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In QoS there is a variety of Queuing methods and one of them is WFQ, which organizes the flows in different queues where each queue has a weight that determines which flow will go first.
Now for calculating the weight the formula used is:
Weight = 4096 / (IP-precedence+1). Where 4096 is the maximum number of queues, so why the maximum number is 4096? It is a pre-established number or it is based on some criteria?
This platform specific limit, so it's just arbitrary limit Cisco came up with at one point in time, probably driven by memory restrictions of device of that era.
W=K/(precedence +1)
K= 4096 with Cisco IOS 12.0(4)T and earlier releases, and 32384 with 12.0(5)T and later releases.
From: http://www.cisco.com/en/US/tech/tk543/tk545/technologies_q_and_a_item09186a00800cdfab.shtml#class
