updated class diagram and design document

git-svn-id: svn://anubis/gvsu@403 45c1a28c-8058-47b2-ae61-ca45b979098e

cs658/html/design.html

@@ -134,9 +134,39 @@
         of the worker nodes going down and still produce the final image.
         </p>
 
+        <span class="update">
+        <p>
+            Update:
+            To implement this distributed algorithm, I thought about using
+            the MPI framework.
+            MPI, however, was not natively designed to handle fault tolerance.
+            So, I decided to implement the distributed framework with raw
+            TCP sockets.
+            This solution is very portable because it only relies on
+            TCP socket availability and not a third-party library.
+        </p>
+        <p>
+            At first TCP was not sending the message data fast enough
+            for my program.
+            I considered switching to UDP but instead turned on the
+            socket option TCP_NODELAY which disables the "Nagle" buffering
+            algorithm and sends the data as soon as it is available.
+            This made using TCP feasible and my CPU utilization grew.
+        </p>
+        <p>
+            The application-level protocol is very simple.
+            It was designed to transmit short messages across the wire.
+            An integer representing the message type is transmitted,
+            followed by the payload of the message.
+            Task identifiers are sent using a single 4-byte integer.
+            Bitmap data is transmitted as packed data, 3 bytes per pixel.
+        </p>
+        </span>
+
         <li>Program Organization</li>
         <p>
-        The follows the object-oriented design paradigm.
+        The program follows the object-oriented design paradigm.
+        It is written in C++ so that it is portable and efficient.
         It is made up of a collection of modules, which are organized
         into functional groupings.
         Each module implements one or more classes of objects for the system.