Chapter 1 Introduction A note on the use of these ppt slides: We’re making these slides freely available to all (faculty, students, readers). They’re in PowerPoint form so you can add, modify, and delete slides (including this one) and slide content to suit your needs. They obviously Computer Networking: represent a lot of work on our part. In return for use, we only ask the A Top Down Approach , following: th If you use these slides (e.g., in a class) in substantially unaltered form, 5 edition. that you mention their source (after all, we’d like people to use our book!) Jim Kurose, Keith Ross If you post any slides in substantially unaltered form on a www site, that you note that they are adapted from (or perhaps identical to) our slides, and Addison-Wesley, April note our copyright of this material. 2009. Thanks and enjoy! JFK/KWR All material copyright 1996-2009 J.F Kurose and K.W. Ross, All Rights Reserved Introduction 1-1 Chapter 1: Introduction Our goal: Overview: get “feel” and what’s the Internet? terminology what’s a protocol? more depth, detail later in course network edge; hosts, access approach: net, physical media use Internet as network core: packet/circuit example switching, Internet structure performance: loss, delay, 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 circuit switching, packet switching, network structure 1.4 Delay, loss and throughput in packet-switched 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 millions of connected Mobile network server computing devices: Global ISP wireless hosts = end systems laptop running network cellular handheld apps Home network Regional ISP communication links access fiber, copper, points radio, satellite Institutional network wired links transmission rate = bandwidth routers: forward router packets (chunks of data) Introduction 1-4 “Cool” internet appliances Web-enabled toaster + weather forecaster IP picture frame http://www.ceiva.com/ Internet refrigerator Internet phones World’s smallest web server http://www-ccs.cs.umass.edu/~shri/iPic.html Introduction 1-5 What’s the Internet: “nuts and bolts” view protocols control sending, Mobile network receiving of msgs Global ISP e.g., TCP, IP, HTTP, Skype, Ethernet Internet: “network of Home network networks” Regional ISP loosely hierarchical public Internet versus Institutional network private intranet Internet standards RFC: Request for comments IETF: Internet Engineering Task Force Introduction 1-6 What’s the Internet: a 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 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 … specific msgs sent governed by protocols … specific actions taken protocols define format, when msgs received, order of msgs sent and or other events received among network entities, and actions taken on msg transmission, receipt Introduction 1-8 What’s a protocol? a human protocol and a computer network protocol: Hi TCP connection request Hi TCP connection Got the response 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 circuit switching, packet switching, network structure 1.4 Delay, loss and throughput in packet-switched 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: applications and hosts access networks, physical media: wired, wireless communication links network core: interconnected routers network of networks Introduction 1-11 The network edge: end systems (hosts): run application programs e.g. Web, email at “edge of network” peer-peer client/server model client host requests, receives service from always-on server client/server e.g. Web browser/server; email client/server peer-peer model: minimal (or no) use of dedicated servers e.g. Skype, BitTorrent Introduction 1-12 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 1-13 Dial-up Modem central office telephone network Internet home home ISP dial-up PC modem modem (e.g., AOL) Uses existing telephony infrastructure Home is connected to central office up to 56Kbps direct access to router (often less) Can’t surf and phone at same time: not “always on” Digital Subscriber Line (DSL) Existing phone line: Internet 0-4KHz phone; 4-50KHz home upstream data; 50KHz-1MHz phone downstream data DSLAM telephone splitter network DSL modem central office home PC Also uses existing telephone infrastruture up to 1 Mbps upstream (today typically < 256 kbps) up to 8 Mbps downstream (today typically < 1 Mbps) dedicated physical line to telephone central office Residential access: cable modems Does not use telephone infrastructure Instead uses cable TV infrastructure HFC: hybrid fiber coax asymmetric: up to 30Mbps downstream, 2 Mbps upstream network of cable and fiber attaches homes to ISP router homes share access to router unlike DSL, which has dedicated access Introduction 1-16 Residential access: cable modems Diagram: http://www.cabledatacomnews.com/cmic/diagram.html Introduction 1-17 Cable Network Architecture: Overview Typically 500 to 5,000 homes cable headend home cable distribution network (simplified) Introduction 1-18 Cable Network Architecture: Overview server(s) cable headend home cable distribution network Introduction 1-19 Cable Network Architecture: Overview cable headend home cable distribution network (simplified) Introduction 1-20 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 home cable distribution network Introduction 1-21 Fiber to the Home ONT Internet optical fibers ONT optical OLT fiber optical central office splitter ONT Optical links from central office to the home Two competing optical technologies: Passive Optical network (PON) Active Optical Network (PAN) Much higher Internet rates; fiber also carries television and phone services Ethernet Internet access 100 Mbps Institutional router Ethernet To Institution’s switch ISP 100 Mbps 1 Gbps 100 Mbps server Typically used in companies, universities, etc 10 Mbs, 100Mbps, 1Gbps, 10Gbps Ethernet Today, end systems typically connect into Ethernet switch Wireless access networks shared wireless access network connects end system to router router via base station aka “access point” base wireless LANs: station 802.11b/g (WiFi): 11 or 54 Mbps wider-area wireless access provided by telco operator ~1Mbps over cellular system mobile (EVDO, HSDPA) hosts next up (?): WiMAX (10’s Mbps) over wide area Introduction 1-24 Home networks Typical home network components: DSL or cable modem router/firewall/NAT Ethernet wireless access point wireless to/from laptops cable router/ cable modem firewall headend wireless access Ethernet point Introduction 1-25 Physical Media Twisted Pair (TP) Bit: propagates between two insulated copper transmitter/rcvr pairs wires physical link: what lies Category 3: traditional between transmitter & phone wires, 10 Mbps receiver Ethernet guided media: Category 5: 100Mbps Ethernet signals propagate in solid media: copper, fiber, coax unguided media: signals propagate freely, e.g., radio Introduction 1-26 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: baseband: high-speed point-to-point single channel on cable transmission (e.g., 10’s - legacy Ethernet 100’s Gps) broadband: low error rate: repeaters multiple channels on spaced far apart ; immune cable to electromagnetic noise HFC Introduction 1-27 Physical media: radio signal carried in Radio link types: electromagnetic terrestrial microwave spectrum e.g. up to 45 Mbps channels no physical “wire” LAN (e.g., Wifi) bidirectional 11Mbps, 54 Mbps propagation wide -area (e.g., cellular) environment effects: 3G cellular: ~ 1 Mbps reflection satellite obstruction by objects Kbps to 45Mbps channel (or interference multiple smaller channels) 270 msec end-end delay geosynchronous versus low altitude Introduction 1-28 Chapter 1: roadmap 1.1 What is the Internet? 1.2 Network edge end systems, access networks, links 1.3 Network core circuit switching, packet switching, network structure 1.4 Delay, loss and throughput in packet-switched networks 1.5 Protocol layers, service models 1.6 Networks under attack: security 1.7 History Introduction 1-29 The Network Core mesh of interconnected routers the fundamental question: how is data transferred through