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
packets along predefined routes in accordance with the
information on the route along which the
packet may travel,
Packets with the same
FEC are routed through the
networkin 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
routerhow to forward the
packet. The label is removed when the
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
[RFC 3031]
(2002-04-14)