《数据通信网络》（英文版）Lecture 1 Introduction

Data networks Lecture 1 Introduction Eytan Modiano

Data Networks Lecture 1 Introduction Eytan Modiano Eytan Modiano Slide 1

6.263: Data Networks Fundamental aspects of network Design and Analysis: Architecture Layering Topology design Protocols Pt -to-Pt Multiple access End-to-end Algorithms Error recovery Routing Flow Contro Analysis tools Probabilistic modeling Queueing Theory

6.263: Data Networks • Fundamental aspects of network Design and Analysis: – Architecture Layering Topology design – Protocols Pt.-to-Pt. Multiple access End-to-end – Algorithms Error recovery Routing Flow Control – Analysis tools Probabilistic modeling Queueing Theory Eytan Modiano Slide 2

Course Information Lecturer: Professor Eytan Modiano Requirements grading About one problem set per week(10% of grade Project (5% of grade Midterm exam(35 %) Final Exam during finals week(50%) Prerequisite Policy: 6.041, or an equivalent class in probability Textbook: Bertsekas Gallager, Data Networks(2nd Edition)

Course Information • Lecturer: Professor Eytan Modiano • Requirements & Grading – About one problem set per week (10% of grade) – Project (5% of grade) – Midterm exam (35 %) – Final Exam during finals week (50%) • Prerequisite Policy: 6.041, or an equivalent class in probability • Textbook: Bertsekas & Gallager, Data Networks (2nd Edition) Eytan Modiano Slide 3

Tentative syllabus LEC# TOPICS Introduction, OSI 7-layer architecture Data Link Layers, Framing, error detection Retransmission algorithms 4 Retransmission algorithms Queueing Models- Introduction Little's theorem M/M/1, M/M/m, queues etc Networks of queues M/G/I queues, M/G/I w/vacations M/G/I queues and reservations, priority queues Stability of queueing systems M/G/1 queue occupancy distribution 0

Tentative syllabus LEC # TOPICS 1 Introduction, OSI 7-layer architecture 2 Data Link Layers, Framing, error detection 3 Retransmission Algorithms 4 Retransmission Algorithms 5 Queueing Models - Introduction & Little's theorem 6 M/M/1, M/M/m, queues etc. 7 Networks of queues 8 M/G/1 queues, M/G/1 w/ vacations 9 M/G/1 queues and reservations, priority queues 10 Stability of queueing systems 11 M/G/1 queue occupancy distribution 12 Quiz Eytan Modiano Slide 4

Tentative syllabus, continued LEC# TOPICS Multiple access aloha Stabilized Aloha. Tree Algorithms CSMACSMA/CD and Ethernet High-Speed LANS, Token rings, Satellite reservations Introduction to switch architecture 18 High Speed Switch Scheduling Broadcast routing spanning trees 20 Shortest path routing 21 Distributed routing algorithms, optimal routing 22 Flow Control-Window/Credit Schemes Flow Control-Rate Based Schemes Transport layer and TCP/IP ATM Networks 26 Special topic: Optical Networks, Wireless networks Final Exam during final exam week, date and time to be announced

Tentative syllabus, continued LEC # TOPICS 13 Multiple access & Aloha 14 Stabilized Aloha, Tree Algorithms 15 CSMA, CSMA/CD and Ethernet 16 High-speed LANs, Token rings, Satellite reservations 17 Int roduction to switch architecture 18 High Speed Switch Scheduling 19 Broadcast routing & Spanning t rees 20 Shortest p ath routing 21 Distributed routing algorithms, optimal routing 22 Flow Control - Window/Credit Schemes 23 Flow Control - Rate Based Schemes 24 Transport layer and TCP/IP 25 ATM Networks 26 Special topic: Optical Networks, Wireless n etworks Final Exam during final exam week. Date and time to be announced. Eytan Modiano Slide 5

Network Applications Resource sharing Computing Mainframe computer(old days) Today, computers cheaper than comm(except LANS) Printers, peripherals Information DB access and updates E.g., Financial, Airline reservations, etc. · Services Email FtP. Telnet, Web access Video conferencing DB access Client/server applications

Network Applications • Resource sharing – Computing – Mainframe computer (old days) Today, computers cheaper than comm (except LANS) Printers, peripherals – Information DB access and updates E.g., Financial, Airline reservations, etc. • Services – Email, FTP, Telnet, Web access – Video conferencing – DB access – Client/server applications Eytan Modiano Slide 6

Network coverage areas Wide Area Networks( WANs) Span large areas(countries, continents, world) Use leased phone lines(expensive!) 1980s:10Kbps,2000s:25Gbps User access rates: 56Kbps-155 Mbps typical Shared comm links: switches and routers E.g, IBM SNA, X 25 networks, Internet Local Area Networks(LANS) Span office or building Single hop(shared channel)(cheap User rates: 10 Mbps-1 Gbps E.g. Ethernet, Token rings apple-talk Metro Area networkS MANS) Storage area networks

Network coverage areas • Wide Area Networks (WANS) – Spa n large areas (countries, continents, world) – Use leased phone lines (expensive!) 1980’s: 10 Kbps, 2000’s: 2.5 Gbps User access rates: 56Kbps – 155 Mbps typical – Shared comm links: switches and routers E.g, IBM SNA, X.25 networks, Internet • Local Area Networks (LANS) – Spa n office or building – Single hop (shared channel) (cheap!) – User rates: 10 Mbps – 1 Gbps E.g., Ethernet, Token rings, Apple-talk • Metro Area networks (MANS) • Storage area networks Eytan Modiano Slide 7

Network services Synchronous Session appears as a continuous stream of traffic(e.g, voice) Usually requires fixed and limited delays Asynchronous Session appears as a sequence of messages Ty pically bursty E.g., Interactive sessions, file transfers, email Connection oriented services Long sustained session Orderly and timely delivery of packets E.g., Telnet, FTP Connectionless services One time transaction(e.g, email) Qos

Network services • Synchronous – Session appears as a continuous stream of traffic (e.g, voice) – Usually requires fixed and limited delays • Asynchronous – Session appears as a sequence of messages – Typically bursty – E.g., Interactive sessions, file transfers, email • Connection oriented services – Long sustained session – Orderly and timely delivery of packets – E.g., Telnet, FTP • Connectionless services – One time transaction (e.g., email) • QoS Eytan Modiano Slide 8

Switching techniques Circuit Switching Dedicated resources Packet Switching Shared resources Virtual circuits Datagrams

Switching Techniques • Circuit Switching – Dedicated resources • Packet Switching – Shared resources – Virtual Circuits – Datagra ms Eytan Modiano Slide 9

Circuit Switching Each session is allocated a fixed fraction of the capacity on each ink along its path Dedicated resources Fixed path If capacity is used, calls are blocked E.g telephone network Advantages of circuit switching Fixed delays Guaranteed continuous delivery Disadvantages Circuits are not used when session is idle Inefficient for bursty traffic Circuit switching usually done using a fixed rate stream(e. g, 64 Kbps) Difficult to support variable data rates

Circuit Switching • Each session is allocated a fixed fraction of the capacity on each link along its path – Dedicated resources – Fixed path – If capacity is used, calls are blocked E.g., telephone network • Advantages of circuit switching – Fixed delays – Guaranteed continuous delivery • Disadvantages – Circuits are not used when session is idle – Inefficient for bursty traffic – Circuit switching usually done using a fixed rate stream (e.g., 64 Kbps) Difficult to support variable data rates Eytan Modiano Slide 10