4605-l7 - Quality of Service 1 Puzzle...

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1 Quality of Service
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Puzzle You have a chain consisting of 63 inter-linked  gold links You have to stay at a motel where the charge  per day is 1 gold link You do not trust the motel manager and  neither does he trust you What is the minimum number of links you  need to break in order to stay for 63 days? Clue: The manager will not sell the links till  you check out
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3 Motivation for QoS? Real-time applications Convergence in the Internet Users willing to pay for better service
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4 QoS Parameters Bandwidth Delay Delay jitter Loss Goodput
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5 Types of QoS Absolute 100Kbps, 5ms delay bound, 2% loss rate Relative Olympic model (gold, silver, bronze) Gold better than silver, etc. Gold gets k times bandwidth as silver
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6 Approaches Integrated Services Model Intserv Can provide per flow QoS Problem? Differentiated Services Model Diffserv Can provide aggregate QoS Problem? Newer approaches Core-stateless schemes
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7 Integrated Services Approach Guaranteed service Controlled load service Best effort service
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8 Guaranteed Service Similar to a leased line Hard guarantees on bandwidth and maximum delay Addressed toward critical applications Advantages? Disadvantages?
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9 Controlled load service Service provided equivalent to that of an “unloaded” network Admission control necessary No hard guarantees for bandwidth, delay, or loss! Advantages? Disadvantages?
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10 Best-effort Service Currently supported in the Internet No guarantees whatsoever Advantages? Disadvantages?
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11 Elements of QoS Flow specifications Routing Reservations Admission control Packet scheduling
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12 Specifications and Buckets Leaky Bucket r Token Bucket r B
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13 QoS Routing Determine a path through a network that can satisfy requirements Bandwidth a min-parameter => determining any one path simple Shortest widest vs. Widest shortest Delay an additive-parameter => cost based routing
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14 RSVP: Resource Reservation Protocol Signaling protocol used to convey specifications of flow and desired quality of service Token bucket specification used in both Tspec (flow characteristics) and Rspec (desired QoS characteristics)
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Can a router accommodate the new incoming request without violating service to existing flows it serves? If yes, admit and appropriately configure
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This note was uploaded on 10/12/2011 for the course ECE 4605 taught by Professor Staff during the Fall '08 term at Georgia Tech.

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4605-l7 - Quality of Service 1 Puzzle...

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