diff --git a/Constants.cs b/Constants.cs
index cfe719b..fb18c66 100644
--- a/Constants.cs
+++ b/Constants.cs
@@ -141,7 +141,6 @@ namespace fnecore
         public const uint RtpGenericClockRate = 8000;
 
         public const byte DVMRtpPayloadType = 0x56;
-        public const byte DVMRtpControlPayloadType = 0x57;
         public const byte DVMFrameStart = 0xFE;
 
         /*
@@ -179,6 +178,12 @@ namespace fnecore
         public const byte NET_TRANSFER_SUBFUNC_ACTIVITY = 0x01;                 // Activity Log Transfer
         public const byte NET_TRANSFER_SUBFUNC_DIAG = 0x02;                     // Diagnostic Log Transfer
 
+        public const byte NET_FUNC_ANNOUNCE = 0x91U;                            // Network Announce Function
+        public const byte NET_ANNC_SUBFUNC_GRP_AFFIL = 0x00U;                   // Announce Group Affiliation
+        public const byte NET_ANNC_SUBFUNC_UNIT_REG = 0x01U;                    // Announce Unit Registration
+        public const byte NET_ANNC_SUBFUNC_UNIT_DEREG = 0x02U;                  // Announce Unit Deregistration
+        public const byte NET_ANNC_SUBFUNC_AFFILS = 0x90U;                      // Update All Affiliations
+
         /*
         ** Protocol Tags (as strings)
         */
diff --git a/FneMaster.cs b/FneMaster.cs
index 20c544f..7e17304 100644
--- a/FneMaster.cs
+++ b/FneMaster.cs
@@ -7,7 +7,7 @@
 * @package DVM / Fixed Network Equipment Core Library
 * @license AGPLv3 License (https://opensource.org/licenses/AGPL-3.0)
 *
-*   Copyright (C) 2022-2023 Bryan Biedenkapp, N2PLL
+*   Copyright (C) 2022-2024 Bryan Biedenkapp, N2PLL
 *
 */
 
@@ -217,6 +217,21 @@ namespace fnecore
         /// </summary>
         public Action<uint, string> DiagnosticTransfer = null;
 
+        /// <summary>
+        /// Event action that handles peer unit registration announcements.
+        /// </summary>
+        public Action<uint, uint> UnitRegistration = null;
+
+        /// <summary>
+        /// Event action that handles peer unit deregistration announcements
+        /// </summary>
+        public Action<uint, uint> UnitDeregistration = null;
+
+        /// <summary>
+        /// Event action that handles peer group affiliation announcements
+        /// </summary>
+        public Action<uint, uint, uint> UnitGroupAffiliation = null;
+
         /*
         ** Methods
         */
@@ -1104,6 +1119,65 @@ namespace fnecore
                             }
                             break;
 
+                        case Constants.NET_FUNC_ANNOUNCE:
+                            {
+                                else if (fneHeader.SubFunction == Constants.NET_ANNC_SUBFUNC_GRP_AFFIL) // Announce Group Affiliation
+                                {
+                                    // can we do activity transfers?
+                                    if (AllowActivityTransfer)
+                                    {
+                                        if (peerId > 0 && peers.ContainsKey(peerId))
+                                        {
+                                            // validate peer (simple validation really
+                                            if (peers[peerId].Connection && peers[peerId].EndPoint.ToString() == frame.Endpoint.ToString())
+                                            {
+                                                uint srcId = FneUtils.Bytes3ToUInt32(buffer, 0);
+                                                uint dstId = FneUtils.Bytes3ToUInt32(buffer, 3);
+                                                if (UnitGroupAffiliation != null)
+                                                    UnitGroupAffiliation(peerId, srcId, dstId);
+                                            }
+                                        }
+                                    }
+                                }
+                                else if (fneHeader.SubFunction == Constants.NET_ANNC_SUBFUNC_UNIT_REG)  // Announce Unit Registration
+                                {
+                                    // can we do activity transfers?
+                                    if (AllowActivityTransfer)
+                                    {
+                                        if (peerId > 0 && peers.ContainsKey(peerId))
+                                        {
+                                            // validate peer (simple validation really
+                                            if (peers[peerId].Connection && peers[peerId].EndPoint.ToString() == frame.Endpoint.ToString())
+                                            {
+                                                uint srcId = FneUtils.Bytes3ToUInt32(buffer, 0);
+                                                if (UnitRegistration != null)
+                                                    UnitRegistration(peerId, srcId);
+                                            }
+                                        }
+                                    }
+                                }
+                                else if (fneHeader.SubFunction == Constants.NET_ANNC_SUBFUNC_UNIT_DEREG) // Announce Unit Deregistration
+                                {
+                                    // can we do diagnostic transfers?
+                                    if (AllowDiagnosticTransfer)
+                                    {
+                                        if (peerId > 0 && peers.ContainsKey(peerId))
+                                        {
+                                            // validate peer (simple validation really)
+                                            if (peers[peerId].Connection && peers[peerId].EndPoint.ToString() == frame.Endpoint.ToString())
+                                            {
+                                                uint srcId = FneUtils.Bytes3ToUInt32(buffer, 0);
+                                                if (UnitDeregistration != null)
+                                                    UnitDeregistration(peerId, srcId);
+                                            }
+                                        }
+                                    }
+                                }
+                                else
+                                    Log(LogLevel.ERROR, $"({systemName}) Unknown transfer opcode {FneUtils.BytesToString(message, 0, 4)} -- {FneUtils.HexDump(message, 0)}");
+                            }
+                            break;
+
                         default:
                             Log(LogLevel.ERROR, $"({systemName}) Unknown opcode {FneUtils.BytesToString(message, 0, 4)} -- {FneUtils.HexDump(message, 0)}");
                             break;