Glossary
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MAC addresses. Multilayer switches are a type of high-speed, special pur-
pose, hardware-based router. See also: multilayer switch and store-and-
forward packet switching.
LAPB
Link Accessed Procedure, Balanced: A bit-oriented Data Link layer
protocol that is part of the X.25 stack and has its origin in SDLC. See also:
SDLC and X.25.
LAPD
Link Access Procedure on the D channel: The ISDN Data Link layer
protocol used specifically for the D channel and defined by ITU-T Recom-
mendations Q.920 and Q.921. LAPD evolved from LAPB and is created to
comply with the signaling requirements of ISDN basic access.
latency
Broadly, the time it takes a data packet to get from one location
to another. In specific networking contexts, it can mean either 1) the time
elapsed (delay) between the execution of a request for access to a network by
a device and the time the mechanism actually is permitted transmission, or
2) the time elapsed between when a mechanism receives a frame and the time
that frame is forwarded out of the destination port.
layer
Term used in networking to define how the OSI model works to
encapsulate data for transmission on the network.
layer-3 switch
See: multilayer switch.
layered architecture
Industry standard way of creating applications to
work on a network. Layered architecture allows the application developer to
make changes in only one layer instead of the whole program.
LCP
Link Control Protocol: The protocol designed to establish, configure,
and test data-link connections for use by PPP. See also: PPP.
leaky bucket
An analogy for the basic cell rate algorithm (GCRA) used in
ATM networks for checking the conformance of cell flows from a user or
network. The bucket's "hole" is understood to be the prolonged rate at
which cells can be accommodated, and the "depth" is the tolerance for cell
bursts over a certain time period.
learning bridge
A bridge that transparently builds a dynamic database of
MAC addresses and the interfaces associated with each address. Transparent
bridges help to reduce traffic congestion on the network.
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