System.Net namespace in .NET Framework Class Library
The System.Net namespace provides a simple programming interface for many of the protocols used on networks today, including FTP, HTTP, SMTP, ICMP, DNS, and others.
The WebRequest and WebResponse classes form the basis of what are called pluggable protocols, an implementation of network services that enables developers to create applications that use Internet resources without worrying about the specific details of the individual protocols. System.Net also includes a full sockets library, including, in the .NET Framework 2.0, an SSL-enabled Stream class.