diff --git a/docs/rh-log.txt b/docs/rh-log.txt
index 4eb084d48b..c50f7d8ed3 100644
--- a/docs/rh-log.txt
+++ b/docs/rh-log.txt
@@ -1,4 +1,13 @@
-February 21, 2009  (Changes by Graf Zahl)
+February 21, 2009
+- Added selective compression of network packets. Interestingly, most packets
+  don't actually compress all that well, even the ones that aren't too short
+  to possibly compress. (Maybe make the whole thing one long, never-ending
+  zlib data stream with Z_SYNC_FLUSH used to chunk things at packet
+  boundaries? That would probably help the compression ratio, but it would
+  require changing the way the netcode determines sequence, which would be
+  a much more invasive change.)
+
+February 21, 2009  (Changes by Graf Zahl)
 - Fixed: Heretic's fullscreen HUD crashed when the player had armor without
   a valid icon.
 - Fixed: The StrifePlayer was missing a RunHealth setting.
diff --git a/src/d_net.cpp b/src/d_net.cpp
index 3400e45da1..ce16d48d2a 100644
--- a/src/d_net.cpp
+++ b/src/d_net.cpp
@@ -67,35 +67,6 @@ EXTERN_CVAR (Int, autosavecount)
 //#define SIMULATEERRORS		(RAND_MAX/3)
 #define SIMULATEERRORS			0
 
-#define NCMD_EXIT				0x80
-#define NCMD_RETRANSMIT 		0x40
-#define NCMD_SETUP				0x20
-#define NCMD_MULTI				0x10		// multiple players in this packet
-#define NCMD_QUITTERS			0x08		// one or more players just quit (packet server only)
-
-#define NCMD_XTICS				0x03		// packet contains >2 tics
-#define NCMD_2TICS				0x02		// packet contains 2 tics
-#define NCMD_1TICS				0x01		// packet contains 1 tic
-#define NCMD_0TICS				0x00		// packet contains 0 tics
-
-// [RH]
-// New generic packet structure:
-//
-// Header:
-//  One byte with above flags.
-//  One byte with starttic
-//  One byte with master's maketic (master -> slave only!)
-//  If NCMD_RETRANSMIT set, one byte with retransmitfrom
-//  If NCMD_XTICS set, one byte with number of tics (minus 3, so theoretically up to 258 tics in one packet)
-//  If NCMD_QUITTERS, one byte with number of players followed by one byte with each player's consolenum
-//  If NCMD_MULTI, one byte with number of players followed by one byte with each player's consolenum
-//     - The first player's consolenum is not included in this list, because it always matches the sender
-//
-// For each tic:
-//  Two bytes with consistancy check, followed by tic data
-//
-// Setup packets are different, and are described just before D_ArbitrateNetStart().
-
 extern BYTE		*demo_p;		// [RH] Special "ticcmds" get recorded in demos
 extern char		savedescription[SAVESTRINGSIZE];
 extern FString	savegamefile;
diff --git a/src/d_net.h b/src/d_net.h
index 43be497102..3ad0bddede 100644
--- a/src/d_net.h
+++ b/src/d_net.h
@@ -48,7 +48,7 @@
 // Probably not enough.
 #define MAX_MSGLEN		(BACKUPTICS*10)
 #else
-#define MAX_MSGLEN		1400
+#define MAX_MSGLEN		14000
 #endif
 
 #define CMD_SEND	1
@@ -144,4 +144,34 @@ extern	int 			nettics[MAXNETNODES];
 extern	ticcmd_t		netcmds[MAXPLAYERS][BACKUPTICS];
 extern	int 			ticdup;
 
+// [RH]
+// New generic packet structure:
+//
+// Header:
+//  One byte with following flags.
+//  One byte with starttic
+//  One byte with master's maketic (master -> slave only!)
+//  If NCMD_RETRANSMIT set, one byte with retransmitfrom
+//  If NCMD_XTICS set, one byte with number of tics (minus 3, so theoretically up to 258 tics in one packet)
+//  If NCMD_QUITTERS, one byte with number of players followed by one byte with each player's consolenum
+//  If NCMD_MULTI, one byte with number of players followed by one byte with each player's consolenum
+//     - The first player's consolenum is not included in this list, because it always matches the sender
+//
+// For each tic:
+//  Two bytes with consistancy check, followed by tic data
+//
+// Setup packets are different, and are described just before D_ArbitrateNetStart().
+
+#define NCMD_EXIT				0x80
+#define NCMD_RETRANSMIT 		0x40
+#define NCMD_SETUP				0x20
+#define NCMD_MULTI				0x10		// multiple players in this packet
+#define NCMD_QUITTERS			0x08		// one or more players just quit (packet server only)
+#define NCMD_COMPRESSED			0x04		// remainder of packet is compressed
+
+#define NCMD_XTICS				0x03		// packet contains >2 tics
+#define NCMD_2TICS				0x02		// packet contains 2 tics
+#define NCMD_1TICS				0x01		// packet contains 1 tic
+#define NCMD_0TICS				0x00		// packet contains 0 tics
+
 #endif
diff --git a/src/i_net.cpp b/src/i_net.cpp
index caa3a61fb8..7df97a76e3 100644
--- a/src/i_net.cpp
+++ b/src/i_net.cpp
@@ -64,7 +64,9 @@
 
 #include "i_net.h"
 
-
+// As per http://support.microsoft.com/kb/q192599/ the standard
+// size for network buffers is 8k.
+#define TRANSMIT_SIZE		8000
 
 /* [Petteri] Get more portable: */
 #ifndef __WIN32__
@@ -133,6 +135,8 @@ struct PreGamePacket
 	} machines[MAXNETNODES];
 };
 
+BYTE TransmitBuffer[TRANSMIT_SIZE];
+
 //
 // UDPsocket
 //
@@ -191,11 +195,47 @@ void PacketSend (void)
 {
 	int c;
 
-	//printf ("sending %i\n",gametic);
-	c = sendto (mysocket , (const char*)doomcom.data, doomcom.datalength
-				,0,(sockaddr *)&sendaddress[doomcom.remotenode]
-				,sizeof(sendaddress[doomcom.remotenode]));
+	// FIXME: Catch this before we've overflown the buffer. With long chat
+	// text and lots of backup tics, it could conceivably happen. (Though
+	// apparently it hasn't yet, which is good.)
+	if (doomcom.datalength > MAX_MSGLEN)
+	{
+		I_FatalError("Netbuffer overflow!");
+	}
 
+	uLong size = TRANSMIT_SIZE - 1;
+	if (doomcom.datalength >= 10)
+	{
+		assert(!(doomcom.data[0] & NCMD_COMPRESSED));
+		TransmitBuffer[0] = doomcom.data[0] | NCMD_COMPRESSED;
+		c = compress2(TransmitBuffer + 1, &size, doomcom.data + 1, doomcom.datalength - 1, 9);
+		size += 1;
+	}
+	else
+	{
+		c = -1;	// Just some random error code to avoid sending the compressed buffer.
+	}
+	if (c == Z_OK && size < (uLong)doomcom.datalength)
+	{
+//		Printf("send %lu/%d\n", size, doomcom.datalength);
+		c = sendto(mysocket, (char *)TransmitBuffer, size,
+			0, (sockaddr *)&sendaddress[doomcom.remotenode],
+			sizeof(sendaddress[doomcom.remotenode]));
+	}
+	else
+	{
+		if (doomcom.datalength > TRANSMIT_SIZE)
+		{
+			I_Error("Net compression failed (zlib error %d)", c);
+		}
+		else
+		{
+//			Printf("send %d\n", doomcom.datalength);
+			c = sendto(mysocket, (char *)doomcom.data, doomcom.datalength,
+				0, (sockaddr *)&sendaddress[doomcom.remotenode],
+				sizeof(sendaddress[doomcom.remotenode]));
+		}
+	}
 	//	if (c == -1)
 	//			I_Error ("SendPacket error: %s",strerror(errno));
 }
@@ -212,8 +252,8 @@ void PacketGet (void)
 	int node;
 
 	fromlen = sizeof(fromaddress);
-	c = recvfrom (mysocket, (char*)doomcom.data, MAX_MSGLEN, 0
-				  , (sockaddr *)&fromaddress, &fromlen);
+	c = recvfrom (mysocket, (char*)TransmitBuffer, TRANSMIT_SIZE, 0,
+				  (sockaddr *)&fromaddress, &fromlen);
 	node = FindNode (&fromaddress);
 
 	if (node >= 0 && c == SOCKET_ERROR)
@@ -239,6 +279,26 @@ void PacketGet (void)
 			return;
 		}
 	}
+	else if (c > 0)
+	{
+		doomcom.data[0] = TransmitBuffer[0] & ~NCMD_COMPRESSED;
+		if (TransmitBuffer[0] & NCMD_COMPRESSED)
+		{
+			uLongf msgsize = MAX_MSGLEN - 1;
+			int err = uncompress(doomcom.data + 1, &msgsize, TransmitBuffer + 1, c - 1);
+//			Printf("recv %d/%lu\n", c, msgsize + 1);
+			if (err != Z_OK)
+			{
+				I_Error("Net decompression failed (zlib error %d)\n", err);
+			}
+			c = msgsize + 1;
+		}
+		else
+		{
+//			Printf("recv %d\n", c);
+			memcpy(doomcom.data + 1, TransmitBuffer + 1, c - 1);
+		}
+	}
 
 	doomcom.remotenode = node;
 	doomcom.datalength = (short)c;