[c-nsp] traffic shaping inbound wan?

[Clinton Work]

How many traffic shaping implementations actually smooth out bursts? The 
last time I played
with the IOS shaping command on a 7206 with IOS 12.3 it didn't actually 
take packets out of
the queue at the shaping rate. The shaping command would allow the 25ms 
token bucket
queue to be used in 1ms if there was enough packets. The shaper would then
queue packets for another 24ms until the token bucket was refreshed.  
The packets
transmitted in that 1ms burst would be dropped by an upstream ISP policer.

My guess is that the low end software based Cisco routers (2600, 3600, 
7206) don't have
the high-precision hardware timers to implement a configurable transmit 
rate. The sheer
number of interrupt per second to simulate a 40Mbps hardware interface 
might overwhelm
the CPU as well. Maybe the only way to implement a proper traffic shaper 
is in hardware.


Gert Doering wrote:

>Actually, the customer wants to do shaping, to make sure they can make
>best use out of their commited bandwidth.
>
>*You* want to do policing.  
>
>"Send me no more than X mbit, or I will just drop it, no mercy".
>
>gert
>
>  
>
-- 

=======================================================
Clinton Work
Airdrie, AB