CS 204: Advanced Computer Networks Jiasi Chen Lectures: MWF 12:10-1pm Humanities and Social Sciences 1403 http://www.cs.ucr.edu/~jiasi/teaching/cs204_spring17/ 1
Why Networks? Supports the applications that we use today… Social media Video streaming Number of Internet users 97% of Americans between 18-29 • 40% of the world population à • scope for more users http://www.pewinternet.org/data-trend/internet-use/latest-stats/ 2 https://en.wikipedia.org/wiki/List_of_countries_by_number_of_internet_users
Why Networks? But also a source of conflict. Cyber security Network neutrality http://www.huffingtonpost.com/eric-dezenhall/a-look-back-at-the-target_b_7000816.html http://www.nytimes.com/2015/11/12/technology/t-mobile-video-plan-could-test-fccs-new-net-neutrality-rules.html 3
What is networking? • Bunch of acronyms? MAC RED ABR OSPF BGP UMTS REST TCP VLAN DNS MCS IP HTTP NAT DDoS SPDY DHCP 4
What is networking? • Bunch of headers? Source: https://nmap.org/book/tcpip-ref.html 5
Networking is… The search for general principles to guide communication 6
Some Research Topics in Networking • Layering Application • What functionality to place within each layer? (e.g. video streaming) • How many layers should there be? Transport • Protocols (e.g. TCP, UDP) • How to communicate within each layer, and talk to other layers? Network (e.g. routing) • Resource allocation • How to share limited resources between Link competing users? (e.g. scheduling) • Wireless Physical • How to provide a one-to-one communication in an (e.g. OFDM) inherently broadcast environment 7
What You Will Learn in this Course • Knowledge • 1/3: Link layer through application layer • 2/3: current topics in networking (wireless, multimedia, data centers, etc.) • Skills • How to read • How to present • How to discuss • How to use common networking tools 8
Course Structure • Paper reading • 2-3 papers per week • Classroom time • Lecture • Paper discussion • Programming assignments • Multipath-TCP • Mininet + OpenFlow • Project • Proposal, presentation, and final report • Can work individually in or in groups • Can be an extension of existing work or research (subject to approval) 9
Calendar Week Topic Assignment 1 Introduction + MAC layer 2 Network layer 3 Transport layer MPTCP assignment 4 Application layer 5 Content distribution Project proposal 6 Data centers 7 Wireless 8 Security SDN assignment 9 Future Internet (SDN, IoT) 10 Project presentations Finals week Final report due 10
Grading • Paper summaries (20%) • Write a one-paragraph review for each paper • Class participation (20%) • Speak up during discussion! • Assignments (20%) • 2 programming assignments • Project (40%) 11
Review 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 protocol layers, service models Adapted from Computer Networking: A Top-Down Approach , Kurose & Ross
What ’ s the Internet: “ nuts and bolts ” view • millions of connected PC mobile network computing devices: server • hosts = end systems global ISP wireless • running network apps laptop smartphone home v communication links network regional ISP § fiber, copper, radio, wireless satellite links wired § transmission rate: links bandwidth v Packet switches: forward packets (chunks of data) institutional router network § routers and switches
What ’ s the Internet: “ nuts and bolts ” view mobile network • Internet: “ network of networks ” • Interconnected ISPs global ISP • protocols control sending, receiving of msgs home • e.g., TCP, IP, HTTP, Skype, 802.11 network regional ISP • Internet standards • IETF: Internet Engineering Task Force institutional network
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
What ’ s a protocol? human protocols: network protocols: • machines rather than • “ what ’ s the time? ” humans • “ I have a question ” • all communication activity • introductions in Internet governed by protocols … specific msgs sent protocols define format, order … specific actions taken when msgs received, or of msgs sent and received other events among network entities, and actions taken on msg transmission, receipt
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 <file> time
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 protocol layers, service models
A closer look at network structure: • network edge: mobile network • hosts: clients and servers • servers often in data centers global ISP home v access networks, physical network regional ISP media: wired, wireless communication links v network core: § interconnected routers § network of networks institutional network
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?
Access net: home network wireless devices to/from headend or central office often combined in single box cable or DSL modem router, firewall, NAT wireless access point (54 Mbps) wired Ethernet (100 Mbps)
Enterprise access networks (Ethernet) institutional link to ISP (Internet) institutional router Ethernet institutional mail, switch web servers • typically used in companies, universities, etc v 10 Mbps, 100Mbps, 1Gbps, 10Gbps transmission rates v today, end systems typically connect into Ethernet switch
Wireless access networks • shared wireless access network connects end system to router • via base station aka “ access point ” wide-area wireless access wireless LANs: § provided by telco (cellular) § within building (100 ft) operator, 10 ’ s km § 802.11b/g (WiFi): 11, 54 Mbps § between 1 and 10 Mbps transmission rate § 3G, 4G: LTE to Internet to Internet
Host: sends packets of data host sending function: v takes application message v breaks into smaller chunks, two packets, known as packets , of length L L bits each bits v transmits packet into access network at transmission rate R 1 2 § link transmission rate, aka link capacity, aka link R: link transmission rate bandwidth host time needed to L (bits) packet = = transmission transmit L -bit R (bits/sec) packet into link delay
Review 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 protocol layers, service models
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
Packet-switching: store-and-forward L bits per packet 1 3 2 source destination R bps R bps • takes L / R seconds to transmit one-hop numerical (push out) L -bit packet into example: link at R bps § L = 7.5 Mbits • store and forward: entire § R = 1.5 Mbps packet must arrive at router § one-hop transmission before it can be transmitted delay = 5 sec on next link v end-end delay = 2 L / R (assuming zero propagation delay)
Packet Switching: queueing delay, loss C R = 100 Mb/s A D R = 1.5 Mb/s B E queue of packets waiting for output link queuing and loss: v 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
Two key network-core functions routing: determines source- forwarding : move packets destination route taken by from router ’ s input to packets appropriate router output § routing algorithms routing algorithm local forwarding table header value output link 1 0100 3 0101 2 2 0111 2 3 1001 1 dest address in arriving packet ’ s header
Internet structure: network of networks Question: given millions of access ISPs, how to connect them together? access access net net access net access net access net access access net net access access net net access net access net access net access net access access net net access net
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