Contention ratio

From Wikipedia, the free encyclopedia

In computer networking, the contention ratio is the ratio of the potential maximum demand to the actual bandwidth. The higher the contention ratio, the greater the number of users that may be trying to use the actual bandwidth at any one time and, therefore, the lower the effective bandwidth offered, especially at peak times. ^[1]

In the UK, an RADSL (Rate Adaptive Digital Subscriber Line) connection usually has a contention ratio between 20:1 and 50:1 per BT guidelines, meaning that 20 to 50 computers, each assigned or sold a bandwidth of "up to" 1 Mbit/s for instance, may be sharing 1 Mbit/s of uplink bandwidth. A good account of the state of the issue in the UK is found in a 2004 OFCOM report on wireless internet.

In the US and on satellite internet connections, the contention ratio is often higher, and other formulas are used, such as counting only those users who are actually online at a particular time. It is also less often divulged by ISPs than it is in the UK. The connection speed for each user will therefore differ depending on the number of computers using the uplink connection at the same time because the uplink (where all the low bandwidth connections join) will only handle the speed that has been implemented on that line.

Source.

Slowness can come from a number of places including those you have just indicated. This next week will be 'interesting'.

What I was trying to say is more like this:

Right now, the kids are at school and the majority of people at work. There are fewer people on the Internet in any one location. Come 4pm, the kids come home and add a fair load to the Internet with their MSN, Youtube, playing music, whatever. Come 6pm the adults are joining them. It is not until the kids go to bed that these Users decrease and this begins about 10pm and tapers off till about midnight.

If you consider that you are actually sharing your bandwidth with 15-50 others depending on your ISP, these others will affect your throughput but not your speed. The the lower the ratio the more likely you are to have a consistant connection.

In other words, if you are sharing your connection with big downloaders, your speed will deteriorate drastically, even if you are not asking much of it.

Watch out for these times. Here in the UK, 10am is about as fast as the Internet gets and that is about the time that Sandy posted. If this is consistant, it tends to indicate that the main bottle-neck is local to her. If it doesn't match that pattern closely, it indicates something else.

One of the first things I do if yuku goes slow is to check other sites. I check local ones and I check East Coast USA ones and I check West coast USA ones. If they are all fast, the problem is likely yuku end. If I find a slowness elsewhere, I investigate that further, if I can be bothered. Often I find bits of the Internet are not so good and if it is not related to time of day, it is likely a major hub down somewhere.

My experience generally agrees with yours then. Let's see what this week produces.