This content is 20 years old. I don't routinely update old blog posts as they are only intended to represent a view at a particular point in time. Please be warned that the information here may be out of date.
As security becomes ever more paramount and network administrators implement extra layers of security, including client PCs running personal firewall products, systems administrators and support staff need to know which ports and protocols Microsoft operating systems and programs require for network connectivity in a segmented network.
Microsoft have addressed this with Microsoft knowledge base article 832017, which details the essential network ports, protocols and services that are used by Microsoft client and server operating systems, server-based programs and their subcomponents in the Microsoft Windows server system.