Any Network where different types of systems from different companies and having different technology are connected and must communicate with each other successfully is known as a Multi Vendor Network Environment. The important thing here is that the Protocol layers such as TCP/IP and SS7 allow for such a communication and are thus important for this reason.
Simplest example is the internet. Thousands of Windows and Linuxs and Macintoshes and UNIXs connected together to create the internet and ll communicating efficiently all thanks to the TCP/IP set of protocols...
~eNjoy~
