Glossary
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Layer 2 switching
Layer 2 switching is hardware based, which means it
uses the MAC address from the hosts' NIC cards to filter the network.
Switches use Application-Specific Integrated Circuits (ASICs) to build and
maintain filter tables. It is okay to think of a Layer 2 switch as a multiport
bridge.
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.
LE ARP
LAN Emulation Address Resolution Protocol: The protocol pro-
viding the ATM address that corresponds to a MAC address.
leased lines
Permanent connections between two points leased from the
telephone companies.
LEC
LAN Emulation Client: Software providing the emulation of the Data
Link layer interface that allows the operation and communication of all
higher-level protocols and applications to continue. The LEC client runs in
all ATM devices, which include hosts, servers, bridges, and routers. The LEC
is responsible for address resolution, data transfer, address caching, inter-
facing to the emulated LAN, and driver support for higher-level services. See
also: ELAN and LES.
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