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Computer Networks: Performance and Quality of Service Ivan Marsic Rutgers University Slides, Part 2
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Switching and Queuing Delay Models Chapter 4
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Topic: Packet Switching in Routers Router Architecture Forwarding Table Lookup Switching Fabric Design How Queuing Happens
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Routing Delays
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How Router Forwards Packets
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Services to Incoming Packets
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Distribution of Protocol Layers
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Router Architectures
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Switching via Memory / via Bus
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Banyan Switch Fabric
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Batcher Network
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Batcher-Banyan Network
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This figure is meant to illustrate why a concentrator is needed, because otherwise the gap in the input sequence will cause collision in the Banyan, but the example does not work for a 4x4 network -- need an 8x8 network example!!!!
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Delay Components in Forwarding
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Road Intersection Analogy
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An Input-queued Switch
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Topic: Queuing Models M / M / 1 M / M / 1/ m M / G / 1 Networks of Queues
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General Service Model
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Simple Queuing Model
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Delay Time
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Why Queuing Happens?
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Arrival Sequences
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Intuition for the Balance Principle See: Global Balance Equations
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Transition Probability Diagram
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M/G/1 Example
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Expected Residual Time
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Mechanisms for Quality-of-Service Chapter 5
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Topic: Scheduling Max-Min Fair Share Fair Queuing (FQ) Weighted Fair Queuing (WFQ)
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Scheduler
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Resource Fair Share
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Max-Min Fair Share (1)
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Max-Min Fair Share (2)
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Max-Min Fair Share (3)
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Example 5.1: Max-Min Fair Share
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Example: Airport Check-in
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Bit-by-bit GPS
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Bit-by-bit GPS -- Example
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GPS Round Number vs. Time
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Example 5.3: GPS Round Numbers
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016,384@1 04,096@3 316,384@2 38,192@4 64,096@3 124,096@3 Example 5.3: GPS Round Numbers (Cont’d)
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Example 5.3: Fair Queuing
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Example 4.4: Fair Queuing (1)
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Example 4.4: Fair Queuing (2b)
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Topic: Policing Leaky Bucket Algorithm
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Delay Magnitude & Variability
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Leaky Bucket
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Wireless Networks Chapter 6
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Topic: Routing in Wireless Networks Dynamic Source Routing (DSR) Protocol Ad Hoc On-Demand Distance-Vector (AODV) Protocol
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Route Discovery in DSR (1)
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Route Discovery in DSR (2) Broadcast Tx Represents a node that has received RREQ for H from C
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Route Discovery in DSR (3)
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Route Discovery in DSR (4)
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Route Discovery in DSR (5)
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Route Discovery in AODV (1)
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Multihop Throughput Challenge: more hops, less throughput Links in route share radio spectrum Extra hops reduce throughput Throughput = 1 Throughput = 1/2 Throughput = 1/3
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Topic: IEEE 802.11n Multiple Input Multiple Output (MIMO) Physical Layer Enhancements MAC Layer Enhancements: Frame Aggregation, Block Acknowledgement, Reverse Direction Protocol Backward Compatibility
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IEEE 802.11n - MIMO
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802.11n Channel Bonding and 20/40 MHz Operation
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802.11n PHY-layer Frame Format
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IEEE 802.11 Terminology
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802.11n MAC-layer Frame Format
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Packet Aggregation
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802.11n Frame Aggregation
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Frame Aggregation: A-MSDU and A-MPDU
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Block Acknowledgement Session
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Block Acknowledgement Frame
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Block ACK Frame Subfields
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Block ACK Example
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Reverse Direction (RD) Protocol Unidirectional vs. Bidirectional RTS/CTS Access Scheme
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802.11n Backwards Compatibility Modes: CTS-to-Self
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Dual-CTS protection (CTS-to-self)
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Example of L-SIG Duration Setting
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802.11n Phased Coexistence Operation (PCO)
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Topic: QoS in Wireless Networks IEEE 802.11e
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Classification of QoS Techniques in 802.11
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Network Monitoring Chapter 7
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Packet-pair Dispersion
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Internet Protocols Chapter 8
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Topic: IPv6 IPv6 Addresses IPv6 Extension Headers Transitioning from IPv4 to IPv6
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IPv6 Header
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IPv6 Address Prefix Assignments
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IPv6 Global Unicast Address
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Example IPv6 Extension Headers
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Format of IPv6 Extension Headers
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Topic: Internet Routing Protocols Routing Information Protocol (RIP) Open Shortest Path First (OSPF) Border Gateway Protocol (BGP): Routing Between and Within ASs, BGP Messages & Path Attributes Multicast Routing Protocols
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RIP Header (for IPv4)
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eBGP and iBGP Sessions
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BGP Finite State Machine
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BGP Header & Message Formats
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BGP UPDATE Message
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Example BGP UPDATE Message
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BGP MULTI_EXIT_DISC ( MED ) Attribute
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Topic: Address Translation Protocols Address Resolution Protocol (ARP)
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Address Resolution Protocol (ARP) Need for multiple addresses, hierarchical vs. non-hierarchical
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Address Resolution Protocol (ARP)
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ARP Packet Format (for IPv4)
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Future Trends Chapter 9
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Wireless Applications Fixed radio cheaper for startup and difficult terrain Wire technologies usually win for large bandwidth non-mobile continuing needs Mobile voice is a “killer app” for wireless Mobile messaging – growth Mobile data has limited usefulness
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Home Area Networks (HANs)
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Wired long-distance infrastructure Future Consumer Networks Small islands of wireless on the periphery Bottlenecks are close to the edges
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Spectrum of Wireless Bandwidth WANs (cellular, satellite) LANs (IEEE 802.11/WiFi, HiperLAN) PANs (Bluetooth) How to achieve seamless mobility between these?
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Cloud Computing
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Internet Future Computing Trends Compute-intensive applications run in the Internet core ( e.g., the Computing Grid ) At the Internet periphery: mostly editing, visualization, browsing, querying,… Data sharing and collaboration are key applications Computing Cloud Client p2pc/s Mostly Wireless, Mobile Mostly Fixed
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Probability Refresher Appendix
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Jar with Black & White Balls
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Random Events Possible outcomes of two coin tosses: “Tree diagram” of possible outcomes of two coin tosses:
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Drawing from Jar/Urn Decided by Rolling a Die
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Probability Matrix for Ball Drawing
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Illustration for Bayes Theorem
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Poisson Process average arrival rate = 5
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Partitioning of Areas Under Normal Curve
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How to Read Table A-1
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