Mpls Traffic Engineering; Lsp Backup - Juniper BGP - CONFIGURATION GUIDE V 11.1.X Configuration Manual

The targeted hello includes the LDP identifier for the label space that the LSR intends
to use. In the JUNOSe implementation, this is always the platform label space, so
the LDP identifier specifies the LSR ID and a value of 0 for the label space. The
targeted hello also includes other information, such as the targeted-hello hold time,
which is configured globally. The targeted-hello hold time configures how long an
LSR waits for another targeted hello from its peer before declaring the adjacency to
be down.
Unlike basic discovery, where hellos are sent by all LSRs, extended discovery is
initiated by one LSR that targets a specific LSR. The initiating LSR periodically sends
targeted hellos to the targeted LSR. The targeted LSR then determines whether to
respond to the targeted hello or to ignore it. If the targeted LSR responds to the
sender, it does so by periodically sending targeted hellos to the initiating LSR. The
exchange of targeted hellos constitutes a hello adjacency for the two LSRs.
Targeted hello values are configured globally with the mpls ldp targeted-hello
holdtime, mpls ldp targeted-hello interval, mpls ldp targeted-hello receive list,
and mpls ldp targeted hello send list commands.
Related Topics

MPLS Traffic Engineering

MPLS traffic engineering (TE) is the ability to establish LSPs according to particular
criteria (constraints) in order to meet specific traffic requirements rather than relying
on the path chosen by the conventional IGP. The constraint-based IGP examines the
available network resources and calculates the shortest path for a particular tunnel
that has the resources required by that tunnel. Traffic engineering enables you to
make the best use of your network resources by reducing overuse and underuse of
certain links.
Constraint-based routing (CR) makes traffic engineering possible by considering
resource requirements and resource availability rather than merely the shortest path
calculations. Constraints are determined at the edge of the network and include
criteria such as required values for bandwidth or required explicit paths. You can
use RSVP-TE as the label distribution protocol for traffic engineering. The IGP
propagates resource information throughout its network. RSVP-TE employs
downstream-on-demand, ordered control for label mapping and distribution.
Explicit routing specifies a list or group of nodes (hops) that must be used in setting
up the tunnels. CR explicit paths can be strict or loose. Strict paths specify an exact
physical path, including every physical node. Loose paths include hops that have
local flexibility; the hop can be a traditional interface, an autonomous system, or an
LSP.

LSP Backup

You can configure multiple LSPs to the same destination. By configuring different
tunnel metrics for these LSPs, you can force a ranking or priority of use for the LSPs.
MPLS Label Switching and Packet Forwarding on page 209
MPLS Label Distribution Protocols on page 229
Chapter 2: MPLS Overview
MPLS Traffic Engineering
243