18 November 2006

Why Teenagers are bad.

Teenagers are bad. Well at least they are if you run an Internet Service (ISP).

I work at an ISP in Arusha, Tanzania. My company is called AFAM Ltd and we have a contract to manage the day to day running of the ISP, Arusha Node Marie, better known as "habari". Once upon a time I was the main technical person but as we grew to 40 emmployees I am more of a manager than a techie.

Recently I was reading on the website of our Bandwidth Mangagement software. They kept saying: "Kids are bad, teenagers are bad. Teenagers are bad." This is in reference to what they can do to bandwidth.

The following incident is a common occurrance in our business and something we discuss with clients every day. It could be a home situation or an office situation.

We have a client with a home connection. The family's name is Penda (fictional of course). There is a mom and dad, a 17 year old boy and a 14 year old girl. They have a DSL connection for a couple of years and are fairly happy with it but they never tell the ISP that.

One fine day the son, Wimbo, learns about downloading music from a buddy at school. That evening he goes home and installs a file sharing programme on his PC. I will call this type of programme peer-to-peer or p2p from now on. He downloads a few songs and gets pretty excited listening to free music. So he downloads another 10 and listens to a few. He calls his friend to tell him how cool it is. His friend invites him to come over. Wimbo declines as he wants to download music. Hassan explains that he should spend 15 minutes choosing 200 songs to download, then leave the songs downloading and come over for some food and watching a movie. Cool.

They have a good evening and Wimbo goes home and finds 80 songs on his computer. He puts another 500 songs on and goes to bed.

The Penda family is still happy, and Wimbo is really really happy.

On Friday Mama Penda wants to use the computer, email some friends, chat with some friends, and read some news. She has been busy the last couple of days and only now has the opportunity to sit at the computer.

Wimbo comes home and tells mom he is going out for pizza with friends in a bit after using the computer. Mama says okay and reads her mail.

Wimbo, the teenager, goes to his room and quickly chooses 500 songs and 2 movies to download over night, switches off the monitor and leaves the computer CPU downloading his choices. He says goodbye to mama and goes out for the evening.

Mama Penda suddenly sees the speed of the Internet access become slower and slower until most of the time she can't open her mail or read any news. She is slightly irritated and goes to the kitchen and gets a coke and goes back to the Internet.

Lets leave Mama Penda for a bit and look at p2p on the Internet.
The clever people who created p2p created new protocols for data transfer, much more sophisticated than email and web browsing protocols created in the 1980's. I mean very sophisticated. ISPs hate p2p stuff

First mail and web traffic, how does it flow? Over simplified, the home PC initiates(requests) a webpage. The host site recieves the request and sends the first part of the website. This might be the whole page or might be one part of 100 pieces of the website. It doesnt send the next part until the PC sends an acknowledgement (called an 'ack') that it recieved the first piece of the webpage. When the host webserver gets the ack (acknowledgement) packet it sends the next, and so on and so forth. The faster the ack is sent back the faster the packets are sent by the webserver. Same for email. When the network is congested (slow) the speed slows down.

Now p2p works differently. It doesn't wait for acks, it just sends packets and doesn't care if they are in the wrong order or missing, that will be sorted out later. In addition p2p looks for the file on multiple servers (actually a PC that has allowed sharing of their files), and they all participate in transfering the file according to complicated protocols. There are some acks, but basically p2p will not care about congestion, it will try to fill up the pipe as it were. So p2p runs faster and web and mail run slower and slower when on the same network.

If on a network connection, like this home, if someone is seriously using p2p it will tend to consume all the allocated bandwidth for that connection, and the mail and web will keep slowing down as the network is congested. Especially when the p2p user has chosen many files/music to download.

Back to the Penda Family. Mama is pretty fed up now as she really wants to do these emails. It is 6pm and she calls the ISP.

Customer support(CS): "Hello."
Mama Penda(MP): "My connection is soooooo slow. I am not happy. Why are you giving such poor service? I cant even read my emails."

CS: "I am sorry to hear that, let me check your connecton. What is your name?"
MP: "Penda"

CS: "Ok, give me a few seconds."

CS: "Hmmm, we see that the link quality is okay but that you have a very large amount of traffic. In fact it has been going on for a few hours. Are you downloading music?"

MP: "What is downloading music? NO, I am not doing that. I am reading my emails only on hotmail. Stop asking questions and fix the connection!"

CD: "Well, we see a constant upload and download of peer to peer traffic. Just a second."

CS: "From our database we see that you have a number of computers connected, is someone else using a seperate computer?"

MP: NO! I am the only person at home right now.

CS: Even though the person is not there they could have set it up to download music while they are away. Could you turn off that computer if it is on.

MP: I am sure it is not on, my son went out for the evening.

CS Maa'm, could you please check.

MP: Well okay, but I wish you would fix your lousy service instead of not trusting me.

Mama penda goes away for two minutes and comes back on line.

MP: My son's computer is off. So now will you believe me and fix my connection so I can work. I pay you every month, and alot of money. Do your goddam job!

CS: Ok lets try this. Please unplug the network cable to your PC.

CS explains how to do this and it takes awhile but Mama Penda agrees to find the cable and removes it.

CS: Hmm there is still traffic. I am sorry but are you sure there isn't another computer?

MP: I TOLD you we only have the two computers.

CS: Ok, please plug the cable back into your computer and could you do the same thing on your son's computer.

MP: I dont see how that will help.

CS: Please maa'm.

MP: well ok..........

CS: and see if any lights are on on that PC

a minute later Mama Penda comes back

MP: I removed the cable and there was a green light flashing back there.

CS: Okay now we are getting somewhere. Your traffic is starting to drop drastically, now try to look at your email.

MP: ok, wait a minute

a minute later

MP: Okay now I can get my emails. What did you do?

CS: Your son is downloading music and that consumes all the bandwdith and leaves no bandwidth for you to browse. Have your son schedule the p2p music downloads after you have finished your work and turn it off in the morning.

MP: Okay but please keep the speed like this from now on, I dont want more problems.

CS: Maa'm, the problem was the way your son uses the Internet.

MP: any way bye.

Son Wimbo comes home and finds his computer hasn't finished and he can't browse. So he calls the ISP in the morning to complain that the Internet doesn't work. It takes 10 minutes to get him to plug the cable back in.

Next night Mama penda calls again about the slow connection.

P2p traffice has protocols that behave differently that mail and web traffic. Web and mail traffic are self throttling, if the connection is slow or congested the traffic slows down. P2P traffic tries to run faster and faster regardless of congestion. Eventually it takes all the bandwidth if enough files are downloading.

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