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MPLS Guide
3.2 MPLS
Multiprotocol Label Switching (MPLS) is a label switching technology that provides
the ability to set up connection-oriented paths over a connectionless IP network.
MPLS facilitates network traffic flow and provides a mechanism to engineer network
traffic patterns independently from routing tables. MPLS sets up a specific path for a
sequence of packets. The packets are identified by a label inserted into each packet.
MPLS is independent of any routing protocol but is considered multiprotocol because
it works with protocols such as IP, ATM, Ethernet, and circuit emulation.
This section contains the following topics:
3.2.1 Traffic Engineering for MPLS
Without traffic engineering (TE), routers route traffic according to the Shortest Path
First (SPF) algorithm, disregarding congestion or packet types.
With traffic engineering, network traffic is routed efficiently to maximize throughput
and minimize delay. Traffic engineering facilitates traffic flows to be mapped to the
destination through a less-congested path than the one selected by the SPF
algorithm.
MPLS directs a flow of IP packets along a label switched path (LSP). LSPs are
simplex, meaning that the traffic flows in one direction (unidirectional) from an
ingress router to an egress router. Two LSPs are required for duplex (bidirectional)
traffic. Each LSP carries traffic in a specific direction, forwarding packets from one
router to the next across the MPLS domain.
When an ingress router receives a packet, it adds an MPLS header to the packet and
forwards it to the next hop in the LSP. The labeled packet is forwarded along the LSP
path (from next hop to next hop) until it reaches the destination point. The MPLS
header is removed and the packet is forwarded based on Layer 3 information such
as the IP destination address. The physical path of the LSP is not constrained to the
shortest path that the IGP would choose using SPF to reach the destination IP
address.
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Traffic Engineering for MPLS
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MPLS Label Stack
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MPLS Entropy Labels
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Label Edge and Label Switch Routers
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LSP Types
Use subject to Terms available at: www.nokia.com
© 2022 Nokia.
MPLS and RSVP-TE
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