The SIP Center is a public resource for the commercial development of SIP (Session Initiation Protocol.) Serving both the SIP developer community as well as the wider industry since July of 2000, The SIP Center offers technical and market resources as well as a 24 x 7 public SIP proxy for testing SIP implementations. There are free SIP User Agent downloads, a comprehensive products and services directory, the latest SIP news and special interest articles, tutorials, whitepapers, developers tools and resources and much more. Visit The SIP Center for information on all things SIP www.sipcenter.com.