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Novice

Wifi to Wifi lag

Whenever I try to ping from one Wifi device to another Wifi, I get high ping response times, and sometimes even some packet losses
Example:
PING 10.0.0.10 (10.0.0.10) 56(84) bytes of data.
64 bytes from 10.0.0.10: icmp_seq=1 ttl=64 time=245 ms
64 bytes from 10.0.0.10: icmp_seq=2 ttl=64 time=5.26 ms
64 bytes from 10.0.0.10: icmp_seq=3 ttl=64 time=287 ms
64 bytes from 10.0.0.10: icmp_seq=4 ttl=64 time=308 ms
64 bytes from 10.0.0.10: icmp_seq=5 ttl=64 time=229 ms
64 bytes from 10.0.0.10: icmp_seq=6 ttl=64 time=251 ms
64 bytes from 10.0.0.10: icmp_seq=7 ttl=64 time=5.16 ms
64 bytes from 10.0.0.10: icmp_seq=8 ttl=64 time=95.2 ms
64 bytes from 10.0.0.10: icmp_seq=9 ttl=64 time=218 ms
^C
--- 10.0.0.10 ping statistics ---
9 packets transmitted, 9 received, 0% packet loss, time 8010ms
rtt min/avg/max/mdev = 5.167/182.867/308.156/110.273 ms


All my wifi devices are connected through 5GHz.
Ping from Cable -> Cable, Wifi->Cable, Cable->Wifi, Cable->Internet, Wifi->Internet are all fine (eg. under 10 ms). I just can't seem to figure out why every ping from Wifi to Wifi is lagging.

I don't think I had this problem when I bought this router, so I suspect it came with an firmware update. Is there any way to get back to an old firmware?
Message 1 of 9
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Virtuoso

Re: Wifi to Wifi lag

Wifi does not perform like wired on how the traffic flow

When one device send request first it has to go first then second device. That is when you have single wifi device and on single wired device has less in ping.
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Message 2 of 9
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Novice

Re: Wifi to Wifi lag

I agree it should take longer from wifi to wifi, but I'd expect it to be around 20 ms given wifi to cable is less than 10 ms. Do you also get 200+ ms on wifi to wifi pings?
Message 3 of 9
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Retired_Member
Not applicable

Re: Wifi to Wifi lag

Responding to ping request is not a priority. Traffic other than the ping request will causes the ping times to increase. I pinged my iPhone and they were all over, this test doesn't mean squat because I don't know what iphone traffic was occurring during ping.
Message 4 of 9
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Novice

Re: Wifi to Wifi lag

That makes sense, but I noticed this problem due to serious delays with keystrokes in SSH. SSH should work normally, right?
Message 5 of 9
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Retired_Member
Not applicable

Re: Wifi to Wifi lag

Not familiar with SSH.

I would ping router only using some ping program like meta ping to get an idea of what's happening. Then ping as you were with WAN port disconnected
Message 6 of 9
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Mentor

Re: Wifi to Wifi lag

If I might, I'd like to explain how two devices both on the same WiFi network communicate with one another.

First - WiFi communication is what is known as "half duplex" - data can only flow in one direction at a time - transmit or receive; second, if the network is an "infrastructure network" or built around an access point (or router), then all other WiFi devices can only communicate with the access point, they do not communicate directly with one another; and finally WiFi uses CSMA/CA - Carrier Sense Multiple Access with Collision Avoidance - what this means is that before a device can transmit, it must first request permission from the access point to transmit and wait for that permission to be granted, and before granting permission, the access point must allow prior requests to be completed.

What does all this mean for your ping times - well - device #1 needs to send a ping request to device #2- device #1 must first request permission to send the ping request, which will go to the access point or router, the access point or router will then relay the ping request to device #2, and when device #2 receives the ping request, it needs to request channel access before sending the ping response, which of course goes back to the access point to be relayed.

We're talking four separate transmissions intermingled with other WiFi network traffic in order to achieve a single ping - and you can expect the delays in receiving clearance to send to vary based on what other requests the access point is dealing with at any given time.

I recognize that not everyone shares my point of view, and that for some users it may not be an option - but - having implemented wireless networks from the 802.11 days (note the lack of an alpha character at the end - I'm talking the days of 1mbps FHSS), it is my contention that WiFi should be used for convenience and mobility - if what you need is a robust, reliable network, then wired is the only way to achieve it.

If wired is not an option, then the users need to be aware of the limitations of wireless and accept that they have to live with them.

Give a man a fish, feed him for a day
Teach a man to fish, feed him for life.
Message 7 of 9
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Retired_Member
Not applicable

Re: Wifi to Wifi lag

I agree with you.

Would you expect better results if one is on 2.4 another on 5g on same router?
Message 8 of 9
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Novice

Re: Wifi to Wifi lag

Just to clear this up, after all I did fix it. It turned out there was a bittorrent client running with a port opened with UPnP. Apparently there were hundreds of connections per second made from outside, which caused this massive lag. Haven't figured out why it only occured on wifi to wifi, but atleast I get consistent around 5-6 ms for wifi to wifi ping.
Message 9 of 9
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