A bandwidth cap, also known as a band cap or a data cap, limits the transfer of data to a specified amount over a period of time. Internet service providers commonly apply a cap when a channel intended to be shared by many users becomes overloaded, causing a strain on the provider. The provider then charges based on the amount the subscriber goes over the cap. Implementation of a bandwidth cap is sometimes termed a fair access policy, fair usage policy, or usage-based billing.
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Standard cap
Generally, each user of a network is expected to use high speed transmission for a short time, for example to download a megabyte web page in less than a second. Continuous usage, such as when sharing files or streaming videos can seriously impair service for others. In DSL, where the core network is shared but the access network is not, this concept is less relevant. However, it becomes more relevant in cable internet, where both the core network and the access network are shared. This issue is most relevant with wireless internet where both the core network and the access network are shared and the total network bandwidth is relatively narrow.
Capping might be handled by the user's cable modem. Knowledge of capping has led to attempts at uncapping, though this is considered by ISPs to be a theft of service. When uncapping succeeds, the resulting data transfer rate is supposed to be extremely fast, but users who are caught are said to be banned permanently by broadband ISPs.
Example cap
In 2016 in the United States a home Internet service provider offered a service plan with a data cap of 1 terabyte. At contemporary data consumption rates, each member of a family of four would need to separately watch 100 movies in a month to approach the cap. In that case, typical data usage habits would not exceed that cap.
Caps to limit competition
The increasing popularity of online video streaming services such as Netflix has caused some consumers to cancel their cable TV services in favor of Internet-only plans. This has caused cable providers to respond by creating data caps, which according to Gigi Sohn, are intended to discourage the use of video streaming. Cable companies have also resorted in some cases to requiring video streaming services to pay special fees to avoid being slowed down via throttling.
Unlimited data
"Unlimited data" is a marketing promotion in which an Internet service provider offers access to Internet without cutting service at the bandwidth cap. However, after a user passes some bandwidth cap, the provider will begin bandwidth throttling to decrease the user's speed of access to data.
By region
As of October 2015, there were 58 wired broadband providers in the US that used data caps, among them major wireless cell phone providers such as Verizon Wireless and AT&T.
Before 2010 there was a trend of providing unlimited data without bandwidth throttling. In the United States the Federal Communication Commission has fined service providers for offering unlimited data in a way that misled consumers. In June 2015, the FCC fined AT&T Mobility US$100,000,000 for misleading consumers. In October 2016 the FCC reached a settlement with T-Mobile in which they would pay US$48,000,000 for failing to disclose restrictions on their unlimited data plans.