Throttled ISP connection

[config t]

I've noticed I am only getting 1Mb download speed in my flat, however when I do a speedtest it's showing close to 10Mb. It's been going on for the last 5 months, I just didn't care enough to look into it until now. I got a new laptop and need to download video games from Steam.

At this point I have updated the NIC drivers on my laptop and tried both wired and wireless connection to the router (it's less than 20 feet from my laptop). I noticed this behavior on a different lapop as well. It's not just isolated to Steam either. It happens when I download anything.

When I logged into the router I didn't see any settings that could potentially throttle the connection.

Any ideas? It's happening somewheres, I just can't figure out where yet. Thinking I will complain to management soon and they can ping the ISP if I can't find a solution.

[icecream-guy]

wired or wireless?  if wireless, can you try wired, see if same result?
have you tried reboot?

what media is this?  fiber, cable, dish?
have your tried at different times of the day to rule out contention on shared media?

try a packet capture when downloading, that should tell lots.

[deanwebb]

I'd stick with a wired connection for troubleshooting, as you can go direct to the router without worrying about interference.

And test both at the end of the month and at the start of a new one, in case you got throttled because you exceeded your plan's data limit or some garbage like that.

[config t]

I finally got around to doing a packet capture while downloading an update for Wireshark 

I am either not seeing what points to the connection being throttled, or I don't know where to look. What would be some of the indicators?

Also I know for a fact it is throttled to 1.2MB by the ISP, because I learned that's all my flat is paying for as part of my rent package. If I want more I need to upgrade it. Now I'm simply curious.

[Otanx]

You are looking for dropped packets. Of course those don't just show up in wireshark so you need to look for the symptoms of packet drops. This will also depend on the direction. I also assume you are capturing on the client.

Packets dropped from server to client: Look for your system sending selective acknowledgements with breaks in the ack. This means one or more packets got dropped. This also will cause TCP to reduce the window size. So if you don't see selective acknowledgements you can also look for reductions in the TCP window size. There are other reasons for reduction in window size so it isn't fool proof. The window size increasing is normal. If it drops by half that is an indication of dropped packets. If it drops directly to 0 then that is an indication the receiver ran out of buffer space to hold packets for processing. I know there are ways to filter in Wireshark for this, but I don't have wireshark on my laptop.

Packets dropped from client to server: This is probably rare. You are going to hit a cap on the download not upload. Look for duplicate packets from the server. Especially if you have an ACK in the capture for the original copy of the packet. If your ACK got dropped then the server isn't going to know you got the packet, and resend it. This is probably going to be rare. Potentially never as I think about it. There are alot of ways this will get recovered without a problem.

-Otanx

[icecream-guy]

You are looking for dropped packets. Of course those don't just show up in wireshark so you need to look for the symptoms of packet drops. This will also depend on the direction. I also assume you are capturing on the client.

Packets dropped from server to client: Look for your system sending selective acknowledgements with breaks in the ack. This means one or more packets got dropped. This also will cause TCP to reduce the window size. So if you don't see selective acknowledgements you can also look for reductions in the TCP window size. There are other reasons for reduction in window size so it isn't fool proof. The window size increasing is normal. If it drops by half that is an indication of dropped packets. If it drops directly to 0 then that is an indication the receiver ran out of buffer space to hold packets for processing. I know there are ways to filter in Wireshark for this, but I don't have wireshark on my laptop.

Packets dropped from client to server: This is probably rare. You are going to hit a cap on the download not upload. Look for duplicate packets from the server. Especially if you have an ACK in the capture for the original copy of the packet. If your ACK got dropped then the server isn't going to know you got the packet, and resend it. This is probably going to be rare. Potentially never as I think about it. There are alot of ways this will get recovered without a problem.

-Otanx

don't forget the TCP re transmits.  you see those, definitely dropping packets.   that and TCP out-of-order