WATS and leased lines

What are the differences between Wide Area Telecommunications Service (WATS) and leased lines?

PBX and Centrex

What is the difference between Private Branch eXchange (PBX) and Centrex?

OSI Open Systems Interconnect

Briefly, what are the functions different layers of the International Standards Organization-Open Systems Interconnection (ISO-OSI) model?

Windows Server 2003 Network problem

I'm having a trouble with a local Pioneer hospital that has just moved to a brand new location. The Pioneer hospital has decided to use Windows 2003 for its computing environment. I have been hired to lead the implementation, management, and maintenance of their network. My initial task is to setup one server and 20 client machines. I need to discuss the facilities and services provided by Pioneer hospital and suggest a possible preliminary network design. I also need to compare the following editions of windows 2003 Server and give examples of suitability of usage for each edition: Web Edition Standard Edition Enterprise Edition Data Center Edition

Network Design

Please see the attached file for background information. Problem: Describe in detail the technologies involved in the proposal to educate management. What additional information is needed from ICI to determine the feasibility of the proposal?