Friday, March 19, 2010


I was having some trouble after looking at the output pasted in my previous post regarding shaping.  What is the difference in these commands:

shape average 64000
shape peak 64000

Both have a byte limit of 2000 bytes per Tc, the same Tc, and average rate.  The only differences were the target rate, and increment bytes.  Well, the difference was truly in those numbers.  Sure, both can send 2000 bytes per interval, if the bytes are in the bucket.  But the true difference is that with the shape peak command, the higher number of bits can be realized.  This is because of the increment bytes.  When you shape to the peak you get Bc + Be replenished every Tc, letting you truly send 2000 bytes per interval.  When you shape to the average you only get Bc every Tc, so under periods of high congestion you will only be able to send 1000 bytes, even though you have the ability to send 2000, because your Be bucket is empty, and only your Bc is getting filled back up every Tc.  Once the network becomes a little less congested, you should once again be able to send those 2000 bytes.  Thanks to great archived posts on and INE's blog by Petr for clearing this up in my head.

I scheduled my exam for Tues. the 23rd.

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