This feature extends the functionality of WRED. In previous releases, you specified the WRED actions based on the number of packets. With the byte-based WRED, you can specify WRED actions based on the number of bytes.

In Cisco IOS XE Release 2.4, the Cisco ASR 1000 Series Aggregation Services Routers support the addition of bytes as a unit of configuration for both queue limits and WRED thresholds. Therefore, as of this release, packet-based and byte-based limits are configurable, with some restrictions.

1.    enable


2.    configure terminal


3.    class-map class-map-name


4.    match ip precedence ip-precedence-value


5.    exit

6.    policy-map policy-name


7.    class class-name


8.    random-detect


9.    random-detect precedence precedence min-threshold bytes max-threshold bytes mark-prob-denominator

Router> enable

Router# configure terminal

Router(config)# class-map c1

Router(config-cmap)# match ip precedence 1

Router(config-cmap)# exit

Router(config)# policy-map p1

Router(config-pmap)# class c1

Router(config-pmap-c)# random-detect

Router(config-pmap-c)# random-detect precedence 1 2000 bytes 3000 bytes 200

Before You Begin

Be sure that your configuration satisfies the following conditions when configuring the queue depth and WRED thresholds:

• When configuring byte-based mode, the queue limit must be configured prior to the WRED threshold and before the service policy is applied.

• When setting the queue depth and WRED thresholds in an enhanced QoS policies aggregation configuration, the limits are supported only for the default class at a subinterface policy map and for any classes at the main interface policy map.

Note

Consider the following restrictions when you configure the queue depth and WRED thresholds: Do not configure the queue limit unit before you configure a queueing feature for a traffic class. If you do not configure a queue limit, then the default mode is packets. When you configure WRED thresholds, the following restrictions apply: The WRED threshold must use the same unit as the queue limit. For example, if the queue limit is in packets, then the WRED thresholds also must be in packets. If you do not configure a queue limit in bytes, then the default mode is packets and you must also configure the WRED threshold in packets. The queue limit size must be greater than the WRED threshold. The unit modes for either the queue limit or WRED thresholds cannot be changed dynamically after a service policy is applied. >

1.    enable


2.    configure terminal


3.    policy-map policy-map-name


4.    class class-name


5.    qos-queueing-feature


6.    queue-limit queue-limit-size [bytes | packets]


7.    random-detect [dscp-based | prec-based]


8.    Do one of the following:

• random-detect dscp dscp-value {min-threshold max-threshold | min-threshold bytes max-threshold bytes} [max-probability-denominator]
• random-detect precedence precedence {min-threshold max-threshold | min-threshold bytes max-threshold bytes} max-probability-denominator

Router> enable

Router# configure terminal

Router(config)# policy-map main-interface

Router(config-pmap)# class AF1

Router(config-pmap-c)# bandwidth remaining ratio 90

Router(config-pmap-c)# queue-limit 547500 bytes

Router(config-pmap-c)# random-detect dscp-based

Router(config-pmap-c)# random-detect precedence 8 750000 bytes 750000 bytes

class AF1
	bandwidth remaining ratio 90
		queue-limit 750000 bytes

class AF1
	queue-limit 750000 bytes
		bandwidth remaining ratio 90

class AF1
	bandwidth remaining ratio 90
		queue-limit 750000 bytes
			random-detect dscp-based
				random-detect dscp 8 750000 bytes 750000 bytes

class AF1
	bandwidth remaining ratio 90
	random-detect dscp-based
	random-detect dscp 8 750000 bytes 750000 bytes

1.    enable


2.    configure terminal


3.    interface type number


4.    no service-policy output policy-map-name


5.    exit


6.    policy-map policy-map-name


7.    class class-name


8.    queue-limit queue-limit-size [bytes | packets]


9.    Do one of the following:

• no random-detect dscp dscp-value {min-threshold max-threshold | min-threshold bytes max-threshold bytes} [max-probability-denominator]
• no random-detect precedence precedence {min-threshold max-threshold | min-threshold bytes max-threshold bytes} max-probability-denominator

10.    Do one of the following:

• random-detect dscp dscp-value {min-threshold max-threshold | min-threshold bytes max-threshold bytes} [max-probability-denominator]
• random-detect precedence precedence {min-threshold max-threshold| min-threshold bytes max-threshold bytes} max-probability-denominator

Router> enable

Router# configure terminal

Router(config)# policy-map main-interface

Router(config-if)# no service-policy output main-interface-policy

Router(config-if)# exit

Router(config)# policy-map main-interface-policy

Router(config-pmap)# class AF1

Router(config-pmap-c)# queue-limit 5000 packets

Router(config-pmap-c)# no random-detect dscp 8 750000 bytes 750000 bytes

Router(config-pmap-c)# random-detect dscp 8 4000 4000

interface GigabitEthernet1/2/0
no service-policy output main-interface-policy
end
policy-map main-interface-policy
class AF1
	queue-limit 5000 packets
	no random-detect dscp 8 750000 bytes 750000 bytes
	random-detect dscp 8 4000 4000

1.    show policy-map


2.    The show policy-map interface command shows output for an interface that is configured for byte-based WRED.

Router# show policy-map
Policy Map pol1
  Class class c1
Bandwidth 10 (%)
exponential weight 9
        class   min-threshold(bytes)   max-threshold(bytes)  mark-probability
        -------------------------------------------------------------------
 
        0       -                       -                      1/10
        1       20000                   30000                  1/10
        2       -                       -                      1/10
        3       -                       -                      1/10
        4       -                       -                      1/10
        5       -                       -                      1/10
        6       -                       -                      1/10
        7       -                       -                      1/10
        rsvp    -                       -                      1/10

Router# show policy-map interface 
serial3/1
Service-policy output: pol
Class-map: silver (match-all)
366 packets, 87840 bytes
30 second offered rate 15000 bps, drop rate 300 bps
Match: ip precedence 1 
Queueing
Output Queue: Conversation 266 
Bandwidth 10 (%)
(pkts matched/bytes matched) 363/87120
depth/total drops/no-buffer drops) 147/38/0
exponential weight: 9
mean queue depth: 25920
class     Transmitted       Random drop      Tail drop     Minimum Maximum Mark
          pkts/bytes        pkts/bytes       pkts/bytes    thresh  thresh  prob
                                                           (bytes)  (bytes)
0             0/0               0/0               0/0      20000    40000  1/10
1           328/78720          38/9120            0/0      22000    40000  1/10
2             0/0               0/0               0/0      24000    40000  1/10
3             0/0               0/0               0/0      26000    40000  1/10
4             0/0               0/0               0/0      28000    40000  1/10