CMPE 252A : Computer Networks Chen Qian Computer Engineering UCSC Baskin Engineering Lecture 1 Slides source: Kurose and Ross, Simon Lam, Katia Obraczka Introduction

Welcome to CE 252A! Class information: When: Tu Th 01:30PM-03:05PM. Where: Engineering 2 192. Class Web page: https://cmpe252a-fall17-01.courses.soe.ucsc.edu/home It is your responsibility to read EVERY sentence on the class website. You also need to check the website at least twice every week to access timely updates to the class

About the Instructor Chen Qian. Office: E2 231. E-mail: qian "at" ucsc.edu Office hours: Tuesday, 11am-12pm Research lab: E2 211

Pre-Requisites CMPE 150 or undergrad level networking course. Graduate level computer programming skills (for project).

Teaching Assistants Xin Li xli178 at ucsc.edu Huazhe Wang hwang137 at ucsc.edu

Highly recommend to buy it! It is good based on my experience. Books Lecture: Computer Networking: A Top Down Approach, by Kurose and Ross 5th, 6th and 7th ed are all good You are recommended to read the book BEFORE some classes. However the exam questions are ALL related to the material in the slides. Highly recommend to buy it! It is good based on my experience.

Grading Reading reports 10% Survey study 25% Midterm 25% Course project 40%

Student Responsibilities: Academic Integrity All submitted work must be individual. OK to have discussions on ideas but turn in your own work. Survey is individual! Project can be done in a group of at most three students. But each student must submit her/his own report about her/his own contribution. Ask instructor and TAs if there are any questions. For more info, go to: www.ucsc.edu/academics/academic_integrity/

Student Responsibilities: Academic Integrity Academic integrity violations will not be tolerated. Cheating quizzes.

Student Responsibilities Attendance. Lectures. Keep up with material covered in lecture Readings (chapters in the book). Sample questions. Keep up with reading assignments and project. Turn in the assignments on time!

Resources Instructor. TAs. Class Web page. Lecture notes will be posted before class. Office hours

Student Feedback Feedback is always welcome! Chance to do it at the end of the quarter. But you can also do it during the quarter…

Lectures The more interactivity, the better! Ask questions! Or answer my questions. Lecture notes: Will be posted on-line before class. But…

Project You may choose one of the following. 1. Recommended Project Will be announced later 2. Self-defined Project Any topic related to networking Submit your proposal by 10/17 Need approval from me to continue

Reading reports Introduction

Survey paper Introduction

Midterm Exam November 9th. Close book, can bring one-side 8.5"x11" note Introduction

Assignment Submission Submit hardcopy of your reading reports and survey paper Email the project report and code

Assignment late submission policy 20% deduction for each day late.

Administrative Info Communication: E-mail preferred. Send e-mail to both instructor AND TAs.

Course Outline Basic Knowledge of computer networking Application layer Transport layer Network layer Link layer Advanced topics Software defined networks Cloud and data center networks Wireless and mobile networks Internet of things Network security

My background PhD in Computer Science (2013), University of Texas at Austin Advisor: Simon Lam – researcher of the chapter for “The Link Layer” pp 511 22

BTW…. Simon Lam’s PhD advisor was Leonard Kleinrock, Professor at UCLA researcher of the chapter for “Chapter 1” Introduction

My Research Network algorithms, protocols, and systems Routing, switching, management, etc. Current focus: Internet of Things, Software Defined Networking, and Network Security Introduction

Networks: overview 1.1 Terms of a network 1.2 network edge end systems, access networks, links 1.3 network core packet switching, circuit switching, network structure 1.4 protocol layers Introduction 25

What are the components of a computer (communication) network? Links, nodes, and Terminals/hosts/end systems/servers What’s the difference between “nodes” and “hosts”?

Nodes and hosts Source: K. Salah Module 3.4

Nodes and Terminals Terminals = Hosts, End-User Devices

What are the performance metrics we care about? Latency Bandwidth/throughput Bandwidth: the max throughput a communication link can provide Scalability When size is large, will there be a problem? Memory, cpu, latency, etc. Reliability When some nodes/hosts fail Security Financial cost Introduction

Any network design is a trade-off What are the trade-offs of the following designs: Encryption/decryption Redundancy Peer-to-peer networks Introduction

What’s the Internet: “Nuts and Bolts” View Internet: “network of networks” hierarchical Institutional network Mobile network Global ISP Home network Regional ISP

What’s the Internet: “Service” View Communication Infrastructure enables distributed applications: Web, VoIP, email, games, e-commerce, file sharing Communication services provided to apps: reliable data delivery from source to destination “best effort” (unreliable) data delivery Institutional network Mobile network Global ISP Home network Regional ISP

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

The network core 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

Packet Switching: queueing delay, loss R = 100 Mb/s D R = 1.5 Mb/s B E queue of packets 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

Alternative core: circuit switching end-end resources allocated to, reserved for “call” between source & dest: dedicated resources: no sharing circuit-like (guaranteed) performance circuit segment idle if not used by call (no sharing) Commonly used in traditional telephone networks

Packet switching versus circuit switching packet switching allows more users to use network! example: 1 Mb/s link each user: 100 kb/s when “active” active 10% of time circuit-switching: 10 users packet switching: with 35 users, probability > 10 active at same time is less than .0004 * ….. N users 1 Mbps link Q: how did we get value 0.0004? Q: what happens if > 35 users ?

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: human analogies of reserved resources (circuit switching) versus on-demand allocation (packet-switching)?

Internet protocol stack application: supporting network applications FTP, SMTP, HTTP transport: process-process data transfer TCP, UDP network: routing of datagrams from source to destination IP, routing protocols link: data transfer between neighboring network elements Ethernet, 802.111 (WiFi), PPP physical: bits “on the wire” application transport network link physical

Encapsulation source destination application transport network link message M application transport network link physical segment Ht M Ht datagram Ht Hn M Hn frame Ht Hn Hl M link physical switch destination network link physical Ht Hn M Ht Hn Hl M M application transport network link physical Ht Hn M Ht M Ht Hn M router Ht Hn Hl M

Next class Please read Chapter 2 of the textbook BEFORE Class 41