Ola Liljedahl
New Around Here
I have intermittent problems with multisecond RTT latencies on my wifi network. It seems like packets get stuck for multiple seconds and then after a while show up. It's not only pings, other traffic as well. My ssh sessions from a wireless client to a wired machine (Ethernet to the router/AP) also hang during these "occurrences".
Pinging from a Dell XPS 13 running Linux Mint to my Archer C7 V2 router:
64 bytes from 192.168.1.1: icmp_seq=303 ttl=64 time=9575 ms
64 bytes from 192.168.1.1: icmp_seq=304 ttl=64 time=8576 ms
64 bytes from 192.168.1.1: icmp_seq=305 ttl=64 time=7576 ms
64 bytes from 192.168.1.1: icmp_seq=306 ttl=64 time=6576 ms
64 bytes from 192.168.1.1: icmp_seq=307 ttl=64 time=5576 ms
64 bytes from 192.168.1.1: icmp_seq=309 ttl=64 time=3576 ms
64 bytes from 192.168.1.1: icmp_seq=310 ttl=64 time=2576 ms
64 bytes from 192.168.1.1: icmp_seq=311 ttl=64 time=1576 ms
64 bytes from 192.168.1.1: icmp_seq=312 ttl=64 time=594 ms
64 bytes from 192.168.1.1: icmp_seq=313 ttl=64 time=1.63 ms
64 bytes from 192.168.1.1: icmp_seq=314 ttl=64 time=2.02 ms
See the pattern? Ping transmits a packet every second. 9 of them get stuck somewhere. Then all of them (bar one in this case, #308 is missing) are suddenly "released" and received by the client. After that I get the expected latency. Sometimes the pings (requests or replies) are also lost.
I originally had a TP-LINK TL-WR1043ND V1.8 (w. latest firmware). It showed the same problem (pinging from a Samsung ChromeBook 2 (ARM) running ChromeOS). I thought it was a software problem so installed OpenWRT on the 1043ND. The problem did not go away. OK maybe it is a hardware problem. Thus I bought the Archer C7 V2 (one of the few 802.11ac router/AP with OpenWRT support, I liked OpenWRT and plan to install it later). Upgraded to the latest stock firmware. Pinging the AP from the XPS13 machine. Same problem.
So I have tested with different router HW and SW and with different clients but the problem persists. It seems to happen (more frequently or only?) and with worse latency when there are other heavy wifi users (e.g. someone streaming youtube to a tablet, this happens a lot). I can understand that that should cause more latency and jitter, I sometimes see that type of behaviour from ping (intermittent random latencies up to 200ms). But not the above very regular behaviour.
It happened again! This time I was pinging a machine (192.168.1.2) connected to the router (192.168.1.1) using Ethernet (wireless client -> AP ->(Ethernet) 192.168.1.2 and back) so the router is just forwarding the packets between wireless and wired networks. I assume this is done in SW and not automatically by the switch in the router.
olli@xps13 ~ $ iwconfig
lo no wireless extensions.
wlan0 IEEE 802.11abgn ESSID:"olli"
Mode:Managed Frequency:2.437 GHz Access Point: XXXXXXXXXXXX
Bit Rate=39 Mb/s Tx-Power=16 dBm
Retry long limit:7 RTS thrff Fragment thrff
Power Managementn
Link Quality=40/70 Signal level=-70 dBm
Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0
Tx excessive retries:0 Invalid misc:310 Missed beacon:0
olli@xps13 ~ $ ping 192.168.1.2
PING 192.168.1.2 (192.168.1.2) 56(84) bytes of data.
64 bytes from 192.168.1.2: icmp_seq=1 ttl=64 time=4036 ms
64 bytes from 192.168.1.2: icmp_seq=2 ttl=64 time=3029 ms
64 bytes from 192.168.1.2: icmp_seq=3 ttl=64 time=2024 ms
64 bytes from 192.168.1.2: icmp_seq=4 ttl=64 time=1018 ms
64 bytes from 192.168.1.2: icmp_seq=5 ttl=64 time=13.2 ms
64 bytes from 192.168.1.2: icmp_seq=6 ttl=64 time=3.77 ms
^C
--- 192.168.1.2 ping statistics ---
6 packets transmitted, 6 received, 0% packet loss, time 5031ms
rtt min/avg/max/mdev = 3.777/1687.749/4036.380/1501.003 ms, pipe 5
olli@xps13 ~ $ iwconfig
lo no wireless extensions.
wlan0 IEEE 802.11abgn ESSID:"olli"
Mode:Managed Frequency:2.437 GHz Access Point: XXXXXXXXXXXX
Bit Rate=52 Mb/s Tx-Power=16 dBm
Retry long limit:7 RTS thrff Fragment thrff
Power Managementn
Link Quality=41/70 Signal level=-69 dBm
Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0
Tx excessive retries:0 Invalid misc:310 Missed beacon:0
See anything strange?
Pinging from a Dell XPS 13 running Linux Mint to my Archer C7 V2 router:
64 bytes from 192.168.1.1: icmp_seq=303 ttl=64 time=9575 ms
64 bytes from 192.168.1.1: icmp_seq=304 ttl=64 time=8576 ms
64 bytes from 192.168.1.1: icmp_seq=305 ttl=64 time=7576 ms
64 bytes from 192.168.1.1: icmp_seq=306 ttl=64 time=6576 ms
64 bytes from 192.168.1.1: icmp_seq=307 ttl=64 time=5576 ms
64 bytes from 192.168.1.1: icmp_seq=309 ttl=64 time=3576 ms
64 bytes from 192.168.1.1: icmp_seq=310 ttl=64 time=2576 ms
64 bytes from 192.168.1.1: icmp_seq=311 ttl=64 time=1576 ms
64 bytes from 192.168.1.1: icmp_seq=312 ttl=64 time=594 ms
64 bytes from 192.168.1.1: icmp_seq=313 ttl=64 time=1.63 ms
64 bytes from 192.168.1.1: icmp_seq=314 ttl=64 time=2.02 ms
See the pattern? Ping transmits a packet every second. 9 of them get stuck somewhere. Then all of them (bar one in this case, #308 is missing) are suddenly "released" and received by the client. After that I get the expected latency. Sometimes the pings (requests or replies) are also lost.
I originally had a TP-LINK TL-WR1043ND V1.8 (w. latest firmware). It showed the same problem (pinging from a Samsung ChromeBook 2 (ARM) running ChromeOS). I thought it was a software problem so installed OpenWRT on the 1043ND. The problem did not go away. OK maybe it is a hardware problem. Thus I bought the Archer C7 V2 (one of the few 802.11ac router/AP with OpenWRT support, I liked OpenWRT and plan to install it later). Upgraded to the latest stock firmware. Pinging the AP from the XPS13 machine. Same problem.
So I have tested with different router HW and SW and with different clients but the problem persists. It seems to happen (more frequently or only?) and with worse latency when there are other heavy wifi users (e.g. someone streaming youtube to a tablet, this happens a lot). I can understand that that should cause more latency and jitter, I sometimes see that type of behaviour from ping (intermittent random latencies up to 200ms). But not the above very regular behaviour.
It happened again! This time I was pinging a machine (192.168.1.2) connected to the router (192.168.1.1) using Ethernet (wireless client -> AP ->(Ethernet) 192.168.1.2 and back) so the router is just forwarding the packets between wireless and wired networks. I assume this is done in SW and not automatically by the switch in the router.
olli@xps13 ~ $ iwconfig
lo no wireless extensions.
wlan0 IEEE 802.11abgn ESSID:"olli"
Mode:Managed Frequency:2.437 GHz Access Point: XXXXXXXXXXXX
Bit Rate=39 Mb/s Tx-Power=16 dBm
Retry long limit:7 RTS thrff Fragment thrff
Power Managementn
Link Quality=40/70 Signal level=-70 dBm
Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0
Tx excessive retries:0 Invalid misc:310 Missed beacon:0
olli@xps13 ~ $ ping 192.168.1.2
PING 192.168.1.2 (192.168.1.2) 56(84) bytes of data.
64 bytes from 192.168.1.2: icmp_seq=1 ttl=64 time=4036 ms
64 bytes from 192.168.1.2: icmp_seq=2 ttl=64 time=3029 ms
64 bytes from 192.168.1.2: icmp_seq=3 ttl=64 time=2024 ms
64 bytes from 192.168.1.2: icmp_seq=4 ttl=64 time=1018 ms
64 bytes from 192.168.1.2: icmp_seq=5 ttl=64 time=13.2 ms
64 bytes from 192.168.1.2: icmp_seq=6 ttl=64 time=3.77 ms
^C
--- 192.168.1.2 ping statistics ---
6 packets transmitted, 6 received, 0% packet loss, time 5031ms
rtt min/avg/max/mdev = 3.777/1687.749/4036.380/1501.003 ms, pipe 5
olli@xps13 ~ $ iwconfig
lo no wireless extensions.
wlan0 IEEE 802.11abgn ESSID:"olli"
Mode:Managed Frequency:2.437 GHz Access Point: XXXXXXXXXXXX
Bit Rate=52 Mb/s Tx-Power=16 dBm
Retry long limit:7 RTS thrff Fragment thrff
Power Managementn
Link Quality=41/70 Signal level=-69 dBm
Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0
Tx excessive retries:0 Invalid misc:310 Missed beacon:0
See anything strange?