A volume software license from Microsoft for customers with 250 or more PCs. Introduced in 2001 to become effective in 2002, it offers a Software Assurance option that entitles the customer to all upgrades within the annual licensing period. Although the cost of each upgrade is reduced, customers are paying for all the upgrades. If customers do not elect this plan, they must pay a much higher cost of the product when they do choose to upgrade, because they feel it is necessary. Licensing 6.0 was controversial because it was the beginning of an annual-fee-for-software strategy.