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WRT54GL Abnormal Lag Spikes

Discussion in 'Tomato Firmware' started by rmdec, Sep 23, 2010.

  1. rmdec

    rmdec Serious Server Member

    Hi, I have a WRT54GL v1.1. I am posting this in the Tomato Firmware forum because it is the current firmware I have on it. I have been through default Linksys firmware, DD-WRT as well. My wireless network has some strange lag issues that I hope someone can shed light on. If I do a ping 192.168.1.1 -t while on wireless, I get 80% <1-2ms, 15% ~15ms, and 5% 30-300ms.
    I have been checking on many forums and cannot find a problem that looks like this. I've been through several firmwares, 30/30/30 between each change. I've played around with almost every single setting on/off including Frameburst, CTS, STP, etc. Wired connection has no problem. Other routers all ping 1ms consistently. I've tried channels from 1 - 11. I've given everything a shot and I'm about to settle on the fact that I have defective router/antennae. If anyone sees something that I've missed or has an idea what kind of problem this could be, please respond.
  2. FattysGoneWild

    FattysGoneWild Addicted to LI Member

    Sounds like you know what you are doing and done good troubleshooting. I would say the router is defective.
  3. rmdec

    rmdec Serious Server Member

    Ok I changed back to DD WRT and set the clock speed down to 183. Disabled CTS again, and now its very slightly better (i think, could be wishful thinking). Can anyone tell from this whats could be causing the frequent spiking. I want to know for sure this isn't fixable before shipping it back to Newegg.

    Pinging 192.168.1.1 with 32 bytes of data:
    Reply from 192.168.1.1: bytes=32 time=1ms TTL=64
    Reply from 192.168.1.1: bytes=32 time=1ms TTL=64
    Reply from 192.168.1.1: bytes=32 time=12ms TTL=64
    Reply from 192.168.1.1: bytes=32 time=1ms TTL=64
    Reply from 192.168.1.1: bytes=32 time=1ms TTL=64
    Reply from 192.168.1.1: bytes=32 time=3ms TTL=64
    Reply from 192.168.1.1: bytes=32 time=1ms TTL=64
    Reply from 192.168.1.1: bytes=32 time=3ms TTL=64
    Reply from 192.168.1.1: bytes=32 time=1ms TTL=64
    Reply from 192.168.1.1: bytes=32 time=1ms TTL=64
    Reply from 192.168.1.1: bytes=32 time=1ms TTL=64
    Reply from 192.168.1.1: bytes=32 time=5ms TTL=64
    Reply from 192.168.1.1: bytes=32 time=1ms TTL=64
    Reply from 192.168.1.1: bytes=32 time=8ms TTL=64
    Reply from 192.168.1.1: bytes=32 time=1ms TTL=64
    Reply from 192.168.1.1: bytes=32 time=4ms TTL=64
    Reply from 192.168.1.1: bytes=32 time=318ms TTL=64
    Reply from 192.168.1.1: bytes=32 time=1ms TTL=64
    Reply from 192.168.1.1: bytes=32 time=1ms TTL=64
    Reply from 192.168.1.1: bytes=32 time=2ms TTL=64
    Reply from 192.168.1.1: bytes=32 time=1ms TTL=64
    Reply from 192.168.1.1: bytes=32 time=1ms TTL=64
    Reply from 192.168.1.1: bytes=32 time=1ms TTL=64
    Reply from 192.168.1.1: bytes=32 time=1ms TTL=64
    Reply from 192.168.1.1: bytes=32 time=1ms TTL=64
    Reply from 192.168.1.1: bytes=32 time=1ms TTL=64
    Reply from 192.168.1.1: bytes=32 time=1ms TTL=64
    Reply from 192.168.1.1: bytes=32 time=9ms TTL=64
    Reply from 192.168.1.1: bytes=32 time=1ms TTL=64
    Reply from 192.168.1.1: bytes=32 time=1ms TTL=64
    Reply from 192.168.1.1: bytes=32 time=16ms TTL=64
    Reply from 192.168.1.1: bytes=32 time=54ms TTL=64
    Reply from 192.168.1.1: bytes=32 time=28ms TTL=64

    Sometimes theres a request timed out thrown in there randomly.
  4. Kiwi8

    Kiwi8 LI Guru Member

    I dun think it's defective, cos sometimes I have the same issue too.

    I think it might be due to my neighbourhood having many other APs.
  5. RonWessels

    RonWessels LI Guru Member

    I'm hard-pressed to imagine what hardware defect the router could have to generate that effect. If there was a hardware problem in Rx/Tx, it would show up as lost packets not as delayed packets. If it was the router "freezing up", it would also freeze the timing ticks, so the router would have no idea that a greater interval elapsed.

    It looks like what is happening is that periodically the router gets busy doing something else just after/as the ICMP echo packet is being sent, causing it to delay before processing the reply. I suppose it could be a hardware fault in some other peripheral that is causing a mutex'ed operation to have to retry perhaps multiple times.

    Do you have anything not "vanilla Tomato" running? Any scripts? Is your QOS running, and if so what are your rules like? Do you have L7 enabled? What is your network traffic like during these tests?
  6. rmdec

    rmdec Serious Server Member

    I always try the default setup of all the firmware. And I don't think I've added anything extra. QoS is not enabled and I'm not sure what L7 is. Scrap what I said earlier about the spikes becoming smaller. They seems to become more serious at random intervals, like right now:

    Reply from 192.168.1.1: bytes=32 time=66ms TTL=64
    Reply from 192.168.1.1: bytes=32 time=33ms TTL=64
    Reply from 192.168.1.1: bytes=32 time=2ms TTL=64
    Reply from 192.168.1.1: bytes=32 time=3ms TTL=64
    Reply from 192.168.1.1: bytes=32 time=2ms TTL=64
    Reply from 192.168.1.1: bytes=32 time=2ms TTL=64
    Reply from 192.168.1.1: bytes=32 time=19ms TTL=64
    Reply from 192.168.1.1: bytes=32 time=184ms TTL=64
    Reply from 192.168.1.1: bytes=32 time=212ms TTL=64
    Reply from 192.168.1.1: bytes=32 time=50ms TTL=64

    As for other interference from other routers, I usually switch between channel 4 or 8-9, since the scan shows most people here are on 1 6 or 11.

    I uploaded an image, I know this is DD-WRT not tomato, but I've been switching back and forth between the firmwares to try and solve the issue, is there anything that looks wrong here? 3 People are connected, bandwidth usage is fairly low right now, 1-3 Mbps total.
    [​IMG]
  7. Toastman

    Toastman Super Moderator Staff Member Member

    If you have other strong local AP's on channels 1,6,11 you should not try to use channels in between. You will both cause and receive severe interference from the other AP's. A "WIFI" transmitter actually occupies several of the numbered "channels" in the 2.4GHz bandplan. This causes some confusion with the term "channel" being used in two different ways.

    Here is how things are supposed to work. If a router or PC recognizes another transmission on the channel it is using, it will hold off transmitting until that transmission is finished, before sending it's own data. Other devices will do the same, and wait for a clear channel before sending. This works only if each device can hear and correctly identify each other's transmissions as data. Of course, there will ALWAYS be delays if several people are sharing the same space! But at least this strategy minimizes the delays.

    But. if you put your router on an intermediate channel, now you have messed things up. Other devices can no longer identify it as data and will transmit over the top of it, causing interference. In turn, they will appear as noise to your own router and won't be correctly identified as a data transmission, so you will transmit at the same time as they do. You end up jamming each other. Since most routers are set to channel 6 "out of the box" by default, 1,6, and 11 are the ones in use almost everywhere. That is why it is understood that there are only 3 WIFI channels REALLY available, not only in North America but in most other countries too. Since you can't change that, stick with it yourself.

    The diagram below will show you how a WIFI signal uses the channels in the 2.4GHz bandplan, and how WIFI "channels" must be chosen so that they do not overlap with each other. Placing your router on 1,6, or 11 will make sure that those other AP's **DO** decode your router's signal - they will recognize it as a data transmission, and then they will hold off transmission to avoid interfering with it until it's finished transmitting. There will be some delays still, but at least the system will work the way it's supposed to.

    In most places around the world, anyone not using either 1,6, or 11 is effectively creating problems not only for themselves, for everybody else too.

    Also, don't forget that if you can see say 10 AP's with your router, there may be several PC's or laptops using each of those AP's which you CANNOT see. Maybe 50-100 or more "invisible" wifi devices all sharing that channel with you! Not to mention mobile phones, security and baby alarms, security & baby monitor cameras, radar, bluetooth, interference from microwaves (mostly microwaves are towards the top of the band), some types of lighting, and so on.

    It may be your router receiving interference, or your computer, or probably both. There's a very good chance that's what is happening in your case. You might check like this. Screen the antennas from your router (and PC if possible) and see if it makes a difference when the router can't hear other local AP's.

    It is also quite possible that someone near you has N routers in use. When used on the 2.4GHz band they do tend to wipe out G transmissions. There are many places these days where the only way to get 100% reliable operation is a nice piece of CAT5 cable ..

    [​IMG]

    Look at the first line, channels 1,6,11 and then look at the others and see how all of them will overlap and cause interference.

    On recent issues of firmware based on TomatoUSB in particular, there is a setting called "Interference Mitigation". It is usually set by default to WLAN-Manual. It is often wise to disable this until you ascertain what it does and how to use it. Many problems have been down to this setting.

    5GHz will be a better band to use for those who have interference problems. That's not without it's own quirks, though.

    Now, you will also see that if something is detected and incorrectly identified as radar, the transfer stops ...
  8. rmdec

    rmdec Serious Server Member

    Things seem to have improved very slightly, but it could be the router is just in a good mood (for lack of a more proper explanation). I believe the problem still lies elsewhere. I mean, these routers should all be coming off stock the same. If the firmware works for other routers, it should work for mine. And it does what its supposed to as far as I can see, the ethernet is perfect, so I don't think any of these settings are at fault. This will be the 3rd defective router, in addition to a defective modem from Comcast, that I've bought in a row. *sigh* I can't believe my luck.
    Thanks for your all help anyways, I like the responsiveness of this forum.
  9. Toastman

    Toastman Super Moderator Staff Member Member

    I agree with you - I also don't believe it can be your hardware or a firmware problem. You've had the same problem with too many dissimilar devices. It has to be something external - the radio is the only thing I can think of. In fact, it sounds very much like a shopping mall here where they have several N routers in the IT shops, all very close to each other, and the G services are stomped on.

    Good luck !
  10. myersw

    myersw LI Guru Member

    In my experience with networks it is not unusual to see a ping packet get delayed now and then. Keep in mind this is ICMP which is a best effort basis. I doubt that seeing a ping packet delayed once in awhile will show up in end user performance. On our DS3 network we will see a ping ttl high once in awhile but no end user complaints. In our case these usually occur when the circuit is under load. Depending on what the other clients are doing at the time and what interference you have from other AP's in the hood this could be normal and nothing to worry about,
    --bill
  11. rmdec

    rmdec Serious Server Member

    Thanks for the reply bill. I know what you mean. I noticed, or rather didn't notice, much effect with the small spikes, anything up to 100ms was hard to notice to my surprise. However, this is what its like in a good mood. Still trying to figure out the cause, but at random intervals it will start getting into the 200's and even higher. This is when the lag gets really noticeable, and any sort of online game becomes unplayable.
  12. TexasFlood

    TexasFlood Network Guru Member

    If you live in an apartment building or other high density environment, you could be getting occasional interference from other routers, microwave ovens, cordless telephones, bluetooth devices, some alarm systems, baby monitors, etc. Basically any device that uses the 2.4 GHz ISM band can cause this. Or if you don't live in a high density environment you could be getting the interference from something in your own house like my sister did from her phone and I did from my microwave. Also what sort of signal strength do you see? If you're on the ragged edge in terms of range, the signal might be fluctuating a bit and marginal for brief periods of time.
  13. rmdec

    rmdec Serious Server Member

    Yes, I suppose thats possible. I live in apartments and theres about another 30 networks in range. I had a friend who said their wireless stopped working completely when they were microwaving food. That would explain the relatively random timing of the router failing as it doesn't necessarily have anything to do with what my roommates and I are doing.
  14. TexasFlood

    TexasFlood Network Guru Member

    As Toastman said, an N router operating in the 2.4GHz range can really nuke a G router that's close. My sister got a new phone that wasn't 2.4GHz to solve her problem. I didn't get a new microwave but found that microwave interference tends to be towards the higher end of the spectrum so setting my router to channel 1 makes it fairly immune. It was years till I found that out there, so for a long time my wireless network was basically unusable while my microwave was running. I can see networks from my house that number in the mid to upper twenties but only 1 or 2 besides mine that even approach usable signal strength. So I even there there are a lot of networks around me, I don't think most are close enough or have a strong enough signal to be a problem. I could be wrong about that but in reality I don't observe any issues so I'm happy.
  15. Toastman

    Toastman Super Moderator Staff Member Member

    Remember that as long as your router can decode a remote signal, it will hold off transmitting until the other one has finished. It doesn't have to be strong to cause a delay.

    You mention you can see 30 networks. Add the PC's using those networks, which you can't see, phones, microwaves, baby alarms, and you might well have around a hundred devices all capable of preventing your router from transmitting. What you are describing is perfectly normal for wireless systems, I'm afraid.

    The fact is, the only way you will get reliable performance is a piece of CAT5 cable plugged into your laptop's LAN port. Wireless connection should be considered a last resort and for mobile use.

    If you have N routers nearby, then this extract from an article I found might interest you.

    You don't really have any way of knowing what is happening but it seems most likely that the radio is your problem. What might you do about it? If you are in a high rise block or something like that, it may be hopeless. But try to place the router where it is as far away from windows as possible, as far away from the outer walls as possible, the aim being to prevent it from receiving a lot of the other routers. Same with your PC's. Use cable. Pray.

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