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#265 - 09/14/00 03:10 PM PL(%) vs Err (Count) do not match
Anonymous
Unregistered


Hi.<br>Im running 2.20 and get mixed results on packet count and % (percentage).<br>Sometimes they do not fit mathematicly.<br><br>Has someone any suggestion?<br>Thanks<br><br>

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#266 - 09/14/00 03:32 PM Re: PL(%) vs Err (Count) do not match
Anonymous
Unregistered


Sorry for the above posting.<br>I think I found the answer a couple of postings before.<br>(I know: RTFM)<br>Sorry again.<br><br>

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#267 - 09/14/00 03:42 PM Re: PL(%) vs Err (Count) do not match
Pete Ness Offline



Registered: 08/30/99
Posts: 1106
Loc: Boise, Idaho
Hi.<br><br>Do you have any examples of this?<br><br>Without knowing the specifics, my theory on this is that not all samples have been received, so the divisor deosn't equal "samples to include".<br><br>Example: You have trace interval set to 1 second and traces to include = 20. Your timeout time is 9999 ms.<br><br>Let's say hop 4 is getting 50% packet loss (to be easy, let's say that every other packet is being dropped). With a 10 second timeout and a 1 second trace interval, that means that at any time, you have 5 packets still outstanding (roughly) that will eventually time out. Until Ping Plotter knows that it's a timeout, it can't factor this into packet loss, so it just doesn't include these numbers in the total.<br><br>So, let's say you've sent out 20 packets. In the first 10 samples, you got 50% packet loss, but in the next 10 samples, there are still 5 packets that haven't responded yet (and there are 5 that have). This means Ping Plotter is only going to use 15 samples for the divisor. It's received 10 good samples back and 5 bad samples, so packet loss will only show 33% (even though you're very clearly getting 50% packet loss).<br><br>To help counter this problem, in one of the 2.03 versions, Ping Plotter started "predicting" timeouts. If sample 15 hasn't responded by the time sample 16 does, then it assumes that sample 15 will timeout. If sample 15 ever does come back, then it will back-fill and recalculate the correct packet loss, but it helps the problem from above not show up. At any time, though, you may have 19 samples returned - which is statistically different than having 20 samples - and that will show up in the PL% quite often.<br><br>When the above problem is *VERY* visible, though, is when you're getting a lot of timeouts in a row (without getting good responses). This will stop the percentages from moving until it gets some kind of response. There's really no solution for this - as you don't want to assume it's going to time out too soon. As a user, you can handle this by reducing your timeout time (in advanced options) to something significantly smaller.<br><br>Hope this helps rather than confuses!<br><br>

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#268 - 09/14/00 04:34 PM Re: PL(%) vs Err (Count) do not match [Re: Pete Ness]
Anonymous
Unregistered


Thanks, Pete, for your rapid response.<br>Im sorry for logging in as Anonymous before.<br><br>Via separate Mail you will receive an example of a trace showing the discrepancy between absolut and relative figures. The older thread "Explanation of PL%" does not fit my case, as I did hope before. <br><br>Im going to change Timeout, as advised, to lets say 5000.<br>in addition I probably will change interval from 25 to 50 msec, even being slower in performance.<br><br>Thanks again, good evening from Germany.<br>CU WBL<br><br><br><br>

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#269 - 09/14/00 04:53 PM Re: PL(%) vs Err (Count) do not match
Pete Ness Offline



Registered: 08/30/99
Posts: 1106
Loc: Boise, Idaho
Ahhh. Your pictures and sample data helped a great deal.<br><br>In the data you sent me, you had 4 route changes. The hops at the end of the route are the hops that changed.<br><br>When calculating lost packets and packet loss, Ping Plotter uses the last X number of samples sent out total - not to a specific hop. <br><br>Example:<br><br>You have 10 hours of data collected. Your samples to include is set to "all".<br><br>For the first 5 hours of collecting data, your route was stable. After 5 hours, however, the route changed - and hop 10 is now being serviced by a different router.<br><br>Obviously, Ping Plotter can't report packet loss for a router that wasn't even responding during the time period, so it just shows packet loss for the current router.<br><br>In addition, the current router has only been collecting data for the last 5 hours (for the first 5 hours, it was a different router), so it can only use the number of samples sent to this router during that period to calculate packet loss.<br><br>If this route change is relatively normal, you can put both routers in your route change exlusion list and Ping Plotter will treat it as a single router for future sessions.<br><br>

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#270 - 09/14/00 05:04 PM Re: PL(%) vs Err (Count) do not match [Re: Pete Ness]
Anonymous
Unregistered


how can I find out which routers did change and when?<br>btw i cant remember any red PopUp during the day running the job mostly in BG.<br><br><br><br>

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#271 - 09/14/00 05:17 PM Re: PL(%) vs Err (Count) do not match
Pete Ness Offline



Registered: 08/30/99
Posts: 1106
Loc: Boise, Idaho
Open the "Route Change" window right below the address history list. If you don't see a window there, click on the divider right above the word "Sampling" and below the history window - the Route Change window should appear - it has a list of all the route changes. Double clicking on one of these times will show the routers that were in that route. Toggling between two routes this way will show you which routers changed.<br><br>When there's a route change, you should see the word "New route chagnes logged" in your highlighted text color (blue in my case) right below the address history window. If you're not getting this, you might check in Advanced options and make sure you don't have this turned off (Show route change indicator when list hidden).<br><br><br>

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#272 - 09/14/00 05:39 PM Re: PL(%) vs Err (Count) do not match [Re: Pete Ness]
Anonymous
Unregistered


thanks, everything is now (close to) perfect.<br>CU WBL<br><br>

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