Hi,
here a question about practical difference between shape average and shape peak. In my understanding the difference between average and peak is that "peak" put Bc+Be token in the tocken bucket every Tc while "average" put just Bc token. By default Be is equal to Bc. So I make the following sample config; what I expect is that they do exactly the same shaping:
policy-map SHAPE
class class-default
shape peak 10000000 150000
policy-map SHAPE2
class class-default
shape average 20000000 300000 0
I applied the policy and this is the result:
R1(config-pmap)#do sh policy-map int
FastEthernet0/0
Service-policy output: SHAPE
Class-map: class-default (match-any)
1296 packets, 116083 bytes
5 minute offered rate 0 bps, drop rate 0 bps
Match: any
Traffic Shaping
Target/Average Byte Sustain Excess Interval Increment
Rate Limit bits/int bits/int (ms) (bytes)
20000000/10000000 37500 150000 150000 15 37500
Adapt Queue Packets Bytes Packets Bytes Shaping
Active Depth Delayed Delayed Active
- 0 1296 116083 0 0 no
FastEthernet0/1
Service-policy output: SHAPE2
Class-map: class-default (match-any)
244 packets, 20629 bytes
5 minute offered rate 0 bps, drop rate 0 bps
Match: any
Traffic Shaping
Target/Average Byte Sustain Excess Interval Increment
Rate Limit bits/int bits/int (ms) (bytes)
20000000/20000000 7500 300000 0 15 37500
Adapt Queue Packets Bytes Packets Bytes Shaping
Active Depth Delayed Delayed Active
- 0 244 20629 0 0 no
As expected Target rate is the same, and Tc and bucket size are also the same. So I my understanding this two config would shape a traffic flow in the same way. Is it correct ?
Second question: which is the default policy for delayed traffic: FIFO o WFQ ? In IOS documentation I read:
When packets are placed in a queue, the default queueing mechanism used is weighted fair queueing (WFQ). However, with Class-Based Traffic Shaping, class-based WFQ (CBWFQ) can be configured as an alternative queueing mechanism.
http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/qos_regpkt/configuration/15-mt/qos-regpkt-15-mt-book/qos-regpkt-cls.html#GUID-3C890022-49C2-424B-827F-6090ED50FF81
But in "CCIE Routing&Switching Certifciation Guide" (Odom, Healy, Donohue, 4th Edtion), pg 1615:
Example 14-2 in the previous section shows default settings for queuing for the interface software
queues (WFQ) and for the shaping queue (FIFO)
Which is true ?
Bye,
enrico
