11.3.2 Graph representing a computer network

Here we sketch a very simple example representing the structure of a computer network using class Graph. A Node in the graph represent a computer (server) and an Edge represents a cable.

   class Network: Graph
      class Node::< 
         send(receiver: ref Node,P: ref Packet):
            :::
         receive(send: ref Node,P: ref Packet): 
            ...
         :::
         ...
      class Edge::<
         bandWidth: var integer
         send(receiver: ref Node,P: ref Packet):
            ...
         ...
      class Packet(S: var String):
          ...

Class Network is a subclass of Graph.
It has further bindings of Node and Edge from Graph.
It adds a class Packet representing the packets being communicated in the network.

Class Node is extended with:

A method send that send the Packet P to the node represents by receiver.
A method receive that receives a a Packet P from the Node represented by receiver.

Class Edge is extended with:

An integer bandWidth representing the bandwidth of the cable represented by the Edge.

Th details of send in Node may be sketched as follows:

send(receiver: ref Node,P: ref Packet):
   map(receiver).send(receiver,P)

Send uses an ancillary method map to find the edge representing the cable that has the fastest connection to the receiver, and the invokes send on this Edge.

We do not add further details of this examples. It is major task to implement a computer network. It also involves using parallel programming for listening on input/output ports for packages being transmitted / received. Parallel programming is described in chapter