Well-known web servers such as Apache and web proxies like Squid support event logging using a common log format. The logs produced using these de facto standard formats are invaluable to system administrators for troubleshooting a server and tool writers to craft tools that mine the log files and produce reports and trends. Furthermore@ these log files can also be used to train anomaly detection systems and feed events into a security event management system. The Session Initiation Protocol (SIP) does not have a common log format@ and@ as a result@ each server supports a distinct log format that makes it unnecessarily complex to produce tools to do trend analysis and security detection. This document describes a framework@ including requirements and analysis of existing approaches@ and specifies an information model for development of a SIP common log file format that can be used uniformly by user agents@ proxies@ registrars@ and redirect servers as well as back-to-back user agents.