Symmetrical Throughput

Symmetrical throughput means that your upload speed is the same as your download speed.

For most people that have a DSL connection this is not the case.  Your download speed is much, much greater than our upload speed (usually 10/1).  The reason behind this is a technical one but it actually works out for most of us because generally we are consuming (downloading), more internet content than we are generating (uploading).

But, when we do need to upload something generally what happens is your entire internet connection becomes unusable.  The reason why is a little bit technical.

A typical internet “conversation” goes like this.

You: send me some information, and the internet responds ‘OK’ here it comes.

Internet: here is your information, and you respond back ‘OK’, I got it.

Each of those ‘OK’s is what is called an Acknowledge, or ACK packet.  They are very small, but very important, because until you or the internet acknowledges that the information has been received, generally the connection stops.

Lets say you are watching a movie, using a bunch of your download capacity.  Each time a chunk of movie comes down the pipe, you send back an ‘ACK’ packet, which tells the internet to keep sending your movie.  The only use for your upload capacity is sending back these ‘ACK’ packets.  But because they are so small, you are not using it up.

As you are watching your movie, your daughter decides to email a picture she just took to her friend.  The picture starts to go out, using up ALL of your upload capacity, which is VERY easy to do because your upload capacity is generally 1/10th the amount of your download capacity.

Suddenly your movie just stops.  Why?

Because the ‘ACK’ packets you were sending back to continue to get your movie are now not going out because they are jammed up competing with your daughters picture being emailed.

And until that email gets sent and your upload capacity becomes available again, you are screwed.  You can’t download anything.  The ‘ACK’ packets for the email come through easily because there is plenty of available download capacity.

Other times when you might be using your upload to capacity.

  • Backing up your computer to the cloud.
  • Syncing your DropBox/Google Drive, or other cloud based information.
  • Uploading pictures to Facebook or other photo sharing sites.
  • Uploading a video to Youtube or other video sharing site.

In general we do consume more than we generate, but when we need to generate something, it should not affect what we are consuming.

Internet connections like fiber and wireless are capable of having the same upload and download speeds.  DSL does not and is one of the reasons why DBIUA is not looking at using this technology to bring internet to it’s members.