#!/bin/bash
# https://github.com/tohojo/sqm-scripts
# adapt for small/slow link
UPLINK=1000 # in kbps
DOWNLINK=2000 # in kbps
MTU=1500 # default ethernet 1500
get_target_interval() {
# for ATM the worst case expansion including overhead seems to be 33 clls of
# 53 bytes each, max delay in us at 1kbps
MAX_DELAY=$((1000 * 1000 * 33 * 53 * 8 / 1000))
TARGET=$((MAX_DELAY / $2))
# do not change anything for fast links
if [ "$TARGET" -lt 5000 ]; then
TARGET=5000
fi
INTERVAL=$(((100 - 5) * 1000 + TARGET))
echo "target $1 = $((TARGET / 1000))"
echo "interval $1 = $((INTERVAL / 1000))"
}
get_quantum() {
SHAPER_BURST_US=1000 # default duration of the burst in us
# lets assume ATM/AAL5 to be the worst case encapsulation
# and 48 Bytes a reasonable worst case per packet overhead
# for MTU 1489 to 1536 this will result in MIN_BURST = 1749 Bytes
MIN_BURST=$((MTU + 48))
MIN_BURST=$((MIN_BURST + 47))
MIN_BURST=$((MIN_BURST / 48))
MIN_BURST=$((MIN_BURST * 53))
# htb/tbf expect burst to be specified in bytes, while bandwidth is in kbps
BURST=$((((SHAPER_BURST_US * $2) / 8000)))
if [ ${BURST} -lt ${MIN_BURST} ]; then
BURST=${MIN_BURST}
fi
echo "quantum $1 = ${BURST}"
}
get_limit() {
LIMIT=10240 # default limit
# limits are tuned towards a <10Mb uplink <60Mb downlink
if [ "$2" -lt "10000" ] && [ "$1" = "UPLOAD" ]; then
LIMIT=1001
elif [ "$2" -lt "60000" ] && [ "$1" = "DOWNLOAD" ]; then
LIMIT=1001
fi
echo "limit $1 = ${LIMIT}"
}
get_target_interval "UPLOAD" ${UPLINK}
get_quantum "UPLOAD" ${UPLINK}
get_limit "UPLOAD" ${UPLINK}
get_target_interval "DOWNLOAD" ${DOWNLINK}
get_quantum "DOWNLOAD" ${DOWNLINK}
get_limit "DOWNLOAD" ${DOWNLINK}
