Two-Rate Three-Color Marker For Traffic Policing - Cisco 10000 Series Configuration Manual

Two-Rate Three-Color Marker for Traffic Policing

Two-Rate Three-Color Marker for Traffic Policing
The two-rate three-color marker improves bandwidth management by allowing you to police traffic
streams according to two separate rates. Unlike the single-rate policer, which allows you to manage
bandwidth by setting the excess burst size (be), the two-rate policer allows you to manage bandwidth by
setting the committed information rate (CIR) and the peak information rate. Therefore, the two-rate
policer supports a higher level of bandwidth management and a sustained excess rate. The two-rate
policer also enables you to implement differentiated services (DiffServ) assured forwarding (AF)
per-hop behavior (PHB) traffic conditioning (see the "Implementing DiffServ for End-to-End Quality of
Service" section in the Cisco IOS Quality of Service Solutions Configuration Guide, Release 12.3).
For information about the single-rate color marker, see the
Note
Policing" section on page
The two-rate policer is often configured on interfaces at the edge of a network to limit the rate of traffic
entering or leaving the network. In addition to rate-limiting traffic, the policer's three-color marker can
mark packets according to whether the packet conforms (green), exceeds (yellow), or violates (red) a
specified rate. You decide the actions you want the router to take for conforming, exceeding, and
violating traffic. For example, you can configure conforming packets to be sent, exceeding packets to be
sent with a decreased priority, and violating packets to be dropped. In most common configurations,
traffic that conforms is sent and traffic that exceeds is sent with decreased priority or is dropped. You
can change these actions according to your network needs.
With packet marking, you can partition your network into multiple priority levels or classes of service
(CoS). For example, you can configure the two-rate three-color marker to do the following:
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The three-color marker distinguishes between the nonconforming traffic that occasionally bursts a
certain number of bytes more than the CIR and violating traffic that continually violates the PIR
allowance. Applications can utilize the three-color marker to provide three service levels: guaranteed,
best effort, and deny. The three-color marker is useful in marking packets in a packet stream with
different, decreasing levels of assurances (either absolute or relative). For example, a service might
discard all red packets because they exceed both the committed and excess burst sizes, forward yellow
packets as best effort, and forward green packets with a low drop probability.
Note The router maintains the behavior of the two-color marker by automatically setting the violate action to
be the same as the exceed action (unless you configure the violate action). Therefore, you can continue
to use the two-color marker. However, it is important to note that the router collects statistics for
conforming, exceeding, and violating packets. Therefore, when verifying packet counts be sure to
observe all three statistical categories to ensure an accurate count.
Cisco 10000 Series Router Quality of Service Configuration Guide
6-8
6-4.
Assign packets to a QoS group, which the router then uses to determine how to prioritize packets
within the router.
Set the IP precedence level, IP DSCP value, or the MPLS experimental value of packets entering the
network. Networking devices within your network can then use this setting to determine how to treat
the traffic. For example, a weighted random early detection (WRED) drop policy can use the IP
precedence value to determine the drop probability of a packet.
Set the ATM cell loss priority (CLP) bit in ATM cells. The ATM CLP bit is used to prioritize packets
in ATM networks and is set to either 0 or 1. During congestion, the router discards cells with a CLP
bit setting of 1 before it discards cells with a CLP bit setting of 0.
Chapter 6
"Single-Rate Color Marker for Traffic
Policing Traffic
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