Chapter 1 Introduction

Chapter 1 Introduction

Chapter 1 Introduction A note on the use of these Powerpoint slides: We’re making these slides freely available to all (faculty, students, readers). They’re in PowerPoint form so you see the animations; and can add, modify, and delete slides (including this one) and slide content to suit your needs. They obviously represent a lot of work on our part. In return for use, we only ask the following: Computer § If you use these slides (e.g., in a class) that you mention their source (after all, we’d like people to use our book!) Networking: A Top § If you post any slides on a www site, that you note that they are adapted from (or perhaps identical to) our slides, and note our copyright of this Down Approach material. th Thanks and enjoy! JFK/KWR 7 edition Jim Kurose, Keith Ross All material copyright 1996-2016 Pearson/Addison Wesley J.F Kurose and K.W. Ross, All Rights Reserved April 2016 Introduction 1-1 Chapter 1: introduction our goal: overview: § get “feel” and § what’s the Internet? terminology § what’s a protocol? § network edge; hosts, access net, § more depth, detail physical media later in course § network core: packet/circuit § approach: switching, Internet structure • use Internet as § performance: loss, delay, example throughput § security § protocol layers, service models § history Introduction 1-2 Chapter 1: 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 Introduction 1-3 What’s the Internet: “nuts and bolts” view PC § billions of connected mobile network server computing devices: wireless • hosts = end systems global ISP laptop smartphone • running network apps home network § communication links regional ISP wireless • fiber, copper, radio, links satellite wired links • transmission rate: bandwidth § packet switches: forward router packets (chunks of data) institutional • routers and switches network Introduction 1-4 “Fun” Internet-connected devices Web-enabled toaster + weather forecaster IP picture frame http://www.ceiva.com/ Tweet-a-watt: Slingbox: watch, monitor energy use control cable TV remotely sensorized, bed mattress Internet refrigerator Internet phones Introduction 1-5 What’s the Internet: “nuts and bolts” view § Internet: “network of networks” mobile network • 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 Introduction 1-6 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 network § provides programming 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 Introduction 1-7 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 Introduction 1-8 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 Q: other human protocols? Introduction 1-9 Chapter 1: 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 Introduction 1-10 A closer look at network structure: § network edge: mobile network • hosts: clients and servers • servers often in data global ISP centers home § access networks, physical network media: wired, wireless regional ISP communication links § network core: • interconnected routers • network of networks institutional network Introduction 1-11 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? Introduction 1-12 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) Introduction 1-13 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 Introduction 1-14 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 Introduction 1-15 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) Introduction 1-16 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 Introduction 1-17 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 Introduction 1-18 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) Introduction 1-19 Physical media § bit: propagates between transmitter/receiver pairs § physical link: what lies twisted pair (TP) between transmitter & § two insulated copper receiver wires § guided media: • Category 5: 100 Mbps, 1 Gbps Ethernet • signals propagate in solid media: copper, fiber, coax • Category 6: 10Gbps § unguided media: • signals propagate freely, e.g., radio Introduction 1-20 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 Introduction 1-21 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 Introduction 1-22 Chapter 1: 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 Introduction 1-23 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 Introduction 1-24 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

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