L2TP Session
L2TP Session, also known as L2TP call, refers to the communications transactions using Layer 2 Tunneling Protocol (L2TP) between the L2TP Access Concentrator (LAC) and the L2TP Network Server (LNS) that support tunneling of a single PPP connection. L2TP session (or call) is established within the tunnel for each higher-level protocol such as PPP. Either the LAC or LNS may initiate sessions. The traffic for each session is isolated by L2TP, so it is possible to set up multiple virtual networks across a single tunnel.

L2TP Tunnel
L2TP Tunnel refers to the logic link between the two Layer 2 Tunneling Protocol (L2TP) endpoints: the LAC (L2TP Access Concentrator) and the LNS (L2TP Network Server). The LAC is the initiator of the tunnel while the LNS is the server which waits for new tunnels. Once a tunnel is established, the network traffic between the peers is bidirectional. To be useful for networking, higher-level protocols such as Point-to-Point Protocol (PPP) are then run through the L2TP tunnel.

LAA: Locally Administered Address
Locally Administered Address (LAA) is a type of MAC address when the burned-in address (BIA) within the MAC address is overridden by the user. In these cases, the second bit of the most significant byte of the Organisationally Unique Identifier (OUI) is changed to a binary 1. The burned-in address (BIA) is the last six bytes of a MAC address that are assigned by the manufacturer of a network interface card (NIC). When this happens, the Network Interface Card (NIC) is using a Locally Administered Address (LAA) as its MAC address. If the NIC is not configured to use an LAA as its BIA, then the second bit of the most significant byte of the OUI is changed to a binary 0. In this case, the NIC is using a Universally Administered Address (UAA) as its MAC address.

Label Imposition
Label Imposition is the act of putting the first label or tag on a packet, which is a necessary procedure in a Multiprotocol label switching (MPLS) network for tunnel establishment.

Label Swapping
Label Swapping is a routing algorithm used by IBM APPN in which each router that a message passes through on its way to its destination independently determines the best path to the next router.

Label Switch
Label Switch is a technology that forwards units of data (packets or cells) on the basis of labels. The most popular protocol for this is the Multiprotocol Label Switching (MPLS).

LAC: L2TP Access Concentrator
L2TP Access Concentrator (LAC) is a node that acts as one side of an L2TP tunnel endpoint and is a peer to the L2TP network server (LNS). The LAC sits between an LNS and a remote system and forwards packets to and from each. Packets sent from the LAC to the LNS require tunneling with the L2TP protocol as defined in this document. The connection from the LAC to the remote system is either local or a PPP link.

laddr: Local address
Local address (laddr) is the address of an internal host on a protected interface.

Lag
Lag in networking refers to the time taken for a packet of data to travel between the local computer, the destination and back again. Whilst in the strictest sense every packet experiences lag, the term lag is implied to refer to noticeable delays to the user caused as a result of extended or unexpected delay.

LAN Manager
The LAN Manager was a Network Operating System (NOS) from Microsoft developed in cooperation with 3Com Corporation. It is based on the Operating System/2 (OS/2) and NetBEUI protocol similar to its predecessors MS-NET for MS-DOS and Xenix-NET for MS-Xenix. There was also LAN Manager/X (LMX) for UNIX-based systems. LAN Manager was superseded by Windows NT Server, and many parts of LAN Manager are used in NT.

LAN Server
LAN Server is an IBM Network Operating System (NOS). The IBM LAN Server started as a close cousin of Microsoft LAN Manager and first shipped in early 1988. It was originally designed to run on top of Operating System/2 Extended Edition. The network client was called IBM LAN Requester and was included with OS/2 EE 1.1 by default. LAN Server basically refers to the IBM OS/2 LAN Server product. There were also LAN Server products for other operating systems, notably AIX (now called Fast Connect) and OS/400.

LAN Switch
LAN Switch is specially designed and optimized for local area network switching that forwards packets between data-link segments. Most LAN switches forward traffic based on MAC addresses. LAN switches are often categorized according to the method they use to forward traffic: cut-through packet switching or store-and-forward packet switching. Multilayer switches are an intelligent subset of LAN switches. LAN switches are available for Ethernet, Fast Ethernet, Token Ring and FDDI.

LAN: Local Area Network
Local Area Network (LAN) is a data communications network connecting terminals, computers and printers within a building or other geographically limited areas. These devices could be connected through wired cables or wireless links. Ethernet, Token Ring and Wireless LAN are examples of standard LAN technologies.

LANE: LAN Emulation
LAN Emulation (LANE) is a technology that allows an ATM network to function as a LAN backbone. The ATM network must provide multicast and broadcast support, address mapping (MAC-to-ATM), SVC management, and a usable packet format. LANE also defines Ethernet and Token Ring Emulated LANs (ELANs).

LAT: Local Address Table
Local Address Table (LAT) is a table of all IP address ranges in the internal network protected by a server computer. The LAT is configured during installation and can be modified after. The LAT can be used to define "trusted" computers on the internal network. Anything not in the LAT is considered external and "untrusted".

Late Collision
Late Collision is a failure of the network in which the collision indication arrives too late in the frame transmission to be automatically dealt with by the medium access control (MAC) protocol.

Latency
Latency is a time delay between the moment something is initiated, and the moment one of its effects begins. In computer neworking, Latency is measured either one-way (the time from the source sending a packet to the destination receiving it), or round-trip (the one-way latency from source to destination plus the one-way latency from the destination back to the source). Round-trip latency is more often quoted, because it can be measured from a single point. Note that round trip latency excludes the amount of time that a destination system spends processing the packet.

Layer
Layer, in the networking communication, is a logical level of network processing functions defined by OSI model, in which 7 layers are defined for the complete network communications. Processing takes place in layers starting from the physical transmission of data up through to the commands of an end-user (application layer).

Layer 4 router
A typical network router is a layer 3 network device which simply sends incoming packets onto the appropriate IP address on its network. A layer 4 router, which uses the Transport Layer information when making decisions on where to send the packets, can send incoming packets to one or more machines which are hidden behind a single IP address.

LBR: Label Bit Rate
Label Bit Rate (LBR) is a service category for label VC traffic in an ATM network. Link and per-VC bandwidth sharing can be controlled by relative bandwidth configuration at the edge and each switch along a label VC. No ATM traffic-related parameters are specified.

LC-ATM Interface
Label-controlled ATM interface (LC-ATM Interface) is an MPLS interface in which labels are carried in the VPI or VCI fields of the ATM cells and in which VC connections are established under the control of MPLS software.

LCC: Line Card Control
Line Card Control (LCC) is a process that runs on the ATM switch to establishes VCCs, maintains the link management protocol for the line card, continually monitors line quality on each trunk using TUD, and performs other functions.

LCF: Location Confirm Message
Location Confirm Message (LCF) is a Registration, Admission and Status(RAS) message that a Gatekeeper sends to the requesting Gatekeeper/endpoint accepting the LRQ.

LCI: Logical Channel Identifier
Logical channel identifier (LCI), also known as Logical Channel Number (LCN) or Virtual circuit number (VCN) is a 12-bit field in an X.25 PLP header that identifies an X.25 virtual circuit. It allows DCE to determine how to route a packet through the X.25 network.

LCN: Logical Channel Number
Logical channel number (LCN), also known as Logical Channel identifier (LCI) or Virtual circuit number (VCN) is a 12-bit field in an X.25 PLP header that identifies an X.25 virtual circuit. It allows DCE to determine how to route a packet through the X.25 network.

Leaf Internetwork
Leaf Internetwork is a type of interworking topology in a star topology, where an internetwork whose sole access to other internetworks in the star is through a core router.

Leaky Bucket
Leaky Bucket, a metaphor for the general cell rate algorithm (GCRA) in ATM, is used for conformance checking of cell flows from a user or a network. The hole in the bucket represents the sustained rate at which cells can be accommodated, and the bucket depth represents the tolerance for cell bursts over a period of time.

Learning Bridge
Learning Bridge is a network device that performs MAC address learning to reduce traffic on the network. Learning bridges manage a database of MAC addresses and the interfaces associated with each address. They add each new MAC address, along with the port number of the port on which it learned of the MAC address, to an address table.

Leased Line
Leased Line is a transmission line reserved by a communications carrier for a customer's private use. A leased line is a type of dedicated line, such as T1/E1 and T3/E3 etc.

LEC: LAN Emulation Client
LAN Emulation Client (LEC) is an entity in an end system (ES) of ATM network that performs data forwarding, address resolution, and other control functions for a single ES within a single Emulated LAN (ELAN). An LEC also provides a standard LAN service interface to any higher-layer entity that interfaces to the LEC. Each LEC is identified by a unique ATM address, and is associated with one or more MAC addresses reachable through that ATM address.

LECS: LAN Emulation Configuration Server
LAN Emulation Configuration Server (LECS) is an entity in an ATM network that assigns individual LANE clients to particular Emulated LANs (ELANs) by directing them to the LAN Emulation Server (LES) that corresponds to the ELAN. There is logically one LECS per administrative domain, and this serves all ELANs within that domain.

LEN Node: Low-entry Networking Node
Low-entry Networking Node (LEN Node) is a PU 2.1 in the IBM SNA network that supports LU protocols, but whose CP cannot communicate with other nodes. Because there is no CP-to-CP session between a LEN node and its NN, the LEN node must have a statically defined image of the APPN network.

Leonard Kleinrock
Leonard Kleinrock, born 1934, is a computer scientist who made several extremely important contributions to the field of computer networking, in particular to the theoretical side of computer networking. His most well-known and significant work is his early work on queueing theory, which has applications in many fields, among them as a key mathematical background to packet switching, the basic technology behind the Internet.

LES: LAN Emulation Server
LAN Emulation Server (LES) is an entity in the ATM network that implements the control function for a particular Emulated LAN (ELAN). There is only one logical LES per ELAN, and it is identified by a unique ATM address.

Level 1 Router
Level 1 Router is the device that routes traffic within a single DECnet or OSI area. In the OSI network, level 1 router uses IS-IS protocol to router intra-area traffic. Many routers based on IS-IS protocol can do both intra- and inter- area routing. In this case it is called level 1-2 router.

Level 2 Router
Level 2 Router is a device that routes traffic between DECnet or OSI areas. All Level 2 routers must form a contiguous network. In the OSI network, level 2 router uses IS-IS protocol to router inter-area traffic. Many routers based on IS-IS protocol can do both intra- and inter- area routing. In this case it is called level 1-2 router.

LFIB: Label Forwarding Information Base
Label forwarding information base (LFIB) is a data structure and way of managing forwarding in which destinations and incoming labels are associated with outgoing interfaces and labels.

LFSR: Linear Feedback Shift Register
Linear Feedback Shift Register (LFSR) is a mechanism for generating a sequence of binary bits. The register consists of a series of cells that are set by an initialization vector that is, most often, the secret key. The behavior of the register is regulated by a clock. At each clocking instant, the contents of the cells of the register are shifted right by one position, and the exclusive-or of a subset of the cell contents is placed in the leftmost cell. One bit of output usually is derived during this update procedure. Applications of LFSRs include generating pseudo-random numbers, pseudo-noise sequences, fast digital counters, and whitening sequences. Both hardware and software implementations of LFSRs are common.

LGN: Logical Group Node
Logical Group Node (LGN), a concept in the ATM PNNI network topology, is the node that represents its peer group in the peer group's parent peer group. The concept of the logical group node provides a recursion mechanism to partition and aggregate ATM networks. PNNI protocol partitions a network into a hierarchy of peer groups (PG) of logical group nodes (LGN). Each peer group at a lower hierarchical level is aggregated into a logical group node at a higher level. The logical group node is represented by the PNNI complex node representation that retains the most important link state and topology information of the peer group.

Limited Resource Link
Limited Resource Link is the resource defined by a device operator to remain active only when being used.

Line Code Type
Line Code Type is one of a number of coding schemes used on serial lines to maintain data integrity and reliability. The line code type used is determined by the carrier service provider.

Line Conditioning
Line Conditioning refers to the use of equipment on leased voice-grade channels to improve analog characteristics, thereby allowing higher transmission rates.

Line Driver
Line Driver is an inexpensive amplifier and signal converter that conditions digital signals to ensure reliable transmissions over extended distances.

Line of Sight
Line of Sight refers to a characteristic of certain transmission systems, such as laser, microwave, and infrared systems, in which no obstructions in a direct path between transmitter and receiver can exist.

Link
Link, sometimes referred to as a line or a transmission link, is a network communication channel consisting of a circuit or transmission path and all related equipment between a sender and a receiver. Most often it refers to a WAN connection. In the context of a transmission network, a link is a point-to-point connection between adjacent nodes. There can be more than one link between adjacent nodes.

Link Aggregation
Link Aggregation, also called trunking or port trunking, is a technique of combining physical network links into a single logical link for increased bandwidth, achieving load balancing and increase fault tolerance. Link aggregation may be used to improve access to public networks by aggregating modem links or digital lines. Link aggregation may also be used in the enterprise network to build multi-gigabit backbone links between Gigabit Ethernet switches.

Link State Routing Algorithm
Link State Routing Algorithm is a routing algorithm in which each router broadcasts or multicasts information regarding the cost of reaching each of its neighbors to all nodes in the internetwork. The entire routing table is not distributed from any router, only the part of the table containing its neighbors. Link state algorithms create a consistent view of the network and are therefore not prone to routing loops, but they achieve this at the cost of relatively greater computational difficulty and more widespread traffic. Some of the routing protocols using the Link State Routing Algorithm are the OSPF, IS-IS and EIGRP.

LIS: Logical IP Subnet
Logical IP Subnet (LIS) is a group of IP nodes (such as hosts and routers) that connects to a single ATM network and belongs to the same IP subnet.

Listserv
Listserv is an automated mailing list distribution system originally designed for the Bitnet/EARN but now still used on the Internet. Listserv allows users to add or delete themselves from mailing lists without (other) human intervention.

LITNET: Academic and Research Network in Lithuania
Academic and Research Network in Lithuania (LITNET) is an Academic and Research Network in Lithuania, established in 1991.

Little-endian
Little-endian is a method of storing or transmitting data in which the least significant bit or byte is presented first, compared with big-endian, which transfers the most important bit/byte first.

LMI: Local Management Interface
Local Management Interface (LMI) is a set of enhancements to the basic Frame Relay specification. LMI includes support for a keepalive mechanism, which verifies that data is flowing; a multicast mechanism, which provides the network server with its local DLCI and the multicast DLCI; global addressing, which gives DLCIs global rather than local significance in Frame Relay networks; and a status mechanism, which provides an on-going status report on the DLCIs known to the switch. Known as LMT in ANSI terminology.

LMT: Last mile technology
Last-mile technology refers to the telecommunications technologies that provide connection services to and from the home or business. The typical last-mile technologies include xDSL, Cable and cable modem access (DOCSIS), wireless access (802.16), and optic fiber and its transmission technologies.

LMU: LAN Manager for UNIX
LAN Manager for UNIX (LMU or LMX) is a Microsoft tool to monitor LAN devices in UNIX environments. LMU is an enhanced version of the Microsoft LAN Manager for DOS and OS/2 systems. Included in the LMU are Unix System client support, IBM-compatible NetBEUI transport support, virtual-terminal facilities for Unix System logins, etc.

LNM: LAN Network Manager
LAN Network Manager (LNM) is the Source Route Bridging (SRB) and Token Ring management package provided by IBM. Typically running on a PC, it monitors SRB and Token Ring devices, and can pass alerts up to NetView.

LNNI: LAN Emulation Network-to-Network Interface
LAN Emulation Network-to-Network Interface (LNNI), a technology in ATM LANE, supports communications between the server components within a single Emulated LAN (ELAN).

LNS: L2TP Network Server
L2TP Network Server (LNS) is a node that acts as one side of an L2TP tunnel endpoint and is a peer to the L2TP access concentrator (LAC). The LNS is the logical termination point of a PPP session that is being tunneled from the remote system by the LAC.

Load Balancing
Load Balancing generally refers to distributing processing and communications activity evenly across a computer network so that no single device is overwhelmed. In routing it means the ability of a router to distribute traffic over all its network ports that are the same distance from the destination address. Load balancing increases the utilization of computers and network bandwidth. In Web services load balancing scheme is also applied by employing two or more Web servers. If one server starts to get swamped, requests are forwarded to another server with more capacity.

Local Acknowledgment
Local Acknowledgment is a method whereby an intermediate network node, such as a router, responds to acknowledgments for a remote end host. Use of local acknowledgments reduces network overhead and, therefore, the risk of time-outs.

Local adjacency
Local adjacency refers to the situation in a Frame Relay network where two Virtual Network Switches (VNSs) that control different areas, but communicate with one another through a Frame Relay Permanent Virtual Circuit (PVC).

Local Bridge
Local Bridge is a bridge that directly interconnects networks in the same geographic area.

Local Explorer Packet
Local Explorer Packet is generated by an end system in a Source-route Bridging (SRB) network to find a host connected to the local ring. If the local explorer packet fails to find a local host, the end system produces either a spanning explorer packet or an all-routes explorer packet.

Local Traffic Filtering
Local Traffic Filtering is the process by which a bridge filters out (drops) frames whose source and destination MAC addresses are located on the same interface on the bridge, thus preventing unnecessary traffic from being forwarded across the bridge. Local traffic filtering is defined in the IEEE 802.1 standard.

LOCD: Loss of Cell Delineation
Loss of Cell Delineation (LOCD) is a SONET port status indicator that activates when an LOCD defect occurs and does not clear for an interval of time equal to the alarm integration period, which is typically 2.5 seconds.

LOF: Loss of Frame
Loss of frame (LOF) is an indication in a network device or software that one or more network frames did not get through the networking device. When LOF occurs, it typically indicates the device is over capacity or mis-configured.

Logical Channel
Logical Channel is a nondedicated, packet-switched communications path between two or more network nodes. Packet switching allows many logical channels to exist simultaneously on a single physical channel.

Longest Prefix Match
Longest Prefix Match is an algorithm used by routers in Internet Protocol (IP) networking to select an entry from a routing table. Because each entry in a routing table may specify a network, one destination address may match more that one routing table entry. The most specific table entry — the one with the highest subnet mask — is called the longest prefix match. It is called this because it is also the entry where the largest number of leading address bits in the table entry match those of the destination address.

Look-Aside Interface
The Look-Aside Interface is a computer interface that was specified by an interface interoperability agreement produced by the Network Processing Forum. It specifies the method to interface a Network Processing Element (of which a NPU is an example) to a Network Search Element (of which a CAM is an example). The interface is used by devices that off-load certain tasks from the network processor.

Loop
Loop is a situation in network routing where packets never reach their destination, but simply cycle repeatedly through a constant series of network nodes.

Loopback
A loopback is a communications channel with only one endpoint. Any message transmitted through such a channel is received by the sender. Loopback is often used as a testing method in networking. Some devices include built-in loopback capability. TCP/IP specifies a loopback network. Most IP implementations support a loopback interface, which represents the loopback facility. Any traffic that a computer program sends on the loopback network is addressed to the same computer. The most commonly used IP address on the loopback network is 127.0.0.1 or 127.0.0.0/8 for IPv4 and ::1 for IPv6.

Loopback Address
The loopback address is a pseudo address that always refers back to the local host and is never sent out onto a network. In the IPv4 the address 127.0.0.0 (or the CIDR address of 127.0.0.0/8) is reserved for this. Most systems assign the address 127.0.0.1 to this interface with the name of localhost. In IPv6, the loopback interface is ::1. On Unix-like systems, the loopback interface is commonly called lo or lo0.

Loopback interface
Lookback interface is a special address or interface reserved for loopback purpose. A loopback interface has several uses. It may be used by network client software on a computer to communicate with server software on the same computer–viz., on a computer running a web server, pointing a web browser at the URL http://127.0.0.1/ will access that computer's own web site. This can be done without the computer being connected to any network, so it is useful for testing services without exposing them to remote network access. Likewise, to ping the loopback interface is a basic test to see if one's IP stack working properly.

Loopback Packet
Loopback Packet is a test packet sent by a network adapter with a destination address equal to the adapter's own hardware address. The purpose of this test is typically to establish that the adapter is connected to a network that is functional enough to support a data transmission.

Loopback Test
Loopback Test is a test that a loopback packet is sent by a network adapter with a destination address equal to the adapter's own hardware address. The purpose of this test is typically to establish that the adapter is connected to a network that is functional enough to support a data transmission.

LOP: Loss of Pointer
Loss of Pointer (LOP) is a failure state in the SONET signal where a receiving network cannot identify/lock on the pointer value of the H1 and H2 bytes to show the location of SPE.

LOS: Line of Sight
Line of Sight (LOS) refers to the fact that there must be a clear, unobstructed path between the transmitters and receivers. This is essential for our LMDS products and enhances general performance in every RF deployment as opposed to partial or completely obstructed data paths. The opposite to LOS is NLOS, or Non Line of Sight.

LOS: Loss of Signal
Loss of Signal (LOS) is a condition where the received signal drops below threshold due to a terrain obstruction or other phenomenon increasing the link budget loss beyond design parameters. Loss of Signal (LOS) occurs when "n" consecutive zeros is detected on an incoming signal.

Lossy
Lossy is a characteristic of a network that is prone to lose packets when it becomes highly loaded.

Low speed link
Low-speed links are the links that have a data transmission speed below 128Kps.

LPD: Line Printer Daemon
Line Printer Daemon (LPD) is a protocol used to send print jobs between UNIX systems.

LR: Long Reach
Long Reach (LR) refers to the distance specification for optical systems that operate effectively from 20 to 100 km (12.5 to 62 mi).

LRE: Long Reach Ethernet
Long Reach Ethernet (LRE) is a developing set of networking protocols intended to support multi-megabit (5 to 15 Mbit/s) performance over telephone-grade Category 1/2/3 wiring over distances up to 5,000 feet (1.5 km). LRE is technically classified a Metropolitan area network (MAN) technology. The technology is sometimes referred to as Ethernet in the First Mile (EFM).

LRJ: Location ReJect Message
Location ReJect Message (LRJ) is a Registration, admission, and status (RAS) message that a Gatekeeper/endpoint sends to the requesting Gatekeeper rejecting the LRQ.

LRQ: Location ReQuest
Location ReQuest (LRQ) is a Registration, admission, and status (RAS) message sent as a location request in the H.323 VOIP netowrk.

LSA: Link-State Advertisement
Link-State Advertisement (LSA) is a packet used by link-state protocols that contain information about neighbors and path costs. LSAs are used by the receiving routers to maintain their routing tables.

LSAP: Link Service Access Point
Link Service Access Point(LSAP), a field in the Logic Link Control (LLC) defined in IEEE 802.2, is the identifier field to indicate data types. LSAP includes both Destination Service Access Point (DSAP) and Source Service Access Point (SSAP).

LSB: Least Significant Bit
Least Significant Bit (LSB) is the bit position in a binary integer giving the units value, that is, determining whether the number is even or odd. The LSB is sometimes referred to as the right-most bit, due to the convention in positional notation of writing less significant digits further to the right. It is analogous to the least significant digit of a decimal integer, which is the digit in the ones (right-most) position.

LSC: Label Switch Controller
Label Switch Controller (LSC), formerly referred to as Tag Switch Controller (TSC), is the controller that creates cross-connects in an ATM switch so that labeled packets are forwarded through the switch.

LSC: Link State Control
Link State Control (LSC) is the SS7 MTP 2 function that provides the overall coordination of a session.

LSP tunnel: Label switched path tunnel
Label switched path tunnel(LSP) is a configured connection between two routers that uses MPLS to carry the packets.

LSP: Label Switched Path
Label Switched Path (LSP), a concept in the Multiprotocol Label Switching (MPLS) networking, is a path through an MPLS network, set up by a signaling protocol such as LDP, RSVP-TE, or CR-LDP. The path is set up based on criteria in the forwarding equivalence class (FEC). The path begins at a Label Edge Router (LER), which makes a decision on which label to prepend to a packet based on the appropriate FEC. It then forwards the packet along to the next router in the path, which swaps the packet's outer label for another label, and forwards it to the next router.

LSR: Label Switch Router
A Label Switch Router (LSR) is a type of a router located in the middle of a Multiprotocol Label Switching (MPLS) network. It is responsible for switching the labels used to route packets. When a LSR receives a packet, it uses the label included in the packet header as an index to determine the next hop on the Label Switched Path (LSP) and a corresponding label for the packet from a look-up table. The old label is then removed from the header and replaced with the new label before the packet is routed forward.

LSRR: Loose Source and Record Route
Loose Source and Record Route (LSRR) is an option that provides a means for the source of an internet datagram to supply routing information to be used by the gateway in forwarding the datagram to the destination, and to record the route information.

LSSU: Link Status Signal Unit
Link Status Signal Unit (LSSU) is an SS7 message that carries one or two octets (8-bit bytes) of link status information between signalling points at either end of a link. It is used to control link alignment and to provide the status of a signalling point (such as a local processor outage) to the remote signalling point.

LTE: Line-terminating Equipment
Line-terminating Equipment (LTE) is a network element that originates and/or terminates line (OC-n) signals. LTEs originate, access, modify, and/or terminate the transport overhead.

LUNI: LAN Emulation User-to-Network Interface
LAN Emulation User-to-Network Interface (LUNI) is the ATM Forum standard for LAN emulation on ATM networks, which defines the interface between the LEC and the LAN Emulation Server components.

LUSerNet
LUSerNet is a file sharing network that was designed to run on Local Area Network. It implements a simple low overhead P2P protocol that relies on UDP Broadcasts. These broadcasts limit LUSerNet to only working within the LAN, however the bandwidth used between the peers is far less than other peer to peer protocols. LUSerNet was originally made for use on the Lancaster University network, and quickly became popular among the students.

LVC: Label switched controlled virtual circuit
Label switched controlled virtual circuit (LVC) is a virtual circuit (VC) established under the control of MPLS. An LVC is neither a PVC nor an SVC. The LVC must traverse only a single hop in a label-switched path (LSP) but the LVC can traverse several ATM hops only if the LVC exists within a VP tunnel.