This contract outlines a maximum amount of usable data, usually highlighted in either megabytes or gigabytes, allotted per month for the user.
The limits imposed on unlimited plans are designed to fight against attempts to misuse the network, such as a DDoS attack, but are more commonly reasoned as a method to increase the number of people that can use one tower simultaneously.
When a network is near reaching peak capacity data speeds may be slowed down by carriers as part of most major telecom contracts.
Users are required to pay flat-rate additional fees that occur when they go above the amount of data given to them in their contract, utility, or prepaid plan.
The cost per gigabyte of this fee is usually higher than what the contract itself offers, which discourages users from over-utilizing data and incurring a charge for the carrier.