e for makes them less costly than proprietary telephone calls, audio conferencing, click- switches based on circuit-switched technol- to-dial from the Web, and instant message ogy. Softswitches manage and control traffic exchanges between devices. It is also used to in IP networks. link IP telephones from different manufac- turers to SIP-compatible IP telephones. It is SONET (Synchronous Optical used in landline and mobile networks. Network) An older standard for multiplexing high- SLA (Service-Level Agreement) speed digital bits onto fiber-optic cabling. Often provided to customers by carriers that SONET converts electronic impulses to light sell MPLS. The SLA defines service param- impulses, and vice versa. Telephone compa- eters such as uptime and response time. nies use SONET to transmit data from mul- tiple customers over the same fiber cables. smart grids Upgraded utility networks for metering that spectrum can carry two-way messages on cellular Made up of frequency bands or airwaves that networks between customers and electric carry either analog or digital wireless signals. Glossary Spectrum consists of the multitude of invis- potential customers via computers connected ible electric energy in frequency bands that to the Internet at dispersed sites. surround the Earth and are used to transmit segregated radio waves. Radio waves carry signals as electrical energy on unseen waves. A North American and Japanese standard for communicating at 1.54Mbps. A T1 line has SSL (Secure Sockets Layer) the capacity for 24 voice or data channels. A newer type of security for VPNs than IPsec. It is embedded in browsers SO that organiza- tions aren't required to install special client A North American standard for communicat- software in each user's computer. ing at speeds of 44Mbps. T3 lines have 672 channels for voice and/or data. Fiber-optic statistical multiplexing Assumes that not all devices are active all the cabling or digital microwave is required for T3 transmissions. time. A statistical multiplexer does not save