number of path vectors; a router for one region needs only to advertize a single path vector. n Assignation of network addresses is manageable: ¨ a central authority assigns region addresses ¨ Station addresses are assigned by a regional authority. n The table lookup more complicated: (1) extract the region (2) forward to another region or forward within own region. n The path may no longer the shortest, the information provided by the path vector is less accurate. n The network addresses are location dependent. A mobile device must get a new address when it is connected in a different location. 66
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5/13/10 Physical and logical addresses n All devices have a physical address of the interface n Must obtain a logical address n ARP – address resolution protocol & is a protocol used by the Internet Protocol (IP), specifically IPv4, to map IP addresses to the hardware addresses used by a data link protocol. ¨ ARP operates only across the local link that a host is connected
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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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Lecture12 - COP 5611 Operating Systems Spring 2010 Dan C....

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