This document provides an overview of basic IT infrastructure components and how they connect and interact. It describes common hardware components like desktop computers, servers, switches and routers. It explains client/server architecture and how software like operating systems and applications run on both. It also maps how local area networks connect to wide area networks and the internet via internet service providers. Common network protocols, IP addressing schemes, and security measures like firewalls are also summarized at a high level.

3. Your desktop computer

4. Networking Switch

5. Network Ethernet cable

6. Network Base station

7. L ocal A rea N etwork

8. Servers

9. Desk-side servers

10. Rack mounted server

11. Client / server architecture Clients Server View and edit Store and process

12. Software and the OS Operating system Application software Operating system Server software Desktop Server Desktop Hardware Server Hardware Firmware (BIOS) Firmware (BIOS)

13. Software Operating system Server software (eg Web Server) Firmware/BIOS Operating system Applications (eg Web Browser) Firmware/BIOS Desktop Server Network

14. L ocal A rea N etwork

15. W ide A rea N etwork

16. ISP ISP ISP ISP Internet Leased Line / ADSL Router

17. Bandwidth LAN ADSL Inter-ISP 100Mb/s 0.5Mb/s send, 6Mb/s receive 100 to 1000Mb/s

18. ISP ISP ISP ISP Internet

19. Data centres

20. Data centres (Maximilien Brice; Claudia Marcelloni, © CERN)

22. ISP ISP ISP ISP Internet

23. IP Address 192.168.99.201

26. ISP ISP ISP ISP Internet Public addresses Private NAT

27. Network Address Translation 10.0.0.12 (private) NAT 17.0.0.29 (public) ISP Rest of the internet

30. ISP ISP ISP ISP Internet Firewall goes here

31. Putting it altogether Operating system (Mac OS X) Operating system (Solaris) Desktop Server Network Desktop Hardware Server Hardware Firmware (BIOS) Firmware (BIOS) Application (Firefox web browser) Server software (Apache web server)

32. ISP ISP ISP ISP Internet

33. Magic?