from
The Free On-line Dictionary of Computing (8 July 2008)
Multiprotocol Label Switching
MPLS
<networking> (MPLS) A {packet switching} {protocol} developed
by the {IETF}. Initially developed to improve switching
speed, other benefits are now seen as being more important.
MPLS adds a 32-{bit} label to each {packet} to improve
{network} efficiency and to enable {routers} to direct
{packets} along predefined routes in accordance with the
required {quality of service}. The label is added when the
{packet} enters the MPLS {network}, and is based on an
analysis of the {packet} {header}. The label contains
information on the route along which the {packet} may travel,
and the {forwarding equivalence class} (FEC) of the {packet}.
Packets with the same {FEC} are routed through the {network}
in the same way.
Routers make forwarding decisions based purely on the contents
of the label. This simplifies the work done by the {router},
leading to an increase in speed. At each {router}, the label
is replaced with a new label, which tells the next {router}
how to forward the {packet}. The label is removed when the
{packet} leaves the MPLS {network}.
Modern {ASIC}-based routers can look up routes fast enough to
make the speed increase less important. However, MPLS still
has some benefits. The use of {FECs} allows {QoS} levels to
be guaranteed, and MPLS allows {IP} {tunnels} to be created
through a {network}, so that {VPNs} can be implemented without
{encryption}.
MPLS Resource Center (http://mplsrc.com/).
[RFC 3031]
(2002-04-14)