2. 1: Introduction1 Internet Services and Protocols Adapted from “Computer Networking: A Top Down Approach Featuring the Internet” Kurose and Ross, Addison Wesley 2001

3. 1: Introduction2 What’s the Internet: “nuts and bolts” view r millions of connected computing devices: hosts, end-systems m pc’s workstations, servers m PDA’s phones, toasters running network apps r communication links m fiber, copper, radio, satellite r routers: forward packets (chunks) of data thru network local ISP company network regional ISP router workstation server mobile

4. 1: Introduction3 What’s the Internet: “nuts and bolts” view r protocols: control sending, receiving of msgs m e.g., TCP, IP, HTTP, FTP, PPP r Internet: “network of networks” m loosely hierarchical m public Internet versus private intranet r Internet standards m RFC: Request for comments m IETF: Internet Engineering Task Force local ISP company network regional ISP router workstation server mobile

5. 1: Introduction4 What’s the Internet: a service view r communication infrastructure enables distributed applications: m WWW, email, games, e- commerce, database., voting, m more? r communication services provided: m connectionless m connection-oriented r cyberspace [Gibson]: “a consensual hallucination experienced daily by billions of operators, in every nation,...."

6. 1: Introduction5 What’s a protocol? human protocols: r “what’s the time?” r “I have a question” r introductions … specific msgs sent … specific actions taken when msgs received, or other events network protocols: r machines rather than humans r 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

7. 1: Introduction6 What’s a protocol? a human protocol and a computer network protocol: Q: Other human protocol? Hi Got the time? 2:00 TCP connection req. TCP connection reply. Get http://gaia.cs.umass.edu/index.htm time

8. 1: Introduction7 A closer look at network structure: r network edge: applications and hosts r network core: m routers m network of networks r access networks, physical media: communication links

9. 1: Introduction8 The network edge: r end systems (hosts): m run application programs m e.g., WWW, email m at “edge of network” r client/server model m client host requests, receives service from server m e.g., WWW client (browser)/ server; email client/server r peer-peer model: m host interaction symmetric m e.g.: teleconferencing