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How to send a unicast packet?

How to send a unicast packet?. Procedure. Roughly takes the following path (when no errors or congestion): recv() -> send() -> sendDATA() and sendRTS() -> start defer timer -> deferHandler() -> check_pktRTS() -> transmit() -> recv() -> receive timer started

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How to send a unicast packet?

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  1. How to send a unicast packet?

  2. Procedure Roughly takes the following path (when no errors or congestion): recv() -> send() -> sendDATA() and sendRTS() -> start defer timer -> deferHandler() -> check_pktRTS() -> transmit() -> recv() -> receive timer started -> recv_timer() -> recvCTS() -> tx_resume() -> start defer timer -> rx_resume() -> deferHandler() -> check_pktTx() -> transmit() -> recv() -> receive timer started -> recv_timer() -> recvACK() -> tx_resume() -> callback_ -> rx_resume() -> done!

  3. recv ( ) void Mac802_11::recv(Packet *p, Handler *h) { struct hdr_cmn *hdr = HDR_CMN(p); assert(initialized()); if( hdr->direction() == hdr_cmn::DOWN ) { send(p, h); return; } if(tx_active_ && hdr->error() == 0) { hdr->error() = 1; } if(rx_state_ == MAC_IDLE) { setRxState(MAC_RECV); pktRx_ = p; mhRecv_.start(txtime(p)); } else { ……………………………………………………………………………………… } } back to procedure

  4. send( ) void Mac802_11::send(Packet *p, Handler *h) { double rTime; struct hdr_mac802_11* dh = HDR_MAC802_11(p); EnergyModel *em = netif_->node()->energy_model(); if (em && em->sleep()) { em->set_node_sleep(0); em->set_node_state(EnergyModel::INROUTE); } callback_ = h; sendDATA(p); sendRTS(ETHER_ADDR(dh->dh_ra)); dh->dh_scontrol = sta_seqno_++; if(mhBackoff_.busy() == 0) { if(is_idle()) { if (mhDefer_.busy() == 0) { rTime = (Random::random() % cw_) * (phymib_.getSlotTime()); mhDefer_.start(phymib_.getDIFS() + rTime); } } else { mhBackoff_.start(cw_, is_idle()); } } } back to procedure

  5. if((u_int32_t)ETHER_ADDR(dh->dh_ra) != MAC_BROADCAST) { /* store data tx time for unicast packets */ ch->txtime() = txtime(ch->size(), dataRate_); dh->dh_duration = usec(txtime(phymib_.getACKlen(), basicRate_) + phymib_.getSIFS()); } else { /* store data tx time for broadcast packets (see 9.6) */ ch->txtime() = txtime(ch->size(), basicRate_ ); dh->dh_duration = 0; } pktTx_ = p; } Mac802_11::sendDATA(Packet *p) { hdr_cmn* ch = HDR_CMN(p); struct hdr_mac802_11* dh = HDR_MAC802_11(p); assert(pktTx_ == 0); ch->size() += phymib_.getHdrLen11(); dh->dh_fc.fc_protocol_version = MAC_ProtocolVersion; dh->dh_fc.fc_type = MAC_Type_Data; dh->dh_fc.fc_subtype = MAC_Subtype_Data; dh->dh_fc.fc_to_ds = 0; dh->dh_fc.fc_from_ds = 0; dh->dh_fc.fc_more_frag = 0; dh->dh_fc.fc_retry = 0; dh->dh_fc.fc_pwr_mgt = 0; dh->dh_fc.fc_more_data = 0; dh->dh_fc.fc_wep = 0; dh->dh_fc.fc_order = 0; /* store data tx time */ ch->txtime() = txtime(ch->size(), dataRate_); Back to send ( ) sendDATA( ) Back to procedure

  6. void Mac802_11::sendRTS(int dst) { Packet *p = Packet::alloc(); hdr_cmn* ch = HDR_CMN(p); struct rts_frame *rf = (struct rts_frame*)p->access(hdr_mac::offset_); assert(pktTx_); assert(pktRTS_ == 0); if( (u_int32_t) HDR_CMN(pktTx_)->size() < macmib_.getRTSThreshold() || (u_int32_t) dst == MAC_BROADCAST) { Packet::free(p); return; } ch->uid() = 0; ch->ptype() = PT_MAC; ch->size() = phymib_.getRTSlen(); ch->iface() = -2; ch->error() = 0; bzero(rf, MAC_HDR_LEN); rf->rf_fc.fc_protocol_version = MAC_ProtocolVersion; rf->rf_fc.fc_type = MAC_Type_Control; rf->rf_fc.fc_subtype = MAC_Subtype_RTS; rf->rf_fc.fc_to_ds = 0; rf->rf_fc.fc_from_ds = 0; rf->rf_fc.fc_more_frag = 0; rf->rf_fc.fc_retry = 0; rf->rf_fc.fc_pwr_mgt = 0; rf->rf_fc.fc_more_data= 0; rf->rf_fc.fc_wep = 0; rf->rf_fc.fc_order = 0; STORE4BYTE(&dst, (rf->rf_ra)); ch->txtime() = txtime(ch->size(), basicRate_ ); STORE4BYTE(&index_, (rf->rf_ta)); rf->rf_duration = usec(phymib_.getSIFS() + txtime(phymib_.getCTSlen(), basicRate_) + phymib_.getSIFS()+ txtime(pktTx_) + phymib_.getSIFS() + txtime(phymib_.getACKlen(), basicRate_)); pktRTS_ = p; } sendRTS( ) Back to send ( ) Back to procedure

  7. deferHandler( ) void Mac802_11::deferHandler() { assert(pktCTRL_ || pktRTS_ || pktTx_); if( check_pktCTRL() == 0) return; assert(mhBackoff_.busy() == 0); if( check_pktRTS() == 0) return; if( check_pktTx() == 0) return; } Back to procedure

  8. Check_pktCTRL() int Mac802_11::check_pktCTRL() { struct hdr_mac802_11 *mh; double timeout; if(pktCTRL_ == 0) return -1; ……………………. } Back to deferHandler() Back to procedure

  9. check_pktRTS() int Mac802_11::check_pktRTS() { struct hdr_mac802_11 *mh; double timeout; assert(mhBackoff_.busy() == 0); if(pktRTS_ == 0) return -1; mh = HDR_MAC802_11(pktRTS_); switch(mh->dh_fc.fc_subtype) { case MAC_Subtype_RTS: if(! is_idle()) { inc_cw(); mhBackoff_.start(cw_, is_idle()); return 0; } setTxState(MAC_RTS); timeout = txtime(phymib_.getRTSlen(), basicRate_) + DSSS_MaxPropagationDelay + phymib_.getSIFS()+ txtime(phymib_.getCTSlen(), basicRate_)+ DSSS_MaxPropagationDelay; break; default: fprintf(stderr, "check_pktRTS:Invalid MAC Control subtype\n"); exit(1); } transmit(pktRTS_, timeout); return 0; } Back to deferHandler() Back to procedure

  10. check_pktTx() Int Mac802_11::check_pktTx() { struct hdr_mac802_11 *mh; double timeout; assert(mhBackoff_.busy() == 0); if(pktTx_ == 0) return -1; mh = HDR_MAC802_11(pktTx_); switch(mh->dh_fc.fc_subtype) { case MAC_Subtype_Data: if(! is_idle()) { sendRTS(ETHER_ADDR(mh->dh_ra)); inc_cw(); mhBackoff_.start(cw_, is_idle()); return 0; } setTxState(MAC_SEND); if((u_int32_t)ETHER_ADDR(mh->dh_ra) != MAC_BROADCAST) timeout = txtime(pktTx_) + DSSS_MaxPropagationDelay + phymib_.getSIFS() + txtime(phymib_.getACKlen(), basicRate_) + DSSS_MaxPropagationDelay; else timeout = txtime(pktTx_); break; default: fprintf(stderr, "check_pktTx:Invalid MAC Control subtype\n"); exit(1); } transmit(pktTx_, timeout); return 0; } Back to deferHandler() Back to procedure

  11. check_pktTx() Int Mac802_11::check_pktTx() { struct hdr_mac802_11 *mh; double timeout; assert(mhBackoff_.busy() == 0); if(pktTx_ == 0) return -1; mh = HDR_MAC802_11(pktTx_); switch(mh->dh_fc.fc_subtype) { case MAC_Subtype_Data: if(! is_idle()) { sendRTS(ETHER_ADDR(mh->dh_ra)); inc_cw(); mhBackoff_.start(cw_, is_idle()); return 0; } setTxState(MAC_SEND); if((u_int32_t)ETHER_ADDR(mh->dh_ra) != MAC_BROADCAST) timeout = txtime(pktTx_) + DSSS_MaxPropagationDelay + phymib_.getSIFS() + txtime(phymib_.getACKlen(), basicRate_) + DSSS_MaxPropagationDelay; else timeout = txtime(pktTx_); break; default: fprintf(stderr, "check_pktTx:Invalid MAC Control subtype\n"); exit(1); } transmit(pktTx_, timeout); return 0; } Back to recv_timer() Back to procedure

  12. Void Mac802_11::recv_timer() { …………………. switch(type) { case MAC_Type_Management: ……………………………………… goto done; case MAC_Type_Control: switch(subtype) { case MAC_Subtype_RTS: recvRTS(pktRx_); break; case MAC_Subtype_CTS: recvCTS(pktRx_); break; case MAC_Subtype_ACK: recvACK(pktRx_); break; default: ………………………………………… } break; case MAC_Type_Data: switch(subtype) { case MAC_Subtype_Data: recvDATA(pktRx_); break; default: fprintf(stderr, "recv_timer2:Invalid MAC Data Subtype %x\n", subtype); exit(1); } break; default: fprintf(stderr, "recv_timer3:Invalid MAC Type %x\n", subtype); exit(1); } done: pktRx_ = 0; rx_resume(); } recv_timer() Back to procedure

  13. } else if(pktTx_) { if (mhBackoff_.busy() == 0) { hdr_cmn *ch = HDR_CMN(pktTx_); struct hdr_mac802_11 *mh = HDR_MAC802_11(pktTx_); if ((u_int32_t) ch->size() < macmib_.getRTSThreshold() || (u_int32_t) ETHER_ADDR(mh->dh_ra) == MAC_BROADCAST) { rTime = (Random::random() % cw_) * phymib_.getSlotTime(); mhDefer_.start(phymib_.getDIFS() + rTime); } else { mhDefer_.start(phymib_.getSIFS()); } } } else if(callback_) { Handler *h = callback_; callback_ = 0; h->handle((Event*) 0); } setTxState(MAC_IDLE); } void Mac802_11::tx_resume() { double rTime; assert(mhSend_.busy() == 0); assert(mhDefer_.busy() == 0); if(pktCTRL_) { mhDefer_.start(phymib_.getSIFS()); } else if(pktRTS_) { if (mhBackoff_.busy() == 0) { rTime = (Random::random() % cw_) * phymib_.getSlotTime(); mhDefer_.start( phymib_.getDIFS() + rTime); } tx_resume() Back to recvCTS Back to recvACK Back to procedure

  14. rx_resume( ) Void Mac802_11::rx_resume() { assert(pktRx_ == 0); assert(mhRecv_.busy() == 0); setRxState(MAC_IDLE); } Back to recv_timer Back to procedure

  15. recvCTS( ) Void Mac802_11::recvCTS(Packet *p) { if(tx_state_ != MAC_RTS) { discard(p, DROP_MAC_INVALID_STATE); return; } assert(pktRTS_); Packet::free(pktRTS_); pktRTS_ = 0; assert(pktTx_); mhSend_.stop(); /* * The successful reception of this CTS packet implies * that our RTS was successful. * According to the IEEE spec 9.2.5.3, you must * reset the ssrc_, but not the congestion window. */ ssrc_ = 0; tx_resume(); mac_log(p); } Back to recv_timer() Back to procedure

  16. recvACK( ) Void Mac802_11::recvACK(Packet *p) { struct hdr_cmn *ch = HDR_CMN(p); if(tx_state_ != MAC_SEND) { discard(p, DROP_MAC_INVALID_STATE); return; } assert(pktTx_); mhSend_.stop(); if((u_int32_t) HDR_CMN(pktTx_)->size() <= macmib_.getRTSThreshold()) ssrc_ = 0; else slrc_ = 0; rst_cw(); Packet::free(pktTx_); pktTx_ = 0; assert(mhBackoff_.busy() == 0); mhBackoff_.start(cw_, is_idle()); tx_resume(); mac_log(p); } Back to recv_timer() Back to procedure

  17. inline void Mac802_11::transmit(Packet *p, double timeout) { tx_active_ = 1; if (EOTtarget_) { assert (eotPacket_ == NULL); eotPacket_ = p->copy(); } /* * If I'm transmitting without doing CS, such as when sending an ACK, any incoming packet will be * "missed“ and hence, must be discarded. */ if(rx_state_ != MAC_IDLE) { struct hdr_mac802_11 *dh = HDR_MAC802_11(p); assert(dh->dh_fc.fc_type == MAC_Type_Control); assert(dh->dh_fc.fc_subtype == MAC_Subtype_ACK); assert(pktRx_); struct hdr_cmn *ch = HDR_CMN(pktRx_); ch->error() = 1; /* force packet discard */ } /* * pass the packet on the "interface" which will in turn* place the packet on the channel. * NOTE: a handler is passed along so that the Network Interface can distinguish between incoming * and outgoing packets. */ downtarget_->recv(p->copy(), this); mhSend_.start(timeout); mhIF_.start(txtime(p)); } Back to check_pktRTS() Back to procedure

  18. txtime( ) /* * txtime() - calculate tx time for packet of size "psz" bytes * at rate "drt" bps */ double Mac802_11::txtime(double psz, double drt) { double dsz = psz - phymib_.getPLCPhdrLen(); int plcp_hdr = phymib_.getPLCPhdrLen() << 3; int datalen = (int)dsz << 3; double t = (((double)plcp_hdr)/phymib_.getPLCPDataRate()) + (((double)datalen)/drt); return(t); } Back to sendDATA() Back to procedure

  19. When mhSend_ timer expires void Mac802_11::send_timer() { switch(tx_state_) { case MAC_RTS: RetransmitRTS(); break; case MAC_CTS: assert(pktCTRL_); Packet::free(pktCTRL_); pktCTRL_ = 0; break; case MAC_SEND: RetransmitDATA(); break; case MAC_ACK: assert(pktCTRL_); Packet::free(pktCTRL_); pktCTRL_ = 0; break; case MAC_IDLE: break; default: assert(0); } tx_resume(); } Back to transmit() Back to procedure

  20. When mhIF_ timer expires void Mac802_11::txHandler() { if (EOTtarget_) { assert(eotPacket_); EOTtarget_->recv(eotPacket_, (Handler *) 0); eotPacket_ = NULL; } tx_active_ = 0; } Back to transmit() Back to procedure

  21. References • mac-802_11.cc, mac-802_11.h • mac-timers.cc, mac-timers.h • http://www.ece.rice.edu/~jpr/ns/docs/802_11.html#DeferTimer

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