The many-to-one upload trouble arises when many of users needs to upload data to a single server. Uploads correspond to an important class of scenarios, many of which are limited by a deadline. This includes, e.g., electronic submissions of income tax forms, online shopping for limited-time bargain products, and gathering data from sensor networks. Such services create hot spots, which is a major hurdle in achieving scalability in network-based applications. Two-tier protocols attempt to relieve hot spots in many-to-one applications.