CS640 Project Design Issues

0. Read "Proposal Grading Info" online. Make sure you include an overall 
   picture on your design modules, i.e., threads and  the communication / 
   synchronization among themselves. Please follow the other guidelines 
   listed in this file.

1. Make sure the first bit of your MNP packet is for control bit. 
   0: data, 1: control

2. Control packets reliability at MNP layer. For different types of 
   control packets, you may want to have different reliability ensurance 
   policies. (e.g. Signalling messages can be stop-and-wait; Periodically 
   flooding messages doesn't have to be acked)

3. Virtual Circuit Issues:
   Requirements:
   a) As long as there is a path from the source to the destination, a 
      virtual circuit should be set up along the shortest path. 
   b) In case of node/link failure, existing VCs should be rerouted if 
      effected; in addition, invalid VC entries should be removed from all 
      the nodes along its path within 10s. 
   c) When a node is down and back up again, no rerouting is REQUIRED on 
      the existing VCs. But later connection should be able to use the new 
      configuration to achieve shortest path from the source to the 
      destination.

   Issues:
   1) How to deal with node/link down in the middle of virtual circuit 
      setup or tearing down? 
  
   2) How to get rid of useless VC? A simple TTL on VC entries would not 
      work. The VC should not be tear down unless either side of the 
      connection calls the disconnect or some node on the VC fails. 

   3) Maintenance of Virtual Circuit. A virtual circuit should survive in 
      case of temporary failure of a node. For example, one node goes down 
      and is back up again without anyone in the network noticing this 
      change. In this case, everyone else considers the node the same as 
      before while the node itself loses all its routing table and virtual 
      circuit table!!! No data can be sent through this node while others 
      don't know what's wrong. How would you deal with this?

4. Disconnect can be called by either side of the connection disregarding 
   who positively does the rtp_connect(..)

5. When a connect request arrives at the other side of the connection, if 
   the listen_accept function is not called at that node, this request 
   should be rejected. On the other hand, a disconnect request should be 
   buffered until the upper layer receives all the packets it should have 
   received through that connection and calls the listen_accept.

//
Midpoint Demo: Nov. 17th 
	No garbler, no link/node down.