http://www.rfc-editor.org/rfc/rfc3149.txt
RFC 3149: MGCP Business Phone Packages, A. Srinath, G. Levendel, K. Fritz, R. Kalyanaram2001-09-01T23:00:00-00:00This document describes a collection of MGCP (Media Gateway Control Protocol) packages that can be used to take advantage of the feature keys and displays on digital business phones and IP-Phones. This memo provides information for the Internet community.