L2F - Layer 2 Forwarding protocol, permits the tunneling of the link layer of higher layer protocols (PPP suite).

L2TP - Layer 2 Tunneling Protocol, used for integrating multi-protocol dial-up services into existing ISP POP.

LAPB - Link Access Protocol, Balanced, derived from HDLC and used to carry X.25 packets.

LAPD - Link Access Protocol, Channel D, layer 2 protocol defined in CCITT.

LAPF - Link Access Procedure F (Frame Relay), modified LAPD standard for Frame Relay.

LAT - Local Area Transport protocol, designed to handle multiplexed terminal traffic to/from timesharing hosts (DECnet).

LAVC - Local Area VAX Cluster protocol, communications between DEC VAX computers in a cluster (DECnet).

LDAP - Lightweight Directory Access Protocol

LDP - Label Distribution Protocol

LCP - Link Control Protocol, establishes, configures and tests the data link connection (PPP suite).

LLC - Logical Link Control protocol (IEEE 802.2), provides a link mechanism for upper layer protocols.

LQR - Link Quality Report, specifies the mechanism for link quality monitoring with PPP.