EE450, USC, Zahid 1 Overview EE450: Introduction to Computer Networks Professor A. ZahidEE450, USC, Zahid 2 Course Overview Part 1: Data Communications & Networking Part 2: Computer Networking Protocols (TCP/IP) Part 3: Wide Area Networks (WANs) Part 4: Local Area Networks (LANs) Part 5: Internetworking Part 6: Transport Layer Protocols Part 7: Network Applications Part 8: Network Security Focus throughout the course is on the public InternetGrowth of Computer Networks  Computer Networking has grown explosively  Since the 1970s, computer communication has changed from a research topic to an essential part of infrastructure  Networking is used in every aspect of our lives:  Business  Education  Advertising  Social  Entertainment  Production  Planning  Billing  Accounting EE450, USC, Zahid 3Growth of CN (Continued)  In short, computer networks are everywhere  In 1980, the Internet was a research project that involved a few dozen sites. Today, the Internet has grown into a huge Network that reaches all of the world  The advent and utility of networking has created dramatic economic shifts  Network has made telecommuting available to individuals  An entire industry emerged that develops networking technologies, products, and services  The importance of computer networks has produced a demand in all industries for people with more networking expertise  Companies need professionals to plan, acquire, install, operate, and manage the hardware and software systems for networks EE450, USC, Zahid 4EE450, USC, Zahid 5 Multimedia Convergence Network Telephone companies (Telco) Internet Service Providers (ISP) Computer Hardware/Software Telco/wireless Hardware Video - pre-recorded / on-demand (e.g., MPEG, Real Net) - live (video phone, video teleconference) Broadcast TV Film Data - e-mail - files -- executables -- source code -- data -- html -- image Computer Software Financial, e-Commerce, etc. Major Industries Recording Broadcast Radio Voice / Audio - pre-recorded /on-demand (streaming or file [mp3]) - live (Real Net, VoIP) PDA Cell phone Pager WirelessEE450, USC, Zahid 6 Computer (?) Networks  A Computer Network is a set of nodes such as routers, switches, hosts, etc.. interconnected via transmission facilities such as copper, cable, fiber, satellite, radio, microwave, etc.. for the purpose of providing services to end systems/users  So why the question mark?? Non traditional end systems (Laptops, Cell Phones, Tablets, gaming Consoles, Sensor devices, Toasters, Refrigerators, etc...) are being connected to the internet  Point-to-point communication is not practical!  Devices are too far apart  Large set of devices would need impractical number of connections. See illustration next chartGeneric Computer Network EE450, USC, Zahid 7EE450, USC, Zahid 8 Example: Telephone Network Fully-Connected Mesh # of FDX links = N(N-1)/2 e.g., N=6; 6(5)/2=15 links Total # ports = N(N-1) e.g., N=6; 6(5)=30 ports Central Office (CO) With Central Office # of FDX links = N e.g., N=6; 6 links Total # of ports = N e.g. N=6, 6 portsEE450, USC, Zahid 9 Clients, Servers and Peers  A network computer can either provide service or request service  A server is a service provider, providing access to network resources  A Client is a service requester  A Peer-to-Peer network does not have a dedicated server. All computers are equal and they both provide and request services.EE450, USC, Zahid 10 Server Roles  Servers can assume several roles and a single server could also have several roles  Examples of Servers include:  File Servers: Manages user access to shared files  Print Servers: Manages user access to print resources  Application Servers: Similar to FS with some processing  Mail Servers: Manages electronic messages between users  Communications (Remote Access) Servers: Manages data flow and e-messages from one network to another  Web Servers: Runs WWW and FTP servers for access via the Internet/Intranet  Directory (DNS) Servers: Locates information about networks such as domains.EE450, USC, Zahid 11 Client/Server Model Client (web browser) -source- Network Server (web server) -destination- html file image file Example: World Wide Web Request (GET index.html) Response (HTML file gif, jpeg, .. Http://www.yahoo.com <html> </html>EE450, USC, Zahid 12 Peer-to-Peer Model  Peer-to-Peer  Each host has both client and server functionalities  CPU cycle sharing  Example: Gnutella, KaZaA, Skype, BitTorrent, etc... Client Server Request Response Network Server Client ServerNetwork Applications  E-mail  WWW  Instant messaging  Remote login  P2P file sharing  Multi-user network games  Streaming audio/video  You Tube, Hulu, Netflix  Voice over IP (e.g. Skype)  Real-time video conferencing  Grid computing  On-line Social Network  Facebook, Twitter, etc…  E-Commerce  Distributed Databases  Search EE450, USC, Zahid 13 Note: different applications may have different • Requirements (delay, loss, Throughput, jitter bounds, security) • Number of participants (unicast, multicast, broadcast, etc…) • Architecture (client-server, p2p, flat, hierarchical, hybrid, etc…) • All applications can communicate over a single shared networkCreating a Networked Application EE450, USC, Zahid 14 Write programs that:  run on (different) end systems  communicate over network  e.g., web server software communicates with browser software No need to write software for network-core devices  network-core devices do not run user applications  applications on end systems allows for rapid application development application transport network data link physical application transport network data link physical application transport network data link physicalClient Server Architecture EE450, USC, Zahid 15 Server:  Always-on host  Permanent IP address  Data centers for scaling Clients:  Communicate with server  May be intermittently connected  May have dynamic IP addresses  Do not communicate directly with each other client/serverP2P Architecture EE450, USC, Zahid 16  No always-on server  arbitrary end systems directly communicate  Peers request service from other peers, provide service in return to other peers  self scalability – new peers bring new