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Random huge jumps in latency (wireless)

Posted on 2006-10-20
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Last Modified: 2008-03-06
I pinged my wireless router over the wireless connection and was surprised to notice random and intermittent large spikes in latency. What could be the explanation ? My connection is otherwise fine.

Netgear WG311v2 PCI adapter , WEP128, signal strength = 75%
 
C:\>ping -t 192.168.1.1
 
Pinging 192.168.1.1 with 32 bytes of data:
 
Reply from 192.168.1.1: bytes=32 time=1ms TTL=254
Reply from 192.168.1.1: bytes=32 time=1ms TTL=254
Reply from 192.168.1.1: bytes=32 time=1ms TTL=254
Reply from 192.168.1.1: bytes=32 time=2ms TTL=254
Reply from 192.168.1.1: bytes=32 time=1ms TTL=254
Reply from 192.168.1.1: bytes=32 time=1ms TTL=254
Reply from 192.168.1.1: bytes=32 time=6ms TTL=254
Reply from 192.168.1.1: bytes=32 time=1ms TTL=254
Reply from 192.168.1.1: bytes=32 time=2ms TTL=254
Reply from 192.168.1.1: bytes=32 time=4ms TTL=254
Reply from 192.168.1.1: bytes=32 time=1ms TTL=254
Reply from 192.168.1.1: bytes=32 time=1157ms TTL=254
Reply from 192.168.1.1: bytes=32 time=1ms TTL=254
Reply from 192.168.1.1: bytes=32 time=1ms TTL=254
Reply from 192.168.1.1: bytes=32 time=1ms TTL=254
Reply from 192.168.1.1: bytes=32 time=2ms TTL=254
Reply from 192.168.1.1: bytes=32 time=2ms TTL=254
Reply from 192.168.1.1: bytes=32 time=1ms TTL=254
Reply from 192.168.1.1: bytes=32 time=1ms TTL=254
Reply from 192.168.1.1: bytes=32 time=1ms TTL=254
Reply from 192.168.1.1: bytes=32 time=1ms TTL=254
Reply from 192.168.1.1: bytes=32 time=1ms TTL=254
Reply from 192.168.1.1: bytes=32 time=1001ms TTL=254
Reply from 192.168.1.1: bytes=32 time=2ms TTL=254
Reply from 192.168.1.1: bytes=32 time=4ms TTL=254
Reply from 192.168.1.1: bytes=32 time=5ms TTL=254
Reply from 192.168.1.1: bytes=32 time=1ms TTL=254
Reply from 192.168.1.1: bytes=32 time=1ms TTL=254
Reply from 192.168.1.1: bytes=32 time=1ms TTL=254
Reply from 192.168.1.1: bytes=32 time=1001ms TTL=254
Reply from 192.168.1.1: bytes=32 time=1ms TTL=254
Reply from 192.168.1.1: bytes=32 time=1ms TTL=254
.....
.....
pattern repeats
.....

This isn't really a problem I guess, but just curious why would it happen like that. Giving 250pts to those who can adequately explain it. Thanks!
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Question by:amoruso
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Accepted Solution

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Jeffesmi earned 250 total points
ID: 17772620
Without more information like:
-Router brand, model, & network type (A,B,G,N?)
-NIC brand & model
-Distance of pinging workstation to Router
-Does long ping happen from other workstation(s)

I can only speculate... even if I had the above information. :-)  

1) Radio Frequency networks are notorious for dropped packets, delays, etc. You could have a motor kicking in, a cordless phone scanning channels, other nearby networks interfering, sunspots, ghostly RFI, or a hamster running too fast in it's wheel. {grin} Bottom line is that wifi connections will go up and down in ping times much more than hard wired connections.  However, the protocols and equipment handle these ups & downs pretty well, so don't go start running cable in your house to stabilize the ping times.
2) The router may be the issue.  On my Netgear router, I used to get pings like yours without the high pings. My new router on a hardwired connection looks like this:
Pinging 192.168.130.1 with 1024 bytes of data:

Reply from 192.168.130.1: bytes=1024 time=-614ms TTL=64
Reply from 192.168.130.1: bytes=1024 time=-614ms TTL=64
Reply from 192.168.130.1: bytes=1024 time<1ms TTL=64
Reply from 192.168.130.1: bytes=1024 time=-614ms TTL=64
Reply from 192.168.130.1: bytes=1024 time<1ms TTL=64
Reply from 192.168.130.1: bytes=1024 time<1ms TTL=64
Reply from 192.168.130.1: bytes=1024 time=-614ms TTL=64
Reply from 192.168.130.1: bytes=1024 time<1ms TTL=64
Reply from 192.168.130.1: bytes=1024 time=-614ms TTL=64
Reply from 192.168.130.1: bytes=1024 time=-614ms TTL=64
Reply from 192.168.130.1: bytes=1024 time<1ms TTL=64
Reply from 192.168.130.1: bytes=1024 time=-614ms TTL=64
Reply from 192.168.130.1: bytes=1024 time<1ms TTL=64
Reply from 192.168.130.1: bytes=1024 time=-614ms TTL=64
Reply from 192.168.130.1: bytes=1024 time=-614ms TTL=64
Reply from 192.168.130.1: bytes=1024 time<1ms TTL=64
Reply from 192.168.130.1: bytes=1024 time=-614ms TTL=64
Reply from 192.168.130.1: bytes=1024 time=-614ms TTL=64
Reply from 192.168.130.1: bytes=1024 time<1ms TTL=64
Reply from 192.168.130.1: bytes=1024 time=-614ms TTL=64
Reply from 192.168.130.1: bytes=1024 time=-614ms TTL=64
Reply from 192.168.130.1: bytes=1024 time<1ms TTL=64

And you thought your pings were crazy.  This is on a hard wired connection through a GB switch. Obviously some issue with the router, network configuration, clock drift, or some other phenomena is giving me the crazy pings of -614ms.
3) From: http://www.openh323.org/pipermail/openh323/2003-April/060942.html

"The key to understanding latency is to understand the concept of
micro-congestion:  It doesn't matter what the overall utilization is on
the network:  Quoting numbers like "30%" even when measured with any of
the numerous tools, is unlikely to yield the issues that contribute so
heavily to latency overall.  If 2 packets arrive at the input queue at
the same time, even if the output queue is empty, there's gonna be a
collision.  If you can enforce some queuing priority, then the higher
priority packet(s) get pushed through first.  Ask yourself, now, what
happens when 2 high priority packets arrive at the input queue at the
same time?  Uhoh. micro-congestion, again."
4) If you have packet burst technology enabled, I think it could account for the long delay as the backoff interval kicks in. I'm not sure of this, but there is a good paper about G+ networking http://focus.ti.com/lit/ml/sply009/sply009.pdf.

Well, that is all my tired brain has right now.  I'm looking forward to seeing what others come up with.

Best Wishes,

Jeffery Smith
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Author Comment

by:amoruso
ID: 17779527
This is a normal wireless home LAN. All router/adapters are Netgear, on 802.11 G mode.

There are practically no major sources of interference in my house like microwave ovens/cordless/water/metal/etc. I did the pings on my PC which does not have direct LOS to the router( about 20 feet distance), but signal strength is around 75%.

Today i just tried the ping on my sister laptop which does have direct LOS, and we got no intermittent high pings.

I'm gonna haveto check out this packet burst feature you mentioned, I don't recall seeing this in my router specs. Thanks.
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Expert Comment

by:Jeffesmi
ID: 17781299
Upon further thought, it could also be firewall or processor usage issues. Try disabling any firewalls (DONT FORGET TO TURN THEM BACK ON) and ping.  Then try booting into Safemode with networking (this may or may not work depending on the driver for your wireless NIC and pinging.  If you can't boot to safemode with wireless, use MSCONFIG to disable all Startup items and all non-microsoft services and try pinging.

Good Luck,

Jeffery Smith
0
 

Author Comment

by:amoruso
ID: 17794203
All the suggestions have already been tried with to no effect.
I backup my partitions & reinstall WinXP clean with just the network drivers...same thing too.
During all these ping tests no other client is connected to my wireless router(i turned off WAN too), so maybe something specific to my adapter card or motherboard perhaps.

Anyway I plan to change my adapter card soon as I'll be upgrading to WPA..we'll see how that goes.

Since you're the only one to respond so far, your first post gives a lot of insight into how latency works and troubleshooting them. I'm sure it'll help me in discovering the cause..
250pts into your pocket sir :)
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LVL 2

Expert Comment

by:Jeffesmi
ID: 17802955
Thanks.  Helping others is the true reward... but I'll take the points. (grin)

Best Wishes,

Jeffery Smith
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