Thursday, March 18, 2010

Shaping--Part 2

Just following up a bit after my last post.  Remember I ended up shaping to the average with 64000 bps as my shaping rate?  I ended up with a policy that looked like this:

Now I went in a did a bit of reconfiguration. Heres what I did:

R2(config)#policy-map shape_all
R2(config-pmap)#class class-default
R2(config-pmap-c)#no shape average 64000
R2(config-pmap-c)#shape peak 64000

Now look at the output of a show policy-map interface:

So here you can probably see some differences from above.  Right off the bat you should notice that the target rate is double what we had originally configured!  Our bucket of tokens now is Bc + Be, instead of just Bc in our previous example.  We get our target shaping rate from the following formula:
Rate = configured rate(1 + Be/Bc) or 64000 (1+(8000/8000)) or 64000(2)....128

So essentially this guy is configured to send up to 2000 bytes (8000 bits x 2) each 125ms interval (if the bucket(s) have that many tokens of course!).  But also notice the increment bytes in this example.  They are double what they were in the previous example.  This is because when you shape to the peak, Bc + Be are going to be replenished each Tc.

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