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To: cs551@merlot.usc.edu
Subject: Re: cs551
Date: Tue, 28 Oct 2008 07:39:51 -0700
From: Bill Cheng <william@bourbon.usc.edu>

Someone wrote:

  > One of the tests in the grading guidelines is the following
  > 
  > (c) (+2 points) one beacon node, 3 regular nodes, linear network,
  >                 killing the only beacon node
  > 
  >             Restart the beacon node in the first window as follows:
  >                 ./sv_node c8-n07.ini
  >                     (wait for all nodes to start)
  > 
  >             in 2nd window, do:
  >                 ./sv_node c8-n04.ini
  >                     (wait for all nodes to start)
  > 
  >             in 3rd window, do:
  >                 ./sv_node c8-n09.ini
  >                     (wait for all nodes to start)
  > 
  >             in 4th window, do:
  >                 ./sv_node c8-n06.ini
  > 
  >             type "shutdown" in the 1st window
  >                 (all nodes should eventually shutdown)
  > 
  >             *wait* for all nodes to autoshutdown
  > 
  >             *in 5th window, do:
  >                 more ~/tmp/final1/n04/init_neighbor_list
  >                 more ~/tmp/final1/n09/init_neighbor_list
  >                 more ~/tmp/final1/n06/init_neighbor_list
  >                     (none of these files should exist)*
  > 
  >             in 5th window, do:
  >                 more ~/tmp/final1/n04/servant.log
  >                 more ~/tmp/final1/n09/servant.log
  >                 more ~/tmp/final1/n06/servant.log
  > 
  > 
  > In this, it is said that the init_neighbor_list file should not exist for
  > the non-beacon nodes (highlighted by bold above). What is the reason for
  > this ?

You are talking about the (B.2.c) case where there is only
one beacon node (node 07) with topology:

    topology:  n07* <- n04 <- n09 <- n06

If you shutdown the beacon node, node 04 will flood a CHECK
and CHECK would fail.  Then it restarts.  It has only node
07 in its init_neighbor_list and cannot connect to node 07,
so it deletes its init_neighbor_list and restart.  Then it
cannot find any beacon node, so it quits.  Node 09 and 06
should also do the same thing eventually.
--
Bill Cheng // bill.cheng@usc.edu <URL:http://merlot.usc.edu/william/usc/>