[ns] Dedicated Buffers

[t . ashish]

Hi

I am working on QoS in tiny buffer networks. As a part of my work I have
made changes in the drop tail queue management so as to give some
dedicated buffer size to real time traffic but even after changing the
drop tail queue management I get the same results.

Here is the changes made

void DropTail::enque(Packet* p)
{
        if (summarystats) {
                Queue::updateStats(qib_?q_->byteLength():q_->length());
        }
        int qlimBytes = qlim_ * mean_pktsize_;

        int limit_udp=LIMIT_UDP*qlim_;                          //**
        int limit_tcp=LIMIT_TCP*qlim_;                          //**
        packet_t type;
        type=hdr_cmn::access(p)->ptype_;

        int tcp_count=0;
        int udp_count=0;

        for(int i=0;i < q_->length();i++)
        {
          Packet *pkt=q_->lookup(i);
          if(hdr_cmn::access(pkt)->ptype_==PT_TCP)
            tcp_count++;
          if(hdr_cmn::access(pkt)->ptype_==PT_EXP)
            udp_count++;
        }

        tcp_count=tcp_count/100;
        udp_count=udp_count/100;


        if(type==PT_TCP)
        {
          if (((!qib_ && (q_->length() + 1) >= qlim_) ||(qib_ &&
(q_->byteLength() + hdr_cmn::access(p)->size()) >=
qlimBytes))&&(!(tcp_count<=PT_TCP))) {
            // if the queue would overflow if we added this packet...
                if (drop_front_) { // remove from head of queue
                        q_->enque(p);
                        Packet *pp = q_->deque();
                        drop(pp);
                } else {
                        drop(p);
                }
        } else {
                q_->enque(p);
        }
        }

        if(type==PT_EXP)
        {
          if (((!qib_ && (q_->length() + 1) >= qlim_) ||(qib_ &&
(q_->byteLength() + hdr_cmn::access(p)->size()) >=
qlimBytes))&&(!(udp_count<=PT_EXP))) {
            // if the queue would overflow if we added this packet...
                if (drop_front_) { // remove from head of queue
                        q_->enque(p);
                        Packet *pp = q_->deque();
                        drop(pp);
                } else {
                        drop(p);
                }
        } else {
                q_->enque(p);
        }
        }
        //Original Code
        /*if ((!qib_ && (q_->length() + 1) >= qlim_) ||
        (qib_ && (q_->byteLength() + hdr_cmn::access(p)->size()) >= qlimBytes)){
                // if the queue would overflow if we added this packet...
                if (drop_front_) { // remove from head of queue
                        q_->enque(p);
                        Packet *pp = q_->deque();
                        drop(pp);
                } else {
                        drop(p);
                }
        } else {
                q_->enque(p);
        }*/

}

the file drop-tail.c can be found at following location
ns-allinone-2.30/ns-2.30/queue

Any help wud be appreciated

Ashish