Cisco Systems Bell Labs Mozilla The SIPCLF working group has defined a Common Log Format (CLF) framework for Session Initiation Protocol (SIP) servers. This CLF mimics the successful event logging format found in well-known web servers like Apache and web proxies like Squid. This document proposes an indexed text encoding format for the SIP CLF that retains the key advantages of a text-based format while significantly increasing processing performance over a purely text-based implementation. This file format adheres to the SIP CLF information model and provides an effective encoding scheme for all mandatory and optional fields that appear in a SIP CLF record.