1. Lecture 1 1-1 Chapter 1: 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 packet-switched networks 1.5 Protocol layers, service models 1.6 Networks under attack: security 1.7 History

2. Lecture 1 1-2 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 !

3. 1-3 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)

4. 1-4 Lecture 1 What’s the Internet: “nuts and bolts” view  protocols control sending, receiving of messages  e.g., TCP, IP, HTTP, Skype, Ethernet etc.  Internet: “network of networks”  public Internet versus private intranet  Internet standards  RFC: Request for comments Home network Institutional network Mobile network Global ISP Regional ISP

5. 1-5 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

6. 1-6 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

7. 1-7 Lecture 1 What’s a protocol? a human protocol and a computer network protocol: Internet protocol example Hi Got the time? 2:00 TCP connection req. TCP connection reply. Get http://jjcweb.jjay.cuny.edu/ssengupta/slide.ppt time human protocol

8. 1-8 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 protocols define format, order of msgs sent and received among network entities, and actions taken on msg transmission, receipt What’s the Internet: an operational view

9. Lecture 1 1-9 Take home messages  According to you, what are the three most important physical components of Internet?  Name four Internet applications?  What does an Internet protocol do?

10. Lecture 1 1-10 We have studied a high-level overview of the Internet! Now, A closer look at the Internet structure!

11. 1-11 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

12. 1-12 Lecture 1 The network edge:  End-users (hosts):  run application programs  e.g. Web, email client/server peer-peer  client/server model  client host requests, receives service from always-on server  e.g. Web browser/server; email client/server  peer-peer model:  minimal (or no) use of dedicated servers  e.g. Skype, BitTorrent

13. 1-13 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 Keep in mind:  bandwidth (bits per second) of access network?  shared or dedicated?

14. 1-14 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

15. 1-15 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

16. 1-16 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

17. 1-17 Lecture 1 Wireless access networks  shared wireless access network connects end system to router  wireless LANs:  radio spectrum replaces wire  e.g., 802.11b/g (WiFi): 11 or 54 Mbps  wider-area wireless access  next up (?): WiMAX (10’s Mbps) over wide area base station mobile hosts router

18. Lecture 1 1-18 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!

19.  What is Internet?  Components…  System view…  Client-server and peer to peer model…  Access Networks…  Little bit of layered Internet architecture view… Lecture 1 1-19 Summary: What have we learnt?