diff --git a/OpenSim/Framework/Servers/BaseOpenSimServer.cs b/OpenSim/Framework/Servers/BaseOpenSimServer.cs
index 36f8d2eede..aa93f6ecab 100644
--- a/OpenSim/Framework/Servers/BaseOpenSimServer.cs
+++ b/OpenSim/Framework/Servers/BaseOpenSimServer.cs
@@ -428,25 +428,6 @@ namespace OpenSim.Framework.Servers
             }
 
             m_version += string.IsNullOrEmpty(buildVersion) ? "      " : ("." + buildVersion + "     ").Substring(0, 6);
-
-            // Add operating system information if available
-            string OSString = "";
-
-            if (System.Environment.OSVersion.Platform != PlatformID.Unix)
-            {
-                OSString = System.Environment.OSVersion.ToString();
-            }
-            else
-            {
-                OSString = Util.ReadEtcIssue();
-            }
-
-            if (OSString.Length > 45)
-            {
-                OSString = OSString.Substring(0, 45);
-            }
-
-            m_version += " (OS " + OSString + ")";
         }
     }
 }
diff --git a/OpenSim/Framework/Servers/VersionInfo.cs b/OpenSim/Framework/Servers/VersionInfo.cs
index 8f848596e8..c6a43ecf09 100644
--- a/OpenSim/Framework/Servers/VersionInfo.cs
+++ b/OpenSim/Framework/Servers/VersionInfo.cs
@@ -27,11 +27,27 @@
 
 namespace OpenSim
 {
-    /// <summary>
-    /// This is the OpenSim version string.  Change this if you are releasing a new OpenSim version.
-    /// </summary>
     public class VersionInfo
     {
+        /// <value>
+        /// This is the OpenSim version string.  Change this if you are releasing a new OpenSim version.
+        /// </value>        
         public readonly static string Version = "OpenSimulator Server  0.6.0";  // stay with 27 chars (used in regioninfo)
+        
+        /// <value>
+        /// This is the external interface version.  It is separate from the OpenSimulator project version.  
+        /// 
+        /// This version number should be 
+        /// increased by 1 every time a code change makes the previous OpenSimulator revision incompatible
+        /// with the new revision.  This will usually be due to interregion or grid facing interface changes.
+        /// 
+        /// Changes which are compatible with an older revision (e.g. older revisions experience degraded functionality
+        /// but not outright failure) do not need a version number increment.
+        /// 
+        /// Having this version number allows the grid service to reject connections from regions running a version
+        /// of the code that is too old. 
+        ///   
+        /// </value>
+        public readonly static int MajorInterfaceVersion = 0;
     }
 }
diff --git a/OpenSim/Framework/Util.cs b/OpenSim/Framework/Util.cs
index 7caa414d12..f72797f705 100644
--- a/OpenSim/Framework/Util.cs
+++ b/OpenSim/Framework/Util.cs
@@ -799,6 +799,33 @@ namespace OpenSim.Framework
             x += rx;
             y += ry;
         }
+        
+        /// <summary>
+        /// Get operating system information if available.  Returns only the first 45 characters of information
+        /// </summary>
+        /// <returns>
+        /// Operating system information.  Returns an empty string if none was available.
+        /// </returns>
+        public static string GetOperatingSystemInformation()
+        {
+            string os = String.Empty;
+
+            if (System.Environment.OSVersion.Platform != PlatformID.Unix)
+            {
+                os = System.Environment.OSVersion.ToString();
+            }
+            else
+            {
+                os = ReadEtcIssue();
+            }         
+                      
+            if (os.Length > 45)
+            {
+                os = os.Substring(0, 45);
+            }
+            
+            return os;
+        }
 
         /// <summary>
         /// Is the given string a UUID?
diff --git a/OpenSim/Grid/GridServer/GridManager.cs b/OpenSim/Grid/GridServer/GridManager.cs
index 0fc2147092..32b7554082 100644
--- a/OpenSim/Grid/GridServer/GridManager.cs
+++ b/OpenSim/Grid/GridServer/GridManager.cs
@@ -53,6 +53,22 @@ namespace OpenSim.Grid.GridServer
         private List<MessageServerInfo> _MessageServers = new List<MessageServerInfo>();
 
         public GridConfig Config;
+        
+        /// <value>
+        /// Used to notify old regions as to which OpenSim version to upgrade to
+        /// </value>
+        private string m_opensimVersion;
+        
+        /// <summary>
+        /// Constructor
+        /// </summary>
+        /// <param name="opensimVersion">
+        /// Used to notify old regions as to which OpenSim version to upgrade to
+        /// </param>
+        public GridManager(string opensimVersion)
+        {
+            m_opensimVersion = opensimVersion;
+        }
 
         /// <summary>
         /// Adds a new grid server plugin - grid servers will be requested in the order they were loaded.
@@ -360,7 +376,7 @@ namespace OpenSim.Grid.GridServer
 
             if (!requestData.ContainsKey("UUID") || !UUID.TryParse((string)requestData["UUID"], out uuid))
             {
-                m_log.Warn("[LOGIN PRELUDE]: Region connected without a UUID, sending back error response.");
+                m_log.Debug("[LOGIN PRELUDE]: Region connected without a UUID, sending back error response.");
                 return ErrorResponse("No UUID passed to grid server - unable to connect you");
             }
 
@@ -370,21 +386,33 @@ namespace OpenSim.Grid.GridServer
             }
             catch (FormatException e)
             {
-                m_log.Warn("[LOGIN PRELUDE]: Invalid login parameters, sending back error response.");
+                m_log.Debug("[LOGIN PRELUDE]: Invalid login parameters, sending back error response.");
                 return ErrorResponse("Wrong format in login parameters. Please verify parameters." + e.ToString());
             }
+            
+            m_log.InfoFormat("[LOGIN BEGIN]: Received login request from simulator: {0}", sim.regionName);            
 
             if (!Config.AllowRegionRegistration)
             {
-                m_log.InfoFormat(
+                m_log.DebugFormat(
                     "[LOGIN END]: Disabled region registration blocked login request from simulator: {0}",
                     sim.regionName);
 
-                return ErrorResponse("The grid is currently not accepting region registrations.");
+                return ErrorResponse("This grid is currently not accepting region registrations.");
+            }            
+            
+            int majorInterfaceVersion = 0;
+            if (requestData.ContainsKey("major_interface_version"))
+                int.TryParse((string)requestData["major_interface_version"], out majorInterfaceVersion);
+            
+            if (majorInterfaceVersion != VersionInfo.MajorInterfaceVersion)
+            {
+                return ErrorResponse(
+                    String.Format(
+                        "Your region is the wrong version to connect to this grid.  Try changing to version {0} (interface version {1})",
+                        m_opensimVersion, VersionInfo.MajorInterfaceVersion));
             }
 
-            m_log.InfoFormat("[LOGIN BEGIN]: Received login request from simulator: {0}", sim.regionName);
-
             existingSim = GetRegion(sim.regionHandle);
 
             if (existingSim == null || existingSim.UUID == sim.UUID || sim.UUID != sim.originUUID)
diff --git a/OpenSim/Grid/GridServer/GridServerBase.cs b/OpenSim/Grid/GridServer/GridServerBase.cs
index 36ea238bc8..9652765171 100644
--- a/OpenSim/Grid/GridServer/GridServerBase.cs
+++ b/OpenSim/Grid/GridServer/GridServerBase.cs
@@ -153,7 +153,7 @@ namespace OpenSim.Grid.GridServer
         protected virtual void SetupGridManager()
         {
             m_log.Info("[DATA]: Connecting to Storage Server");
-            m_gridManager = new GridManager();
+            m_gridManager = new GridManager(m_version);
             m_gridManager.AddPlugin(m_config.DatabaseProvider, m_config.DatabaseConnect);
             m_gridManager.Config = m_config;
         }
diff --git a/OpenSim/Region/Communications/OGS1/OGS1GridServices.cs b/OpenSim/Region/Communications/OGS1/OGS1GridServices.cs
index a4fa3bb0a5..0c131203e0 100644
--- a/OpenSim/Region/Communications/OGS1/OGS1GridServices.cs
+++ b/OpenSim/Region/Communications/OGS1/OGS1GridServices.cs
@@ -130,6 +130,7 @@ namespace OpenSim.Region.Communications.OGS1
             GridParams["originUUID"] = regionInfo.originRegionID.ToString();
             GridParams["server_uri"] = regionInfo.ServerURI;
             GridParams["region_secret"] = regionInfo.regionSecret;
+            GridParams["major_interface_version"] = VersionInfo.MajorInterfaceVersion.ToString();
 
             if (regionInfo.MasterAvatarAssignedUUID != UUID.Zero)
                 GridParams["master_avatar_uuid"] = regionInfo.MasterAvatarAssignedUUID.ToString();
diff --git a/OpenSim/Region/Environment/Scenes/Scene.cs b/OpenSim/Region/Environment/Scenes/Scene.cs
index 68fac590b5..fd4eb58a35 100644
--- a/OpenSim/Region/Environment/Scenes/Scene.cs
+++ b/OpenSim/Region/Environment/Scenes/Scene.cs
@@ -319,6 +319,7 @@ namespace OpenSim.Region.Environment.Scenes
             m_statsReporter.SetObjectCapacity(objectCapacity);
 
             m_simulatorVersion = simulatorVersion
+                + " (OS " + Util.GetOperatingSystemInformation() + ")"
                 + " ChilTasks:" + m_seeIntoRegionFromNeighbor.ToString()
                 + " PhysPrim:" + m_physicalPrim.ToString();