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#508 - 04/20/01 12:49 AM why ping is OK and PP not?
Anonymous
Unregistered


a "pure ping" using -t switch shows no problems, but PP shows many packet losses... why is that?<br><br>

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#509 - 04/20/01 01:25 AM Re: why ping is OK and PP not?
Pete Ness Offline



Registered: 08/30/99
Posts: 1106
Loc: Boise, Idaho
There are a few possible reasons:<br><br>1) The packet size could be different and that different packet size in Ping Plotter may be causing some packet loss. Note that this is a problem with the router, not Ping Plotter, but you can change the packet size to something smaller than default to see if this affects it.<br><br>2) Having multiple simultaneous outstanding ICMP echo requests may be causing a problem in one of the routers. This isn't too uncommon, but is almost always traced back to a hub on your local side (bios updates often help this). See the instructions here <A HREF="http://www.pingplotter.com/netgear-rt314.html" target="_new">http://www.pingplotter.com/netgear-rt314.html</A> (follow the instructions in the workaround section) if you want to make Ping Plotter only do one outstanding request at a time.<br><br>Ping Plotter actually uses the exact same ICMP engine that PING does (the ICMP.DLL provided with Windows), so you should be getting the same results if the tests are exactly the same.<br><br>

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#510 - 06/13/01 08:58 AM Re: why ping is OK and PP not?
Anonymous
Unregistered


I experience the same problems. Even after taking out the multithreaded ICMP (as said in the FAQ), I see still a differance between PingPlotter and PING. So zero loss in PING and some 30% loss in PingPlotter.<br>In both case the same packetsize (1024 Byte).<br>Any hints to overcome this? The routers in this path are all Cisco12000 and it is not the router type I would say. <br>It could be that the interface where the problem starts in PingPlotter is a dual channalized gigabitethernet. But again with PING no problem what so ever.<br><br>

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#511 - 06/13/01 11:49 AM Re: why ping is OK and PP not?
Pete Ness Offline



Registered: 08/30/99
Posts: 1106
Loc: Boise, Idaho
In some *very* isolated cases, I've seen a difference in packet loss based on the *contents* of the packets. Ping -t uses a repeating sequence of "abcdefghijklmnopqurstuvw" while Ping Plotter uses repeating $AA. You can change Ping Plotter to be the same as Ping by creating a text file with the same thing that PING sends (ie: create the file with abcdefghijklmnopqrstuvw in it), and then go to Advanced options and change the packet cargo to use this file. This is kind of a long shot, though, as in all cases where I've seen this make a difference, Ping Plotter was used to simulate and extrodinary bytes sequence that stimulated the packet loss, and the $AA wasn't that sequence. This is worth trying those - since it's quite easy to do.<br><br>Also, I'm wondering if this same packet loss results when you use a smaller packet size (ie: 32 bytes or similar).<br><br>Just to put my mind at ease here, as well, please re-check to make sure there are not multiple threads involved. You should be able to recognize a non-threaded Ping Plotter by seeing that the results come in very much 1 at a time. When using threads, your hop 12 may come in before the timeouts in hop 10 and 11 happen. When not using threads, hop 10 and 11 have to return results (timeouts in your case) before hop 12 can even be dispatched. This should be very noticable in the performance of your trace. Once you've verified that this is happening, make sure your "Trace Interval" on the main screen gives you enough time to make it through all hosts. Ideally, you'd have this set to be at least (Number of hops times Timeout Speed (set in advanced options)) plus some headroom. For example, in your case, you might have your Timeout Speed set to 1000ms (1 second), you'd want to have your trace interval set to at least 15 seconds (13 hops at 1 second each plus some headroom).<br><br>I'm not saying that Ping Plotter never makes mistakes, but in 99.8% of the cases where PING and Ping Plotter show different results, it's been some kind of a networking issue and the packet loss shown in Ping Plotter is *actual* packet loss. Finding the difference often helps troubleshoot the network and shows ways that ICMP echo requests can be lost (which doesn't always translate into packet loss on other kinds of traffic, to be sure).<br><br>Let me know if any of this gets rid of the packet loss in Ping Plotter.<br><br>

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#512 - 06/29/01 07:42 AM Re: why ping is OK and PP not? [Re: Pete Ness]
Anonymous
Unregistered


Hello Pete,<br><br>Your long shot is in the bulls eye!!! The equipment involved in this case is:<br>an Cisco cat 4003 Cisco cat 4920 switch alle gigabit ethernet interfaces. <br>We will discuss this issues with Cisco of course. Network should not be dependant on $AA!!!<br><br>So as you say at the end of your message, this differance between PingPlotter and ping helps us debugging some problems in our network (www.surfnet.nl)<br><br>All the best,<br><br><br>Victor<br><br>

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