diff --git a/NmapOps.cc b/NmapOps.cc
index fd7a68013..ff3139c83 100644
--- a/NmapOps.cc
+++ b/NmapOps.cc
@@ -195,6 +195,7 @@ void NmapOps::Initialize() {
 #endif
   debugging = 0;
   verbose = 0;
+  min_packet_send_rate = 0.0; /* Unset. */
   randomize_hosts = 0;
   sendpref = PACKET_SEND_NOPREF;
   spoofsource = 0;
diff --git a/NmapOps.h b/NmapOps.h
index 5d3f8db94..f9b0590a7 100644
--- a/NmapOps.h
+++ b/NmapOps.h
@@ -178,6 +178,8 @@ class NmapOps {
   bool openOnly() { return open_only; }
   void setOpenOnly(bool oo) { open_only = oo; }
   int verbose;
+  /* The requested minimum packet sending rate, or 0.0 if unset. */
+  float min_packet_send_rate;
   int randomize_hosts;
   int spoofsource; /* -S used */
   int fastscan;
diff --git a/docs/refguide.xml b/docs/refguide.xml
index dbf2751c8..0f639732b 100644
--- a/docs/refguide.xml
+++ b/docs/refguide.xml
@@ -2300,6 +2300,44 @@ threshold based intrusion detection and prevention systems (IDS/IPS).</para>
         </listitem>
       </varlistentry>
 
+      <varlistentry>
+        <term>
+        <option>--min-rate &lt;number&gt;</option>
+        (Specify a minimum scanning rate)
+        <indexterm><primary>--min-rate</primary></indexterm>
+        </term>
+        <listitem>
+
+<para>Nmap's dynamic timing does a good job of finding an appropriate
+speed at which to scan. Sometimes, however, you may happen to know an
+appropriate speed for a network, or you may have to guarantee that a
+scan will be finished by a certain time. When the
+<option>--min-rate</option> is given Nmap will do its best to send
+packets as fast or faster than the given rate. The argument is a
+positive real number representing a packet rate in packets per second.
+For example, using <command>--min-rate 300</command> will ensure that
+the packet sending rate doesn't fall below 300 packets per second.
+Specifying a minimum rate does not keep Nmap from going faster if
+conditions warrant.</para>
+
+<para>There are two conditions when the actual scanning rate may fall
+below the specified minimum. The first is if the minimum is faster than
+the fastest rate at which Nmap can send, which is dependent on hardware.
+In this case Nmap will send packets as fast a possible, but be aware
+that such high rates are likely to cause a loss of accuracy. The second
+case is when Nmap has nothing to send, for example at the end of a scan
+when the last probes have been sent and Nmap is waiting for them to time
+out or be responded to. It's normal to see the scanning rate drop at the
+end of a scan or in between groups of hosts.</para>
+
+<para>The <option>--min-rate</option> option is global, affecting an
+entire scan, not individual hosts. It only affects port and host
+discovery scans. Other features like OS detection implement their own
+timing.</para>
+
+        </listitem>
+      </varlistentry>
+
       <varlistentry>
         <term><option>--defeat-rst-ratelimit</option>
         <indexterm><primary>--defeat-rst-ratelimit</primary></indexterm></term>
diff --git a/nmap.cc b/nmap.cc
index c130f9807..5d2e66f5f 100644
--- a/nmap.cc
+++ b/nmap.cc
@@ -278,6 +278,7 @@ printf("%s %s ( %s )\n"
        "  --max-retries <tries>: Caps number of port scan probe retransmissions.\n"
        "  --host-timeout <time>: Give up on target after this long\n"
        "  --scan-delay/--max-scan-delay <time>: Adjust delay between probes\n"
+       "  --min-rate <number>: Send packets no slower than <number> per second\n"
        "FIREWALL/IDS EVASION AND SPOOFING:\n"
        "  -f; --mtu <val>: fragment packets (optionally w/given MTU)\n"
        "  -D <decoy1,decoy2[,ME],...>: Cloak a scan with decoys\n"
@@ -634,6 +635,7 @@ int nmap_main(int argc, char *argv[]) {
 #endif
       {"ip_options", required_argument, 0, 0},
       {"ip-options", required_argument, 0, 0},
+      {"min-rate", required_argument, 0, 0},
       {0, 0, 0, 0}
     };
 
@@ -888,6 +890,9 @@ int nmap_main(int argc, char *argv[]) {
 	o.traceroute = true;
       } else if(strcmp(long_options[option_index].name, "reason") == 0) {
      o.reason = true;
+      } else if(optcmp(long_options[option_index].name, "min-rate") == 0) {
+        if (sscanf(optarg, "%f", &o.min_packet_send_rate) != 1 || o.min_packet_send_rate <= 0.0)
+          fatal("Argument to --min-rate must be a positive floating-point number");
       } else {
 	fatal("Unknown long option (%s) given@#!$#$", long_options[option_index].name);
       }
@@ -1483,6 +1488,7 @@ int nmap_main(int argc, char *argv[]) {
     log_write(LOG_PLAIN, "  max-scan-delay: TCP %d, UDP %d\n", o.maxTCPScanDelay(), o.maxUDPScanDelay());
     log_write(LOG_PLAIN, "  parallelism: min %d, max %d\n", o.min_parallelism, o.max_parallelism);
     log_write(LOG_PLAIN, "  max-retries: %d, host-timeout: %ld\n", o.getMaxRetransmissions(), o.host_timeout);
+    log_write(LOG_PLAIN, "  min-rate: %g\n", o.min_packet_send_rate);
     log_write(LOG_PLAIN, "---------------------------------------------\n");
   }
 
diff --git a/scan_engine.cc b/scan_engine.cc
index 83b8bdd76..6943c315c 100644
--- a/scan_engine.cc
+++ b/scan_engine.cc
@@ -346,8 +346,9 @@ public:
   struct sockaddr_storage latestip; 
   GroupScanStats(UltraScanInfo *UltraSI);
   ~GroupScanStats();
+  void probeSent();
   /* Returns true if the GLOBAL system says that sending is OK. */
-  bool sendOK(); 
+  bool sendOK(struct timeval *when); 
   /* Total # of probes outstanding (active) for all Hosts */
   int num_probes_active; 
   UltraScanInfo *USI; /* The USI which contains this GSS.  Use for at least
@@ -373,6 +374,9 @@ public:
   /* Value of numprobes_sent at lastping_sent time -- to ensure that we don't
      send too many pings when probes are going slowly. */
   int lastping_sent_numprobes; 
+  /* When to send the next probe, to keep the minimum up. Used only when a
+     minimum sending rate (o.min_packet_send_rate) is set. */
+  struct timeval send_no_later_than;
 
   /* The host to which global pings are sent. This is kept updated to be the
      most recent host that was found up. */
@@ -653,6 +657,7 @@ public:
   list<HostScanStats *> completedHosts;
 
   ScanProgressMeter *SPM;
+  RateMeter send_rate_meter;
   struct scan_lists *ports;
   int rawsd; /* raw socket descriptor */
   pcap_t *pd;
@@ -874,6 +879,7 @@ GroupScanStats::GroupScanStats(UltraScanInfo *UltraSI) {
   probes_sent = probes_sent_at_last_wait = 0;
   probes_replied_to = 0;
   lastping_sent = lastrcvd = USI->now;
+  send_no_later_than = USI->now;
   lastping_sent_numprobes = 0;
   pinghost = NULL;
   gettimeofday(&last_wait, NULL);
@@ -884,10 +890,27 @@ GroupScanStats::~GroupScanStats() {
   delete CSI;
 }
 
+void GroupScanStats::probeSent() {
+  /* Find the next scheduled send time for minimum-rate scanning. */
+  if (TIMEVAL_SUBTRACT(send_no_later_than, USI->now) > 0) {
+    /* The next scheduled send is in the future. That means we're ahead of
+       schedule, but it also means there's slack time during which the sending
+       rate could drop. Reschedule the send to keep that from happening. */
+    send_no_later_than = USI->now;
+  }
+  TIMEVAL_ADD(send_no_later_than, send_no_later_than,
+    (time_t) (1000000.0 / o.min_packet_send_rate));
+}
+
   /* Returns true if the GLOBAL system says that sending is OK.*/
-bool GroupScanStats::sendOK() {
+bool GroupScanStats::sendOK(struct timeval *when) {
   int recentsends;
 
+  /* In case it's not okay to send, arbitrarily say to check back in one
+     second. */
+  if (when)
+    TIMEVAL_MSEC_ADD(*when, USI->now, 1000); 
+
   if ((USI->scantype == CONNECT_SCAN || USI->ptech.connecttcpscan)
       && CSI->numSDs >= CSI->maxSocketsAllowed)
     return false;
@@ -914,13 +937,34 @@ bool GroupScanStats::sendOK() {
   if (recentsends >= 50)
     return false;
 
+  /* Enforce a minimum scanning rate, if necessary. If we're ahead of schedule,
+     record the time of the next scheduled send. If we're behind schedule,
+     return true to indicate that we need to send now, regardless of any
+     congestion control. */
+  if (o.min_packet_send_rate != 0.0) {
+    if (TIMEVAL_SUBTRACT(send_no_later_than, USI->now) > 0) {
+      if (when)
+        *when = send_no_later_than;
+    } else {
+      if (when)
+        *when = USI->now;
+      return true;
+    }
+  }
+
   /* When there is only one target left, let the host congestion
      stuff deal with it. */
-  if (USI->numIncompleteHostsLessThan(2))
+  if (USI->numIncompleteHostsLessThan(2)) {
+    if (when)
+      *when = USI->now;
     return true;
+  }
 
-  if (timing.cwnd >= num_probes_active + 0.5)
+  if (timing.cwnd >= num_probes_active + 0.5) {
+    if (when)
+      *when = USI->now;
     return true;
+  }
 
   return false;
 }
@@ -1053,6 +1097,16 @@ bool HostScanStats::sendOK(struct timeval *when) {
   struct timeval probe_to, earliest_to, sendTime;
   long tdiff;
 
+  /* If the group stats say we need to send a probe to enforce a minimum
+     scanning rate, then we need to step up and send a probe. */
+  if (o.min_packet_send_rate != 0.0) {
+    if (TIMEVAL_SUBTRACT(USI->gstats->send_no_later_than, USI->now) <= 0) {
+      if (when)
+        *when = USI->now;
+      return true;
+    }
+  }
+
   if (target->timedOut(&USI->now) || completed()) {
     if (when) *when = USI->now;
     return false;
@@ -1293,6 +1347,7 @@ void UltraScanInfo::Init(vector<Target *> &Targets, struct scan_lists *pts, styp
   seqmask = get_random_u32();
   scantype = scantp;
   SPM = new ScanProgressMeter(scantype2str(scantype));
+  send_rate_meter.start(&now);
   tcp_scan = udp_scan = prot_scan = ping_scan = noresp_open_scan = false;
   ping_scan_arp = false;
   memset((char *) &ptech, 0, sizeof(ptech));
@@ -1447,11 +1502,12 @@ bool UltraScanInfo::sendOK(struct timeval *when) {
   bool hgood = false;
   bool thisHostGood = false;
   bool foundgood = false;
-  ggood = gstats->sendOK();
+
+  ggood = gstats->sendOK(when);
 
   if (!ggood) {
     if (when) {
-      TIMEVAL_MSEC_ADD(lowhtime, now, 1000); 
+      lowhtime = *when;
       // Can't do anything until global is OK - means packet receipt
       // or probe timeout.
       for(host = incompleteHosts.begin(); host != incompleteHosts.end(); 
@@ -1482,6 +1538,13 @@ bool UltraScanInfo::sendOK(struct timeval *when) {
     assert(foundgood);
   }
   
+  /* Defer to the group stats if they need a shorter delay to enforce a minimum
+     packet sending rate. */
+  if (o.min_packet_send_rate != 0.0) {
+    if (TIMEVAL_MSEC_SUBTRACT(gstats->send_no_later_than, lowhtime) < 0)
+      lowhtime = gstats->send_no_later_than;
+  }
+
   if (TIMEVAL_MSEC_SUBTRACT(lowhtime, now) < 0)
     lowhtime = now;
 
@@ -2483,11 +2546,14 @@ static UltraProbe *sendConnectScanProbe(UltraScanInfo *USI, HostScanStats *hss,
   else sin6->sin6_port = htons(probe->pspec()->pd.tcp.dport);
 #endif
   hss->lastprobe_sent = probe->sent = USI->now;
+  USI->gstats->probeSent();
   rc = connect(CP->sd, (struct sockaddr *)&sock, socklen);
   gettimeofday(&USI->now, NULL);
   if (rc == -1) connect_errno = socket_errno();
   PacketTrace::traceConnect(IPPROTO_TCP, (sockaddr *) &sock, socklen, rc, 
 			    connect_errno, &USI->now);
+  /* We don't record a byte count for connect probes. */
+  USI->send_rate_meter.record(0, &USI->now);
   /* This counts as probe being sent, so update structures */
   hss->probes_outstanding.push_back(probe);
   probeI = hss->probes_outstanding.end();
@@ -2579,11 +2645,13 @@ static UltraProbe *sendArpScanProbe(UltraScanInfo *USI, HostScanStats *hss,
 		     ETH_ADDR_BROADCAST,  *hss->target->v4hostip());
   gettimeofday(&USI->now, NULL);
   hss->lastprobe_sent = probe->sent = USI->now;
+  USI->gstats->probeSent();
   if ((rc = eth_send(USI->ethsd, frame, sizeof(frame))) != sizeof(frame)) {
     int err = socket_errno();
     error("WARNING:  eth_send of ARP packet returned %i rather than expected %d (errno=%i: %s)", rc, (int) sizeof(frame), err, strerror(err));
   }
   PacketTrace::traceArp(PacketTrace::SENT, (u8 *) frame, sizeof(frame), &USI->now);
+  USI->send_rate_meter.record(sizeof(frame), &USI->now);
   probe->tryno = tryno;
   probe->pingseq = pingseq;
   /* First build the probe */
@@ -2656,6 +2724,7 @@ static UltraProbe *sendIPScanProbe(UltraScanInfo *USI, HostScanStats *hss,
 	probe->setIP(packet, packetlen, pspec);
 	hss->lastprobe_sent = probe->sent = USI->now;
       }
+      USI->gstats->probeSent();
       send_ip_packet(USI->rawsd, ethptr, packet, packetlen);
       free(packet);
     }
@@ -2671,6 +2740,7 @@ static UltraProbe *sendIPScanProbe(UltraScanInfo *USI, HostScanStats *hss,
 	probe->setIP(packet, packetlen, pspec);
 	hss->lastprobe_sent = probe->sent = USI->now;
       }
+      USI->gstats->probeSent();
       send_ip_packet(USI->rawsd, ethptr, packet, packetlen);
       free(packet);
     }
@@ -2726,6 +2796,7 @@ static UltraProbe *sendIPScanProbe(UltraScanInfo *USI, HostScanStats *hss,
 	probe->setIP(packet, packetlen, pspec);
 	hss->lastprobe_sent = probe->sent = USI->now;
       }
+      USI->gstats->probeSent();
       send_ip_packet(USI->rawsd, ethptr, packet, packetlen);
       free(packet);
     }
@@ -2748,10 +2819,12 @@ static UltraProbe *sendIPScanProbe(UltraScanInfo *USI, HostScanStats *hss,
 	probe->setIP(packet, packetlen, pspec);
 	hss->lastprobe_sent = probe->sent = USI->now;
       }
+      USI->gstats->probeSent();
       send_ip_packet(USI->rawsd, ethptr, packet, packetlen);
       free(packet);
     }
   } else assert(0); /* TODO:  Maybe RPC scan and the like */
+  USI->send_rate_meter.record(packetlen, &USI->now);
   /* Now that the probe has been sent, add it to the Queue for this host */
   hss->probes_outstanding.push_back(probe);
   USI->gstats->num_probes_active++;
@@ -2811,7 +2884,7 @@ static void doAnyNewProbes(UltraScanInfo *USI) {
      sending a probe. */
   unableToSend = NULL;
   hss = USI->nextIncompleteHost();
-  while (hss != NULL && hss != unableToSend && USI->gstats->sendOK()) {
+  while (hss != NULL && hss != unableToSend && USI->gstats->sendOK(NULL)) {
     if (hss->freshPortsLeft() && hss->sendOK(NULL)) {
       sendNextScanProbe(USI, hss);
       unableToSend = NULL;
@@ -2834,7 +2907,7 @@ static void doAnyRetryStackRetransmits(UltraScanInfo *USI) {
      sending a probe. */
   unableToSend = NULL;
   hss = USI->nextIncompleteHost();
-  while (hss != NULL && hss != unableToSend && USI->gstats->sendOK()) {
+  while (hss != NULL && hss != unableToSend && USI->gstats->sendOK(NULL)) {
     if (!hss->retry_stack.empty() && hss->sendOK(NULL)) {
       sendNextRetryStackProbe(USI, hss);
       unableToSend = NULL;
@@ -2901,7 +2974,7 @@ static void doAnyPings(UltraScanInfo *USI) {
 	hss->numprobes_sent >= hss->lastping_sent_numprobes + 10 &&
 	TIMEVAL_SUBTRACT(USI->now, hss->lastrcvd) > USI->perf.pingtime && 
 	TIMEVAL_SUBTRACT(USI->now, hss->lastping_sent) > USI->perf.pingtime &&
-	USI->gstats->sendOK() && hss->sendOK(NULL)) {
+	USI->gstats->sendOK(NULL) && hss->sendOK(NULL)) {
       sendPingProbe(USI, hss);
       hss->lastping_sent = USI->now;
       hss->lastping_sent_numprobes = hss->numprobes_sent;
@@ -2914,7 +2987,7 @@ static void doAnyPings(UltraScanInfo *USI) {
       USI->gstats->probes_sent >= USI->gstats->lastping_sent_numprobes + 20 && 
       TIMEVAL_SUBTRACT(USI->now, USI->gstats->lastrcvd) > USI->perf.pingtime && 
       TIMEVAL_SUBTRACT(USI->now, USI->gstats->lastping_sent) > USI->perf.pingtime && 
-      USI->gstats->sendOK()) {
+      USI->gstats->sendOK(NULL)) {
     sendGlobalPingProbe(USI);
     USI->gstats->lastping_sent = USI->now;
     USI->gstats->lastping_sent_numprobes = USI->gstats->probes_sent;
@@ -2966,6 +3039,12 @@ static void doAnyOutstandingRetransmits(UltraScanInfo *USI) {
   int retrans = 0; /* Number of retransmissions during a loop */
   unsigned int maxtries;
 
+  struct timeval tv_start = {0};
+  if (o.debugging) {
+    gettimeofday(&USI->now, NULL);
+    tv_start = USI->now;
+  }
+
   gettimeofday(&USI->now, NULL);
 
   /* Loop until we get through all the hosts without a retransmit or we're not
@@ -2973,7 +3052,7 @@ static void doAnyOutstandingRetransmits(UltraScanInfo *USI) {
   do {
     retrans = 0;
     for (hostI = USI->incompleteHosts.begin();
-         hostI != USI->incompleteHosts.end() && USI->gstats->sendOK();
+         hostI != USI->incompleteHosts.end() && USI->gstats->sendOK(NULL);
          hostI++) {
       host = *hostI;
       /* Skip this host if it has nothing to send. */
@@ -3006,7 +3085,14 @@ static void doAnyOutstandingRetransmits(UltraScanInfo *USI) {
         } 
       } while (probeI != host->probes_outstanding.begin());
     }
-  } while (USI->gstats->sendOK() && retrans != 0);
+  } while (USI->gstats->sendOK(NULL) && retrans != 0);
+
+  if (o.debugging) {
+    long tv_diff;
+    gettimeofday(&USI->now, NULL);
+    tv_diff = TIMEVAL_MSEC_SUBTRACT(USI->now, tv_start);
+    if (tv_diff > 30) log_write(LOG_PLAIN, "%s took %lims\n", __func__, tv_diff);
+  }
 }
 
 /* Print occasional remaining time estimates, as well as
@@ -3041,6 +3127,13 @@ static void printAnyStats(UltraScanInfo *USI) {
                   hss->target->to.rttvar);
       }
     }
+
+    log_write(LOG_PLAIN, "Current sending rates: %.2f packets / s, %.2f bytes / s.\n",
+      USI->send_rate_meter.getCurrentPacketRate(),
+      USI->send_rate_meter.getCurrentByteRate());
+    log_write(LOG_PLAIN, "Overall sending rates: %.2f packets / s, %.2f bytes / s.\n",
+      USI->send_rate_meter.getOverallPacketRate(),
+      USI->send_rate_meter.getOverallByteRate());
   }
 
   /* Now time to figure out how close we are to completion ... */
@@ -4694,12 +4787,20 @@ void ultra_scan(vector<Target *> &Targets, struct scan_lists *ports,
        avgdone /= USI->gstats->numtargets;
               
        USI->SPM->printStats(avgdone, NULL); // This prints something like SYN Stealth Scan Timing: About 1.14% done; ETC: 15:01 (0:43:23 remaining);
+       /* Don't update when getting the current rates, otherwise we can get
+          anomalies (rates are too low) from having just done a potentially long
+          waitForResponses without sending any packets. */
+       log_write(LOG_STDOUT, "Current sending rates: %.2f packets / s, %.2f bytes / s.\n",
+          USI->send_rate_meter.getCurrentPacketRate(&USI->now, false),
+          USI->send_rate_meter.getCurrentByteRate(&USI->now, false));
        
        log_flush(LOG_STDOUT);
 
     }
   }
 
+  USI->send_rate_meter.stop(&USI->now);
+
   /* Save the computed timeouts. */
   if (to != NULL)
     *to = USI->gstats->to;
@@ -4718,6 +4819,9 @@ void ultra_scan(vector<Target *> &Targets, struct scan_lists *ports,
 		   USI->gstats->num_hosts_timedout, 
 		   (USI->gstats->num_hosts_timedout == 1)? "host" : "hosts");
     USI->SPM->endTask(NULL, additional_info);
+    log_write(LOG_STDOUT, "Overall sending rates: %.2f packets / s, %.2f bytes / s.\n",
+      USI->send_rate_meter.getOverallPacketRate(),
+      USI->send_rate_meter.getOverallByteRate());
   }
 
   if (o.debugging > 2 && USI->pd != NULL)
diff --git a/timing.cc b/timing.cc
index e5f27c026..54ddedef9 100644
--- a/timing.cc
+++ b/timing.cc
@@ -238,6 +238,156 @@ void enforce_scan_delay(struct timeval *tv) {
   return;    
 }
 
+/* Initialize the constant CURRENT_RATE_HISTORY that defines how far back we
+   look when calculating the current rates. */
+RateMeter::RateMeter() : CURRENT_RATE_HISTORY(5.0) {
+  start_tv.tv_sec = 0;
+  start_tv.tv_usec = 0;
+  stop_tv.tv_sec = 0;
+  stop_tv.tv_usec = 0;
+  last_update_tv.tv_sec = 0;
+  last_update_tv.tv_usec = 0;
+  num_packets = 0;
+  num_bytes = 0;
+  current_packet_rate = 0.0;
+  current_byte_rate = 0.0;
+  assert(!isSet(&start_tv));
+  assert(!isSet(&stop_tv));
+}
+
+void RateMeter::start(const struct timeval *now) {
+  assert(!isSet(&start_tv));
+  assert(!isSet(&stop_tv));
+  if (now == NULL)
+    gettimeofday(&start_tv, NULL);
+  else
+    start_tv = *now;
+}
+
+void RateMeter::stop(const struct timeval *now) {
+  assert(isSet(&start_tv));
+  assert(!isSet(&stop_tv));
+  if (now == NULL)
+    gettimeofday(&stop_tv, NULL);
+  else
+    stop_tv = *now;
+}
+
+/* Record a packet of length len. If now is not NULL, use it as the time the
+   packet was received rather than calling gettimeofday. */
+void RateMeter::record(u32 len, const struct timeval *now) {
+  update(1, len, now);
+}
+
+double RateMeter::getOverallPacketRate(const struct timeval *now) const {
+  return num_packets / elapsedTime(now);
+}
+
+/* Get the "current" packet rate (actually a moving average of the last few
+   seconds). If update is true (its default value), lower the rate to account
+   for the time since the last packet was received. */
+double RateMeter::getCurrentPacketRate(const struct timeval *now, bool update) {
+  if (update)
+    this->update(0, 0, now);
+
+  return current_packet_rate;
+}
+
+double RateMeter::getOverallByteRate(const struct timeval *now) const {
+  return num_bytes / elapsedTime(now);
+}
+
+/* Get the "current" byte rate (actually a moving average of the last few
+   seconds). If update is true (its default value), lower the rate to account
+   for the time since the last bytes were received. */
+double RateMeter::getCurrentByteRate(const struct timeval *now, bool update) {
+  if (update)
+    this->update(0, 0, now);
+
+  return current_byte_rate;
+}
+
+/* Update the rates to include packets additional packets and bytes additional
+   bytes. If now is not NULL, use it as the time the packets and bytes were
+   received rather than calling gettimeofday. */
+void RateMeter::update(u32 packets, u32 bytes, const struct timeval *now) {
+  struct timeval tv;
+  double diff;
+  double d;
+  double count;
+
+  assert(isSet(&start_tv));
+  assert(!isSet(&stop_tv));
+
+  /* Update the overall counters. */
+  num_packets += packets;
+  num_bytes += bytes;
+
+  if (now == NULL) {
+    gettimeofday(&tv, NULL);
+    now = &tv;
+  }
+  if (!isSet(&last_update_tv))
+    last_update_tv = start_tv;
+
+  /* Calculate approximate moving averages of how many packets and bytes were
+     recorded in the last CURRENT_RATE_HISTORY seconds. These averages are what
+     are returned as the "current" rates. */
+  /* How long since the last update? */
+  diff = TIMEVAL_SUBTRACT(*now, last_update_tv) / 1000000.0;
+  /* Look back CURRENT_RATE_HISTORY seconds, or to when the last sample was
+     recorded, whichever is longer, but don't look back past the start. */
+  d = MAX(CURRENT_RATE_HISTORY, diff);
+  d = MIN(d, TIMEVAL_SUBTRACT(*now, start_tv) / 1000000.0);
+  assert(d >= 0);
+  /* If we get packets in the very same instant that the timer is started,
+     there's no way to calculate meaningful rates. Ignore it. */
+  if (d == 0.0)
+    return;
+  /* To calculate the approximate average of the packet rate over the last d
+     seconds, we assume that the rate was constant over that interval. We
+     calculate how many packets would have been received in that interval,
+     ignoring the first diff seconds' worth, (d - diff) * current_packet_rate.
+     Then we add how many packets were received in the most recent diff seconds.
+     Divide by the width of the interval to get the average. */
+  count = (d - diff) * current_packet_rate + packets;
+  current_packet_rate = count / d;
+  assert(current_packet_rate >= 0.0);
+  /* Likewise with the byte rate. */
+  count = (d - diff) * current_byte_rate + bytes;
+  current_byte_rate = count / d;
+  assert(current_byte_rate >= 0.0);
+
+  last_update_tv = *now;
+}
+
+/* Get the number of seconds the meter has been running: if it has been stopped,
+   the amount of time between start and stop, or if it is still running, the
+   amount of time between start and now. */
+double RateMeter::elapsedTime(const struct timeval *now) const {
+  struct timeval tv;
+  const struct timeval *end_tv;
+
+  assert(isSet(&start_tv));
+
+  if (isSet(&stop_tv)) {
+    end_tv = &stop_tv;
+  } else if (now == NULL) {
+    gettimeofday(&tv, NULL);
+    end_tv = &tv;
+  } else {
+    end_tv = now;
+  }
+
+  return TIMEVAL_SUBTRACT(*end_tv, start_tv) / 1000000.0;
+}
+
+/* Returns true if tv has been initialized; i.e., its members are not all
+   zero. */
+bool RateMeter::isSet(const struct timeval *tv) {
+  return tv->tv_sec != 0 || tv->tv_usec != 0;
+}
+
 ScanProgressMeter::ScanProgressMeter(char *stypestr) {
   scantypestr = strdup(stypestr);
   gettimeofday(&begin, NULL);
diff --git a/timing.h b/timing.h
index 8879b9c50..d78d1a059 100644
--- a/timing.h
+++ b/timing.h
@@ -129,6 +129,42 @@ void adjust_timeouts(struct timeval sent, struct timeout_info *to);
    time is recorded in it */
 void enforce_scan_delay(struct timeval *tv);
 
+/* This class implements current and lifetime average data rates for packets and
+   bytes. */
+class RateMeter {
+  public:
+    RateMeter();
+
+    void start(const struct timeval *now = NULL);
+    void stop(const struct timeval *now = NULL);
+    void record(u32 len, const struct timeval *now = NULL);
+    double getOverallPacketRate(const struct timeval *now = NULL) const;
+    double getCurrentPacketRate(const struct timeval *now = NULL, bool update =true);
+    double getOverallByteRate(const struct timeval *now = NULL) const;
+    double getCurrentByteRate(const struct timeval *now = NULL, bool update =true);
+
+  private:
+    /* How many seconds to look back when calculating the "current" rates. */
+    const double CURRENT_RATE_HISTORY;
+
+    /* When this meter started recording. */
+    struct timeval start_tv;
+    /* When this meter stopped recording. */
+    struct timeval stop_tv;
+    /* The last time the current sample rates were updated. */
+    struct timeval last_update_tv;
+
+    unsigned long long num_packets;
+    unsigned long long num_bytes;
+
+    double current_packet_rate;
+    double current_byte_rate;
+
+    void update(u32 packets, u32 bytes, const struct timeval *now);
+    double elapsedTime(const struct timeval *now = NULL) const;
+    static bool isSet(const struct timeval *tv);
+};
+
 class ScanProgressMeter {
  public:
   /* A COPY of stypestr is made and saved for when stats are printed */
diff --git a/utils.h b/utils.h
index 1c25eb508..9f794528f 100644
--- a/utils.h
+++ b/utils.h
@@ -175,8 +175,8 @@
 #define TIMEVAL_SEC_SUBTRACT(a,b) ((a).tv_sec - (b).tv_sec + (((a).tv_usec < (b).tv_usec) ? - 1 : 0))
 
 /* assign one timeval to another timeval plus some msecs: a = b + msecs */
-#define TIMEVAL_MSEC_ADD(a, b, msecs) (a).tv_sec = (b).tv_sec + ((msecs) / 1000); (a).tv_usec = (b).tv_usec + ((msecs) % 1000) * 1000; (a).tv_sec += (a).tv_usec / 1000000; (a).tv_usec %= 1000000
-#define TIMEVAL_ADD(a, b, usecs) (a).tv_sec = (b).tv_sec + ((usecs) / 1000000); (a).tv_usec = (b).tv_usec + ((usecs) % 1000000); (a).tv_sec += (a).tv_usec / 1000000; (a).tv_usec %= 1000000
+#define TIMEVAL_MSEC_ADD(a, b, msecs) { (a).tv_sec = (b).tv_sec + ((msecs) / 1000); (a).tv_usec = (b).tv_usec + ((msecs) % 1000) * 1000; (a).tv_sec += (a).tv_usec / 1000000; (a).tv_usec %= 1000000; }
+#define TIMEVAL_ADD(a, b, usecs) { (a).tv_sec = (b).tv_sec + ((usecs) / 1000000); (a).tv_usec = (b).tv_usec + ((usecs) % 1000000); (a).tv_sec += (a).tv_usec / 1000000; (a).tv_usec %= 1000000; }
 
 /* Return num if it is between min and max.  Otherwise return min or
    max (whichever is closest to num), */