[ns] Questions about classifier

[Chien-Lung Wu <cwu4@unity.ncsu.edu>]

Hi, ns-experts:

I got following questions about classifier class.

Q.1 In the classifier class there is recv function as following

/*
 * objects only ever see "packet" events, which come either
 * from an incoming link or a local agent (i.e., packet source).
 */ void Classifier::recv(Packet* p, Handler*h) {
    NsObject* node = find(p);
    if (node == NULL) {
        /*
         * XXX this should be "dropped" somehow.  Right now,
         * these events aren't traced.
         */
        Packet::free(p);
        return;
    }
    node->recv(p,h);
}                                           

 It is understandable in processing a received packet and then calling
  node->recv(p,h).

 However, I check the NsObject::recv (node is an object of
NsObject) fuction as following:

/*
 * Packets may be handed to NsObjects at sheduled points
 * in time since a node is an event handler and a packet
 * is an event.  Packets should be the only type of event
 * scheduled on a node so we can carry out the cast below.
 */
 void NsObject::handle(Event* e) {
    recv((Packet*)e); }
 
void NsObject::recv(Packet *p, const char*) {
    Packet::free(p); 
}
                                          
 Why does it free this packet in the recv fuction? Am I correct?



Q2. If a node received a packet, it will go througt the classifier::recv.

    After the classifier::recv(pkt, h), what is the next process to deal
    with this packets? Does it send the incoming packet to "agent"
    or any other process missed? Are the processes like:
    
    classifier::recv()--> agent:recv-->routing process

   or
   classifier:recv(pkt, h)--(need forward)--> routing--->forwarding--->out
                          |
			  |
			  +--for this node--> agent::recv


Q3. If I want to see all of pkt-types traffic, where can I insert the
    fuction? in the agent::recv or in the classfier::recv() or
    somewhereelse?

Any help will be appreciated. Thanks.


Regards,


Chien-Lung Wu