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NE20E-S V800R010C10SPC500 Feature Description - MPLS 01

This is NE20E-S V800R010C10SPC500 Feature Description - MPLS
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Automatic Bandwidth Adjustment

Automatic Bandwidth Adjustment

Automatic bandwidth adjustment enables the ingress of an MPLS TE tunnel to dynamically update tunnel bandwidth after traffic changes and to reestablish the MPLS TE tunnel using changed bandwidth values, all of which optimizes bandwidth resource usage.

Background

MPLS TE tunnels are used to optimize traffic distribution over a network. Traffic that frequently changes wastes MPLS TE tunnel bandwidth; therefore, automatic bandwidth adjustment is used to prevent this waste. A bandwidth is initially set to meet the requirement for the maximum volume of services to be transmitted over an MPLS TE tunnel, to ensure uninterrupted transmission.

Related Concepts

Automatic bandwidth adjustment allows the ingress to dynamically detect bandwidth changes and periodically attempt to reestablish a tunnel with the needed bandwidth.

Table 4-6 lists concepts and their descriptions.
Table 4-6 Variables used in automatic bandwidth adjustment

Variable

Notation

Description

Adjustment frequency

A

Interval at which bandwidth adjustment is performed.

Sampling frequency

B

Interval at which traffic rates on a specific tunnel interface are sampled.

Current bandwidth

C

Configured bandwidth.

Target bandwidth

D

Updated bandwidth after adjustment.

Threshold

Threshold

An average bandwidth is calculated after the sampling interval time elapses. If the ratio of the difference between the average bandwidth and actual bandwidth to the actual bandwidth exceeds a specific threshold, automatic bandwidth adjustment is triggered.

Implementation

Automatic bandwidth adjustment is enabled on a tunnel interface of the ingress. The automatic bandwidth adjustment procedure on the ingress is as follows:
  1. Samples traffic.

    The ingress starts a bandwidth adjustment timer (A) and samples traffic at a specific interval (B seconds) to obtain the instantaneous bandwidth during each sampling period. The ingress records the instantaneous bandwidths.

  2. Calculates an average bandwidth.

    After timer A expires, the ingress uses the records to calculate an average bandwidth (D) to be used as a target bandwidth.

  3. Calculates a path.

    The ingress runs CSPF to calculate a path with bandwidth D and establishes a new CR-LSP over that path.

  4. Switches traffic to the new CR-LSP.

    The ingress switches traffic to the new CR-LSP before tearing down the original CR-LSP.

The preceding procedure repeats each time automatic bandwidth adjustment is triggered. Bandwidth adjustment is not needed if traffic fluctuates below a specific threshold. The ingress calculates an average bandwidth after the sampling interval time elapses. The ingress performs automatic bandwidth adjustment if the ratio of the difference between the average and existing bandwidths to the existing bandwidth exceeds a specific threshold. The following inequality applies:

[(D - C)/D] x 100% > Threshold

Other Usage

The following functions are supported based on automatic bandwidth adjustment:
  • The ingress only samples traffic on a tunnel interface, and does not perform bandwidth adjustment.
  • The upper and lower limits can be set to define a range, within which the bandwidth can fluctuate.
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Updated: 2019-01-03

Document ID: EDOC1100055123

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