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Transcript
Internet Overview: roadmap 1.1 What is the Internet? 1.2 Network edge end systems, access networks, links 1.3 Network core network structure, circuit switching, packet switching 1.4 Delay, loss and throughput in Internet 1.5 Protocol layers, service models 1.6 Networks under attack: security Lecture 1 1-1 How is the Internet Organized A hierarchical structure. hosts combine to form a Local Area Network (LAN). LANs combine to form an Autonomous System (AS) Autonomous Systems combine to form the Internet. Internetworked networks – Internet ! Lecture 1 1-2 What’s the Internet: “nuts and bolts” view PC millions of connected computing devices: hosts = end systems wireless laptop running network cellular handheld apps communication links fiber, copper, access points radio, satellite wired links transmission rate = bandwidth routers: forward router packets (chunks of data) Mobile network server Lecture 1 Global ISP Home network Regional ISP Institutional network 1-3 What’s the Internet: “operational” view Mobile network Internet: “network of networks” Global ISP Requires sending, receiving of messages protocols control sending, Home network Regional ISP receiving of messages e.g., TCP, IP, HTTP, Skype, Ethernet etc. Institutional network Design of protocols is the key for Internet Lecture 1 1-4 What’s the Internet: an operational view a human protocol and a computer network protocol: Hi Hi Got the time? 2:00 human protocol time Lecture 1 1-5 What’s the Internet: an operational view human protocols: … specific msgs sent … specific actions taken when msgs received, or other events network protocols: machines rather than humans all communication activity in Internet governed by protocols Lecture 1 1-6 What’s a protocol? a human protocol and a computer network protocol: Hi Connection req. Hi connection reply Got the time? Get http://jjcweb.jjay.cuny.edu/ssengupta/slide.ppt 2:00 human protocol <file> time Internet protocol example Lecture 1 1-7 What’s the Internet: an operational view Thus protocols define • format, order of messages sent and received among network entities, • actions taken on message transmission and receipt • address conflicts among network entities Lecture 1 1-8 We have studied a high-level overview of the Internet! Now, A closer look at the Internet structure! Lecture 1 1-9 Components of Internet: Hosts (end-users) e.g. computers access networks, physical media: wired, wireless communication links network core: interconnected routers network of networks Lecture 1 1-10 The network edge: End-users (hosts): run application programs e.g. Web, email 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 Lecture 1 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 Lecture 1 1-12 Residential access: point to point access Dialup via modem up to 56Kbps direct access to router (conceptually) ADSL: asymmetric digital subscriber line up to 1 Mbps home-to-router up to 8 Mbps router-to-home ADSL deployment: happening Lecture 1 1-13 Residential access: cable modems HFC: hybrid fiber coax asymmetric: up to 10Mbps upstream, 1 Mbps downstream network of cable and fiber attaches homes to ISP router shared access to router among home issues: congestion deployment: available via cable companies, e.g., MediaOne, CableVision Lecture 1 1-14 Institutional access: local area networks company/univ local area network (LAN) connects end system to edge router Ethernet: shared or dedicated cable connects end system and router 10 Mbps, 100Mbps, Gigabit Ethernet deployment: institutions, home LANs happening now Lecture 1 1-15 Wireless access networks shared wireless access network connects end system to router wireless LANs: router radio spectrum replaces wire e.g., 802.11b/g (WiFi): 11 or 54 Mbps base station wider-area wireless access next up (?): WiMAX (10’s Mbps) over wide area Lecture 1 mobile hosts 1-16 The Client/Server Model Client/server model is a basic design for Internet applications server - is the information provider client - is the information consumer example web server and a client running web browser a CNN web server simultaneously serves thousands of clients. In this class, we will also learn how to construct Web pages at the client end! Lecture 1 1-17 Summary: What have we learnt? What is Internet? Components… Operational view… System (structure) view… Client-server and peer to peer model… Access Networks… Lecture 1 1-18 Next Up… 1.1 What is the Internet? 1.2 Network edge end systems, access networks, links 1.3 Network core network structure, circuit switching, packet switching 1.4 Delay, loss and throughput in Internet 1.5 Protocol layers, service models 1.6 Networks under attack: security Lecture 1 1-19