Chapter1-part2 - Chapter 1 roadmap 1.1 What is the Internet...

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Chapter 1: roadmap 1.1 What is the Internet? 1.2 Network edge v end systems, access networks, links 1.3 Network core v circuit switching, packet switching v hierarchical Internet structure 1.4 Performance: v delay, loss and throughput 1.5 Protocol layers, service models 1.6 Networks under attack: security 1.7 History Introduction 1-45
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Introduction q mesh of interconnected routers The network core 1-46 Source Destination Router 1 Router n ….
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Internet Design Principles 1. Packet vs Circuit Switching (BC 6 or KR 1.3) 2. Hierarchy: Network of Networks ( BC 6 or KR 1.3) 3. Layered Architecture (BC 7 or KR 1.5) Through a Historical Perspective (or KR 1.7) “Networks Illustrated: Principles without Calculus” by Brinton & Chiang Book: Coursera:
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Sharing Resources q FDMA, TDMA, CDMA v Circuit-switched : Dedicate / assign network resources v Negative – Not all resources used constantly! q Paradigm shift v Packet-switched : Let everyone share the resources q Session v Application-level v Unicast : One source, one dest.
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Circuit Switching Advantage q Debate runs far and deep 1. Guarantee of Quality q Circuit Switching v Each session has a dedicated circuit v Throughput and delay performance will not change ! q Packet Switching v Best-effort service : no guarantees (“NO effort) v Links get congested, messages arrive out of order, …
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Packet Switching Advantages 2. Ease of Connectivity v No need to allocate resources first v Transmit at will , as long as protocols are followed 3. Scalability v Large number of diverse sessions v Obtained through high efficiency v (1) Statistical multiplexing v (2) Resource pooling
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Packet Switching Advantages q Statistical multiplexing v Multiple sessions can share one path q Resource pooling v One session can use multiple paths q No wasted/idle network resources through reservations
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Packet vs. Circuit Switching q In the end, packet switching won the day q Not clear until early 2000s q Scalability first , then search for other quality control solutions
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Resource Allocation Human Analogies: v reservation at a restaurant v a reserved lane on the highway v Q: other human analogies of reserved resources vs. on-demand allocation? Networks: v Resources (bandwidth, buffer) divided into pieces and allocated to calls or packets v Reservations: circuit-switching v No reservations: packet-switching Introduction 1-57
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Introduction + great for bursty data v network’s pov: resource sharing (“statistical multiplexing”) v user’s pov: simpler (no call setup), less delay to start service - excessive congestion possible v packet delay and loss v protocols needed for reliable data transfer, congestion control v no bandwidth guarantees needed for audio/video apps Is packet switching a clear winner? Packet Switching vs. Circuit Switching 1-58
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Introduction example: § 1 Mb/s link § each user:
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