7 files changed, 156 insertions, 37 deletions

diff --git a/OpenSim/Region/ClientStack/Linden/UDP/LLUDPClient.cs b/OpenSim/Region/ClientStack/Linden/UDP/LLUDPClient.cs
index 8f14806..de91856 100644
--- a/OpenSim/Region/ClientStack/Linden/UDP/LLUDPClient.cs
+++ b/OpenSim/Region/ClientStack/Linden/UDP/LLUDPClient.cs
@@ -229,7 +229,7 @@ namespace OpenSim.Region.ClientStack.LindenUDP
             m_throttleClient 
                 = new AdaptiveTokenBucket(
                     string.Format("adaptive throttle for {0} in {1}", AgentID, server.Scene.Name), 
-                    parentThrottle, 0, rates.Total, rates.AdaptiveThrottlesEnabled);
+                    parentThrottle, 0, rates.Total, rates.MinimumAdaptiveThrottleRate, rates.AdaptiveThrottlesEnabled);
 
             // Create an array of token buckets for this clients different throttle categories
             m_throttleCategories = new TokenBucket[THROTTLE_CATEGORY_COUNT];
diff --git a/OpenSim/Region/ClientStack/Linden/UDP/OpenSimUDPBase.cs b/OpenSim/Region/ClientStack/Linden/UDP/OpenSimUDPBase.cs
index 94300f8..9bee3ad 100644
--- a/OpenSim/Region/ClientStack/Linden/UDP/OpenSimUDPBase.cs
+++ b/OpenSim/Region/ClientStack/Linden/UDP/OpenSimUDPBase.cs
@@ -107,6 +107,62 @@ namespace OpenMetaverse
         /// </summary>
         public float AverageReceiveTicksForLastSamplePeriod { get; private set; }
 
+        #region PacketDropDebugging
+        /// <summary>
+        /// For debugging purposes only... random number generator for dropping
+        /// outbound packets.
+        /// </summary>
+        private Random m_dropRandomGenerator;
+        
+        /// <summary>
+        /// For debugging purposes only... parameters for a simplified
+        /// model of packet loss with bursts, overall drop rate should
+        /// be roughly 1 - m_dropLengthProbability / (m_dropProbabiliy + m_dropLengthProbability)
+        /// which is about 1% for parameters 0.0015 and 0.15
+        /// </summary>
+        private double m_dropProbability = 0.0030;
+        private double m_dropLengthProbability = 0.15;
+        private bool m_dropState = false;
+
+        /// <summary>
+        /// For debugging purposes only... parameters to control the time
+        /// duration over which packet loss bursts can occur, if no packets
+        /// have been sent for m_dropResetTicks milliseconds, then reset the
+        /// state of the packet dropper to its default.
+        /// </summary>
+        private int m_dropLastTick = 0;
+        private int m_dropResetTicks = 500;
+        
+        /// <summary>
+        /// Debugging code used to simulate dropped packets with bursts
+        /// </summary>
+        private bool DropOutgoingPacket()
+        {
+            double rnum = m_dropRandomGenerator.NextDouble();
+
+            // if the connection has been idle for awhile (more than m_dropResetTicks) then
+            // reset the state to the default state, don't continue a burst
+            int curtick = Util.EnvironmentTickCount();
+            if (Util.EnvironmentTickCountSubtract(curtick, m_dropLastTick) > m_dropResetTicks)
+                m_dropState = false;
+
+            m_dropLastTick = curtick;
+
+            // if we are dropping packets, then the probability of dropping
+            // this packet is the probability that we stay in the burst
+            if (m_dropState)
+            {
+                m_dropState = (rnum < (1.0 - m_dropLengthProbability)) ? true : false;
+            }
+            else
+            {
+                m_dropState = (rnum < m_dropProbability) ? true : false;
+            }
+
+            return m_dropState;
+        }
+        #endregion PacketDropDebugging
+
         /// <summary>
         /// Default constructor
         /// </summary>
@@ -117,6 +173,10 @@ namespace OpenMetaverse
         {
             m_localBindAddress = bindAddress;
             m_udpPort = port;
+
+            // for debugging purposes only, initializes the random number generator
+            // used for simulating packet loss
+            // m_dropRandomGenerator = new Random();
         }
 
         /// <summary>
@@ -395,6 +455,12 @@ namespace OpenMetaverse
         {
 //            if (IsRunningOutbound)
 //            {
+
+                // This is strictly for debugging purposes to simulate dropped
+                // packets when testing throttles & retransmission code
+                // if (DropOutgoingPacket())
+                //     return;
+            
                 try
                 {
                     m_udpSocket.BeginSendTo(
diff --git a/OpenSim/Region/ClientStack/Linden/UDP/Tests/ThrottleTests.cs b/OpenSim/Region/ClientStack/Linden/UDP/Tests/ThrottleTests.cs
index 0560b9b..3c82a78 100644
--- a/OpenSim/Region/ClientStack/Linden/UDP/Tests/ThrottleTests.cs
+++ b/OpenSim/Region/ClientStack/Linden/UDP/Tests/ThrottleTests.cs
@@ -141,7 +141,7 @@ namespace OpenSim.Region.ClientStack.LindenUDP.Tests
 
             udpServer.Throttle.DebugLevel = 1;
             udpClient.ThrottleDebugLevel = 1;
-
+            
             int resendBytes = 1000;
             int landBytes = 2000;
             int windBytes = 3000;
@@ -173,6 +173,8 @@ namespace OpenSim.Region.ClientStack.LindenUDP.Tests
             IniConfigSource ics = new IniConfigSource();
             IConfig config = ics.AddConfig("ClientStack.LindenUDP");
             config.Set("enable_adaptive_throttles", true);
+            config.Set("adaptive_throttle_min_bps", 32000);
+
             TestLLUDPServer udpServer = ClientStackHelpers.AddUdpServer(scene, ics);
 
             ScenePresence sp 
@@ -184,8 +186,8 @@ namespace OpenSim.Region.ClientStack.LindenUDP.Tests
             udpServer.Throttle.DebugLevel = 1;
             udpClient.ThrottleDebugLevel = 1;
 
-            // Total is 280000
-            int resendBytes = 10000;
+            // Total is 275000
+            int resendBytes = 5000; // this is set low to test the minimum throttle override
             int landBytes = 20000;
             int windBytes = 30000;
             int cloudBytes = 40000;
@@ -197,28 +199,28 @@ namespace OpenSim.Region.ClientStack.LindenUDP.Tests
             SetThrottles(
                 udpClient, resendBytes, landBytes, windBytes, cloudBytes, taskBytes, textureBytes, assetBytes);
 
-            // Ratio of current adaptive drip rate to requested bytes
-            // XXX: Should hard code this as below so we don't rely on values given by tested code to construct
-            // expected values.
-            double commitRatio = (double)udpClient.FlowThrottle.AdjustedDripRate / udpClient.FlowThrottle.TargetDripRate;
+            // Ratio of current adaptive drip rate to requested bytes, minimum rate is 32000
+            double commitRatio = 32000.0 / totalBytes;
 
             AssertThrottles(
                 udpClient, 
                 LLUDPServer.MTU, landBytes * commitRatio, windBytes * commitRatio, cloudBytes * commitRatio, taskBytes * commitRatio,
                 textureBytes * commitRatio, assetBytes * commitRatio, udpClient.FlowThrottle.AdjustedDripRate, totalBytes, 0);
 
-            // Test an increase in target throttle
-            udpClient.FlowThrottle.AcknowledgePackets(35000);
-            commitRatio = 0.2;
+            // Test an increase in target throttle, ack of 20 packets adds 20 * LLUDPServer.MTU bytes
+            // to the throttle, recompute commitratio from those numbers
+            udpClient.FlowThrottle.AcknowledgePackets(20);
+            commitRatio = (32000.0 + 20.0 * LLUDPServer.MTU) / totalBytes;
 
             AssertThrottles(
                 udpClient, 
-                resendBytes * commitRatio, landBytes * commitRatio, windBytes * commitRatio, cloudBytes * commitRatio, taskBytes * commitRatio,
+                LLUDPServer.MTU, landBytes * commitRatio, windBytes * commitRatio, cloudBytes * commitRatio, taskBytes * commitRatio,
                 textureBytes * commitRatio, assetBytes * commitRatio, udpClient.FlowThrottle.AdjustedDripRate, totalBytes, 0);
 
-            // Test a decrease in target throttle
+            // Test a decrease in target throttle, adaptive throttle should cut the rate by 50% with a floor
+            // set by the minimum adaptive rate
             udpClient.FlowThrottle.ExpirePackets(1);
-            commitRatio = 0.1;
+            commitRatio = (32000.0 + (20.0 * LLUDPServer.MTU)/Math.Pow(2,1)) / totalBytes;
 
             AssertThrottles(
                 udpClient, 
diff --git a/OpenSim/Region/ClientStack/Linden/UDP/ThrottleRates.cs b/OpenSim/Region/ClientStack/Linden/UDP/ThrottleRates.cs
index dd15cc7..7a2756b 100644
--- a/OpenSim/Region/ClientStack/Linden/UDP/ThrottleRates.cs
+++ b/OpenSim/Region/ClientStack/Linden/UDP/ThrottleRates.cs
@@ -58,7 +58,14 @@ namespace OpenSim.Region.ClientStack.LindenUDP
 
         /// <summary>Flag used to enable adaptive throttles</summary>
         public bool AdaptiveThrottlesEnabled;
-        
+ 
+        /// <summary>
+        /// Set the minimum rate that the adaptive throttles can set. The viewer
+        /// can still throttle lower than this, but the adaptive throttles will
+        /// never decrease rates below this no matter how many packets are dropped
+        /// </summary>
+        public Int64 MinimumAdaptiveThrottleRate;
+ 
         /// <summary>Amount of the texture throttle to steal for the task throttle</summary>
         public double CannibalizeTextureRate;
 
@@ -84,7 +91,8 @@ namespace OpenSim.Region.ClientStack.LindenUDP
                 Total = throttleConfig.GetInt("client_throttle_max_bps", 0);
 
                 AdaptiveThrottlesEnabled = throttleConfig.GetBoolean("enable_adaptive_throttles", false);
-                
+                MinimumAdaptiveThrottleRate = throttleConfig.GetInt("adaptive_throttle_min_bps", 32000);
+
                 CannibalizeTextureRate = (double)throttleConfig.GetFloat("CannibalizeTextureRate", 0.0f);
                 CannibalizeTextureRate = Util.Clamp<double>(CannibalizeTextureRate,0.0, 0.9);
             }
diff --git a/OpenSim/Region/ClientStack/Linden/UDP/TokenBucket.cs b/OpenSim/Region/ClientStack/Linden/UDP/TokenBucket.cs
index 4ca83ff..4616203 100644
--- a/OpenSim/Region/ClientStack/Linden/UDP/TokenBucket.cs
+++ b/OpenSim/Region/ClientStack/Linden/UDP/TokenBucket.cs
@@ -61,7 +61,7 @@ namespace OpenSim.Region.ClientStack.LindenUDP
                 
         /// <summary>
         /// </summary>
-        protected const Int32 m_minimumDripRate = 1400;
+        protected const Int32 m_minimumDripRate = LLUDPServer.MTU;
         
         /// <summary>Time of the last drip, in system ticks</summary>
         protected Int32 m_lastDrip;
@@ -392,13 +392,19 @@ namespace OpenSim.Region.ClientStack.LindenUDP
         }
                 
         /// <summary>
-        /// The minimum rate for flow control. Minimum drip rate is one
-        /// packet per second. Open the throttle to 15 packets per second
-        /// or about 160kbps.
+        /// The minimum rate for adaptive flow control. 
         /// </summary>
-        protected const Int64 m_minimumFlow = m_minimumDripRate * 15;
+        protected Int64 m_minimumFlow = 32000;
 
-        public AdaptiveTokenBucket(string identifier, TokenBucket parent, Int64 requestedDripRate, Int64 maxDripRate, bool enabled) 
+        /// <summary>
+        /// Constructor for the AdaptiveTokenBucket class
+        /// <param name="identifier">Unique identifier for the client</param>
+        /// <param name="parent">Parent bucket in the hierarchy</param>
+        /// <param name="requestedDripRate"></param>
+        /// <param name="maxDripRate">The ceiling rate for adaptation</param>
+        /// <param name="minDripRate">The floor rate for adaptation</param>
+        /// </summary>
+        public AdaptiveTokenBucket(string identifier, TokenBucket parent, Int64 requestedDripRate, Int64 maxDripRate, Int64 minDripRate, bool enabled) 
             : base(identifier, parent, requestedDripRate, maxDripRate)
         {
             AdaptiveEnabled = enabled;
@@ -406,34 +412,53 @@ namespace OpenSim.Region.ClientStack.LindenUDP
             if (AdaptiveEnabled)
             {
 //                m_log.DebugFormat("[TOKENBUCKET]: Adaptive throttle enabled");
+                m_minimumFlow = minDripRate;
                 TargetDripRate = m_minimumFlow;
                 AdjustedDripRate = m_minimumFlow;
             }
         }
                 
-        // <summary>
-        // Reliable packets sent to the client for which we never received an ack adjust the drip rate down.
-        // </summary>
-        public void ExpirePackets(Int32 count)
+        /// <summary>
+        /// Reliable packets sent to the client for which we never received an ack adjust the drip rate down.
+        /// <param name="packets">Number of packets that expired without successful delivery</param>
+        /// </summary>
+        public void ExpirePackets(Int32 packets)
         {
             if (AdaptiveEnabled)
             {
                 if (DebugLevel > 0)
                     m_log.WarnFormat(
                         "[ADAPTIVEBUCKET] drop {0} by {1} expired packets for {2}", 
-                        AdjustedDripRate, count, Identifier);
+                        AdjustedDripRate, packets, Identifier);
 
-                AdjustedDripRate = (Int64) (AdjustedDripRate / Math.Pow(2,count));
+                // AdjustedDripRate = (Int64) (AdjustedDripRate / Math.Pow(2,packets));
+
+                // Compute the fallback solely on the rate allocated beyond the minimum, this
+                // should smooth out the fallback to the minimum rate
+                AdjustedDripRate = m_minimumFlow + (Int64) ((AdjustedDripRate - m_minimumFlow) / Math.Pow(2, packets));
             }
         }
 
-        // <summary>
-        // Reliable packets acked by the client adjust the drip rate up.
-        // </summary>
-        public void AcknowledgePackets(Int32 count)
+        /// <summary>
+        /// Reliable packets acked by the client adjust the drip rate up.
+        /// <param name="packets">Number of packets successfully acknowledged</param>
+        /// </summary>
+        public void AcknowledgePackets(Int32 packets)
         {
             if (AdaptiveEnabled)
-                AdjustedDripRate = AdjustedDripRate + count;
+                AdjustedDripRate = AdjustedDripRate + packets * LLUDPServer.MTU;
+        }
+
+        /// <summary>
+        /// Adjust the minimum flow level for the adaptive throttle, this will drop adjusted
+        /// throttles back to the minimum levels
+        /// <param>minDripRate--the new minimum flow</param>
+        /// </summary>
+        public void ResetMinimumAdaptiveFlow(Int64 minDripRate)
+        {
+            m_minimumFlow = minDripRate;
+            TargetDripRate = m_minimumFlow;
+            AdjustedDripRate = m_minimumFlow;
         }
     }
 }
\ No newline at end of file
diff --git a/OpenSim/Region/ClientStack/Linden/UDP/UnackedPacketCollection.cs b/OpenSim/Region/ClientStack/Linden/UDP/UnackedPacketCollection.cs
index 9d6c09e..b546a99 100644
--- a/OpenSim/Region/ClientStack/Linden/UDP/UnackedPacketCollection.cs
+++ b/OpenSim/Region/ClientStack/Linden/UDP/UnackedPacketCollection.cs
@@ -31,6 +31,9 @@ using System.Net;
 using System.Threading;
 using OpenMetaverse;
 
+//using System.Reflection;
+//using log4net;
+
 namespace OpenSim.Region.ClientStack.LindenUDP
 {
     /// <summary>
@@ -60,6 +63,8 @@ namespace OpenSim.Region.ClientStack.LindenUDP
             }
         }
 
+        //private static readonly ILog m_log = LogManager.GetLogger(MethodBase.GetCurrentMethod().DeclaringType);
+
         /// <summary>Holds the actual unacked packet data, sorted by sequence number</summary>
         private Dictionary<uint, OutgoingPacket> m_packets = new Dictionary<uint, OutgoingPacket>();
         /// <summary>Holds packets that need to be added to the unacknowledged list</summary>
@@ -164,8 +169,8 @@ namespace OpenSim.Region.ClientStack.LindenUDP
                 }
             }
 
-                //if (expiredPackets != null)
-                //   m_log.DebugFormat("[UNACKED PACKET COLLECTION]: Found {0} expired packets on timeout of {1}", expiredPackets.Count, timeoutMS);
+            // if (expiredPackets != null)
+            //     m_log.DebugFormat("[UNACKED PACKET COLLECTION]: Found {0} expired packets on timeout of {1}", expiredPackets.Count, timeoutMS);
 
             return expiredPackets;
         }
@@ -192,7 +197,7 @@ namespace OpenSim.Region.ClientStack.LindenUDP
 
                         // As with other network applications, assume that an acknowledged packet is an
                         // indication that the network can handle a little more load, speed up the transmission
-                        ackedPacket.Client.FlowThrottle.AcknowledgePackets(ackedPacket.Buffer.DataLength);
+                        ackedPacket.Client.FlowThrottle.AcknowledgePackets(1);
 
                         // Update stats
                         Interlocked.Add(ref ackedPacket.Client.UnackedBytes, -ackedPacket.Buffer.DataLength);
@@ -207,9 +212,15 @@ namespace OpenSim.Region.ClientStack.LindenUDP
                     }
                     else
                     {
-                         //m_log.WarnFormat("[UNACKED PACKET COLLECTION]: Could not find packet with sequence number {0} to ack", pendingAcknowledgement.SequenceNumber);
+                        // m_log.WarnFormat("[UNACKED PACKET COLLECTION]: found null packet for sequence number {0} to ack",
+                        //                  pendingAcknowledgement.SequenceNumber);
                     }
                 }
+                else
+                {
+                    // m_log.WarnFormat("[UNACKED PACKET COLLECTION]: Could not find packet with sequence number {0} to ack",
+                    //                  pendingAcknowledgement.SequenceNumber);                    
+                }
             }
 
             uint pendingRemove;
diff --git a/bin/OpenSimDefaults.ini b/bin/OpenSimDefaults.ini
index 3e9514e..212baab 100644
--- a/bin/OpenSimDefaults.ini
+++ b/bin/OpenSimDefaults.ini
@@ -544,6 +544,13 @@
     ;
     ;client_throttle_max_bps = 187500
 
+    ; Minimum bytes per second to send to any single client as a result of
+    ; adaptive throttling. Viewer preferences set to a lower number will 
+    ; override the settin. The example given here ensures that adaptive
+    ; throttling will never decrease per client bandwidth below 256 kbps.
+    ;
+    ;adaptive_throttle_min_bps = 32000
+
     ; Adaptive throttling attempts to limit network overload when multiple
     ; clients login by starting each connection more slowly. Disabled by
     ; default