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 .

[RFC 3031]

(2002-04-14)