Rate Limits For Interfaces Overview - Juniper JUNOSE SOFTWARE FOR E SERIES 11.3.X - POLICY MANAGEMENT CONFIGURATION GUIDE 2010-10-04 Configuration Manual

JunosE 11.3.x Policy Management Configuration Guide

Rate Limits for Interfaces Overview

58
To configure rate limiting for interfaces, you first create a rate-limit profile, which is a set
of bandwidth attributes and associated actions. Your router supports two types of
rate-limit profiles—one-rate and two-rate—for IP, IPv6, LT2P, and MPLS Layer 2 transport
traffic. You next create a policy list with a rule that has rate limit as the action and
associate a rate-limit profile with this rule.
You configure rate limit profiles from Global Configuration Mode.
NOTE: Commands that you issue in Rate Limit Profile Configuration mode
do not take effect until you exit from that mode.
When packets enter an interface that has a rate-limit profile applied, the router performs
the following:
Counts the number of bytes (packets) over time
Categorizes each packet as committed, conformed, or exceeded
Assigns a transmit, drop, or mark action
NOTE: Mark actions and mask values are supported only on IP, IPv6, and
MPLS rate-limit profiles. They are not supported on hierarchical rate limits,
but are replaced by color-mark profiles.
An additional function of rate limiting is to apply a color code to packets assigned to each
category: green for committed, yellow for conformed, and red for exceeded. The system
uses the color code internally to indicate drop preference when an outbound interface
is congested.
Rate limiters are implemented using a dual token bucket scheme: a token bucket for
conformed (yellow) packets and a token bucket for committed (green) packets. One
token is synonymous with one byte. The capacity of the buckets is the maximum number
of tokens that can be placed in each bucket.
You configure the bucket capacity with the peak burst parameter or the committed burst
parameter. The burst parameters are in bytes (not bytes per second), which is the number
of tokens in a full bucket. When a packet passes through a rate limiter, its size is compared
to the contents of both buckets, the packet is categorized, and the rate-limiter action is
taken on the packet.
Peak rate and committed rate determine the fill rate of their respective buckets. If you
set the committed rate to 128,000 bps, tokens are added to the committed (green)
bucket at a rate of 128,000 bps (16 K bytes per second), regardless of the traffic. If no
traffic passes through the rate limiter, the bucket continues to fill until it reaches the
committed burst setting.
Copyright © 2010, Juniper Networks, Inc.