QoS Class-Based Traffic Shaping (what is Be)

Question

Guys,
two questions on the output below :
1. What is the Be, is this an amount per interval that can go over Bc or is it the total amount of data that can be sent?
ie, i interpret the command to read, Bc is the sustained rate per interval and Be is the sustained rate plus another amount, it I would use sommat like this
shape average 128000 7936 8500
this would show that I could send in total up to 8500 bits per interval
or does it work like this ?
shape average 128000 7936 564
this would show that I could send in total up to 8500 bits per interval
if it is the first one, you would not expect to be able to configure a Be of less than Bc?
Also, how can you show what traffic is within the Bc and what is in the Be? ie, how much data is being sent out of contract?
Many kind regards,
Ken
Metro2(config-pmap-c)#policy-map test1_cos
Metro2(config-pmap)# class class-default
Metro2(config-pmap-c)# shape average ?
<8000-154400000> Target Bit Rate (bits per second), the value needs to be
multiple of 8000
percent % of interface bandwidth for Committed information rate
Metro2(config-pmap-c)# shape average 128000 ?
<256-154400000> bits per interval, sustained. Needs to be multiple of 128.
Recommend not to configure it, the algorithm will find out
the best value
<cr>
Metro2(config-pmap-c)# shape average 128000 7936 ?
<0-154400000> bits per interval, excess. Needs to be multiple of 128. Bc
will be used if you don't configure it.
<cr>
Metro2(config-pmap-c)# shape average 128000 7936 1000 ?
<cr>
Metro2(config-pmap-c)# shape average 128000 7936 1000
Metro2(config-pmap-c)#^Z
Metro2#
Metro2#sh policy-map int fa 0/1 out
FastEthernet0/1
Service-policy output: test1_cos
Class-map: class-default (match-any)
5476 packets, 1934775 bytes
30 second 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)
128000/128000 1117 7936 1000 62 992
Adapt Queue Packets Bytes Packets Bytes Shaping
Active Depth Delayed Delayed Active
- 0 5476 1934775 967 1448313 no
Metro2#
Metro2# conf t
Enter configuration commands, one per line. End with CNTL/Z.
Metro2(config)#policy-map test1_cos
Metro2(config-pmap)# class class-default
Metro2(config-pmap-c)# shape average 128000
Metro2(config-pmap-c)#^Z
Metro2#sh policy-map int fa 0/1 out
FastEthernet0/1
Service-policy output: test1_cos
Class-map: class-default (match-any)
5479 packets, 1934955 bytes
30 second 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)
128000/128000 1984 7936 7936 62 992
Adapt Queue Packets Bytes Packets Bytes Shaping
Active Depth Delayed Delayed Active
- 0 5479 1934955 967 1448313 no
Metro2#

Answer 1

Guys,
this is great stuff and I really apprciate it.
The thing is this.
One one URL it says the following :-
For Class-based Shaping - How it Works
When the Be size equals 0, the interface sends no more than the burst size every interval, achieving an average rate no higher than the mean rate. However, when the Be size is greater than 0, the interface can send as many as Bc + Be bits in a burst, if in a previous time period the maximum amount was not sent. Whenever less than the burst size is sent during an interval, the remaining number of bits, up to the Be size, can be used to send more than the burst size in a later interval.
The other URL says :-
DTS How It Works
The Be size allows more than the Bc size to be sent during a time interval under certain conditions. Therefore, DTS provides two types of shape commands: average and peak. When shape average is configured, the interface sends no more than the Bc size for each interval, achieving an average rate no higher than the CIR. When the shape peak command is configured, the interface sends Bc plus Be bits in each interval.
So which one is correct. I am really confused.
As far as I am aware, I am running CB Shaping and not DTS, but when I go into the router configurations I get both options.
average and peak ?
Please see example :-
Metro2(config)#policy-map test1_cos
Metro2(config-pmap)#class class-default
Metro2(config-pmap-c)#shap ?
adaptive Enable Traffic Shaping adaptation to BECN
average configure token bucket: CIR (bps) [Bc (bits) [Be (bits)]],
send out Bc only per interval
fecn-adapt Enable Traffic Shaping reflection of FECN as BECN
fr-voice-adapt Enable rate adjustment depending on voice presence
max-buffers Set Maximum Buffer Limit
peak configure token bucket: CIR (bps) [Bc (bits) [Be (bits)]],
send out Bc+Be per interval
Many kind regards and thx for the help with this :)
Ken