Internet Upload Speed

[dennisgorelik]

About one week ago we noticed that upload from my computer to remote servers became quite slow.
Speed test indicates that while upload speed is good (80 - 90 Mbps), download speed is getting worse on remote servers.

My computer is in Jacksonville area and upload speed to Orlando servers is quite fast:
http://www.speedtest.net/my-result/5837858780
Orlando, FL
Ping: 21 ms
Download speed: 90.13 Mbps
Upload speed: 9.55 Mbps

That is close to 10 Mbps upload speed that Comcast claims to have for my account.

However the further away the server is - the longer is ping time and the worse is upload speed:
http://www.speedtest.net/my-result/5837865645
Dallas, TX
Ping: 47 ms
Download speed: 90.12 Mbps
Upload speed: 5.14 Mbps

http://www.speedtest.net/my-result/5837843259
Remote server: Seattle, WA
Ping: 83 ms
Download speed: 90.13 Mbps
Upload speed: 3.12 Mbps

http://www.speedtest.net/my-result/5837868925
London, UK
Ping: 115 ms
Download speed: 87.99 Mbps
Upload speed: 2.31 Mbps

http://www.speedtest.net/my-result/5837874972
Chelyabinsk, Russia
Ping: 188 ms
Download speed: 86.41 Mbps
Upload speed: 1.52 Mbps


Why does upload speed deteriorate proportionally to the ping to the remote server (but download speed stays the same)?
My hypothesis is that network protocol waits after every chunk of data for the response from the remote server (instead of continuing sending new chunks of data).
By why?
Comcast technician came today and found that there was some network issues with upload frequency. Lost packets during upload may initiate resynchronization waits that would drag upload speed down on connections with slower ping.

Comcast technician promised that within couple of days, Comcast network crew should fix the issues.
We'll see how that would change my upload speed.

Update (thanks to anspa recommendation):
PingPlotter shows a lot of Packet Loss with my Internet connection:

Comments

[lamantyn.livejournal.com]

This Spring I had a similar issue with upload speed with Verizon FIOS.
Tech was puzzled, theorized about issues with some equipment on Verizon side.

At some point I tried another cable socket (on another wall) and magically everything became OK. Seems a bad coaxial splitter.

[dennisgorelik]

So the hypothesis, explaining the issue is:
1) Bad coaxial splitter caused multiple data packets loss.
2) Multiple data packets loss caused smaller size of the congestion window.
3) Smaller size of the congestion window caused slower upload speed.

Does this hypothesis sound about right?

Hopefully I have similar issue with the network between cable box on my front yard and Comcast modems (connection between my home and Internet box on my frontyard seems to be good, according to the Comcast tech).
If it is the case, when they would fix their network issues I would get better upload speed.