cancel
Showing results for 
Search instead for 
Did you mean: 
cancel
450
Views
6
Helpful
4
Replies

Traffic Shaping

blakeslatter
Level 1
Level 1

Is there any difference in the shaping behaviour of the below policy maps?

 

policy-map SHAPE
 class class-default
  shape peak 1843000 18430 0

 

policy-map SHAPE
 class class-default
  shape average 1843000 18430 0

4 Replies 4

Refer below link:

 

http://www.cisco.com/c/en/us/td/docs/ios/12_2/qos/configuration/guide/fqos_c/qcfpolsh.html#wp1004234

 

shape average - interface sends no more than the Bc size for each interval, achieving an average rate no higher than the CIR

shape peak - interface sends Bc plus Be bits in each interval.

 

Thanks Vivek.

 

My understanding from my example is that; as both policies have the Be value set to 0 that they will behave in the the same way 

i.e.

shape average 1843000 18430 0
- sends traffic at 1843kbps with 18430 bits every 10ms with no excess burst

shape peak 1843000 18430 0
- sends traffic at 1843kbps with 18430 bits every 10ms with no excess burst

I am curious to know if the "average" or "peak" shaping types provide any different shaping characteristics in my example or both provide the same outcome?

 

Posts in this discussion have been modified due to possible misconduct. Please refer to the CSC terms of use for more details. 

Joseph W. Doherty
Hall of Fame
Hall of Fame

Disclaimer

The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.

Liability Disclaimer

In no event shall Author be liable for any damages whatsoever (including, without limitation, damages for loss of use, data or profit) arising out of the use or inability to use the posting's information even if Author has been advised of the possibility of such damage.

Posting

On many devices, peak just appears to double the effective transfer rate of average.

Your thinking about Be being set to zero, for peak making it the same at average, is logically correct, but I would say you need to try in on the device under question.

If you review peak shaping, Cisco, I recall, has some documentation Be only refills with unused Bc, but on many devices, Be seems to refill on every Tc.

Traditionally, QoS features don't usually get "wrung out" as often in the field, so in my experience, they are more likely not to work exactly as documented.  (BTW, if you find a clear case of this, and bring it to Cisco's attention, the "fix" might be a revision to the documentation - laugh.)

Review Cisco Networking for a $25 gift card