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#553 - 07/22/01 08:25 PM Route Changing
Anonymous
Unregistered


Why am I seeing continual route changes when I run PP? There also are 10-50% packet loses on various hops. This doesn't seem to manifest itself when I download files. I am connected to Qwest dsl via a Cisco 678 router. <br><br>

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#554 - 07/23/01 12:10 AM Re: Route Changing
Pete Ness Offline



Registered: 08/30/99
Posts: 1106
Loc: Boise, Idaho
Route changes are a pretty normal fact of life with the internet. It sometimes happens for load balancing reasons, sometimes to route your data around problem areas, or a number of other possible reasons.<br><br>Ping Plotter, by default, keeps track of ALL route changes. Normally, this works really well - and pretty much without notice by anyone (unless you're looking for it). The time when it can start to cause problems in the data that Ping Plotter displays is when the length of the route changes (when your destination shows up at different hops, depending on the route being used) - as the changing routes cause problems in the final hop. If the length of your route is changing regularly, I'd like to know any details you have about this (as I've yet to run into a normally oscillating route where the route *lenght* changes!).<br><br>If you want to supress recording information about route changes, you can do this in Ping Plotter (ask if you're interested and I'll walk you through it) - unless the length of the route is changing - in which case recording these changes can't be supressed.<br><br>Now, there are a few different variations of things that could be causing you problems - and causing your packet loss. A big variable in this is whether or not your route length is changing.<br><br>One thing to know about Ping Plotter (and all ping tools) compared to HTTP web access is that HTTP uses error correction in its communication. If you get a lost packet when transferring HTTP, you often don't notice this because the protocol corrects for errors. The ICMP protocol (which is used by Ping Plotter and other ping tools) is lossy - so if something along the way drops data, it's never corrected - just reported by whatever tool sent it out. This is one possible reason why you're not seeing lost data when browsing the web or downloading something, but are seeing it with Ping Plotter.<br><br>The symptoms seen when data is lost in an error correcting protocol is that performance suffers. When data is lost, the protocol negotiates for it to be re-sent and this takes time. If you're seeing slow performance when downloading files, or browsing the web, it's possible that the drop in performance is being caused by packet loss.<br><br>It'd really help if you elaborated a bit on the problems you're seeing - and I'll see what I can do to suggest some reasons why you're seeing them - and what you can do to address them. If you want to send some Ping Plotter data (either a safe file in .pp2 format, or some images), I'll have a look at them and see if I can help you understand what you're seeing any better.<br><br>

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#555 - 07/23/01 02:13 AM Re: Route Changing
Bill_MI Offline


Registered: 07/18/01
Posts: 12
Loc: SE Michigan
Neo, Pete is correct. Also, handling these routing changes is no small task and still be able to follow what's going on. I'm new to PingPlotter but not new to routing and was impressed how intuitively PingPlotter handled this messy task.<br><br>My 3rd hop has what I'm sure is a load-balancing example. I'm able to mask it out with a Route-Changes "IP Mask".<br><br>My 2 Cents,<br><br>Bill<br><br><br>

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#556 - 07/24/01 11:10 AM Re: Route Changing [Re: Pete Ness]
Anonymous
Unregistered


I have my trace interval set at 1 sec. Every second, or every-other second my number of hops to my destination increase/decreases with these route changes. When I run the ping plotter over my other dsl (digizip) to the same destination, I don't see any of these route changes and PL% is zero. Interestingly, the route with the PL% (using Qwest) clocks in at 80ms, while the other route with zero PL% runs at 180ms (different paths probably accounting for the differences).<br>The data I am running over these lines must be as clean as possible. I want to be sure packets won't get dropped (or at least very minimally).<br>The "re-routing" is very extreme (and possibly the cause/reason for the packet losses?), every trace has a different 3rd thru 13, 14, etc. (up to the final) hop. While another identical computer at the same location going to the same destination via a different ISP/DSL shows no route changes at all, both with ping plotter set up identically???<br><br><br>

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#557 - 07/24/01 11:24 AM Re: Route Changing
Pete Ness Offline



Registered: 08/30/99
Posts: 1106
Loc: Boise, Idaho
Whenever a route gets *longer*, Ping Plotter will show one lost packet at your final destination. This is possibly what you're seeing there.<br><br>Here's a brief description of why this happens:<br><br>When Ping Plotter determines that the final destination has been reached, it only sends out enough packets to reach the final destination. So if your route is 13 hops long, it only sends out enough packets to reach hop 13. Whenever the route gets longer, another router reports in at hop 13 and Ping Plotter figures out that it needs to send out more packets to reach the final destination - but it doesn't do this until the next sample set is sent out. This means there is always a single lost packet associated with this route lengthening. This doesn't occur when the route shortens - only when it gets longer.<br><br>I've only heard one other report of this kind of thing happening, so I've not had a strong reason to create a solution for this problem yet.<br><br>Some other tools address this by only grabbing the route on the first set, and then just "pinging" each destination directly on future samples. Ping Plotter versions before 2.30 handled this a bit differently - by ignoring the information about the hop's IP address when it came back, and always just using the hop number (rather than the IP address) to decide where to put things. In both of these cases, you wouldn't see packet loss at the final hop - but the data being reported would be flat wrong (because data was being associated with a router that was no longer even in the route!).<br><br>There are a few ways that Ping Plotter could better handle this situation, but unfortunately, all of them take some changing of the Ping Plotter code (rather than a setting) - and they all require some comprimises (maybe a setting that you could change when this happens to have it work a little harder to determine what's happening).<br><br>Maybe knowing what's happening with the tool here will help you understand some of the data - and help you manually factor out some of the issues that are appearing. I'll up the priority of this issue in the defect list.<br><br>

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#558 - 09/04/04 11:41 PM Re: Route Changing [Re: Pete Ness]
Anonymous
Unregistered


I have for you 3hrs of a pp2 file that will show you hop changes along with routing changes http://www.bhczee.com/google.com.pp2

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#559 - 09/05/04 12:18 AM Re: Route Changing
Pete Ness Offline



Registered: 08/30/99
Posts: 1106
Loc: Boise, Idaho
It looks like you have some load balancing happening at either hop 2 or hop 3 (I don't know enough about your network topology to really comment on this too much, but it looks like it starts at hop 2), and this load balancing / route change is happening very often.

The way the route is changing means that PingPlotter has a difficult time giving you a full picture of what's happening route wise - as each packet that goes out might take a different route, so the route dynamics get totally mixed up. This means you don't know for sure if any of the routes that PingPlotter is showing you is a complete route, or if it's a mix of multiple routes.

Now, on the brighter side of things, PingPlotter is telling you that there are significant route changes happening. This, in itself, isn't necessarily bad, but you know it's happening.

Also, you see that the final destination is reporting back really consistent latencies - a good thing. It is, however, showing some packet loss - not such a good thing.

An interesting item is that the packet loss at hop 2 is almost exactly the same as it is at the final destination. This leads me to believe that a significant portion of the packet loss you're seeing could be solved by resolving the issue that's affecting hop 2. To determine the similarities in packet loss between hop 2 and the final destination, I right-clicked on hop 2 and selected "Add route change mask". This merged the two routers that were participating at hop 2 so they are reported together.

You didn't list a description of symptoms, or talk at all about your network topology (is it your load-balancing router that's doing this, or your ISPs? Are you connected via a DSL line, frame relay, wireless ISP, or some other technology). PingPlotter data always needs to be taken in context of the situation, so I can't be *too* inspired on commenting on your data.

The situation you have is a challenging one for PingPlotter because of the route change dynamics. If you're trying to troubleshoot a problem, you'll probably need to engage in a discussion with your service provider to really get to the bottom of things (this is true in all cases, but especially so when it's difficult to understand what's happening, like in your situation).

- Pete

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#560 - 09/05/04 01:52 AM Re: Route Changing [Re: Pete Ness]
Anonymous
Unregistered


Im on cable Im in the area of the Cox upgrades west Texas. Im not on a router im direct into the modem .The symtoms are as you could expect from the packett loss,very eractic page loading and not playable on multiplayer game servers. I have contacted my ISP tech and he has sent this PP2 graph and many others along with some crazy modem logs im getting www.bhczee.com/logs.txt to his engineers. One other thing that i have mentioned to him was that after the upgrades my first hop no longer showed up as being my addy its now showing up as 10.248.144.1 i have no idea how thats hapening its not a cox addy. Im a regular on the http://www.dslreports.com/forum/cable,ath . And i would like to say we use pingplotter quite often for one our diagnosis tools you guys have a great product. The main reason i was posting was to let you see a graph that was showing hop length changes it is happening every second and jumps from 14 hops to 23 so randomly that its just terrible to try and get anythin done. Im sure they are having some serious router problems. When they get it going i will post back to let you know what he found,if i can get some details out of him.Stop by the cox fourums sometimes we can always use another good trouble shooter.

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#561 - 09/05/04 01:54 AM Re: Route Changing
Anonymous
Unregistered


Err http://www.dslreports.com/forum/coxhsi i tried to edit it but it wouldnt let me

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