Chapter 1 Chapter 1: Introduction Introduction Our goal: Overview: v get “feel” and v what’s the Internet? terminology v what’s a protocol? v more depth, detail later in course v network edge; hosts, access net, physical media A note on the use of these ppt slides: v approach: We’re making these slides freely available to all (faculty, students, readers). v network core: packet/circuit They’re in PowerPoint form so you can add, modify, and delete slides § use Internet as (including this one) and slide content to suit your needs. They obviously Computer Networking: switching, Internet structure represent a lot of work on our part. In return for use, we only ask the A Top Down Approach , example following: th v v If you use these slides (e.g., in a class) in substantially unaltered form, that 5 edition. performance: loss, delay, you mention their source (after all, we’d like people to use our book!) Jim Kurose, Keith Ross v If you post any slides in substantially unaltered form on a www site, that throughput you note that they are adapted from (or perhaps identical to) our slides, and Addison-Wesley, April note our copyright of this material. 2009. v security Thanks and enjoy! JFK/KWR v protocol layers, service models All material copyright 1996-2010 J.F Kurose and K.W. Ross, All Rights Reserved v history Introduction 1-1 Introduction 1-2 What’s the Internet: “nuts and bolts” Chapter 1: roadmap view PC v millions of connected Mobile network 1.1 What is the Internet? server computing devices: Global ISP 1.2 Network edge wireless hosts = end systems v end systems, access networks, links laptop § running network apps cellular 1.3 Network core handheld Home network v communication links v circuit switching, packet switching, network structure Regional ISP § fiber, copper, 1.4 Delay, loss and throughput in packet-switched access points radio, satellite networks Institutional network wired § transmission 1.5 Protocol layers, service models links rate = 1.6 Networks under attack: security bandwidth 1.7 History v routers: forward router packets (chunks of data) Introduction 1-3 Introduction 1-4 What’s the Internet: “nuts and bolts” What’s the Internet: a service view view v communication v protocols control sending, Mobile network receiving of msgs infrastructure enables Global ISP distributed applications: § e.g., TCP, IP, HTTP, Skype, Ethernet § Web, VoIP, email, games, v Internet: “network of Home network e-commerce, file sharing networks” Regional ISP v communication services § loosely hierarchical provided to apps: § public Internet versus § reliable data delivery private intranet Institutional network from source to v Internet standards destination § RFC: Request for comments § “best § IETF: Internet Engineering effort” (unreliable) Task Force data delivery Introduction 1-5 Introduction 1-6 1 What’s a protocol? What’s a protocol? human protocols: network protocols: a human protocol and a computer network protocol: v “what’s the v machines rather than time?” humans Hi v “I have a question” v all communication TCP connection request v introductions activity in Internet Hi TCP connection governed by protocols response Got the … specific msgs sent protocols define format, time? Get http://www.awl.com/kurose-ross … specific actions taken order of msgs sent and 2:00 <file> when msgs received, received among network or other events entities, and actions time taken on msg transmission, receipt Q: Other human protocols? Introduction 1-7 Introduction 1-8 Chapter 1: roadmap A closer look at network structure: v network edge: 1.1 What is the Internet? applications and 1.2 Network edge v end systems, access networks, links hosts 1.3 Network core v access networks, v circuit switching, packet switching, network structure physical media: 1.4 Delay, loss and throughput in packet-switched wired, wireless networks communication 1.5 Protocol layers, service models links v network core: 1.6 Networks under attack: security § interconnected 1.7 History routers § network of Introduction 1-9 networks Introduction 1-10 The network edge: Access networks and physical media v end systems (hosts): Q: How to connect end § run application programs systems to edge § e.g. Web, email router? § at “edge of network” peer-peer v residential access nets v client/server model v institutional access § client host requests, receives networks (school, service from always-on server company) client/server § e.g. Web browser/server; email v mobile access networks client/server v peer-peer model: Keep in mind: § minimal (or no) use of v bandwidth (bits per dedicated servers second) of access § e.g. Skype, BitTorrent network? Introduction 1-11 v shared or dedicated? Introduction 1-12 2 Dial-up Modem Digital Subscriber Line (DSL) central Existing phone line: Internet office 0-4KHz phone; 4-50KHz telephone home upstream data; 50KHz-1MHz network Internet phone downstream data DSLAM home home ISP dial-up PC modem telephone modem (e.g., AOL) splitter network DSL modem central office home PC v uses existing telephony infrastructure § home directly-connected to central office v uses existing telephone infrastructure v up to 56Kbps direct access to router (often less) v up to 1 Mbps upstream (today typically < 256 kbps) v can’t surf, phone at same time: not “always on” v up to 8 Mbps downstream (today typically < 1 Mbps) v dedicated physical line to telephone central office Introduction 1-13 Introduction 1-14 Residential access: cable modems Residential access: cable modems v uses cable TV infrastructure, rather than telephone infrastructure v HFC: hybrid fiber coax § asymmetric: up to 30Mbps downstream, 2 Mbps upstream v network of cable, fiber attaches homes to ISP router § homes share access to router § unlike DSL, which has dedicated access Introduction 1-15 Diagram: http://www.cabledatacomnews.com/cmic/diagram.html Introduction 1-16 Cable Network Architecture: Overview Cable Network Architecture: Overview server(s) Typically 500 to 5,000 homes cable headend cable headend home home cable distribution cable distribution network (simplified) network Introduction 1-17 Introduction 1-18 3 Cable Network Architecture: Overview Cable Network Architecture: Overview FDM (more shortly): 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 cable headend cable headend home home cable distribution cable distribution network (simplified) network Introduction 1-19 Introduction 1-20 Fiber to the Home Ethernet Internet access ONT optical Internet 100 Mbps institutional fibers router to institution’s ONT Ethernet optical switch ISP fiber OLT 100 Mbps optical 1 Gbps central office splitter ONT 100 Mbps server v optical links from central office to the home v two competing optical technologies: v typically used in companies, universities, etc § Passive Optical network (PON) v 10 Mbps, 100Mbps, 1Gbps, 10Gbps Ethernet § Active Optical Network (PAN) v today, end systems typically connect into Ethernet v much higher Internet rates; fiber also carries switch television and phone services Introduction 1-21 Introduction 1-22 Wireless access networks Home networks v shared wireless access Typical home network components: network connects end system v DSL or cable modem to router router v router/firewall/NAT § via base station aka “access v ” Ethernet point base v wireless access point v wireless LANs: station § 802.11b/g (WiFi): 11 or 54 Mbps v wider-area wireless access wireless to/from laptops § provided by telco operator cable router/ cable § ~1Mbps over cellular system modem firewall (EVDO, HSDPA) mobile headend hosts wireless § next up (?): WiMAX (10’s Mbps) access over wide area Ethernet point Introduction 1-23 Introduction 1-24 4 Physical Media: coax, fiber Physical Media Twisted Pair (TP) Coaxial cable: Fiber optic cable: v bit: propagates between v two insulated copper v two concentric copper v glass fiber carrying light transmitter/rcvr pairs wires conductors pulses, each pulse a bit v physical link: what lies § Category 3: traditional v bidirectional v high-speed operation: between transmitter & phone wires, 10 Mbps v baseband: § high-speed point-to-point receiver Ethernet § single channel on cable transmission (e.g., § Category 5: ’ ’ v guided media: § 10 s-100 s Gpbs) 100Mbps Ethernet legacy Ethernet § signals propagate in solid v broadband: v low error rate: repeaters media: copper, fiber, coax § multiple channels on spaced far apart ; v unguided media: cable immune to § signals propagate freely, § HFC electromagnetic noise e.g., radio Introduction 1-25 Introduction 1-26 Physical media: radio Chapter 1: roadmap v signal carried in Radio link types: electromagnetic v terrestrial microwave 1.1 What is the Internet? spectrum § e.g. up to 45 Mbps channels 1.2 Network edge v end systems, access networks, links v no physical “wire” v LAN (e.g., WiFi) v bidirectional § 11Mbps, 54 Mbps 1.3 Network core v circuit switching, packet switching, network structure v propagation v wide-area (e.g., cellular) environment effects: § 3G cellular: ~ 1 Mbps 1.4 Delay, loss and throughput in packet-switched § reflection v satellite networks § obstruction by objects § Kbps to 45Mbps channel (or 1.5 Protocol layers, service models § interference multiple smaller channels) 1.6 Networks under attack: security § 270 msec end-end delay 1.7 History § geosynchronous versus low altitude Introduction 1-27 Introduction 1-28 The Network Core Network Core: Circuit Switching 无法显 示图 像。您的计 算机可能因内存不足而无法打开图 像，或图 像已遭损 坏。 v 请 重新启动计 算机，然后再次打开该 文件。如果仍然显 示红 色 x ，则 可能需要