Multiprotocol Label Switching
MPLS
(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>.
[RFC 3031]
(2002-04-14)
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