CONTENTION RATIO/CIR

I was always honest and up-front with my bandwidth clients with contention ratios, bandwidth, CIR, and the use of Skype, etc. I'm really not too sure whether they understood what I was saying and how their use impacted others (of the other way around. I would let my clients move up or down in bandwidth and contention ratio for short periods of time, for instance move down in bw and up in contention if it's just the crew onboard (in the case of a yacht) then juice the bw up and cr down when the owner and guests were onboard. And when the yacht is in port, add in local wifi services to provide higher speed and cost efficiency.

Contention rate inform the user on the minimum bandwidth (CIR) he/she will receive, if a certain number (corresponding to the contention rate) of other people will attempt to access the Internet at the same time. Contention rate in TDMA is a kind of bet for customers, who accepts to share the bandwidth with a certain number of other users, hoping that the others will not use the bandwidth all at the same time and that they will receive more bandwidth than what they are paying for. Usually, the customer subscribes the service with service provider who just start selling capacity, thus they pay only a portion of the bandwidth and benefit from the full capacity for a certain period of time, until service provider succeeds into selling the same bandwidth to multiply customers who then start to contend the bandwidth to each other and some of the users decide to change service provider and look for the one with unsold capacity. And the game starts again...

t would be a good idea if ISP were to provide customers with SLA (Service Level Agreements) so they now if it's a dedicated or shared circuit which would eliminate complaints about poor service. However there are many ISP's who don't wish to provide SLA's for fear of frightening away customers and tweaking the "Packet Shaper" to give a complaining shared service customer better service until the "hue and cry" had subsided when they could then once more tweak the Packet Shaper in some else's favor. When I visited Mexico some time ago and was socializing with expats receiving satellite internet and complaining about the quality of service I asked them what they paid per month for 512kbps full duplex service and they said $60 per month. When I told them that cost of the same dedicated space segment would be closer to $3,000 per month they got the message why the service was often very slow. Obviously the ISP had not informed them about the high contention rate.

Hi Ali, absolutely right. I like to add that the definition used by some players for "Normal Network conditions" may mean that they take average load as baseline and exclude the busy hour traffic from CIR..... same for some TV uplink providers..... Normal network conditions should mean the situation where no serious outages of circuits (like damaged fibre) is occuring. Now for land line that is typically OK but some satellite operators apply very "loose" definitions.

defining and disclosing contention with the customers is really a good practice and on top of it if for example using iDirect than defining BW per application profile and within all the other services making prioritized services contention free by doing right sizing of available capacity is sometimes very good for Quality of Experience.