Using Rsvp-Te For Mpls; Rsvp-Te Extensions For Mpls - Nokia 7705 SAR-W Series Manual

MPLS and RSVP-TE
Upon receiving a PATH message containing a label request object, the eLER
transmits an RESV message that contains a label object. The label object contains
the label binding that the downstream LSR communicates to its upstream neighbor.
The RESV message is sent upstream towards the iLER, in a direction opposite to
that followed by the PATH message. Each LSR that processes the RESV message
carrying a label object uses the received label for outgoing traffic associated with the
specific LSP. When the RESV message arrives at the ingress LSR, the LSP is
established.
3.3.1.1
Hosts and routers that support both MPLS and RSVP-TE can associate labels with
RSVP-TE flows. When MPLS and RSVP-TE are combined, the definition of a flow
can be made more flexible. Once an LSP is established, the traffic through the path
is defined by the label applied at the ingress node of the LSP. The mapping of label
to traffic can be accomplished using a variety of criteria. The set of packets that are
assigned the same label value by a specific node are considered to belong to the
same Forwarding Equivalence Class (FEC) that defines the RSVP-TE flow.
For use with MPLS, RSVP-TE already has the resource reservation component built
in, making it ideal to reserve resources for LSPs.
3.3.1.2
The RSVP-TE extensions enable MPLS to support the creation of explicitly routed
LSPs, with or without resource reservation. Several of the features enabled by these
extensions were implemented to meet the requirements for traffic engineering over
MPLS, which enables the creation of traffic trunks with specific characteristics. None
of the TE extensions result in backward compatibility problems with traditional RSVP
implementations.
To run properly, the traffic engineering capabilities of RSVP-TE require an underlying
TE-enabled IGP routing protocol. The 7705 SAR supports OSPF and IS-IS with TE
extensions.
Routing protocols make it possible to advertise the constraints imposed over various
links in the network. For example, in order for the nodes in a network to choose the
best link for signaling a tunnel, the capacity of a particular link and the amount of
reservable capacity must be advertised by the IGP. RSVP-TE makes use of these
constraints to request the setup of a path or LSP that traverses only those links that
are part of an administrative group (admin groups are described in the following list).
38

Using RSVP-TE for MPLS

RSVP-TE Extensions for MPLS

Use subject to Terms available at: www.nokia.com
© 2022 Nokia.
MPLS Guide
3HE 18686 AAAB TQZZA