L2F
Layer Two Forwarding

L2TP
Layer-Two Tunneling Protocol

LACP
Link Aggregation Control Protocol

LADT
Local Access / Area Data Transport

LAN
Local Area Network

LAP
Link Access Procedure

LAPB
Link Access Procedure Balanced 
The balanced-mode, enhanced, version of HDLC. Used in X.25 packet switching networks

LAPD
Link Access Procedure channel D 
A protocol that operates at the data link layer 2 of the OSI architecture. LAPD is used to convey information between layer 3 entities across the frame relay network. The D-channel carries signaling information for circuit switching. 
Defined by CCITT recommendations Q920 and Q921.

LAPM
Link Access Procedure channel for Modem

LAT
Local Address Table

LAT
Local-Area Transport. 
A network virtual terminal protocol developed by Digital Equipment Corp.®

LAWN
Local Area Wireless Network

LB
Load Balancing 
Whenever a device is receiving too much information, the load is balanced between two devices or more. It could be a bridge or router receiving too many frames. A server receiving too many data. In those two cases a second bridge or router would be installed. For a server a second device card managing the disk(s) could be  installed or a second server can be installed. In routing, the ability of a router to distribute traffic over all its network ports that are the same distance from the destination address. Good load-balancing algorithms use both line speed and reliability information. Load-balancing increases the utilization of a network segments, thus increasing effective network bandwidth.

LBX
Low-Bandwidth X

LCN
Logical Channel Number

LCP
Link Control Protocol - PPP

LD-CELP
Low Delay Code Excited Linear Prediction 
G.728 providing 16Kbps

LDP
Label Distribution Protocol - MPLS

LEC
Local Exchange Carrier

LER
Label Edge Router - MPLS

LGN
Logical Group Number

LI
Length Indicator - OSI

LIA
Liaison Inter Autocommutateur 
Interconnection between 2 PBX using analog links

LINK STATE
A routing algorithm in which each router broadcasts or multicasts information on the cost of reaching each of its neighbors to all nodes in the internetwork. Link-state algorithms creates a consistent view of the network and are therefore not very prone to routing loops, but they achieve this at the cost of relatively greater computational difficulty and somewhat more widespread traffic - compared with distance vector routing algorithms.

LL
Line Layer - Sonet

LLC
Logical Link Control
Provides a link mechanism for upper layer protocols 

LLC2
Logical Link Control, type 2. 
A connection-oriented OSI logical link control sub-layer protocol.

LMDS
Local Multipoint Distribution Service - Telecom

LM Host
LAN Manager host 
The LAN Manager host table is used to associate NetBIOS names to IP addresses, so you can use NetBIOS applications over TCP/IP. Creating an LM host table is optional for using NetBIOS over TCP/IP, and unnecessary if you are not using NetBIOS applications. 
Check if there are WINS servers on your network that you can use to resolve NetBIOS names to IP addresses.  The LM host table is only used after broadcasts and WINS servers are searched, if you use them. 

LMI
Local Management Interface

LNM
Lan Network Manager

LNMF
Local Network Management Function

LOCAL TALK
Apple ® 's proprietary 230-Kbps baseband CSMA/CA network protocol. LP Line Printer - Unix

LSA
Link State Advertisements - Cisco ®

LSAP
Link Service Access Point - OSI

LSE
Local System Environment - OSI

LSL
Link Support Layer

LSP
Label Switching Path - MPLS

LSR
Label Switch Router- MPLS

LSSU
Link Status Signal Unit

LU
Logical Unit - IBM® 
A primary component of SNA, and LU is a type of NAU that enables end users to communicate with each other and gain access to SNA network resources.

LU 6.2
Logical Unit 6.2 - IBM® 
An LU governing peer-to-peer SNA communications. LU 6.2 supports general communication between programs in a distributed processing environment.