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Routing Protocol
MPLS works in coordination with the interior gateway protocol (IGP). Therefore, you
must configure OSPF or IS-IS as the routing protocol on the loopback interface and core
interfaces of both the provider edge and provider switches.
These core interfaces can be either Gigabit Ethernet or 10-Gigabit Ethernet interfaces,
and they can be configured as either individual interfaces or aggregated Ethernet
interfaces.
NOTE: These core interfaces cannot be configured with VLAN tagging or a
VLAN ID. When you configure them to belong to family mpls, they are removed
from the default VLAN. They operate as an exclusive tunnel for MPLS traffic.
Traffic Engineering
Traffic engineering maps traffic flows onto an existing physical topology and provides
the ability to move traffic flow away from the shortest path selected by the IGP and onto
a potentially less congested physical path across a network.
Traffic engineering enables the selection of specific end-to-end paths to send given types
of traffic through your network. For MPLS to work properly, you must enable traffic
engineering for the specified routing protocol.
MPLS Protocol
You must enable the MPLS protocol on all switches that participate in the MPLS network
and apply it to the core interfaces of both the provider edge and provider switches. You
do not need to apply it to the loopback interface, because the MPLS protocol uses the
framework established by the RSVP session to create LSPs. On the provider edge switches,
the configuration of the MPLS protocol must also include the definition of an LSP.
RSVP
Resource Reservation Protocol (RSVP) is a signaling protocol that allocates and
distributes labels throughout an MPLS network. RSVP sets up unidirectional paths
between the ingress provider edge switch and the egress provider edge switch. RSVP
makes the LSPs dynamic; it can detect topology changes and outages and establish new
LSPs to move around a failure.
You must enable RSVP and apply it to the loopback interface and the core interface of
both the provider edge and provider switches. The path message contains the configured
information about the resources required for the LSP to be established.
When the egress switch receives the path message, it sends a reservation message back
to the ingress switch. This reservation message is passed along from switch to switch
along the same path as the original path message. Once the ingress switch receives this
reservation message, an RSVP path is established.
The established LSP stays active as long as the RSVP session remains active. RSVP
continues activity through the transmissions and responses to RSVP path and reservation
3355 Copyright © 2010, Juniper Networks, Inc.
Chapter 121: MPLS—Overview