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Policer Overhead to Account for Rate Shaping in the Traffic Manager

Policer Overhead to Account for Rate Shaping Overview

If you configure ingress or egress traffic-shaping overhead values for an interface, the traffic manager cannot apply these values to any rate-limiting also applied to the interface. To enable the router to account for the additional Ethernet frame length when policing actions are being determined, you must configure the ingress or egress overhead values for policers separately.

Note: When a policer overhead value is changed, the PIC or DPC goes offline and then comes back online.

For Gigabit Ethernet Intelligent Queuing 2 (IQ2) and Enhanced IQ2 (IQ2E) PICs or interfaces on Dense Port Concentrators (DPCs) in MX Series routers, you can control the rate of traffic that passes through all interfaces on the PIC or DPC by configuring a policer overhead. You can configure a policer ingress overhead and a policer egress overhead, each with values from 0 through 255 bytes. The policer overhead values are added to the length of the final Ethernet frame when determining ingress and egress policer actions.

Example: Configuring Policer Overhead to Account for Rate Shaping

This example shows how to configure overhead values for policers when rate-shaping overhead is configured.

• Requirements
• Overview
• Configuration
• Verification

Requirements

• Gigabit Ethernet IQ2 PIC
• IQ2E PIC
• DPCs in MX Series routers

Overview

This example shows how to configure policer overhead values for all physical interfaces on a supported PIC or MPC so that the rate shaping value configured on a logical interface is accounted for in any policing on that logical interface.

Topology

The router hosts a Gigabit Ethernet IQ2 PIC, installed in PIC location 3 of the Flexible PIC Concentrator (FPC) in slot number 1. The physical interface on port 1 on that PIC is configured to receive traffic on logical interface 0 and send it back out on logical interface 1. Class-of-service scheduling includes 100 Mbps of traffic rate-shaping overhead for the output traffic. A policer egress overhead of 100 bytes is configured on the entire PIC so that, for any policers applied to the output traffic, 100 bytes are added to the final Ethernet frame length when determining ingress and egress policer actions.

Traffic rate-shaping and corresponding policer overhead are configured separately: You configure rate shaping at the [edit class-of-service interfaces interface-name unit unit-number] hierarchy level. You configure policer overhead at the [edit chassis fpc slot-number pic pic-number] hierarchy level.

When a policer overhead value is changed, the PIC or DPC goes offline and then comes back online.

Configuration

The following example requires you to navigate various levels in the configuration hierarchy. For information about navigating the CLI, see Using the CLI Editor in Configuration Mode.

To configure this example, perform the following tasks:

• Configuring the Logical Interfaces
• Configuring Traffic Rate-Shaping on the Logical Interface That Carries Output Traffic
• Configuring Policer Overhead on the PIC or MPC That Hosts the Rate-Shaped Logical Interface
• Applying a Policer to the Logical Interface That Carries Input Traffic

CLI Quick Configuration

Configuring the Logical Interfaces

Step-by-Step Procedure

1. Enable configuration of the interface

   [edit]user@host# edit interfaces ge-1/3/1

2. Enable multiple queues for each logical interface (so that you can associate an output scheduler with each logical interface).

   [edit interfaces ge-1/3/1]user@host# set per-unit scheduleruser@host# set vlan-tagging

   Note: For Gigabit Ethernet IQ2 PICs only, use the shared-scheduler statement to enable shared schedulers and shapers on a physical interface.

3. Configure logical interface ge-1/3/1.0.

   [edit interfaces ge-1/3/1]user@host# set unit 0 vlan-id 100user@host# set unit 0 family inet address 10.10.10.1/30

4. Configure logical interface ge-1/3/1.1.

   [edit interfaces ge-1/3/1]user@host# set unit 1 vlan-id 101user@host# set unit 1 family inet address 20.20.20.1/30 arp 20.20.20.2 mac 00:00:11:22:33:44

Results

Configuring Traffic Rate-Shaping on the Logical Interface That Carries Output Traffic

Step-by-Step Procedure

1. Enable configuration of class-of-service features.

   [edit]user@host# edit class-of-service

2. Configure packet scheduling on logical interface ge-1/3/1.0.

   1. Configure schedulers that specify the percentage of transmission capacity.

      [edit class-of-service]user@host# edit schedulers [edit class-of-service schedulers]user@host# set be transmit-rate percent 5user@host# set ef transmit-rate percent 30user@host# set af transmit-rate percent 30user@host# set nc transmit-rate percent 35
      A percentage of zero drops all packets in the queue. When the rate-limit option is specified, the transmission rate is limited to the rate-controlled amount. In contrast with the exact option, a scheduler with the rate-limit option shares unused bandwidth above the rate-controlled amount.

   2. Configure a scheduler map to associate each scheduler with a forwarding class.

      [edit class-of-service]user@host# edit scheduler-maps my-map [edit class-of-service scheduler-maps my-map]user@host# set forwarding-class best-effort scheduler beuser@host# set forwarding-class expedited-forwarding scheduler efuser@host# set forwarding-class network-control scheduler ncuser@host# set forwarding-class assured-forwarding scheduler af

   3. Associate the scheduler map with logical interface ge-1/3/1.0.

      [edit class-of-service]user@host# edit interfaces ge-1/3/1 unit 1 [edit class-of-service interfaces ge-1/3/1 unit 1]user@host# set scheduler-map my-map

3. Configure 100 Mbps of traffic rate-shaping overhead on logical interface ge-1/3/1.1.

   [edit class-of-service interfaces ge-1/3/1 unit 1]user@host# set shaping-rate 100
   Alternatively, you can configure a shaping rate for a logical interface and oversubscribe the physical interface by including the shaping-rate statement at the [edit class-of-service traffic-control-profiles] hierarchy level. With this configuration approach, you can independently control the delay-buffer rate.

Results

Configuring Policer Overhead on the PIC or MPC That Hosts the Rate-Shaped Logical Interface

Step-by-Step Procedure

1. Enable configuration of the supported PIC or MPC.

   [edit]user@host# set chassis fpc 1 pic 3

2. Configure 100 bytes of policer overhead on the supported PIC or MPC.

   [edit]user@host# set ingress-policer-overhead 100user@host# set egress-policer-overhead 100

   Note: These values are added to the length of the final Ethernet frame when determining ingress and egress policer actions for all physical interfaces on the PIC or MPC.

   You can specify policer overhead with values from 0 through 255 bytes.

Results

Applying a Policer to the Logical Interface That Carries Input Traffic

Step-by-Step Procedure

1. Configure the logical interface (aggregate) policer.

   [edit]user@host# edit firewall policer 500Kbps [edit firewall policer 500Kbps]user@host# set logical-interface-policeruser@host# set if-exceeding bandwidth-limit 500kuser@host# set if-exceeding burst-size-limit 625kuser@host# set then discard

2. Apply the policer to Layer 3 input on the IPv4 logical interface.

   [edit]user@host# set interfaces ge-1/3/1 unit 0 family inet policer input 500Kbps

   Note: The 100 Mbps policer overhead is added to the length of the final Ethernet frame when determining ingress and egress policer actions,

Results

If you are done configuring the device, enter commit from configuration mode.

Verification

Confirm that the configuration is working properly.

• Displaying Traffic Statistics and Policers for the Logical Interface
• Displaying Statistics for the Policer

Displaying Traffic Statistics and Policers for the Logical Interface

Purpose

Verify the traffic flow through the logical interface and that the policer is evaluated when packets are received on the logical interface.

Action

• Input: 500Kbps-ge-1/3/1.0-log_int-i
• Output: 500Kbps-ge-1/3/1.0-log_int-o

The log_int-i suffix denotes a logical interface policer applied to input traffic, while the log_int-o suffix denotes a logical interface policer applied to output traffic. In this example, the logical interface policer is applied to Input traffic only.

Displaying Statistics for the Policer

Purpose

Verify the number of packets evaluated by the policer.

Action

• 500Kbps-ge-1/3/1.0-log_int-i
• 500Kbps-ge-1/3/1.0-log_int-o

The log_int-i suffix denotes a logical interface policer applied to input traffic, while the log_int-o suffix denotes a logical interface policer applied to output traffic. In this example, the logical interface policer is applied to input traffic only.