http://www.rfc-editor.org/rfc/rfc4504.txt
RFC 4504: SIP Telephony Device Requirements and Configuration, H. Sinnreich, S. Lass, C. Stredicke2006-05-01T23:00:00-00:00We present a glossary of the most common settings and some of the more widely used values for some settings. This memo provides information for the Internet community.