diff --git a/core/net/sicslowpan.c b/core/net/sicslowpan.c
index 319bb5b01..442b36b73 100644
--- a/core/net/sicslowpan.c
+++ b/core/net/sicslowpan.c
@@ -234,7 +234,7 @@ static uip_buf_t sicslowpan_aligned_buf;
  * length of the ip packet already sent / received.
  * It includes IP and transport headers.
  */
-static uint16_t processed_ip_len;
+static uint16_t processed_ip_in_len;
 
 /** Datagram tag to be put in the fragments I send. */
 static uint16_t my_tag;
@@ -1353,6 +1353,9 @@ output(uip_lladdr_t *localdest)
   /* The MAC address of the destination of the packet */
   rimeaddr_t dest;
 
+  /* Number of bytes processed. */
+  uint16_t processed_ip_out_len;
+
   /* init */
   uncomp_hdr_len = 0;
   rime_hdr_len = 0;
@@ -1443,6 +1446,7 @@ output(uip_lladdr_t *localdest)
           ((SICSLOWPAN_DISPATCH_FRAG1 << 8) | uip_len));
 /*     RIME_FRAG_BUF->tag = uip_htons(my_tag); */
     SET16(RIME_FRAG_PTR, RIME_FRAG_TAG, my_tag);
+    my_tag++;
 
     /* Copy payload and send */
     rime_hdr_len += SICSLOWPAN_FRAG1_HDR_LEN;
@@ -1461,8 +1465,8 @@ output(uip_lladdr_t *localdest)
     queuebuf_free(q);
     q = NULL;
 
-    /* set processed_ip_len to what we already sent from the IP payload*/
-    processed_ip_len = rime_payload_len + uncomp_hdr_len;
+    /* set processed_ip_out_len to what we already sent from the IP payload*/
+    processed_ip_out_len = rime_payload_len + uncomp_hdr_len;
     
     /*
      * Create following fragments
@@ -1475,19 +1479,19 @@ output(uip_lladdr_t *localdest)
     SET16(RIME_FRAG_PTR, RIME_FRAG_DISPATCH_SIZE,
           ((SICSLOWPAN_DISPATCH_FRAGN << 8) | uip_len));
     rime_payload_len = (MAC_MAX_PAYLOAD - rime_hdr_len) & 0xf8;
-    while(processed_ip_len < uip_len) {
+    while(processed_ip_out_len < uip_len) {
       PRINTFO("sicslowpan output: fragment ");
-      RIME_FRAG_PTR[RIME_FRAG_OFFSET] = processed_ip_len >> 3;
+      RIME_FRAG_PTR[RIME_FRAG_OFFSET] = processed_ip_out_len >> 3;
       
       /* Copy payload and send */
-      if(uip_len - processed_ip_len < rime_payload_len) {
+      if(uip_len - processed_ip_out_len < rime_payload_len) {
         /* last fragment */
-        rime_payload_len = uip_len - processed_ip_len;
+        rime_payload_len = uip_len - processed_ip_out_len;
       }
       PRINTFO("(offset %d, len %d, tag %d)\n",
-             processed_ip_len >> 3, rime_payload_len, my_tag);
+             processed_ip_out_len >> 3, rime_payload_len, my_tag);
       memcpy(rime_ptr + rime_hdr_len,
-             (uint8_t *)UIP_IP_BUF + processed_ip_len, rime_payload_len);
+             (uint8_t *)UIP_IP_BUF + processed_ip_out_len, rime_payload_len);
       packetbuf_set_datalen(rime_payload_len + rime_hdr_len);
       q = queuebuf_new_from_packetbuf();
       if(q == NULL) {
@@ -1498,12 +1502,9 @@ output(uip_lladdr_t *localdest)
       queuebuf_to_packetbuf(q);
       queuebuf_free(q);
       q = NULL;
-      processed_ip_len += rime_payload_len;
+      processed_ip_out_len += rime_payload_len;
     }
     
-    /* end: reset global variables  */
-    my_tag++;
-    processed_ip_len = 0;
 #else /* SICSLOWPAN_CONF_FRAG */
     PRINTFO("sicslowpan output: Packet too large to be sent without fragmentation support; dropping packet\n");
     return 0;
@@ -1558,7 +1559,7 @@ input(void)
   /* if reassembly timed out, cancel it */
   if(timer_expired(&reass_timer)) {
     sicslowpan_len = 0;
-    processed_ip_len = 0;
+    processed_ip_in_len = 0;
   }
   /*
    * Since we don't support the mesh and broadcast header, the first header
@@ -1593,10 +1594,10 @@ input(void)
 
       /* If this is the last fragment, we may shave off any extrenous
          bytes at the end. We must be liberal in what we accept. */
-      PRINTFI("last_fragment?: processed_ip_len %d rime_payload_len %d frag_size %d\n",
-              processed_ip_len, packetbuf_datalen() - rime_hdr_len, frag_size);
+      PRINTFI("last_fragment?: processed_ip_in_len %d rime_payload_len %d frag_size %d\n",
+              processed_ip_in_len, packetbuf_datalen() - rime_hdr_len, frag_size);
 
-      if(processed_ip_len + packetbuf_datalen() - rime_hdr_len >= frag_size) {
+      if(processed_ip_in_len + packetbuf_datalen() - rime_hdr_len >= frag_size) {
         last_fragment = 1;
       }
       break;
@@ -1604,7 +1605,7 @@ input(void)
       break;
   }
 
-  if(processed_ip_len > 0) {
+  if(processed_ip_in_len > 0) {
     /* reassembly is ongoing */
     /*    printf("frag %d %d\n", reass_tag, frag_tag);*/
     if((frag_size > 0 &&
@@ -1690,22 +1691,22 @@ input(void)
   rime_payload_len = packetbuf_datalen() - rime_hdr_len;
   memcpy((uint8_t *)SICSLOWPAN_IP_BUF + uncomp_hdr_len + (uint16_t)(frag_offset << 3), rime_ptr + rime_hdr_len, rime_payload_len);
   
-  /* update processed_ip_len if fragment, sicslowpan_len otherwise */
+  /* update processed_ip_in_len if fragment, sicslowpan_len otherwise */
 
 #if SICSLOWPAN_CONF_FRAG
   if(frag_size > 0) {
     /* Add the size of the header only for the first fragment. */
     if(first_fragment != 0) {
-      processed_ip_len += uncomp_hdr_len;
+      processed_ip_in_len += uncomp_hdr_len;
     }
     /* For the last fragment, we are OK if there is extrenous bytes at
        the end of the packet. */
     if(last_fragment != 0) {
-      processed_ip_len = frag_size;
+      processed_ip_in_len = frag_size;
     } else {
-      processed_ip_len += rime_payload_len;
+      processed_ip_in_len += rime_payload_len;
     }
-    PRINTF("processed_ip_len %d, rime_payload_len %d\n", processed_ip_len, rime_payload_len);
+    PRINTF("processed_ip_in_len %d, rime_payload_len %d\n", processed_ip_in_len, rime_payload_len);
 
   } else {
 #endif /* SICSLOWPAN_CONF_FRAG */
@@ -1717,15 +1718,15 @@ input(void)
    * If we have a full IP packet in sicslowpan_buf, deliver it to
    * the IP stack
    */
-  PRINTF("sicslowpan_init processed_ip_len %d, sicslowpan_len %d\n",
-         processed_ip_len, sicslowpan_len);
-  if(processed_ip_len == 0 || (processed_ip_len == sicslowpan_len)) {
+  PRINTF("sicslowpan_init processed_ip_in_len %d, sicslowpan_len %d\n",
+         processed_ip_in_len, sicslowpan_len);
+  if(processed_ip_in_len == 0 || (processed_ip_in_len == sicslowpan_len)) {
     PRINTFI("sicslowpan input: IP packet ready (length %d)\n",
            sicslowpan_len);
     memcpy((uint8_t *)UIP_IP_BUF, (uint8_t *)SICSLOWPAN_IP_BUF, sicslowpan_len);
     uip_len = sicslowpan_len;
     sicslowpan_len = 0;
-    processed_ip_len = 0;
+    processed_ip_in_len = 0;
 #endif /* SICSLOWPAN_CONF_FRAG */
 
 #if DEBUG