Lecture 1_1.pdf

CSC/CPE 138 COMPUTER NETWORK FUNDAMENTALS Lecture 1_1: Computer Network and the Internet – Part 1 California State University, Sacramento Fall 2024 Slide Courtesy: Computer Networking: A Top-Down Approach, Kurose Ross, 8...

CSC/CPE 138 COMPUTER NETWORK FUNDAMENTALS Lecture 1_1: Computer Network and the Internet – Part 1 California State University, Sacramento Fall 2024 Slide Courtesy: Computer Networking: A Top-Down Approach, Kurose Ross, 8th Edition About the Course Instructor: Dr. Syed Badruddoja Class Time and Location: Tu,Th, 10:30 AM – 11:45 AM, Alpine Hall 156 Office Hours (Online): Tu,Th, 2:30 PM – 4:00 PM Office Hours Zoom Link: https://csus.zoom.us/j/82588604485 Mode of Instruction: In-person E-mail: [email protected] 1-2 Course Objectives Explain the basic principles, architecture, layered models, and implementations of computer networks. Describe the details of important network protocols on different layers across the protocol stack. Apply reliable communication including the various methods for error detection, correction, retransmission, flow control, and congestion control. Explain the working mechanisms of routing, forwarding, internet addressing, and switching. Identify professional and ethical responsibilities, security issues and countermeasures. 1-3 Prerequisite and Materials Prerequisite Introduction to Systems Programming - CSC60, Data Structures and Algorithm Analysis - CSC130 Textbook Computer Networking: A Top-Down Approach, 7/8th edition, Kurose and Ross, Pearson, ISBN-10: 9780133594140, 1292405465 ISBN-13: 978-0133594140, 978-1292405469 Supplemental Materials Slides are adapted from Computer Networking: A Top-Down Approach, 8th edition, J.F Kurose and K.W. Ross Coding examples, online resources and Youtube videos 1-4 Grading Policy - Assignments Assignment Categories Grade Percentage In-Class Activity 5.0% Homework & Programming 20.0% Lab Assignment 15.0% Project 10.0% Midterm Exam 25.0% Final Exam 25.0% Total 100.0% 1-5 Grading Policy - Assignments In-Class activities Quiz Self-reflection Think-pair-share Prompt questions Concept-Map Homework and Programming Assignments Lab Assignments Programming Project Exams 1-6 Submission Policy Submission guidelines Submit assignments on due date Pdf files submission for homework Code files submission for programs (zipped folder) Recheck submission Late submissions will be penalized by the following rules. 10% deduction for one day late submission. 20% deduction for two days late submission. 30% deduction for three days late submission. 100% deduction from, 4th day onwards 1-7 Other Policies in Syllabus Check emails and canvas regularly Make-up exams are not allowed Exempted from extreme circumstances with evidence Require instructor approval Syllabus may be modified in the semester Any changes to the syllabus will be communicated 1-8 Tentative Class Schedule Week Date Materials to Cover Remarks Textbook Chapters 1 8/26 – 1/30 Computer Networks and The - Internet 1 2 9/2 – 9/6 Computer Networks and The ASSIGNMENT 1 Internet 3 9/9 – 9/13 Application Layer - 4 9/16 – 9/20 Application Layer ASSIGNMENT 2 2 5 9/23 – 9/27 Application Layer - 6 9/30 – 10/4 Transport Layer LAB 1 7 10/7 – 10/11 Transport Layer MID-TERM EXAM 3 8 10/14 – 10/18 Transport Layer LAB 2 9 10/21 – 10/25 Network Layer: Data Plane ASSIGNMENT 3 4 10 10/28 – 11/1 Network Layer: Data Plane - 11 11/4 – 11/8 Network Layer: Control Plane ASSIGNMENT 4 5 12 11/11 – 11/15 Network Layer: Control Plane - 13 11/18 – 11/22 Link Layer LAB 3 14 11/25 – 11/29 Link Layer PROJECT 6 SUBMISSION 15 12/2 – 12/6 Network Security - 8 16 12/9 – 12/13 - FINAL EXAM - 1-9  Getting Started: Computer Network and the Internet 2-10 Overview The computer network Protocol and Internet Network infrastructure Access networks and physical media Packet switching versus circuit-switching 2-11 Fun Activity: Brainstorm Internet Parking Ecommerce Reservation Training Smart Home TAB Laptop 1-12 Connected-world Web-enabled toaster + weather forecaster IP picture frame http://www.ceiva.com/ Tweet-a-watt: monitor energy use Streaming Services sensorized, bed mattress Smart refrigerator Internet phones 1-13 Introducing Computer Network ▪ What’s the Internet? ▪ What’s a protocol? ▪ Network edge; hosts, access network, physical media ▪ Network core: packet/circuit switching, Internet structure ▪ Performance: loss, delay, throughput ▪ Security ▪ Protocol layers, service models ▪ History 1-14 What’s the Internet: “nuts and bolts” view ▪ billions of connected mobile network computing devices: hosts = end systems global ISP running network apps home ▪ communication links network regional ISP fiber, copper, radio, satellite transmission rate: bandwidth ▪ packet switches: forward packets (chunks of data) routers and switches institutional network 1-15 What’s the Internet: “nuts and bolts” view mobile network ▪ Internet: “network of networks” Interconnected ISPs global ISP ▪ protocols control sending, receiving of messages e.g., TCP, IP, HTTP, Skype, 802.11 home network ▪ Internet standards regional ISP RFC: Request for comments IETF: Internet Engineering Task Force institutional network 1-16 What’s the Internet: a service view mobile network ▪ infrastructure that provides services to applications: global ISP Web, VoIP, email, games, e- commerce, social nets, … home ▪ provides programming network regional ISP interface to apps hooks that allow sending and receiving app programs to “connect” to Internet provides service options, analogous to postal service institutional network 1-17 What’s a protocol? human protocols: network protocols: ▪ “what’s the time?” ▪ machines rather than ▪ “I have a question” humans ▪ introductions ▪ all communication activity in Internet governed by protocols … specific messages sent … specific actions taken when messages protocols define format, order of received, or other events messages sent and received among network entities, and actions taken on message transmission, receipt 1-18 What’s a protocol? a human protocol and a computer network protocol: Hi TCP connection request Hi TCP connection response Got the time? Get http://www.awl.com/kurose-ross 2:00 time Q: other human protocols? 1-19 Network Infrastructure ▪ network edge: mobile network hosts: clients and servers global ISP servers often in data centers home ▪ access networks, physical network regional ISP media: wired, wireless communication links ▪ network core: interconnected routers network of networks institutional network 1-20 Access networks and physical media Q: How to connect end systems to edge router? ▪ residential access nets ▪ institutional access networks (school, company) ▪ mobile access networks keep in mind: ▪ bandwidth (bits per second) of access network? ▪ shared or dedicated? 1-21 Access network: digital subscriber line (DSL) central office telephone network DSL splitter modem DSLAM ISP voice, data transmitted at different frequencies over DSL access dedicated line to central office multiplexer ▪ 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 ▪ < 2.5 Mbps upstream transmission rate (typically < 1 Mbps) ▪ < 24 Mbps downstream transmission rate (typically < 10 Mbps) 1-22 Access network: cable network cable headend … cable splitter modem C O V V V V V V N I I I I I I D D T D D D D D D A A R E E E E E E T T O O O O O O O A A L 1 2 3 4 5 6 7 8 9 Channels frequency division multiplexing: different channels transmitted in different frequency bands 1-23 Access network: cable network cable headend … cable splitter cable modem modem CMTS termination system data, TV transmitted at different frequencies over shared cable ISP distribution network ▪ HFC: hybrid fiber coax asymmetric: up to 30Mbps downstream transmission rate, 2 Mbps upstream transmission rate. ▪ 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 1-24  Access network: home network wireless devices to/from headend or central office often combined in single box cable or DSL modem wireless access router, firewall, NAT point (54 Mbps) wired Ethernet (1 Gbps) 1-25 Enterprise access networks (Ethernet) institutional link to ISP (Internet) institutional router Ethernet institutional mail, switch web servers ▪ typically used in companies, universities, etc. ▪ 10 Mbps, 100Mbps, 1Gbps, 10Gbps transmission rates ▪ today, end systems typically connect into Ethernet switch 1-26 Wireless access networks ▪ shared wireless access network connects end system to router via base station aka “access point” wireless LANs: wide-area wireless access ▪ within building (100 ft.) ▪ provided by telco (cellular) ▪ 802.11b/g/n (WiFi): 11, 54, 450 operator, 10’s km Mbps transmission rate ▪ between 1 and 10 Mbps ▪ 3G, 4G: LTE to Internet to Internet 1-27 Host: sends packets of data host sending function: ▪ takes application message ▪ breaks into smaller two packets, chunks, known as packets, L bits each of length L bits ▪ transmits packet into access network at 2 1 transmission rate R R: link transmission rate link transmission rate, host aka link capacity, aka link bandwidth packet time needed to L (bits) transmission = transmit L-bit = delay packet into link R (bits/sec) 1-28 Physical media ▪ bit: propagates between twisted pair (TP) transmitter/receiver pairs ▪ two insulated copper ▪ physical link: what lies between wires transmitter & receiver Category 5: 100 Mbps, 1 ▪ guided media: Gbps Ethernet signals propagate in solid Category 6: 10Gbps media: copper, fiber, coax ▪ unguided media: signals propagate freely, e.g., radio 1-29 Physical media: coax, fiber coaxial cable: fiber optic cable: ▪ two concentric copper ▪ glass fiber carrying light conductors pulses, each pulse a bit ▪ bidirectional ▪ high-speed operation: ▪ broadband: high-speed point-to-point multiple channels on cable transmission (e.g., 10’s-100’s Gbps transmission rate) HFC ▪ low error rate: repeaters spaced far apart immune to electromagnetic noise 1-30 Physical media: radio ▪ signal carried in radio link types: electromagnetic spectrum ▪ Terrestrial microwave ▪ no physical “wire” e.g. up to 45 Mbps channels ▪ bidirectional ▪ LAN (e.g., WiFi) ▪ propagation environment 54 Mbps effects: ▪ Wide-area (e.g., cellular) reflection 4G cellular: ~ 10 Mbps obstruction by objects ▪ Satellite interference Kbps to 45Mbps channel (or multiple smaller channels) 270 msec end-end delay geosynchronous versus low altitude 1-31 Minute Paper Differentiate between Internet and Protocol? Identify the elements in hierarchical network infrastructure ? Identify types of access networks and their use case in daily lives? 1-32  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 1-33 Packet-switching: store-and-forward L bits per packet 3 2 1 source destination R bps R bps ▪ takes L/R seconds to transmit one-hop numerical example: (push out) L-bit packet into link at R bps ▪ L = 7.5 Mbits ▪ store and forward: entire ▪ R = 1.5 Mbps packet must arrive at router ▪ Delay = L/R = 7.5/1.5 before it can be transmitted ▪ one-hop transmission on next link delay = 5 sec ▪ end-end delay = 2L/R (assuming zero propagation delay) more on delay shortly … 1-34 Packet Switching: queueing delay, loss R = 100 Mb/s C A D R = 1.5 Mb/s B queue of packets E waiting for output link queuing and 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 1-35  Two key network-core functions routing: determines source- destination route taken by forwarding: move packets from packets router’s input to appropriate ▪ routing algorithms router output routing algorithm local forwarding table header value output link 0100 3 1 0101 2 0111 2 3 2 1001 1 destination address in arriving packet’s header 1-36 Alternative 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 1-37 Minute Paper A C ▪ How many circuits can be active from source computer A to destination computer B simultaneously? ▪ When can C communicate with B? ▪ Answers: 8 circuits can be active. C can communicate when one of the 8 circuits from A-B stops transmission B 1-38 Circuit switching: FDM versus TDM Example: FDM 4 users frequency time TDM frequency time 1-39 A Little more on TDM Synchronous TDM – Time is divided into periods of slots Asynchronous TDM – No periods, anyone can send Source: https://www.cs.emory.edu/~cheung/Courses/455/Syllabus/2-physical/multiplexing2.html 1-40 TDM : Example Suppose that you have a multiplexer (mux) with 2 different inputs at the following bit-rates: (A) 10 Kbps, (B) 8 Kbps, Using a fixed slot size in the frame, how would you organize a single asynchronous TDM link receiving the output of the mux? Solution: Common slot size is 2 Kbps A A A A A B B B B How about the below solution? Is it asynchronous? A B A B A B A B A 1-41 Circuit Switching Vs Packet Switching packet switching allows more users to use network! example: ▪ 1 Mb/s link ▪ each user: N users 100 kb/s when “active” active 10% of time 1 Mbps link ▪ circuit-switching: 10 users can be active ▪ packet switching: Q: how did we get value 0.002? With 35 users, probability of 10 active at same time is less than.002 * 1-42 Efficiency of Packet-Switching Method Measuring probability of users being active Given Total number of users = 35 The probability of a user being active = 0.1 Find Probability of 10 users simultaneously active Solution : 𝑛 Binomial probability distribution = 𝑥 𝑝 𝑥 (1 − 𝑝)𝑛−𝑥 = 35 10 0.110 (1 − 0.1) 35−10 = 0.00131 𝑛 𝑛! Note: 𝑥 = 𝑥! 𝑛−𝑥 ! 1-43 DIY : Computing Binomial Probability Now consider a scenario where 20 users are using the packet switched line and users are active 10% of time. A. Compute probability of 1 user being active B. Compute the summative probability of up to 7 users being active simultaneously C. Compute the probability that more than 7 of 20 users are transmitting at the same time. 1-44 DIY : Solutions A. Compute probability of 1 user being active Binomial probability distribution = 𝑛𝑥 𝑝 𝑥 (1 − 𝑝)𝑛−𝑥 = 201 0.11 (1 − 0.1) 20−1 = 0.27017 B. Compute the summative probability of any upto 7 (0,1,2, …7) users being active Cumulative Binomial distribution for 0 through 7 users 20 20 = 0 0.10 (1 − 0.1) 20−0 + 1 0.11 (1 − 0.1)20−1 +……. + 207 0.1 7 (1 − 0.1) 20−7 = 0.999584 1-45 DIY : Solutions C. Compute the probability of more than 7 of 20 users are transmitting at the same time. = 1 – (summative probability of 7 users) = 1 – 0.999584 = 0.000416 1-46 Packet switching versus 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 protocols needed for reliable data transfer, congestion control ▪ Q: How to provide circuit-like behavior? bandwidth guarantees needed for audio/video apps still an unsolved problem (chapter 7) Q: human analogies of reserved resources (circuit switching) versus on-demand allocation (packet-switching)? 1-47 Summary The computer network Protocol and Internet Network infrastructure Access networks and physical media Packet switching versus circuit-switching 2-48 End of Lecture 1_1 1-49