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class RouteLogic This class defines two methods to configure unicast routing, and one method to query it for routeinformation. It also defines an instance procedure that is applicable when the topology is dynamic. We discuss this lastprocedure in conjunction with the interface to network dynamics.• The instance procedure register{} is invoked by Simulator::rtproto{}. It takes the protocol and a list ofnodes as arguments, and constructs an instance variable, rtprotos_, as an array; the array index is the name of theprotocol, and the value is the list of nodes that will run this protocol.• The configure{} reads the rtprotos_ instance variable, and for each element in the array, invokes route protocolmethods to perform the appropriate initializations. It is invoked by the simulator run procedure.For each protocol 〈rt-proto〉 indexed in the rtprotos_ array, this routine invokes Agent/rtProto/〈rt-proto〉init-all rtprotos_(〈rt-proto〉).If there are no elements in rtprotos_, the routine invokes Static routing, as Agent/rtProto/Static init-all.• The instance procedure lookup{} takes two node numbers, nodeId 1 and nodeId 2 , as argument; it returns the id ofthe neighbor node that nodeId 1 uses to reach nodeId 2 .The procedure is used by the static route computation procedure to query the computed routes and populate the routesat each of the nodes. It is also used by the multicast routing protocols to perform the appropriate RPF check.Note that this procedure overloads an instproc-like of the same name. The procedure queries the appropriate rtObjectentities if they exist (which they will if dynamic routing strategies are used in the simulation); otherwise, the procedureinvokes the instproc-like to obtain the relevant information.class rtObject is used in simulations that use dynamic routing. Each node has a rtObject associated with it, that actsas a co-ordinator for the different routing protocols that operate at a node. At any node, the rtObject at that node tracks eachof the protocols operating at that node; it computes and installs the nest route to each destination available via each of theprotocols. In the event that the routing tables change, or the topology changes, the rtObject will alert the protocols to take theappropriate action.The class defines the procedure init-all{}; this procedure takes a list of nodes as arguments, and creates a rtObject ateach of the nodes in its argument list. It subsequently invokes its compute-routes.The assumption is that the constructor for each of the new objects will instantiate the “Direct” route protocol at eachof these nodes. This route protocol is responsible for computing the routes to immediately adjacent neighbors. Whencompute-routes{} is run by the init-all{} procedure, these direct routes are installed in the node by the appropriateroute object.The other instance procedures in this class are:• init{} The constructor sets up pointers from itself to the node, in its instance variable node_, and from the node toitself, through the Node instance procedure init-routing{} and the Node instance variable rtObject_. It theninitializes an array of nextHop_, rtpref_, metric_, rtVia_. The index of each of these arrays is the handle ofthe destination node.The nextHop_ contains the link that will be used to reach the particular destination; rtpref_ and metric_ are thepreference and metric for the route installed in the node; rtVia_ is the name of the agent whose route is installed inthe node.The constructor also creates the instance of the Direct route protocol, and invokes compute-routes{} for thatprotocol.• add-proto{} creates an instance of the protocol, stores a reference to it in its array of protocols, rtProtos_. Theindex of the array is the name of the protocol. It also attaches the protocol object to the node, and returns the handle ofthe protocol object.254