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Currently, bandwidth (BW) and bandwidth-related information are the only resources

tracked and used for traffic engineering. Admission control determines whether a

setup request can be honored for an MPLS LSP with traffic parameters.

Admission control provides bandwidth information to the IGP protocols, ISIS and

OSPF. As new LSPs are created, the available bandwidth decreases. The IGPs can

subsequently advertise this information and use it for SPF calculations to determine

paths that satisfy the traffic requirements. You can configure readvertisement to

occur periodically or when the change crosses some threshold.

Starting Admission Control

Admission control operates on a router-wide basis rather than a per-virtual-router

basis. Admission control of resources begins when either of the following occurs:

■ You configure resource-related information about an interface, including

bandwidth (either total bandwidth or MPLS reservable bandwidth), flooding

frequency, flooding threshold, administrative weight, or attribute flags.

■ MPLS begins to use admission control services; for example, by attempting to

set up a constraint-based LSP.

Admission Control Interface Table

Configuring bandwidth on an interface creates an entry for the interface in the

admission control interface table. Each entry in the table stores the following

information per interface:

■ Maximum (physical or line-rate) bandwidth

■ Maximum reservable bandwidth

■ The following information per IP class (currently a single, default class)

■ Total available (unreserved) bandwidth

■ Available bandwidth at each MPLS priority level

■ Resource flooding threshold and period

The resource flooding threshold and period together control the flooding of the

resource information by the IGP protocols, IS-IS and OSPF.

Configuring Traffic-Engineering Resources

You can configure the following resource-related information about an MPLS interface

(at either the major interface or subinterface level):

■ Bandwidth—Total bandwidth that can be reserved on the interface

■ Flooding thresholds—Sets of absolute percentages of total reservable bandwidth

that trigger the new bandwidth value to be flooded throughout the network;

flooding is triggered when bandwidth increases past any up threshold value or

decreases past any down threshold value

MPLS Traffic Engineering ■ 245

Chapter 2: MPLS Overview

Juniper BGP - CONFIGURATION GUIDE V 11.1.X User Manual

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