L
LAN	Local-area network. High-speed, low-error data network covering a relatively small geographic area (up to a few thousand meters). LANs connect workstations, peripherals, terminals, and other devices in a single building or other geographically limited area. LAN standards specify cabling and signaling at the physical and data-link layers of the OSI reference model. Ethernet, FDDI, and Token Ring are widely used LAN technologies.
latency	Delay between the time a device requests access to a network and the time it is granted permission to transmit.
Layer 1	Physical layer of the OSI reference model. Responsible for the electric signal being sent and received. This can be viewed as a bit stream coming in, and going out, of the system. Scope must be considered when using this term. For example, Layer 1 on a T1 is 1.544 Mbps but Layer 1 on a DS-0 time slot in the T1 is 64 kbps.
Layer 2	Data-link layer of the OSI reference model. Responsible for point-to-point delivery of a PDU. Layer 2 protocols have two basic classes: reliable (meaning delivery is guaranteed or an error is reported) and unreliable (meaning delivery might not occur with no indication to the upper layers).
Layer 3	Network layer of the OSI reference model. Responsible for the network routing and delivery of messages. Examples of Layer 3 protocols include X.25 and IP. Q.931 is not considered a Layer 3 protocol because it does not route or deliver messages.
LCF message	Location-Confirmation RAS message.
LCS	Line-control signaling. Transport of line-supervision signals in the media stream using NTEs.
LDAP	Lightweight Directory Access Protocol. Protocol that provides access for management and browser applications that provide read/write interactive access to the X.500 Directory.
LEC	Local-exchange carrier. Telephone company that provides customer access to the PSTN through one of its central offices.
leg 1	Call segment between the PSTN and the originating gateway (see also call leg).
leg 2	Call segment between the PSTN and the originating gateway (see also call leg).
leg 3	Call segment between the originating gateway and the IP network (see also call leg).
leg 4	Call segment between the terminating gateway and the PSTN (see also call leg).
LEX	LAN extender (interface).
local route	Routes injected into TRIP at a location server are considered local routes by that location server. These routes may be injected by TGREP or by manual means. Routes received from another TRIP peer through I-TRIP or E-TRIP are not considered local routes.
local speed dial	Speed-dial numbers that are common to all phones and that are accessed through the Directories button on a phone. See also personal speed dial.
location server	Server that provides location services. A SIP redirect or proxy server uses a location service to get information about a caller's locations.
long pound calls	Calls in which the user presses the pound (#) key to make a new call—typically while making calls using a charge or debit card—without having to enter the card number or having to wait to be authenticated again.
loopstart signaling	One of four common forms of CAS signaling; the others are groundstart, EANA, and E&M.
LRJ message	Location Reject RAS message.
LRQ message	Location Request RAS message.
LS	1. Location server. A centralized resource (such as a SIP proxy or redirect server or an H.323 gatekeeper) that identifies the next hop for the VoIP connection and communicates that to the originating gateway or terminal. 2. Low speed. Fax-transmission rate used for capabilities negotiation, defined as 300 baud. See also HS.
LT-S	Subscriber-line termination.
LT-T	Trunk-line termination.