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Basic Single-Rate Three-Color Policers

Single-Rate Three-Color Policer Overview

A single-rate three-color policer defines a bandwidth limit and a maximum burst size for guaranteed traffic and a second burst size for peak traffic. A single-rate three-color policer is most useful when a service is structured according to packet length and not peak arrival rate.

• Committed information rate (CIR)—Bandwidth limit for guaranteed traffic.
• Committed burst size (CBS)—Maximum packet size permitted for bursts of data that exceed the CIR.
• Excess burst size (EBS)—Maximum packet size permitted for peak traffic.

• Green—Traffic that conforms to either the bandwidth limit or the burst size for guaranteed traffic (CIR and CBS). For a green traffic flow, single-rate  marks the packets with an implicit loss priority of low and transmits the packets.
• Yellow—Traffic that exceeds both the bandwidth limit and the burst size for guaranteed traffic (CIR or CBS) but not the burst size for peak traffic (EBS). For a yellow traffic flow, single-rate  marks the packets with an implicit loss priority of medium-high and transmits the packets.
• Red—Traffic that exceeds the burst size for peak traffic (EBS), single-rate  marks packets with an implicit loss priority of high and, optionally, discards the packets.

If congestion occurs downstream, the packets with higher loss priority are more likely to be discarded.

Note: For both single-rate and two-rate three-color policers, the only configurable action is to discard packets in a red traffic flow.

The discard action for a tricolor marking policer for a firewall filter is supported on the M120 routers, M320 routers with Enhanced-III FPCs, M7i and M10i routers with the Enhanced CFEB (CFEB-E), and MX Series routers with Trio MPCs and EX Series switches, so it is not necessary to include the logical-interface-policer statement for them.

Example: Configuring a Single-Rate Three-Color Policer

This example shows how to configure a single-rate three-color policer.

• Requirements
• Overview
• Configuration
• Verification

Requirements

No special configuration beyond device initialization is required before configuring this example.

Overview

• Nonconforming traffic that does not exceed the burst size for excess traffic is categorized as yellow.
• Nonconforming traffic that exceeds the burst size for excess traffic is categorized as red.

Each category is associated with an action. For green traffic, packets are implicitly set with a loss-priority value of low and then transmitted. For yellow traffic, packets are implicitly set with a loss-priority value of medium-high and then transmitted. For red traffic, packets are implicitly set with a loss-priority value of high and then transmitted. If the policer configuration includes the optional action statement (action loss-priority high then discard), then packets in a red flow are discarded instead.

You can apply a three-color policer to Layer 3 traffic as a firewall filter policer only. You reference the policer from a stateless firewall filter term, and then you apply the filter to the input or output of a logical interface at the protocol level.

Topology

In this example, you apply a color-aware, single-rate three-color policer to the input IPv4 traffic at logical interface ge-2/0/5.0. The IPv4 firewall filter term that references the policer does not apply any packet-filtering. The filter is used only to apply the three-color policer to the interface.

You configure the policer to rate-limit traffic to a bandwidth limit of 40 Mbps and a burst-size limit of 100 KB for green traffic but also allow an excess burst-size limit of 200 KB for yellow traffic. Only nonconforming traffic that exceeds the peak burst-size limit is categorized as red. In this example, you configure the three-color policer action loss-priority high then discard, which overrides the implicit marking of red traffic to a high loss priority.

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 a Single-Rate Three-Color Policer
• Configuring an IPv4 Stateless Firewall Filter That References the Policer
• Applying the Filter to the Logical Interface

CLI Quick Configuration

Configuring a Single-Rate Three-Color Policer

Step-by-Step Procedure

1. Enable configuration of a three-color policer.

   [edit]user@host# edit firewall three-color-policer srTCM1-ca

2. Configure the color mode of the single-rate three-color policer.

   [edit firewall three-color-policer srTCM1-ca]user@host# set single-rate color-aware

3. Configure the single-rate guaranteed traffic limits.

   [edit firewall three-color-policer srTCM1-ca]user@host# set single-rate committed-information-rate 40muser@host# set single-rate committed-burst-size 100k

4. Configure the single-rate burst-size limit that is used to classify nonconforming traffic.

   [edit firewall three-color-policer srTCM1-ca]user@host# set single-rate excess-burst-size 200k

5. (Optional) Configure the action for nonconforming traffic.

   [edit firewall three-color-policer srTCM1-ca]user@host# set action loss-priority high then discard
   For three-color policers, the only configurable action is to discard packets in a red traffic flow. In this example, packets in a red traffic flow have been implicitly marked with a high packet loss priority (PLP) level because the traffic flow exceeded the rate-limiting defined by the single rate-limit (specified by the committed-information-rate 40m statement) and the larger burst-size limit (specified by the excess-burst-size 200k statement). Because the optional action statement is included, this example takes the more severe action of discarding packets in a red traffic flow.

Results

Configuring an IPv4 Stateless Firewall Filter That References the Policer

Step-by-Step Procedure

1. Enable configuration of an IPv4 standard stateless firewall filter.

   [edit]user@host# edit firewall family inet filter filter-srtcm1ca-all

2. Specify the filter term that references the policer.

   [edit firewall family inet filter filter-srtcm1ca-all]user@host# set term 1 then three-color-policer single-rate srTCM1-ca
   Note that the term does not specify any match conditions. The firewall filter passes all packets to the policer.

Results

Applying the Filter to the Logical Interface

Step-by-Step Procedure

1. (MX Series routers and EX Series switches only) (Optional) Reclassify all incoming packets on the logical interface ge-2/0/5.0 to assured forwarding, regardless of any preexisting classification.

   [edit]user@host# set class-of-service interfaces ge-2/0/5 unit 0 forwarding-class af
   The classifier name can be a configured classifier or one of the default classifiers.

2. Enable configuration of the logical interface.

   [edit]user@host# edit interfaces ge-2/0/5 unit 0 family inet

3. Configure an IP address.

   [edit interfaces ge-2/0/5 unit 0 family inet]user@host# set address 10.20.130.1/24

4. Reference the filter as an input filter.

   [edit interfaces ge-2/0/5 unit 0 family inet]user@host# set filter input filter-srtcm1ca-all

Results

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

Verification

Confirm that the configuration is working properly.

Displaying the Firewall Filters Applied to the Logical Interface

Purpose

Verify that the firewall filter is applied to IPv4 input traffic at the logical interface.

Action

Use the show interfaces operational mode command for the logical interface ge-2/0/5.0, and specify detail mode. The Protocol inet section of the command output displays IPv4 information for the logical interface. Within that section, the Input Filters field displays the name of the firewall filter applied to IPv4 input traffic at the logical interface.

  Logical interface ge-2/0/5.0 (Index 105) (SNMP ifIndex 556) (Generation 170)
    Flags: Device-Down SNMP-Traps 0x4004000 Encapsulation: ENET2
    Traffic statistics:
     Input  bytes  :                    0
     Output bytes  :                    0
     Input  packets:                    0
     Output packets:                    0
    Local statistics:
     Input  bytes  :                    0
     Output bytes  :                    0
     Input  packets:                    0
     Output packets:                    0
    Transit statistics:
     Input  bytes  :                    0                    0 bps
     Output bytes  :                    0                    0 bps
     Input  packets:                    0                    0 pps
     Output packets:                    0                    0 pps
    Protocol inet, MTU: 1500, Generation: 242, Route table: 0
      Flags: Sendbcast-pkt-to-re
      Input Filters: filter-srtcm1ca-all
      Addresses, Flags: Dest-route-down Is-Preferred Is-Primary
        Destination: 10.20.130/24, Local: 10.20.130.1, Broadcast: 10.20.130.255,
        Generation: 171
    Protocol multiservice, MTU: Unlimited, Generation: 243, Route table: 0
      Policer: Input: __default_arp_policer__