Modified the default RPL probing selection process. Will now probe the least recently updated parent from time to time
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1 changed files with 32 additions and 25 deletions
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@ -331,18 +331,17 @@ rpl_cancel_dao(rpl_instance_t *instance)
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static rpl_parent_t *
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get_probing_target(rpl_dag_t *dag)
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{
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/* Returns the next probing target. The current implementation looks for the
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* best parent to which we have not transmitted since 2 * RPL_PROBING_INTERVAL.
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* This will mostly select the preferred and second best parents. Probing the
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* second best parent is important: if the link is good, RPL might choose to
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* switch to it. If the link is bad, the second best parent will decrease in
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* ranking, and another parent will be probed next time. */
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/* Returns the next probing target. The current implementation probes the current
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* preferred parent if we have not updated its link for 2 * RPL_PROBING_INTERVAL.
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* Otherwise, it picks at random between:
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* (1) selecting the best parent not updated for 2 * RPL_PROBING_INTERVAL
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* (2) selecting the least recently updated parent
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*/
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rpl_parent_t *p;
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rpl_parent_t *probing_target;
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rpl_rank_t probing_target_rank;
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/* Look for a parent we have not sent to since 2 * RPL_PROBING_INTERVAL,
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* e.g. with last_tx_time earlier than min_last_tx */
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rpl_parent_t *probing_target = NULL;
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rpl_rank_t probing_target_rank = INFINITE_RANK;
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/* min_last_tx is the clock time (2 * RPL_PROBING_INTERVAL) in the past */
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clock_time_t min_last_tx = clock_time();
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min_last_tx = min_last_tx > 2 * RPL_PROBING_INTERVAL ? min_last_tx - 2 * RPL_PROBING_INTERVAL : 1;
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@ -357,26 +356,34 @@ get_probing_target(rpl_dag_t *dag)
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return dag->preferred_parent;
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}
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/* Look for the best parent that needs probing. */
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probing_target = NULL;
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probing_target_rank = INFINITE_RANK;
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p = nbr_table_head(rpl_parents);
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while(p != NULL) {
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if(p->dag == dag && p->last_tx_time < min_last_tx) {
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rpl_rank_t p_rank = dag->instance->of->calculate_rank(p, 0);
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/* p is in our dag and needs probing */
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if(probing_target == NULL) {
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probing_target = p;
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probing_target_rank = p_rank;
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} else {
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if(p_rank < probing_target_rank) {
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/* Found better candidate */
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if((random_rand() % 2) == 0) {
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/* With 1/2 probability: probe best parent not updated for 2 * RPL_PROBING_INTERVAL */
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p = nbr_table_head(rpl_parents);
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while(p != NULL) {
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if(p->dag == dag && p->last_tx_time < min_last_tx) {
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/* p is in our dag and needs probing */
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rpl_rank_t p_rank = dag->instance->of->calculate_rank(p, 0);
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if(probing_target == NULL
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|| p_rank < probing_target_rank) {
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probing_target = p;
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probing_target_rank = p_rank;
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}
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}
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p = nbr_table_next(rpl_parents, p);
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}
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p = nbr_table_next(rpl_parents, p);
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} else {
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/* With 1/2 probability: probe the least recently updated parent */
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p = nbr_table_head(rpl_parents);
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while(p != NULL) {
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if(p->dag == dag) {
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if(probing_target == NULL
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|| p->last_tx_time < probing_target->last_tx_time) {
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probing_target = p;
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}
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}
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p = nbr_table_next(rpl_parents, p);
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}
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}
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return probing_target;
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