Multiprotocol Label Switching
<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://www.mplsrc.com/).
[RFC 3031]
