Lecture 1 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 1-1

Lecture 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 ! 1-2

Lecture 1 What’s the Internet: “nuts and bolts” view  millions of connected computing devices: hosts = end systems  running network apps Home network Institutional network Mobile network Global ISP Regional ISP router PC server wireless laptop cellular handheld wired links access points  communication links  fiber, copper, radio, satellite  transmission rate = bandwidth  routers: forward packets (chunks of data) 1-3

Lecture 1 What’s the Internet: “operational” view  Internet: “network of networks”  Requires sending, receiving of messages  protocols control sending, receiving of messages  e.g., TCP, IP, HTTP, Skype, Ethernet etc.  Design of protocols is the key for Internet Home network Institutional network Mobile network Global ISP Regional ISP 1-4

Lecture 1 What’s the Internet: an operational view a human protocol and a computer network protocol: human protocol Hi Got the time? 2:00 time 1-5

Lecture 1 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 What’s the Internet: an operational view 1-6

Lecture 1 What’s a protocol? a human protocol and a computer network protocol: Internet protocol example Hi Got the time? 2:00 Connection req. connection reply Get time human protocol 1-7

Lecture 1 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 What’s the Internet: an operational view 1-8

Lecture 1 We have studied a high-level overview of the Internet! Now, A closer look at the Internet structure! 1-9

Lecture 1 Components of Internet:  Hosts (end-users)  e.g. computers  access networks, physical media: wired, wireless communication links  network core:  interconnected routers  network of networks 1-10

Lecture 1 The network edge:  End-users (hosts):  run application programs  e.g. Web, client/server peer-peer  client/server model  client host requests, receives service from always-on server  e.g. Web browser/server; client/server  peer-peer model:  minimal (or no) use of dedicated servers  e.g. Skype, BitTorrent 1-11

Lecture 1 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 1-12

Lecture 1 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 1-13

Lecture 1 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 1-14

Lecture 1 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 1-15

Lecture 1 Wireless access networks  shared wireless access network connects end system to router  wireless LANs:  radio spectrum replaces wire  e.g., b/g (WiFi): 11 or 54 Mbps  wider-area wireless access  next up (?): WiMAX (10’s Mbps) over wide area base station mobile hosts router 1-16

Lecture 1 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! 1-17

 What is Internet?  Components…  Operational view…  System (structure) view…  Client-server and peer to peer model…  Access Networks… Lecture 1 Summary: What have we learnt? 1-18

Lecture 1 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 1-19