Design Issues for providing Minimum Rate Guarantees to the ATM Unspecified Bit Rate Service

We describe proposed enhancements to the ATM Unspeci ed Bit Rate (UBR) service that guarantee a minimum rate at the frame level to the UBR VCs. These enhancements have been called Guaranteed Frame Rate (GFR). In this paper, we discuss the motivation, design and implementation issues for GFR. We present the design of bu er management and policing mechanisms to implement GFR. We study the e ects of policing, per-VC bu er allocation, and per-VC queuing on providing GFR to TCP/IP tra c. We conclude that when the entire link capacity is allocate to GFR tra c, per-VC scheduling is necessary to provide minimum throughput guarantees to TCP tra c. We examine the role of frame tagging in the presence of scheduling and bu er management for providing minumum rate guarantees.