d to sell local telephone ser- from a common network interface. vices. LATAs cover metropolitan statistical areas based on population sizes. For exam- ISP (Internet Service Provider) ple, Massachusetts has two LATAs and Wis- An organization that connects end users to consin has four, but Wyoming, which has a the Internet via broadband, mobile networks, small population, has one LATA. LATAs are Glossary sometimes used for billing telephone calls in local loop the United States. The telephone line that runs from the local telephone company to the end user's prem- Layer 4 ises. The local loop can use fiber, copper, or One of the seven layers of the OSI model. wireless media. Layer 4 is the Transport layer that routes and prioritizes packets, based on the source LUN (Logical Unit Number) An identifier in Storage Area Networks of the packet, the destination port number, (SANs). It identifies the particular database the protocol type, and the application. For stored in a computer disk. LUNs are part of example, Layer 4 devices can prioritize voice the Fibre Channel protocol used in SANs. and video SO that networks using IP for voice and data can handle voice without the delays LTE (Long-Term Evolution) and lost packets associated with lower-level A 4G mobile protocol that uses packet switch- protocols. ing to carry voice, data, and multimedia traf- fic more efficiently than earlier protocols. It LDAP (Lightweight Directory Access will eventually support broadband speeds of Protocol) up to 100Mbps. LTE was developed by the A directory protocol that describes a uniform 3rd Generation Partnership Project. way of organizing information in directo- MAN (Metropolitan Area Network) ries. Examples of LDAP directories include A network that covers a metropolitan area the address books in e-mail systems. LDAP such as a portion of a city. Hospitals, univer- enables companies to use one central direc- sities, municipalities, and large corporations tory to update multiple corporate directories. often have telephone lines running be