mplementations from the carrier's. In these cases, manufacturers modify their equipment to match the RFC implemented by the carrier for its network. The SIP Forum, a non-profit organization that advances interoperability and hosts interoperability testing, has simplified internetworking between carriers as well as between carriers and enterprises. The forum recommends specific profiles (RFCs) to use when connecting enterprise SIP trunks for VoIP service. Most carriers now use these and other specified profiles. Interconnecting Carriers and Providing Secure Space for Equipment in Co-Location Facilities Co-location facilities are sites where network service providers house their switches and routers and connect to one another's networks. Co-location facilities are also referred to as carrier hotels. There are up to 200 carriers located at the very largest co-location sites. Co-location facilities are connected to the Internet, public and private data networks, and the PSTN. Because SO many network providers depend on co-location facilities, security and sustainability in the face of natural and human-made disasters are critical. For these reasons, co-location facilities are located in secure buildings with few windows and no company logos to identify them. They are also monitored by security cameras and heavily guarded by security firms. They often additionally duplicate their service in a completely separate facility connected by fiber cabling to their main location. www.TechnicalPDF.com Carriers rent space in co-location facilities because no provider has outside cabling everywhere. In addition, certain providers have no cabling facilities. Instead, they own switches, which they connect to other carriers' networks. In both of these circumstances, rather than construct their own buildings to house their switches, carriers lease space in carrier hotels. They place their equipment in cages or lease space in equipment cabinets in the carrier hotel. Locked wire cages surround the equipment and access to the equipment 