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Old 04-05-2006, 08:09 AM   #1
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slow download--insconsistent ping replies

hi there
i have a problem related to slow downloading speed.the situation is ihave about 60 PC's in a domain 2k3 server XP workstations, aDSL internet connection,umanageable switches.
when i ping ISP Gateway from a LAN PC get the replies...22, 25,35, 400, 50ms an some times 22,40,220,50,30,100ms...I get lot of variations
and when i ping from single PC by disconnecting LAN i get these
replies ... 15,16,24.26ms. the range is max from 15 to 26ms.
there is no problem with ISP. problm definitly lies with my LAN.
Now how to detect which PC is culprit is the solution im seeking from

any suggestions appreciated.

Old 04-06-2006, 04:38 AM   #2
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perhaps run a network monitor such as iptraf on the LAN's router to see what kinda traffic gets generated when you plug the other boxes into the switch... also, perhaps the switch itself is acting-up, in which case to test you'd wanna switch it with a known-good switch...
Old 04-06-2006, 09:30 AM   #3
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Looks normal to me. You will get very variable ping times, because other traffic is using the link. Your ping packet only needs to get queued behind a 1500 byte frame and at 512K thats 25mS right there. With a 60 users sharing the link the occasional 400mS is not unusual. If it were running at 400mS all the time or when everyone else was disconnected, THEN you would have a problem. You also need to consider that most IP stacks consider responding to a ping a fairly low priority task, so the loading of the server you are pinging can also significantly affect the delay.
Old 04-06-2006, 11:55 AM   #4
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yeah, but i think it's obvious there will be variable latency while the network is being used, which is why i would assume he's actually talking about the higher latency while the other boxes are (supposedly) NOT being used, but still attached to the network... no??

if it's windows PCs my money is on spyware or downloaders or something like that... but to know for *sure* if the boxes are generating traffic even without anybody using them you'd need to monitor the router... that's IMHO the best way to determine whether the latency toward the WAN is warranted or not...
Old 04-06-2006, 12:10 PM   #5
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Considering only your LAN, do you also have such problems?

You could in anycase (network health) use ethereal and look for lost segments, duplicate,retransmit ... TCP errors which would tell you that there are some late collisions (collisions that appears after the 64bit time) and that would not be detected by an Ethernet Adaptater (and then be handled by the upper layer which retransmits). If you have a lot of this, its not normal. Your network could be too big, wrt to Ethernet Spec or you could have a bad Ethernet Card.

Now to see which one is the problematic, there is a good method:

1)You split,
2)you look
3)you add more
4) goto 2
Old 04-06-2006, 12:18 PM   #6
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The variation could also be from either a bad port or bad cable. Verify these by adding the connections 1 at a time.


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