CSC 4900 Computer Networks: Introduction

Transcription

1 CSC 4900 Computer Networks: Introduction Professor Henry Carter Fall 2017

2 What s this all about? 2

3 A Modern Day Silk Road We live with nearly constant access to the most extensive system ever built by human beings. We may never build anything bigger. The Internet quickens the exchange of ideas, goods, news and improves the quality of life for a large portion of the world s population. It even impacts you where you least expect it. E.g. Shipping/Supply Chain Management 3

4 Why Do I Need This Course? As engineers and scientists, you need to know the underpinnings of our global communications networks. With this information, you will be able to help design and implement the next generation of networked systems. As everything comes online, you need to understand the implications and architecture of these systems. 4

5 Goals My Goal: To provide students with the tools to evaluate current and develop new networked systems. Networking Fundamentals Recognize trade-offs between different technologies. Design and implement software with a communications interface. Prepare you for advanced work in this area. I love this material and want to help you all love it too. 5

6 What Topics Will We Cover? This is an introductory course, so you will get a bit of everything: TCP, IP, UDP, DNS, BGP, , P2P, Routing Algorithms, Congestion Control, Queuing Fundamentals, Network Management, Wireless, Cellular, Security, Ethics and lots more... I will be maintaining the course at: f17/ Assignments, slides and other information will be made available here. 6

7 Textbooks There is one required book and one recommended book for this class: Computer Networking: A Top-Down Approach (7 th edition) TCP/IP Sockets in Java: Practical Guide for Programmers Readings will come from the first; projects will be made much easier from the second. 7

8 Assignments/Workload There will be a reading assignment for nearly every class. Reading must be done before the class period. We will have a total of three homework assignments: Problems will come from the book and the professor. Check the website. We will also do four programming projects: All programming must be done in the specified language - no exceptions. Generally Java - check each assignment. Check the website. 8

9 Course Calendar The course calendar contains a listing of readings, assignments and deadlines. The page also contains links to additional readings. Check frequently! There will be changes! Students are responsible (I will do my best to make announcements). 9

10 Expectations This is going to be a hard course. The key to success is sustained effort. Failure to keep up with readings and assignments will result in poor grades and more critically, little understanding of the material. So what do I get for all my hard work? A building block to help you change the world... 10

11 Grading Grading in this class will be distributed as follows: 15% Homework 20% Projects 25% Midterm 35% Final 5% Class Participation I reserve the right to give Unannounced Learning Experiences. You get the grade that you earn, so be sure that you earn a grade you like. 11

12 Lateness All homework is due at the beginning of class. Projects must be submitted to Blackboard by start of class. Late assignments are assessed a 15% per-day late penalty, with a maximum of three (3) days. Students with legitimate reasons should contact the professor before the deadline to apply for an extension. Unless the problem is apocalyptic, don t give me excuses. 12

13 Academic Integrity As scientists and engineers, we must trust each other to make progress. Numerous examples exist to show the consequences of this breakdown. Jan Hendrik Schon... Academic dishonesty, whether from cheating, copying, fabricating results or through any other dishonest practice will not be tolerated. I take this personally - you should too. 13

14 Course Outline Introduction to Networking (Chapter 1) Application layer (Chapter 2) Transport layer (Chapter 3) Network layer (Chapter 4) Network layer pt 2 (Chapter 5) Link layer (some physical layer topics) (Chapter 6) Wireless, Mobility and Android (Chapter 7) Network security (Chapter 8) Multimedia networking (Chapter 9) 14

15 Chapter 1: Roadmap 1.1 What is the Internet? 1.2 Network edge 1.3 Network core 1.4 Delay & loss in packet-switched networks 1.5 Protocol layers and their service models 1.6 Networks Under Attack 1.7 History of Computer Networking and the Internet 1.8 Summary 15

16 What s the Internet: Nuts and Bolts View millions of connected computing devices: hosts = end systems running network apps communication links fiber, copper, radio, satellite transmission rate: bandwidth Packet switches: forward packets (chunks of data) routers and switches 16

17 Cool Internet Appliances 17

18 What s the Internet: Nuts and Bolts View Internet: network of networks Interconnected ISPs protocols control sending, receiving of msgs e.g., TCP, IP, HTTP, Skype, Internet standards RFC: Request for comments IETF: Internet Engineering Task Force 18

19 What s the Internet: A Service View Infrastructure that provides services to applications: Web, VoIP, , games, e-commerce, social nets, provides programming interface to apps hooks that allow sending and receiving app programs to connect to Internet provides service options, analogous to postal service 19

20 What s a Protocol? human protocols: what s the time? I have a question introductions network protocols: - machines rather than humans - all communication activity in Internet governed by protocols specific msgs sent specific actions taken when msgs received, or other events 20

21 What s a Protocol? Example: A human protocol and a computer protocol: Question: What are some other human protocols? 21

22 Chapter 1: Roadmap 1.1 What is the Internet? 1.2 Network edge 1.3 Network core 1.4 Delay & loss in packet-switched networks 1.5 Protocol layers and their service models 1.6 Networks Under Attack 1.7 History of Computer Networking and the Internet 1.8 Summary 22

23 A Closer Look at Network Structure: network edge: hosts: clients and servers servers often in data centers access networks, physical media: wired, wireless communication links network core: interconnected routers network of networks 23

24 Home Networks PSTN Splitter Internet WiFi AP Cable/DSL Modem CMTS/ DSLAM ISP 24

25 Enterprise Networks typically used in companies, universities, etc 10 Mbps, 100Mbps, 1Gbps, 10Gbps transmission rates today, end systems typically connect into Ethernet switch 25

26 Chapter 1: Roadmap 1.1 What is the Internet? 1.2 Network edge 1.3 Network core 1.4 Delay & loss in packet-switched networks 1.5 Protocol layers and their service models 1.6 Networks Under Attack 1.7 History of Computer Networking and the Internet 1.8 Summary 26

27 The Network Core mesh of interconnected routers packet-switching: hosts break application-layer messages into packets forward packets from one router to the next, across links on path from source to destination each packet transmitted at full link capacity 27

28 Packet-Switching: Store and Forward takes L/R seconds to transmit (push out) L-bit packet into link at R bps store and forward: entire packet must arrive at router before it can be transmitted on next link one-hop numerical example: L = 7.5 Mbits R = 1.5 Mbps one-hop transmission delay = 5 sec end-end delay = 2L/R (assuming zero propagation delay) 28

29 Packet Switching: Queueing Delay, Loss If arrival rate (in bits) to link exceeds transmission rate of link for a period of time: packets will queue, wait to be transmitted on link packets can be dropped (lost) if memory (buffer) fills up 29

30 Network Core: Circuit Switching end-end resources allocated to, reserved for call between source & dest: In diagram, each link has four circuits. call gets 2nd circuit in top link and 1st circuit in right link. dedicated resources: no sharing circuit-like (guaranteed) performance circuit segment idle if not used by call (no sharing) Commonly used in traditional telephone networks 30

31 Circuit Switching: FDM and TDM 31

32 Numerical Example How long does it take to send a file of 640,000 bits from host A to host B over a circuitswitched network? All links are Mbps Each link uses TDM with 24 slots/sec 500 msec to establish end-to-end circuit Let s work it out! 32

33 Packet Switching vs Circuit Switching 33

34 Packet Switching vs Circuit Switching Is Packet Switching a slam-dunk winner? great for bursty data resource sharing simpler, no call setup excessive congestion possible: packet delay and loss Q: How to provide circuit-like behavior? bandwidth guarantees needed for audio/video apps still an unsolved problem Q: human analogies of reserved resources (circuit switching) versus on-demand allocation (packet-switching)? 34

35 Internet Structure: Network of Networks Q: Given millions of access ISPs, how can we connect them together? 35

36 Internet Structure: Network of Networks Option: Connect each access ISP to every other ISP? 36

37 Internet Structure: Network of Networks Option: connect each access ISP to a global transit ISP? Customer and provider ISPs have economic agreement. 37

38 Internet Structure: Network of Networks But if one global ISP is viable business, there will be competitors. 38

39 Internet Structure: Network of Networks But if one global ISP is viable business, there will be competitors. which must be interconnected 39

40 Internet Structure: Network of Networks and regional networks may arise to connect access nets to ISPS 40

41 Internet Structure: Network of Networks and content provider networks (e.g., Google, Microsoft, Akamai ) may run their own network, to bring services, content close to end users 41

42 Tier-1 ISP: Level 3 42

43 Conclusion Welcome to CSC this will be a great class. Go get the books and start doing the reading! Seriously... what are you waiting for? Go to the webpage and figure out when homeworks and projects will be due. Questions? 43

44 Next Time... Textbook Chapter 1 Remember, you need to read it BEFORE you come to class! Homework Introduction assignment #0 44