[c-nsp] Traffic Counters and QoS Policy

[Ivan]

I am sending some test traffic through a Cisco 1841 (12.4(15)T4) and am 
hoping someone can confirm what I have found.

I am sending 64 byte packets (including IP headers) through uniformly at 
110000bps (215 PPS).  The counters on the interface show traffic of 
134000bps and 215 PPS.  This works out to be 78 bytes per packet.  It 
would seem the additional 14 bytes are the layer 2 Ethernet header (6 
bytes source MAC, 6 bytes dest MAC, 2 bytes ether type).


The documentation from Cisco 
(http://www.cisco.com/en/US/docs/ios/12_0/interface/command/reference/irshowin.html#wp1017950) 
states

Five minute input rate,Five minute output rate = Average number of bits 
and packets transmitted per second in the last 5 minutes.
bytes input = Total number of bytes, including data and MAC 
encapsulation, in the error free packets received by the system.


The description of the input rate doesn't really clarify if it includes 
the layer 2 header but the byte count does.  Resetting the counters and 
doing the maths shows to me the the input rate counters do include layer 
2 headers.  Can anyone confirm I am on the right track here?

The interesting part is that when I have a QoS policy on the interface 
the policy counters are also using the layer 2 headers in the 
calculations as I get a "30 second offered rate 134000 bps".  Does this 
mean for example if I apply some kind of QoS policy to 5Mbps 
(5000000bps) it will be including the layer 2 headers in the 
calculations?  I had always assumed the it was only layer 3 and above.


Ivan