Introduction. Abusayeed Saifullah. CS 5600 Computer Networks. These slides are adapted from Kurose and Ross

Transcription

1 Introduction Abusayeed Saifullah CS 5600 Computer Networks These slides are adapted from Kurose and Ross

2 Goals of This Course v Be familiar with Fundamental network topics Some advanced topics State-of-the-art v Implement the course concepts on networked computers or embedded networked devices or through standard simulators

3 Course Outline v Introduction to computer networks v Application layer v Transport layer v Network layer v Media Access Control (MAC) layer v Wireless networks v Basic security concepts

4 Personnel v Instructor Dr. Abusayeed Saifullah

5 Personnel v Instructor Dr. Abusayeed Saifullah Office: 335 Computer Science Building Office hours Tuesday 11:00am-12:00pm or by appointment Feel free to stop by if you see I am in my office v Teaching assistant XXX XXX office hours: TBD

6 Resources v Textbook Computer Networking: A Top-Down Approach, 6/e; Kurose and Ross v Reference books Computer Networks; Tanenbaum and Wetherall Java Network Programming; Elliotte Harold Beej's Guide to Network Programming Using Internet Sockets v Course website

7 Coursework v Homework and literature study: 20% v Midterm: 25% v Final: 25% v Project: 25% v Class participation: 5%

8 Literature study v General Network: SIGCOMM v Wireless: MobiCom v Theory: MobiHoc v Wireless sensor network: SenSys, IPSN, RTSS v Real-Time wireless: RTSS, RTAS

9 Project v Group work: 3-4 students per group v Three options Each group can choose its own project à needs instructor s approval Research project (requiring effort beyond the course req.) Instructor-assigned network protocol implementation v Real implementation or in standard network simulator (NS, QualNet, TOSSIM)

10 Expertise for Project v TinyOS, Contiki v NesC, C/C++, Java v Software Radio v QualNet, NS, TOSSIM v Socket Programming

11 Questions?

12 Lecture Outline our goal: v get feel and terminology v more depth, detail later in course v approach: use Internet as example overview: v what s the Internet? v what s a protocol? v network edge; hosts, access net, physical media v network core: packet/circuit switching, Internet structure v performance: loss, delay, throughput v security v protocol layers, service models v history

13 Roadmap 1.1 what is the Internet? 1.2 network edge end systems, access networks, links 1.3 network core packet switching, circuit switching, network structure 1.4 delay, loss, throughput in networks 1.5 protocol layers, service models 1.6 networks under attack: security 1.7 history

14 What is a Network? v An entity of interconnected computers v Example Internet: the largest and the most well-known network Wireless LAN 3G Mobile Wireless sensor network v Driving applica,ons WWW, , chat, videoconferencing, e- commerce, audio/video streaming, VOIP, file sharing, monitoring, controlling, social networking

15 Distributed Systems vs. Network

16 Distributed Systems vs. Network v A networked system can be either centralized or distributed v Distributed system No centralized computation Local computation Scalable Why? Think why there are 50 states in USA

17 What s the Internet: nuts and bolts view PC server wireless laptop smartphone wireless links wired links v millions of connected computing devices: hosts = end systems running network apps v communication links fiber, copper, radio, satellite transmission rate: bandwidth mobile network home network global ISP regional ISP router v Packet switches: forward packets (chunks of data) routers and switches institutional network

18 Fun internet appliances Web-enabled toaster + weather forecaster IP picture frame Tweet-a-watt: monitor energy use Internet refrigerator Slingbox: watch, control cable TV remotely Internet phones

19 How does the Internet Look Like?

20 Internet Protocol v Drives Internet traffic (see analogy with road traffic)

21 What s a protocol? human protocols: v what s the time? v I have a question v introductions specific msgs sent specific actions taken when msgs received, or other events network protocols: v machines rather than humans v all communication activity in Internet governed by protocols protocols define format, order of msgs sent and received among network entities, and actions taken on msg transmission, receipt

22 What s a protocol? a human protocol and a computer network protocol: Hi Hi Got the time? 2:00 time TCP connection request TCP connection response Get <file>

23 Protocol Standardization v Most widely used protocols are defined in standards v Why standard?

24 Internet Standardization Process v All standards of the Internet are published as RFC (Request for Comments) e.g., the SMTP protocol is specified in RFC821 but not all RFCs are Internet Standards

25 Internet Standardization Process v All standards of the Internet are published as RFC (Request for Comments) e.g., the SMTP protocol is specified in RFC821 but not all RFCs are Internet Standards v A typical (but not the only) way of standardization: Internet draft RFC draft standard (requires 2 working implementations) Internet standard (declared by Internet Architecture Board) v David Clark, 1992: We reject: kings, presidents, and voting. We believe in: rough consensus and running code.

26 Roadmap 1.1 what is the Internet? 1.2 network edge end systems, access networks, links 1.3 network core packet switching, circuit switching, network structure 1.4 delay, loss, throughput in networks 1.5 protocol layers, service models 1.6 networks under attack: security 1.7 history

27 A closer look at network structure: v network edge: hosts: clients and servers servers often in data centers v access networks, physical media: wired, wireless communication links Shared or dedicated v network core: interconnected routers network of networks mobile network home network institutional network global ISP regional ISP

28 Access net: digital subscriber line (DSL) central office telephone network DSL modem splitter voice, data transmitted at different frequencies over dedicated line to central office DSLAM DSL access multiplexer ISP v use existing telephone line to central office DSLAM data over DSL phone line goes to Internet voice over DSL phone line goes to telephone net dedicated v < 2.5 Mbps upstream transmission rate (typically < 1 Mbps) v < 24 Mbps downstream transmission rate (typically < 10 Mbps)

29 Access net: cable network cable modem splitter cable headend Channels V I D E O V I D E O V I D E O V I D E O V I D E O V I D E O D A T A D A T A C O N T R O L frequency division multiplexing: different channels transmitted in different frequency bands

30 Access net: cable network cable headend cable modem splitter CMTS data, TV transmitted at different frequencies over shared cable distribution network ISP v HFC: hybrid fiber coax asymmetric: up to 30Mbps downstream transmission rate, 2 Mbps upstream transmission rate v network of cable, fiber attaches homes to ISP router homes share access network to cable headend unlike DSL, which has dedicated access to central office

31 Wireless access networks v shared wireless access network connects end system to router via base station aka access point wireless LANs: within building (100 ft) b/g (WiFi): 11, 54 Mbps transmission rate wide-area wireless access provided by telco (cellular) operator, 10 s km between 1 and 10 Mbps 3G, 4G: LTE to Internet to Internet

32 Host: sends packets of data host sending function: v takes application message v breaks into smaller chunks, known as packets, of length L bits v transmits packet into access network at transmission rate R link transmission rate, aka link capacity, aka link bandwidth 2 host 1 two packets, L bits each R: link transmission rate packet transmission delay time needed to transmit L-bit packet into link = = L (bits) R (bits/sec)

33 Physical media v bit: propagates between transmitter/receiver pairs v physical link: what lies between transmitter & receiver guided media: signals propagate in solid media: copper, fiber, coax unguided media: signals propagate freely, e.g., radio

34 Physical media: radio v signal carried in electromagnetic spectrum v no physical wire v bidirectional v propagation environment effects: reflection obstruction by objects interference radio link types: v terrestrial microwave e.g. up to 45 Mbps channels v LAN (e.g., WiFi) 11Mbps, 54 Mbps v wide-area (e.g., cellular) 3G cellular: ~ few Mbps v satellite Kbps to 45Mbps channel (or multiple smaller channels)