Providing Rate Guarantees to TCP over the ATM GFR Service

The ATM Guaranteed Frame Rate (GFR) service is intended for best e ort tra c that can bene t from minimum throughput guarantees. Edge devices connecting LANs to an ATM network can use GFR to transport multiple TCP/IP connections over a single GFR VC. These devices would typically multiplex VCs into a single FIFO queue. It has been shown that in general, FIFO queuing is not su cient to provide rate guarantees, and per-VC queuing with scheduling is needed. We show that under conditions of low bu er allocation, it is possible to control TCP rates with FIFO queuing and bu er management. We present analysis and simulation results on controlling TCP rates by bu er management. We present a bu er management policy that provides loose rate guarantees to SACK TCP sources when the total bu er allocation is low. We study the performance of this bu er management scheme by simulation.