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weird packet latency pattern in 802.11b/g network
I sent 56 ICMP "echo request" messages to Wi-Fi host 1.1.1.1. This Wi-Fi host is connected to Cisco HWIC-AP-G-E module(ATHEROS AR5212 chipset). I saw weird pattern where RTT increased roughly ten probes in a row up to ~200ms and then fell to 30-40ms:
What might cause such pattern in 802.11b/g network?
$ ping 1.1.1.1 PING 1.1.1.1 (1.1.1.1): 56 data bytes 64 bytes from 1.1.1.1: icmp_seq=0 ttl=62 time=42.345 ms 64 bytes from 1.1.1.1: icmp_seq=1 ttl=62 time=64.187 ms 64 bytes from 1.1.1.1: icmp_seq=2 ttl=62 time=83.226 ms 64 bytes from 1.1.1.1: icmp_seq=3 ttl=62 time=102.768 ms 64 bytes from 1.1.1.1: icmp_seq=4 ttl=62 time=122.405 ms 64 bytes from 1.1.1.1: icmp_seq=5 ttl=62 time=141.941 ms 64 bytes from 1.1.1.1: icmp_seq=6 ttl=62 time=162.047 ms 64 bytes from 1.1.1.1: icmp_seq=7 ttl=62 time=183.152 ms 64 bytes from 1.1.1.1: icmp_seq=8 ttl=62 time=202.968 ms 64 bytes from 1.1.1.1: icmp_seq=9 ttl=62 time=224.488 ms 64 bytes from 1.1.1.1: icmp_seq=10 ttl=62 time=40.075 ms 64 bytes from 1.1.1.1: icmp_seq=11 ttl=62 time=63.076 ms 64 bytes from 1.1.1.1: icmp_seq=12 ttl=62 time=79.109 ms 64 bytes from 1.1.1.1: icmp_seq=13 ttl=62 time=99.468 ms 64 bytes from 1.1.1.1: icmp_seq=14 ttl=62 time=120.607 ms 64 bytes from 1.1.1.1: icmp_seq=15 ttl=62 time=139.617 ms 64 bytes from 1.1.1.1: icmp_seq=16 ttl=62 time=158.462 ms 64 bytes from 1.1.1.1: icmp_seq=17 ttl=62 time=180.476 ms 64 bytes from 1.1.1.1: icmp_seq=18 ttl=62 time=200.307 ms 64 bytes from 1.1.1.1: icmp_seq=19 ttl=62 time=20.401 ms 64 bytes from 1.1.1.1: icmp_seq=20 ttl=62 time=35.428 ms 64 bytes from 1.1.1.1: icmp_seq=21 ttl=62 time=55.589 ms 64 bytes from 1.1.1.1: icmp_seq=22 ttl=62 time=75.333 ms 64 bytes from 1.1.1.1: icmp_seq=23 ttl=62 time=95.616 ms 64 bytes from 1.1.1.1: icmp_seq=24 ttl=62 time=116.199 ms 64 bytes from 1.1.1.1: icmp_seq=25 ttl=62 time=134.037 ms 64 bytes from 1.1.1.1: icmp_seq=26 ttl=62 time=157.362 ms 64 bytes from 1.1.1.1: icmp_seq=27 ttl=62 time=176.666 ms 64 bytes from 1.1.1.1: icmp_seq=28 ttl=62 time=196.508 ms 64 bytes from 1.1.1.1: icmp_seq=29 ttl=62 time=216.330 ms 64 bytes from 1.1.1.1: icmp_seq=30 ttl=62 time=30.836 ms 64 bytes from 1.1.1.1: icmp_seq=31 ttl=62 time=51.957 ms 64 bytes from 1.1.1.1: icmp_seq=32 ttl=62 time=75.002 ms 64 bytes from 1.1.1.1: icmp_seq=33 ttl=62 time=94.021 ms 64 bytes from 1.1.1.1: icmp_seq=34 ttl=62 time=115.137 ms 64 bytes from 1.1.1.1: icmp_seq=35 ttl=62 time=136.995 ms 64 bytes from 1.1.1.1: icmp_seq=36 ttl=62 time=157.255 ms 64 bytes from 1.1.1.1: icmp_seq=37 ttl=62 time=180.336 ms 64 bytes from 1.1.1.1: icmp_seq=38 ttl=62 time=198.927 ms 64 bytes from 1.1.1.1: icmp_seq=39 ttl=62 time=217.718 ms 64 bytes from 1.1.1.1: icmp_seq=40 ttl=62 time=32.990 ms 64 bytes from 1.1.1.1: icmp_seq=41 ttl=62 time=53.585 ms 64 bytes from 1.1.1.1: icmp_seq=42 ttl=62 time=72.187 ms 64 bytes from 1.1.1.1: icmp_seq=43 ttl=62 time=92.462 ms 64 bytes from 1.1.1.1: icmp_seq=44 ttl=62 time=114.281 ms 64 bytes from 1.1.1.1: icmp_seq=45 ttl=62 time=132.550 ms 64 bytes from 1.1.1.1: icmp_seq=46 ttl=62 time=153.643 ms 64 bytes from 1.1.1.1: icmp_seq=47 ttl=62 time=173.002 ms 64 bytes from 1.1.1.1: icmp_seq=48 ttl=62 time=193.547 ms 64 bytes from 1.1.1.1: icmp_seq=49 ttl=62 time=15.845 ms 64 bytes from 1.1.1.1: icmp_seq=50 ttl=62 time=232.469 ms 64 bytes from 1.1.1.1: icmp_seq=51 ttl=62 time=47.776 ms 64 bytes from 1.1.1.1: icmp_seq=52 ttl=62 time=68.854 ms 64 bytes from 1.1.1.1: icmp_seq=53 ttl=62 time=89.947 ms 64 bytes from 1.1.1.1: icmp_seq=54 ttl=62 time=107.487 ms 64 bytes from 1.1.1.1: icmp_seq=55 ttl=62 time=128.250 ms ^C --- 1.1.1.1 ping statistics --- 56 packets transmitted, 56 packets received, 0.0% packet loss round-trip min/avg/max/stddev = 15.845/118.880/232.469/59.108 ms $
What might cause such pattern in 802.11b/g network?
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Jackace
Member Posts: 335
I am no wireless expert, but my first guess would be collisions/retransmits causing such a varied latency.