The number of users that you share your potential bandwidth with. Home ADSL products such as PlanetHome 500 have a contention ratio of 50:1. That is, up to 50 users on your exchange share a common "pool" of bandwidth -- and if all 50 were attempting to use all their bandwidth at the same time, all your connections would slow down. In practice, because internet traffic tends to come in short bursts, contention is less of a problem than it sounds. However, our PlanetPlus 1000 and PlanetPlus 2000 products have a lower contention ratio of 20:1, so your level of service will be more consistent throughout the day.