Providing guaranteed bandwidth for TCP/IP traffic in ATM networks

Abstract

Guaranteed frame rate (GFR) aims to provide minimum cell rate (MCR) guarantees for non-real-time traffic like TCP/IP traffic and allow traffic in excess of the MCR to fairly share residual bandwidth in ATM networks. For traffic controls in a frame level, the GFR requires ATM switches to be aware of frame boundaries so that the service can be based on AAL-5 PDUs (frames) that can be delineated at the ATM layer. ATM switch implementation methods that accomplish the GFR service consist of a frame classification algorithm, called frame-based generic cell rate algorithm (F-GCRA), and a frame forwarding mechanism. Combination of the F-GCRA and a simple FIFO-based frame forwarding mechanism is a feasible implementation method because of a low cost in its implementation and operation. But, this method has failed to support guaranteed bandwidth to GFR virtual channels (VCs) with a relatively large MCR. Thus, complex buffer allocation schemes that can properly allot a buffer to each VC or rate-guarantee scheduling disciplines with per-VC queuing are necessary for satisfying GFR service requirements, but it is too complicated to implement them. The objective of this thesis is to develop a feasible switch implementation method that can provide the GFR service guarantee for TCP/IP traffic in ATM networks. For this purpose, we enhance the simple FIFO-based frame forwarding mechanism to improve fairness in the use of residual bandwidth and propose a novel frame classification algorithm that enables the simple FIFO-based frame forwarding mechanism to support MCR guarantees. First, we evaluate the performance of the simple FIFO-based frame forwarding mechanism for three TCP versions, Tahoe, New-Reno and SACK when the basic F-GCRA is applied to ATM switches. Through the performance evaluation, we find out that TCP traffic is not able to sufficiently utilize reserved bandwidth because of its bustness and the simple FIFO-based frame forwarding mechanism does not support fairness i...