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To: cs551@merlot.usc.edu
Subject: Re: Weighted fair Queueing
Date: Sun, 07 Dec 2008 19:41:32 -0800
From: Bill Cheng <william@bourbon.usc.edu>

SOmeone wrote:

  > In the weighted fair queuing example in slide 19 of lecture 17,
  > you indicated that we shrink packet sizes by 2
  > Does this imply that if Y2 arrives at logical time 1.5, it will
  > depart at logical time 2 because packet size is now half (instead
  > of the original departure at 2.5)?

Exactly!  For a packet whose weight is 2, it's packet size
is effectively shrunk by 50%.

  > You also indicated that we count Y twice when queue Y is not
  > empty. Does thisimply that we can have a slope of 1/4 if we have
  > up to two packets from Y in service and both X and Z also have a
  > packet each in service?

No exactly.  The slope is 1/4 if there is at least one packet
in each queue.  (The slope is 1/3 if there is at least one
packet in queue Y and at least one packet in queue X or Z.)
--
Bill Cheng // bill.cheng@usc.edu <URL:http://merlot.usc.edu/william/usc/>