Bandwidth dissappearing (1 Viewer)

[Danny R]

I've got a weird problem.

With 1 internet application open, I get a pretty good download speed of 150kb/sec or so.

With 2 internet apps open, the speeds drop by half.

With the 3rd, the speed drops again, etc.

I'd think this was normal behavior, but for two things:

A) The speed drop is not in proportion to the actual bandwidth used by the new application. I lose about 50Kb/sec bandwidth in one app even though an FTP download is running at 2K/sec or so.

B) the faster speeds don't resume when the apps close. (processes are definately halted). I have to reboot to get the first app back up to full speed.

C) the speed drops even if one app is uploading, and the other is downloading. This is a DSL line and the two speeds should separate.

Any suggestions? This is a Windows XP professional machine, running off an internal DSL modem using PPPoE. QoS is not listed as being installed in any of the network connections. Firewall is also not turned on.

 

[John_Berger]

C) the speed drops even if one app is uploading, and the other is downloading. This is a DSL line and the two speeds should separate.

Well, yes and no. They don't share the same throughput (uploading does not automatically mean that download is reduced by the amount of the upload stream), but they are not "separate" as you might think.
One thing that you need to realize about the TCP/IP stack (and why it's not one of the most efficient protocols) is that when using a TCP connection, which I am assuming is the case, every data packet sends and receives an acknowledgement as well as checksum signal and the order in which the packet should be received. This is the way that the two computers can confirm that the data is being sent in order and that there is no corruption.
So, even if you're downloading, your upstream is being hit pretty hard as well because your computer is saying, "Hey, I just received this packet. Here is the checksum. Did it come across all right?" The downloading computer checks the checksum against its own and sends a signal with a yea or nay. Your computer acknowledges that and either requests the same packet in the event of a failure or the next packet in the event of a success.
This explains why uploading has a direct impact on downloading. Not only is the upload taking up upstream bandwidth, but the download is fighting for upstream bandwidth to confirm with the source server that the download is being sent correctly. Uploading and downloading have different bandwidths, but they are not independent of each other.

 

[MikeyWeitz]

No ofense, but I wouldnt call 150 Kb a good speed by any means (unless you are on dial up ;-)
Actually 150kb is horrible. What type of service do u have?

 

[John_Berger]

I would venture that it's the common misconception that he's referring to kiloBYTES, not kiloBITS. Unfortunately, a lower case "KB" is being more frequently used anymore.

Just for reference to those who don't know what I'm talking about..

The proper notation for kiloBIT is Kb.

The proper notation for kiloBYTE is KB.

Same thing with megabit and megabyte, gigabit, gigabyte, etc.... Lower-case "b" is "bit; uppder-case "B" is byte.

Almost all DSL providers have 1.5 Mb (150KB/sec) as an option as long as you're within the proper distance from the central office, so that what I'm assuming that he meant since just about all applications display transfer speeds in BYTES.

 

[Danny R]

Yes, the speed is kilobytes.

As an update, I think I've narrowed the problem down to my mIRC application. Once its in the mix, it starts hogging all sorts of bandwidth and not giving it back. I run a file server, and with each added connection it loses even more bandwidth.

Anybody else see this problem with mIRC?