Where is the packet loss?

I have recently been having problems with sl, and have noticed that over the last few days I have been getting very high levels of packet loss. This has varied betweem 3% and 150% (?).

Everything else is ok. Ping Sim is generally round about 170, which is fine for me. Everything else is fine. Framerate is good.

So I decided to test the connection, which I did with a program called PingPlotter. I pinged the address of my sim (sim5146.agni.lindenlab.com). This reports that ping is fine at every stage of the connection (UK to San Francisco), never above 146. It also reports zero packet loss throughout the chain.

When Second Life reports packet loss, what is it actually reporting? Could the high packet loss that SL is reporting indicate a problem somewhere in my system?

I think when the performance of the SL client is poor the connection might suffer, what is your FPS?

Btw, next time you got high PL in SL, try this, go to the network tab of the preferences window, move the bandwidth throttle all the way down and wait a while, see if the packet loss goes away by doing this, if it does, you can move the slider back up.

Framerate is between 7 and 15 using the Release Candidate client in shadow mode, which is actually pretty good. The packet loss is continuous. I will go into sl now and try what you suggested. Will let you know what happens.

Ok, the packet loss is reduced when I close the slider, but is still significant, varying between 1 and 20 per cent. Incidentally, I tried it with the regular viewer as well. On that I get a framerate between 15 and 25 fps, but the packet loss is the same on both clients.

It's reporting packet loss. Notice that packet loss conditions become more severe as the connection gets more saturated. If you're on basic DSL, cranking the network bandwidth slider all the way to maximum will do this.

Try going to dslreports.com and doing a speed test, and set your bandwidth to what it says (and if that doesn't do it, divide by 8... I forget who uses kilobits and who uses kilobytes).

Is it? Then why do two programs designed to measure packet loss report that there isn't any? Certainly something is wrong, because sl is performing very badly.

As I have said, reducing the slider to the extreme left-hand position slightly reduces the packet loss that sl reports, but doesn't get rid of it.

OK, I went into sl today to make that alteration to the bandwidth, and to my delight, discovered that for the first time in nearly a week, packet loss is back to zero, and sl is running ok again.

I can only put it down to an sl glitch, but I am really relieved that things appear to be ok. Many thanks to everybody for their help, and I hope that is an end of it.

Although if any passing person has an idea of what caused this, I would be interested to know.

Right, went into sl just now and the packet loss is back.

It's probably the guy next door running a torrent seed.

Hi Argent. I have a low-contention-rate line. And framerate is fine, and consistent, and I would have expected that to be affected by something like what you mention. How would a torrent seed affect my line? Speed is ok. Ping Plotter reports a good connection between my computer and the server running my sim, and both that and the software of my router report zero packet loss. It doesn't make sense to me.

if the PL doesn't go away after keeping the bandwidth throttle all the way down for several seconds, or it returns after you bring the throttle back up then I guess it isn't the same thing that happens with me, with me doing this usually fix the PL for the whole session, or at least for several minutes

Nope, still had the packet loss, even with the bandwidth throttled down to minimum for several minutes.

It's the goatee. Your cable modem thinks you're Gary Oldman and is setting you up to get horribly killed in the third act.

Packet loss, as reported by the sim, is a software thing. It just means that the sim lost track of some part of the communications and had to do a retransmit. Though this could be because of network problems somewhere between you and LL, it could also be that the sim is hurting..

Do you see the same issue if you go to an empty region? I usually go to Linden Estate Services becuause it's pretty isolated and frequently empty..

Dunno PingPlotter but if it's not continuously pinging, you should do a ping -t to the sim and watch that for a bit to get an idea of how stable your connection is.

Sorta like packet loss, the ping reported _by SL_ is telling you how fast the sim software is responding. This is different than doing ping on the command line or running PingPlotter.

Ok Meade, many thanks for the help. This thing is getting more and more weird. I went to the sim you suggested, and after about five minutes the packet loss dropped considerably, although it never stayed at zero. It ranged between zero and 4%, which was acceptable. So then I went to another sim, and discovered the same thing. The reason I thought it was the same everywhere was because it takes so long for the packet loss to drop. I went to a neighbouring sim, and again after being there about 10 minutes the packet loss was mainly zero, but with spikes up to 15%.

As soon as I went back to Umber packet loss shot up to 150%. So on the face of it, it would seem to be the sim. But the odd thing is that other people on Umber are quite happily experiencing zero packet loss. Why do I seem to be the only one affected?

The time dilation of the sim is 1.0, and the sim fps is 45. What is ping-t? The programme I mentioned pings every 15 seconds, but that it adjustable. What sort of rate should I be using? In any event, I will experiment with faster pings.

The only program that can measure the packet loss seen by the Second Life client between the Second Life servers and your computer is Second Life.

Measurements of packet loss when the SL client is not running, or measurements of the packet loss between your computer and anything but the sim you're logged into, are only useful if they show packet loss. If they don't, that just means that they're not losing packets between your computer and wherever the other end is.

If you're seeing packet loss at 50 kilobits per second (the extreme left position) then I suspect a firewall or router problem.

Because something is wrong with the route between your computer and Linden Labs, that is only seen when there is a lot of traffic from the sim to you.

The time dilation of the sim and FPS of the sim are not likely to have any effect on the packet loss you're seeing.

If you're on windows and the sims IP address is, say, 2.4.6.8, do this:
- press the Start button
- type (without the quotes) cmd
- press enter
- a command window will open up
- type (no quotes) ping -t 2.4.6.8
-- note there are spaces between "ping", "-t" and "2.4.6.8"
- press enter
- this will start pinging the sim about once a second forever

Once you get that running, go back and mess around in SL. Every minute or so, go back to the ping window and take a look at the Time numbers. They should be more-or-less consistant. If you see that they're all over the place or you see messages about time outs, that _could_ be an indication that you're got network issues.

To stop the ping, just press ctrl-c. Doing that will give you a little 3-4 line summary. If you copy/paste that summary here, we can critique your network for you..

Or because the sim is borked. This is packet loss as seen by the sim - all the packets could be making it over the wire just fine...

If he's seeing even a few percent packet loss in an empty sim, and he's seeing packet loss when his bandwidth is cranked down to 50 kbps, then I don't think it's the sim.

It could well be a router problem, because I recently changed routers. I really don't see what it can be, though, because the limited options for setup seem to be correct. Incidentally, I have confirmed there is no packet loss on the line by using a trial version of VisualRoute, which found no packet loss and produced this report:- "This trace was started on 15-Jun-2009 22:45:44.
The host 'sim5146.agni.lindenlab.com' has been found, and is reachable in 15 hops. However, it did not respond to HTTP requests on port 80. The TTL value of packets received from it is 55.In general this route offers a good throughput, with hops responding on average within 92ms. However, all hops after hop 9 in network 'Abovenet Communications, Inc' respond slightly slower than average. The DNS lookup was completed almost instantaneously (less than 2ms - this may be the result of caching)."

I will look at the router now, and see if there is anything that could be causing this. Don't know the first thing about modem/routers, apart from how to set them up.

Many thanks for the help, Meade and Argent.

You sure that's packet loss as seen by the sim?

I'm looking at the source to the viewer and it sure looks like LLCircuitData::updateWatchDogTimers is updating gMessageSystem->mDroppedPackets in the client based on the age of packets in mPotentialLostPackets.

Selardor: were you running that trial while you were logged into SL and observing packet loss in SL?

Ok, the problem appears to be solved - unless it's a false dawn like the last time!

I had a look in my router, and based on what you said earlier, I noticed that there was a default setting of SPI Firewall Protection. I unchecked that, and so far everything seems well, with a zero packet loss in Umber. I have no idea what SPI Firewall Protection is, but it certainly seems that I am better off without it!

Many thanks to both of you for your help, and I sincerely hope this is the last contribution I will make to this thread!

"Stateful Packet Inspection", I expect.

Good luck. Watch out for the spiders.

Good luck. Watch out for the spiders.

Slow Packets Immediately!