services, not the information contained on web sites. SIGNALING Signaling is the process of sending control information over landline and mobile net- works to monitor, control, route, and set up sessions between devices. These sessions include video and audio conference calls, data sessions, video calls, and mobile and landline telephone calls. Signaling is also used to set up instant messaging and chat sessions. Signaling is used within public networks and the Internet as well as for inter- carrier connections and billing. Carrier Networks An Overview of Signaling Signaling is used to process every call on the Public Switched Telephone Network (PSTN) and public cellular network. When a caller dials a number, he can hear prog- ress tones such as dial tone, ringing, busy signals, or reorder tones. These are all signal- ing tones. In addition to tones, callers might hear digital messages informing them that the number they dialed is not in service or has been changed. The PSTN uses Signaling System 7 (SS7); IP networks mainly use variations of Session Initiation Protocol (SIP) as the common platforms for call setup, teardown and activation, and control of advanced features. SIP was originally designed for the Internet, but is now used in private packet networks, as well. Signaling is the basis of interconnection between mobile, global wireless, and multiple providers' networks. When AT&T controlled most of the public network in the United States, it had the necessary control of the public network that enabled it to set a standard (SS7) that was followed across the country and was later adopted, with variations, by the international community. SIP is an Internet Engineering Task Force (IETF)-approved standard. In both SIP and SS7 protocols, signaling messages are carried separately from user content. In addition, they both provide common functions. The Basis for Billing and Monitoring Signaling networks monitor traffic on networks around the clock, worldwide. When network problems are detected, alerts are sent over 