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To: cs551@merlot.usc.edu
Subject: Re: cs551 is it a bug in grading-guideline?
Date: Fri, 31 Oct 2008 13:10:23 -0700
From: Bill Cheng <william@bourbon.usc.edu>

Someone wrote:

  > Node doesn't fwd join request to temporary link(haven't receive hello), 
  > is it correct?

Correct.

  > So I guess in (c)(2)(a),(c)(3)(a), and(c)(3)(b), we should also wait 10 
  > seconds between the starting of the nodes. Otherwise, if we start all 
  > regular nodes one after another very quickly, all regular nodes will 
  > have neighbors only with beacon nodes. I think so, but not sure.

Usually, it takes time to switch window.  So, for JoinTimeout=5,
we don't need to wait extra time.  The grader will not be
"starting nodes as fast as she can".  The normal thing is to
start a node, observe that it's doing the right thing, before
starting another node.
--
Bill Cheng // bill.cheng@usc.edu <URL:http://merlot.usc.edu/william/usc/>





  Bill Cheng wrote:
  > Someone wrote:
  > 
  >   > I'm not quite sure it's a bug in the grading-guideline:
  >   > 
  >   > ------------------------------------------------------------------------------
  >   > (C) Network with 2 beacon nodes : +22 points
  >   > ------------------------------------------------------------------------------
  >   > (2) (c) restart only 1 beacon plus all of the 4 regular nodes,
  >   >          all regular nodes should fail
  >   > The conclusion is true only when start 4 regular with -reset.
  >   > 
  >   > But if grader follows the sequence, (2)(a), (2)(b), (2)(c),
  >   > after (2)(b),
  >   > n03 has (n00,n01) in its init_neighbor_list;
  >   > n02 has (n00,n03) in its init_neighbor_list;
  >   > n08 has (n00,n01) in its init_neighbor_list.
  >   > Then in (2)(c), after starting n03, if grader starts n02 quickly,
  >   > n02 will connect n00 and n03 successfully, then keep alive.
  >   > Then n03 got neighbor n02 plus original n00, then also survive.
  >   > And n08 starts, thru n00, it could find new neighbors.
  >   > 
  >   > I've tested it with my code, but not sure.
  > 
  > I think you are correct if the nodes get started quickly.
  > Since JoinTimeout is 5 seconds, I should add "wait 10 seconds"
  > between the starting of the nodes to make sure that all
  > regular nodes will fail to start.
  > 
  > I'll update the grading guidelines soon.  Thanks for catching
  > the bug!
  > --
  > Bill Cheng // bill.cheng@usc.edu <URL:http://merlot.usc.edu/william/usc/>