295 lines
10 KiB
C
295 lines
10 KiB
C
/*
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* Copyright (c) 2010, Swedish Institute of Computer Science.
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. Neither the name of the Institute nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* This file is part of the Contiki operating system.
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*
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*/
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/**
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* \file
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* The Minimum Rank with Hysteresis Objective Function (MRHOF), RFC6719
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*
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* This implementation uses the estimated number of
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* transmissions (ETX) as the additive routing metric,
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* and also provides stubs for the energy metric.
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*
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* \author Joakim Eriksson <joakime@sics.se>, Nicolas Tsiftes <nvt@sics.se>
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* Simon Duquennoy <simon.duquennoy@inria.fr>
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*/
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/**
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* \addtogroup uip6
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* @{
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*/
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#include "net/rpl-lite/rpl.h"
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#include "net/nbr-table.h"
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#include "net/link-stats.h"
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/* Log configuration */
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#include "sys/log.h"
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#define LOG_MODULE "RPL"
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#define LOG_LEVEL LOG_LEVEL_RPL
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/* RFC6551 and RFC6719 do not mandate the use of a specific formula to
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* compute the ETX value. This MRHOF implementation relies on the value
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* computed by the link-stats module. It has an optional feature,
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* RPL_MRHOF_CONF_SQUARED_ETX, that consists in squaring this value.
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* This basically penalizes bad links while preserving the semantics of ETX
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* (1 = perfect link, more = worse link). As a result, MRHOF will favor
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* good links over short paths. Recommended when reliability is a priority.
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* Without this feature, a hop with 50% PRR (ETX=2) is equivalent to two
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* perfect hops with 100% PRR (ETX=1+1=2). With this feature, the former
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* path obtains ETX=2*2=4 and the former ETX=1*1+1*1=2. */
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#ifdef RPL_MRHOF_CONF_SQUARED_ETX
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#define RPL_MRHOF_SQUARED_ETX RPL_MRHOF_CONF_SQUARED_ETX
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#else /* RPL_MRHOF_CONF_SQUARED_ETX */
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#define RPL_MRHOF_SQUARED_ETX 1
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#endif /* RPL_MRHOF_CONF_SQUARED_ETX */
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/* Configuration parameters of RFC6719. Reject parents that have a higher
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* link metric than the following. The default value is 512. */
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#define MAX_LINK_METRIC 512 /* Eq ETX of 4 */
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/* Reject parents that have a higher path cost than the following. */
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#define MAX_PATH_COST 32768 /* Eq path ETX of 256 */
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#if !RPL_MRHOF_SQUARED_ETX
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/* Hysteresis of MRHOF: the rank must differ more than PARENT_SWITCH_THRESHOLD_DIV
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* in order to switch preferred parent. Default in RFC6719: 192, eq ETX of 1.5. */
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#define RANK_THRESHOLD 192 /* Eq ETX of 1.5 */
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#else /* !RPL_MRHOF_SQUARED_ETX */
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#define RANK_THRESHOLD 384 /* Eq ETX of sqrt(3) */
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#endif /* !RPL_MRHOF_SQUARED_ETX */
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/* Additional, custom hysteresis based on time. If a neighbor was consistently
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* better than our preferred parent for at least TIME_THRESHOLD, switch to
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* this neighbor regardless of RANK_THRESHOLD. */
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#define TIME_THRESHOLD (10 * 60 * CLOCK_SECOND)
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/*---------------------------------------------------------------------------*/
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static void
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reset(void)
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{
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LOG_INFO("reset MRHOF\n");
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}
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/*---------------------------------------------------------------------------*/
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static uint16_t
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nbr_link_metric(rpl_nbr_t *nbr)
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{
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const struct link_stats *stats = rpl_neighbor_get_link_stats(nbr);
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return stats != NULL ? stats->etx : 0xffff;
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}
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/*---------------------------------------------------------------------------*/
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static uint16_t
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link_metric_to_rank(uint16_t etx)
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{
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#if RPL_MRHOF_SQUARED_ETX
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uint32_t squared_etx = ((uint32_t)etx * etx) / LINK_STATS_ETX_DIVISOR;
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return (uint16_t)MIN(squared_etx, 0xffff);
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#else /* RPL_MRHOF_SQUARED_ETX */
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return etx;
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#endif /* RPL_MRHOF_SQUARED_ETX */
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}
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/*---------------------------------------------------------------------------*/
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static uint16_t
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nbr_path_cost(rpl_nbr_t *nbr)
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{
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uint16_t base;
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if(nbr == NULL) {
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return 0xffff;
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}
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#if RPL_WITH_MC
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/* Handle the different MC types */
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switch(curr_instance.mc.type) {
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case RPL_DAG_MC_ETX:
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base = nbr->mc.obj.etx;
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break;
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case RPL_DAG_MC_ENERGY:
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base = nbr->mc.obj.energy.energy_est << 8;
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break;
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default:
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base = nbr->rank;
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break;
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}
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#else /* RPL_WITH_MC */
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base = nbr->rank;
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#endif /* RPL_WITH_MC */
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/* path cost upper bound: 0xffff */
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return MIN((uint32_t)base + link_metric_to_rank(nbr_link_metric(nbr)), 0xffff);
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}
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/*---------------------------------------------------------------------------*/
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static rpl_rank_t
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rank_via_nbr(rpl_nbr_t *nbr)
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{
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uint16_t min_hoprankinc;
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uint16_t path_cost;
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if(nbr == NULL) {
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return RPL_INFINITE_RANK;
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}
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min_hoprankinc = curr_instance.min_hoprankinc;
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path_cost = nbr_path_cost(nbr);
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/* Rank lower-bound: nbr rank + min_hoprankinc */
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return MAX(MIN((uint32_t)nbr->rank + min_hoprankinc, RPL_INFINITE_RANK), path_cost);
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}
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/*---------------------------------------------------------------------------*/
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static int
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nbr_has_usable_link(rpl_nbr_t *nbr)
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{
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uint16_t link_metric = nbr_link_metric(nbr);
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/* Exclude links with too high link metrics */
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return link_metric <= MAX_LINK_METRIC;
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}
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/*---------------------------------------------------------------------------*/
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static int
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nbr_is_acceptable_parent(rpl_nbr_t *nbr)
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{
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uint16_t path_cost = nbr_path_cost(nbr);
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/* Exclude links with too high link metrics or path cost (RFC6719, 3.2.2) */
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return nbr_has_usable_link(nbr) && path_cost <= MAX_PATH_COST;
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}
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/*---------------------------------------------------------------------------*/
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static int
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within_hysteresis(rpl_nbr_t *nbr)
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{
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uint16_t path_cost = nbr_path_cost(nbr);
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uint16_t parent_path_cost = nbr_path_cost(curr_instance.dag.preferred_parent);
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int within_rank_hysteresis = path_cost + RANK_THRESHOLD > parent_path_cost;
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int within_time_hysteresis = nbr->better_parent_since == 0
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|| (clock_time() - nbr->better_parent_since) <= TIME_THRESHOLD;
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/* As we want to consider neighbors that are either beyond the rank or time
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hystereses, return 1 here iff the neighbor is within both hystereses. */
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return within_rank_hysteresis && within_time_hysteresis;
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}
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/*---------------------------------------------------------------------------*/
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static rpl_nbr_t *
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best_parent(rpl_nbr_t *nbr1, rpl_nbr_t *nbr2)
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{
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int nbr1_is_acceptable;
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int nbr2_is_acceptable;
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nbr1_is_acceptable = nbr1 != NULL && nbr_is_acceptable_parent(nbr1);
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nbr2_is_acceptable = nbr2 != NULL && nbr_is_acceptable_parent(nbr2);
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if(!nbr1_is_acceptable) {
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return nbr2_is_acceptable ? nbr2 : NULL;
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}
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if(!nbr2_is_acceptable) {
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return nbr1_is_acceptable ? nbr1 : NULL;
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}
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/* Maintain stability of the preferred parent. Switch only if the gain
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is greater than RANK_THRESHOLD, or if the neighbor has been better than the
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current parent for at more than TIME_THRESHOLD. */
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if(nbr1 == curr_instance.dag.preferred_parent && within_hysteresis(nbr2)) {
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return nbr1;
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}
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if(nbr2 == curr_instance.dag.preferred_parent && within_hysteresis(nbr1)) {
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return nbr2;
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}
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return nbr_path_cost(nbr1) < nbr_path_cost(nbr2) ? nbr1 : nbr2;
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}
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/*---------------------------------------------------------------------------*/
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#if !RPL_WITH_MC
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static void
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update_metric_container(void)
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{
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curr_instance.mc.type = RPL_DAG_MC_NONE;
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}
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#else /* RPL_WITH_MC */
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static void
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update_metric_container(void)
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{
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uint16_t path_cost;
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uint8_t type;
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if(!curr_instance.used) {
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LOG_WARN("cannot update the metric container when not joined\n");
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return;
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}
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if(curr_instance.dag.rank == ROOT_RANK) {
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/* Configure MC at root only, other nodes are auto-configured when joining */
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curr_instance.mc.type = RPL_DAG_MC;
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curr_instance.mc.flags = 0;
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curr_instance.mc.aggr = RPL_DAG_MC_AGGR_ADDITIVE;
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curr_instance.mc.prec = 0;
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path_cost = curr_instance.dag.rank;
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} else {
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path_cost = nbr_path_cost(curr_instance.dag.preferred_parent);
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}
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/* Handle the different MC types */
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switch(curr_instance.mc.type) {
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case RPL_DAG_MC_NONE:
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break;
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case RPL_DAG_MC_ETX:
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curr_instance.mc.length = sizeof(curr_instance.mc.obj.etx);
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curr_instance.mc.obj.etx = path_cost;
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break;
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case RPL_DAG_MC_ENERGY:
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curr_instance.mc.length = sizeof(curr_instance.mc.obj.energy);
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if(curr_instance.dag.rank == ROOT_RANK) {
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type = RPL_DAG_MC_ENERGY_TYPE_MAINS;
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} else {
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type = RPL_DAG_MC_ENERGY_TYPE_BATTERY;
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}
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curr_instance.mc.obj.energy.flags = type << RPL_DAG_MC_ENERGY_TYPE;
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/* Energy_est is only one byte, use the least significant byte of the path metric. */
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curr_instance.mc.obj.energy.energy_est = path_cost >> 8;
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break;
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default:
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LOG_WARN("MRHOF, non-supported MC %u\n", curr_instance.mc.type);
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break;
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}
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}
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#endif /* RPL_WITH_MC */
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/*---------------------------------------------------------------------------*/
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rpl_of_t rpl_mrhof = {
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reset,
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nbr_link_metric,
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nbr_has_usable_link,
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nbr_is_acceptable_parent,
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nbr_path_cost,
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rank_via_nbr,
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best_parent,
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update_metric_container,
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RPL_OCP_MRHOF
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};
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/** @}*/
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