Index: uspace/srv/net/tl/udp/udp.c
===================================================================
--- uspace/srv/net/tl/udp/udp.c	(revision 5fe7692333e7cdfa10b72167b2de2563d3ba8e25)
+++ uspace/srv/net/tl/udp/udp.c	(revision 4489117e1577b1819144b2d510d0d104689dff33)
@@ -499,5 +499,9 @@
 	device_id_t device_id;
 	packet_dimension_t *packet_dimension;
+	size_t size;
 	int rc;
+
+	/* In case of error, do not update the data fragment size. */
+	*data_fragment_size = 0;
 	
 	rc = tl_get_address_port(addr, addrlen, &dest_port);
@@ -539,4 +543,14 @@
 		packet_dimension = &udp_globals.packet_dimension;
 //	}
+
+	/*
+	 * Update the data fragment size based on what the lower layers can
+	 * handle without fragmentation, but not more than the maximum allowed
+	 * for UDP.
+	 */
+	size = MAX_UDP_FRAGMENT_SIZE;
+	if (packet_dimension->content < size)
+	    size = packet_dimension->content;
+	*data_fragment_size = size;
 
 	/* Read the first packet fragment */
@@ -740,5 +754,5 @@
 	int socket_id;
 	size_t addrlen;
-	size_t size = 0;
+	size_t size;
 	ipc_call_t answer;
 	size_t answer_count;
@@ -786,13 +800,12 @@
 				break;
 			
+			size = MAX_UDP_FRAGMENT_SIZE;
 			if (tl_get_ip_packet_dimension(udp_globals.ip_phone,
 			    &udp_globals.dimensions, DEVICE_INVALID_ID,
 			    &packet_dimension) == EOK) {
-				SOCKET_SET_DATA_FRAGMENT_SIZE(answer,
-				    packet_dimension->content);
+				if (packet_dimension->content < size)
+					size = packet_dimension->content;
 			}
-
-//			SOCKET_SET_DATA_FRAGMENT_SIZE(answer,
-//			    MAX_UDP_FRAGMENT_SIZE);
+			SOCKET_SET_DATA_FRAGMENT_SIZE(answer, size);
 			SOCKET_SET_HEADER_SIZE(answer, UDP_HEADER_SIZE);
 			answer_count = 3;