diff --git a/OpenSim/Framework/Communications/Cache/AuthedSessionCache.cs b/OpenSim/Framework/Communications/Cache/AuthedSessionCache.cs
new file mode 100644
index 0000000000..b989997adf
--- /dev/null
+++ b/OpenSim/Framework/Communications/Cache/AuthedSessionCache.cs
@@ -0,0 +1,107 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+
+namespace OpenSim.Framework.Communications.Cache
+{
+    public class AuthedSessionCache
+    {
+        public class CacheData
+        {
+            private static readonly DateTime UNIX_EPOCH = new DateTime(1970, 1, 1);
+            private string m_session_id;
+            private string m_agent_id;
+            private int m_expire;
+
+            private int get_current_unix_time()
+            {
+                return (int)(DateTime.UtcNow - UNIX_EPOCH).TotalSeconds;
+            }
+
+            public CacheData(string sid, string aid)
+            {
+                m_session_id = sid;
+                m_agent_id = aid;
+                m_expire = get_current_unix_time() + DEFAULT_LIFETIME;
+            }
+
+            public CacheData(string sid, string aid, int time_now)
+            {
+                m_session_id = sid;
+                m_agent_id = aid;
+                m_expire = time_now + DEFAULT_LIFETIME;
+            }
+
+            public string SessionID
+            {
+                get { return m_session_id; }
+                set { m_session_id = value; }
+            }
+
+            public string AgentID
+            {
+                get { return m_agent_id; }
+                set { m_agent_id = value; }
+            }
+
+            public bool isExpired
+            {
+                get { return m_expire < get_current_unix_time(); }
+            }
+
+            public void Renew()
+            {
+                m_expire = get_current_unix_time() + DEFAULT_LIFETIME;
+            }
+        }
+
+        private static readonly int DEFAULT_LIFETIME = 30;
+        private Dictionary<string, CacheData> m_authed_sessions = new Dictionary<string,CacheData>();
+        private int m_session_lifetime = DEFAULT_LIFETIME;
+
+        public AuthedSessionCache()
+        {
+            m_session_lifetime = DEFAULT_LIFETIME;
+        }
+
+        public AuthedSessionCache(int timeout)
+        {
+            m_session_lifetime = timeout;
+        }
+
+        public CacheData getCachedSession(string session_id, string agent_id)
+        {
+            CacheData ret = null;
+            lock (m_authed_sessions)
+            {
+                if (m_authed_sessions.ContainsKey(session_id))
+                {
+                    CacheData cached_session = m_authed_sessions[session_id];
+                    if (!cached_session.isExpired && cached_session.AgentID == agent_id)
+                    {
+                        ret = m_authed_sessions[session_id];
+                        // auto renew
+                        m_authed_sessions[session_id].Renew();
+                    }
+                }
+            }
+            return ret;
+        }
+
+        public void Add(string session_id, string agent_id)
+        {
+            CacheData data = new CacheData(session_id, agent_id);
+            lock (m_authed_sessions)
+            {
+                if (m_authed_sessions.ContainsKey(session_id))
+                {
+                    m_authed_sessions[session_id] = data;
+                }
+                else
+                {
+                    m_authed_sessions.Add(session_id, data);
+                }
+            }
+        }
+    }
+}
diff --git a/OpenSim/Grid/InventoryServer/GridInventoryService.cs b/OpenSim/Grid/InventoryServer/GridInventoryService.cs
index b8a04369af..63eeced885 100644
--- a/OpenSim/Grid/InventoryServer/GridInventoryService.cs
+++ b/OpenSim/Grid/InventoryServer/GridInventoryService.cs
@@ -38,6 +38,7 @@ using Nwc.XmlRpc;
 
 using OpenSim.Framework;
 using OpenSim.Framework.Communications;
+using OpenSim.Framework.Communications.Cache;
 
 namespace OpenSim.Grid.InventoryServer
 {
@@ -48,8 +49,10 @@ namespace OpenSim.Grid.InventoryServer
     {
         private static readonly ILog m_log
             = LogManager.GetLogger(MethodBase.GetCurrentMethod().DeclaringType);
+        private static readonly int INVENTORY_DEFAULT_SESSION_TIME = 30; // secs
 
         private string m_userserver_url;
+        private AuthedSessionCache m_session_cache = new AuthedSessionCache(INVENTORY_DEFAULT_SESSION_TIME);
 
         public GridInventoryService(string userserver_url)
         {
@@ -72,20 +75,33 @@ namespace OpenSim.Grid.InventoryServer
         public bool CheckAuthSession(string session_id, string avatar_id)
         {
             m_log.InfoFormat("[GRID AGENT INVENTORY]: checking authed session {0} {1}", session_id, avatar_id);
-            Hashtable requestData = new Hashtable();
-            requestData["avatar_uuid"] = avatar_id;
-            requestData["session_id"] = session_id;
-            ArrayList SendParams = new ArrayList();
-            SendParams.Add(requestData);
-            XmlRpcRequest UserReq = new XmlRpcRequest("check_auth_session", SendParams);
-            XmlRpcResponse UserResp = UserReq.Send(m_userserver_url, 3000);
-
-            Hashtable responseData = (Hashtable)UserResp.Value;
-
-            if (responseData.ContainsKey("auth_session") && responseData["auth_session"].ToString() == "TRUE")
+            if (m_session_cache.getCachedSession(session_id, avatar_id) == null)
             {
+                // cache miss, ask userserver
+                Hashtable requestData = new Hashtable();
+                requestData["avatar_uuid"] = avatar_id;
+                requestData["session_id"] = session_id;
+                ArrayList SendParams = new ArrayList();
+                SendParams.Add(requestData);
+                XmlRpcRequest UserReq = new XmlRpcRequest("check_auth_session", SendParams);
+                XmlRpcResponse UserResp = UserReq.Send(m_userserver_url, 3000);
+
+                Hashtable responseData = (Hashtable)UserResp.Value;
+                if (responseData.ContainsKey("auth_session") && responseData["auth_session"].ToString() == "TRUE")
+                {
+                    m_log.Info("[GRID AGENT INVENTORY]: got authed session from userserver");
+                    // add to cache; the session time will be automatically renewed
+                    m_session_cache.Add(session_id, avatar_id);
+                    return true;
+                }
+            }
+            else
+            {
+                // cache hits
+                m_log.Info("[GRID AGENT INVENTORY]: got authed session from cache");
                 return true;
             }
+            m_log.Info("[GRID AGENT INVENTORY]: unknown session_id, request rejected");
             return false;
         }