diff --git a/core/net/rpl/rpl-dag.c b/core/net/rpl/rpl-dag.c
index e103d65f9..08178d5ad 100644
--- a/core/net/rpl/rpl-dag.c
+++ b/core/net/rpl/rpl-dag.c
@@ -987,7 +987,7 @@ rpl_add_dag(uip_ipaddr_t *from, rpl_dio_t *dio)
      instance->dio_redundancy != dio->dag_redund ||
      instance->default_lifetime != dio->default_lifetime ||
      instance->lifetime_unit != dio->lifetime_unit) {
-    PRINTF("RPL: DIO for DAG instance %u uncompatible with previos DIO\n",
+    PRINTF("RPL: DIO for DAG instance %u incompatible with previous DIO\n",
 	   dio->instance_id);
     rpl_remove_parent(p);
     dag->used = 0;
@@ -1171,7 +1171,7 @@ rpl_process_dio(uip_ipaddr_t *from, rpl_dio_t *dio)
 	RPL_LOLLIPOP_INCREMENT(dag->version);
 	rpl_reset_dio_timer(instance);
       } else {
-        PRINTF("RPL: Global Repair\n");
+        PRINTF("RPL: Global repair\n");
         if(dio->prefix_info.length != 0) {
           if(dio->prefix_info.flags & UIP_ND6_RA_FLAG_AUTONOMOUS) {
             PRINTF("RPL : Prefix announced in DIO\n");
diff --git a/core/net/rpl/rpl-icmp6.c b/core/net/rpl/rpl-icmp6.c
index c1cc6060b..a34eb06aa 100644
--- a/core/net/rpl/rpl-icmp6.c
+++ b/core/net/rpl/rpl-icmp6.c
@@ -176,12 +176,14 @@ dis_output(uip_ipaddr_t *addr)
   unsigned char *buffer;
   uip_ipaddr_t tmpaddr;
 
-  /* DAG Information Solicitation  - 2 bytes reserved      */
-  /*      0                   1                   2        */
-  /*      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3  */
-  /*     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ */
-  /*     |     Flags     |   Reserved    |   Option(s)...  */
-  /*     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ */
+  /*
+   * DAG Information Solicitation  - 2 bytes reserved
+   *      0                   1                   2
+   *      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3
+   *     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+   *     |     Flags     |   Reserved    |   Option(s)...
+   *     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+   */
 
   buffer = UIP_ICMP_PAYLOAD;
   buffer[0] = buffer[1] = 0;
@@ -241,7 +243,7 @@ dio_input(void)
       PRINTLLADDR((uip_lladdr_t *)packetbuf_addr(PACKETBUF_ADDR_SENDER));
       PRINTF("\n");
     } else {
-      PRINTF("RPL: Out of Memory, dropping DIO from ");
+      PRINTF("RPL: Out of memory, dropping DIO from ");
       PRINT6ADDR(&from);
       PRINTF(", ");
       PRINTLLADDR((uip_lladdr_t *)packetbuf_addr(PACKETBUF_ADDR_SENDER));
@@ -383,7 +385,7 @@ dio_input(void)
       break;
     case RPL_OPTION_PREFIX_INFO:
       if(len != 32) {
-        PRINTF("RPL: DAG prefix info not ok, len != 32\n");
+        PRINTF("RPL: Invalid DAG prefix info, len != 32\n");
 	RPL_STAT(rpl_stats.malformed_msgs++);
         return;
       }
@@ -420,7 +422,7 @@ dio_output(rpl_instance_t *instance, uip_ipaddr_t *uc_addr)
 #endif /* !RPL_LEAF_ONLY */
 
 #if RPL_LEAF_ONLY
-  /* In leaf mode, we send DIO message only as unicasts in response to 
+  /* In leaf mode, we only send DIO messages as unicasts in response to 
      unicast DIS messages. */
   if(uc_addr == NULL) {
     PRINTF("RPL: LEAF ONLY have multicast addr: skip dio_output\n");
@@ -583,10 +585,11 @@ dao_input(void)
   int len;
   int i;
   int learned_from;
-  rpl_parent_t *p;
+  rpl_parent_t *parent;
   uip_ds6_nbr_t *nbr;
 
   prefixlen = 0;
+  parent = NULL;
 
   uip_ipaddr_copy(&dao_sender_addr, &UIP_IP_BUF->srcipaddr);
 
@@ -616,15 +619,13 @@ dao_input(void)
   sequence = buffer[pos++];
 
   dag = instance->current_dag;
-  /* Is the DAGID present? */
+  /* Is the DAG ID present? */
   if(flags & RPL_DAO_D_FLAG) {
     if(memcmp(&dag->dag_id, &buffer[pos], sizeof(dag->dag_id))) {
       PRINTF("RPL: Ignoring a DAO for a DAG different from ours\n");
       return;
     }
     pos += 16;
-  } else {
-    /* Perhaps, there are verification to do but ... */
   }
 
   learned_from = uip_is_addr_mcast(&dao_sender_addr) ?
@@ -634,23 +635,23 @@ dao_input(void)
          learned_from == RPL_ROUTE_FROM_UNICAST_DAO? "unicast": "multicast");
   if(learned_from == RPL_ROUTE_FROM_UNICAST_DAO) {
     /* Check whether this is a DAO forwarding loop. */
-    p = rpl_find_parent(dag, &dao_sender_addr);
+    parent = rpl_find_parent(dag, &dao_sender_addr);
     /* check if this is a new DAO registration with an "illegal" rank */
     /* if we already route to this node it is likely */
-    if(p != NULL &&
-       DAG_RANK(p->rank, instance) < DAG_RANK(dag->rank, instance)) {
+    if(parent != NULL &&
+       DAG_RANK(parent->rank, instance) < DAG_RANK(dag->rank, instance)) {
       PRINTF("RPL: Loop detected when receiving a unicast DAO from a node with a lower rank! (%u < %u)\n",
-          DAG_RANK(p->rank, instance), DAG_RANK(dag->rank, instance));
-      p->rank = INFINITE_RANK;
-      p->updated = 1;
+          DAG_RANK(parent->rank, instance), DAG_RANK(dag->rank, instance));
+      parent->rank = INFINITE_RANK;
+      parent->updated = 1;
       return;
     }
 
     /* If we get the DAO from our parent, we also have a loop. */
-    if(p != NULL && p == dag->preferred_parent) {
+    if(parent != NULL && parent == dag->preferred_parent) {
       PRINTF("RPL: Loop detected when receiving a unicast DAO from our parent\n");
-      p->rank = INFINITE_RANK;
-      p->updated = 1;
+      parent->rank = INFINITE_RANK;
+      parent->updated = 1;
       return;
     }
   }
@@ -756,7 +757,7 @@ dao_input(void)
     PRINTF("RPL: Neighbor already in neighbor cache\n");
   }
 
-  rpl_lock_parent(p);
+  rpl_lock_parent(parent);
 
   rep = rpl_add_route(dag, &prefix, prefixlen, &dao_sender_addr);
   if(rep == NULL) {
diff --git a/core/net/rpl/rpl-mrhof.c b/core/net/rpl/rpl-mrhof.c
index 9d75f319b..634bec763 100644
--- a/core/net/rpl/rpl-mrhof.c
+++ b/core/net/rpl/rpl-mrhof.c
@@ -104,7 +104,7 @@ calculate_path_metric(rpl_parent_t *p)
 }
 
 static void
-reset(rpl_dag_t *sag)
+reset(rpl_dag_t *dag)
 {
   PRINTF("RPL: Reset MRHOF\n");
 }
diff --git a/core/net/rpl/rpl-private.h b/core/net/rpl/rpl-private.h
index 0df8a91ca..943ef1db8 100644
--- a/core/net/rpl/rpl-private.h
+++ b/core/net/rpl/rpl-private.h
@@ -203,7 +203,7 @@
  * whose integer part can be obtained by dividing the value by 
  * RPL_DAG_MC_ETX_DIVISOR.
  */
-#define RPL_DAG_MC_ETX_DIVISOR		128
+#define RPL_DAG_MC_ETX_DIVISOR		256
 
 /* DIS related */
 #define RPL_DIS_SEND                    1
diff --git a/core/net/rpl/rpl-timers.c b/core/net/rpl/rpl-timers.c
index b4c25df19..d2ff5c97f 100644
--- a/core/net/rpl/rpl-timers.c
+++ b/core/net/rpl/rpl-timers.c
@@ -70,7 +70,7 @@ handle_periodic_timer(void *ptr)
   rpl_recalculate_ranks();
 
   /* handle DIS */
-#ifdef RPL_DIS_SEND
+#if RPL_DIS_SEND
   next_dis++;
   if(rpl_get_any_dag() == NULL && next_dis >= RPL_DIS_INTERVAL) {
     next_dis = 0;
diff --git a/core/net/rpl/rpl.c b/core/net/rpl/rpl.c
index 9fca4c28e..c1384b0b6 100644
--- a/core/net/rpl/rpl.c
+++ b/core/net/rpl/rpl.c
@@ -308,6 +308,8 @@ rpl_init(void)
 #if RPL_CONF_STATS
   memset(&rpl_stats, 0, sizeof(rpl_stats));
 #endif
+
+  RPL_OF.reset(NULL);
 }
 /*---------------------------------------------------------------------------*/
 #endif /* UIP_CONF_IPV6 */
diff --git a/core/net/rpl/rpl.h b/core/net/rpl/rpl.h
index 562961d84..76134e44e 100644
--- a/core/net/rpl/rpl.h
+++ b/core/net/rpl/rpl.h
@@ -189,6 +189,9 @@ struct rpl_of {
   rpl_ocp_t ocp;
 };
 typedef struct rpl_of rpl_of_t;
+
+/* Declare the selected objective function. */
+extern rpl_of_t RPL_OF;
 /*---------------------------------------------------------------------------*/
 /* Instance */
 struct rpl_instance {