Package simplenet

Class Router

java.lang.Object

simplenet.Router

public abstract class Router
extends java.lang.Object

base functionality of a network router. This class represents a network router. It provides all the basic configuration and link-layer communication functionalities available to a router, but it does not provide any particular routing function. In fact, this (abstract) class must be extended in order to implement a functioning router. In particular, a complete router must implementat the initialize() and process_routing_message(RoutingMessage,int) methods.

See Also:

Network

Constructor Summary

Constructors

Constructor	Description
Router()

Method Summary

Modifier and Type	Method	Description
void	clear_forwarding_entry(int address)	removes a forwarding-table mapping.
void	clear_forwarding_table()	clears the forwarding-table completely.
protected double	current_time()	current time in the network.
abstract void	initialize()	router initialization method.
protected int	interfaces()	number of interfaces of this router.
protected double	link_cost(int i)	cost of the link connected to the i-th interface.
protected int	my_address()	address of this node.
protected void	print_debug(java.lang.String msg)	prints a debugging message.
protected void	print_error(java.lang.String msg)	prints an error message.
void	process_event(simplenet.Event e)
abstract void	process_routing_message(RoutingMessage m, int incoming_interface)	entry method for the routing protocol.
protected void	send_message(Message m, int i)	send a message to the i-th interface (neighbor).
void	set_forwarding_entry(int address, int ifx)	defines a forwarding-table mapping.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

Router

public Router()

Method Detail

interfaces

protected final int interfaces()

number of interfaces of this router. The number of interfaces corresponds to the number of neighbor routers of this router.

my_address

protected final int my_address()

address of this node.

link_cost

protected final double link_cost(int i)

cost of the link connected to the i-th interface. Returns the link cost of the link connected to the i-th interface of this router. In this network, the link cost corresponds to the latency of the link.

Notice that the index of the first interface is 0, and that of the last interface is interfaces() - 1.

See Also:

interfaces()

current_time

protected final double current_time()

current time in the network.

send_message

protected final void send_message(Message m,
                                  int i)

send a message to the i-th interface (neighbor). This is a link-layer communication function. The router at the other end of the link will receive the given message with a latency corresponding to the cost of the link.

For example,

  class MyMessage implements {
      String msg;
      public MyMessage(String m) {
          msg = m;
      }
  }

  // ...
  MyMessage
  for(int i = 0; i < interfaces(); ++i) {
     send_message(neighbor_address() " is my neighbor.");
  }
  

Parameters:

m - message to be sent.

i - number of the outgoing interface (starting from 0).

See Also:

link_cost(int)

process_event

public final void process_event(simplenet.Event e)

process_routing_message

public abstract void process_routing_message(RoutingMessage m,
                                             int incoming_interface)

entry method for the routing protocol. This method is invoked every time the router receives a routing-protocol message. A specific router implementation must implement this method.

initialize

public abstract void initialize()

router initialization method. This method is invoked once, when the router is initialized. A specific router implementation must implement this method.

set_forwarding_entry

public final void set_forwarding_entry(int address,
                                       int ifx)

defines a forwarding-table mapping. This is the primary interface to the forwarding table. Once a router has figured out where to forward messages addressed to a given destination address, it must set the appropriate mapping in its forwarding table. If, for example, the best path to address goes through interface i, then the router must execute:

     set_forwarding_entry(address, i);
  

Parameters:

address - destination

ifx - next-hop interface on the best path to address

clear_forwarding_entry

public final void clear_forwarding_entry(int address)

removes a forwarding-table mapping. If for some reason the router needs to remove a mapping, then this method does just that.

Parameters:

address - destination

clear_forwarding_table

public final void clear_forwarding_table()

clears the forwarding-table completely. This method removes all entries from the forwarding table at once.

print_debug

protected final void print_debug(java.lang.String msg)

prints a debugging message. This method prints a message on the standard output. The message starts with the current simulation time, followed by the current node address, and then by the given message. So, for example, the following call:

     print_debug("ciao");
  

might produce the following output:

  102.5: n7: ciao
  

These debugging messages are visible only if the simulation is started with the -d option.

See Also:

Network, print_error(String)

print_error

protected final void print_error(java.lang.String msg)

prints an error message. This method prints an error message. The message starts with the current simulation time, followed by the current node address, and then by the given message. Error messages are printed even if simulation is started without the -d option.

See Also:

Network, print_debug(String)