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Nodes
A node represents a host or a router in the network simulation. It contains a list of links, a set of protocol handlers, and a forwarding table. The main functions of the node are to (a) receive packets that are addressed to it and (b) forward packets that are destined for other nodes.
add_link(link)
delete_link(link)
Adds or delete link for the node.
add_protocol(protocol,handler)
delete_protocol(protocol):
Add or delete a protocol handler. A protocol is a string identifier and a handler is an object. When a packet arrives at its destination, the protocol field in the packet specifies which handler object should be called. The node calls the handle_packet() method on this object.
add_forwarding_entry(address,link)
delete_forwarding_entry(address,link)
Add or delete a forwarding entry for the node. The forwarding entry is given by an integer address, and specifies which link object should be used to reach that address.
By convention, any object can be given a packet to handle using its handle_packet() method. When the handle_packet() method is called on a node, it compares the packet's destination address to the address for each of its links. If a match is found, the packet belongs to this node, so the corresponding packet handler is called, based on the protocol field in the packet. If no match is found, the node uses the forwarding table to send the packet on the link that leads toward the packet's destination.