Rudy Hoebeke

Dynamic bandwidth allocation on SuperPON

Currently, the first FSAN compliant ATM-based Passive Optical Networks (APON) are installed in the field. A possible evolution scenario for these types of access networks could be the so-called SuperPON system. The SuperPON system exploits all possible upgrades of an FSAN APON system. It comprises namely an upgrade on the following parameters: range: 100 km instead of 20 km; split: 2048 instead of 64; and bitrates: 2.4 Gbit/s downstream instead of 622 Mbit/s and 311 Mbit/s upstream instead of 155 Mbit/s. Due to these significant changes in system parameters, it becomes of the utmost importance to implement a dynamic Medium Access Control (MAC) protocol on the SuperPON, since the upstream bit rate is rather limited for such a large number of connected Optical Network Units. Main challenges specific to the SuperPON are the impact of long range and high number of users on the efficiency of the MAC protocol.

ABR functionality in an ATM service multiplexer: implementation, experiments, and simulations

This paper considers the implementation of ABR functionality in a queuing point located in the access part of the network. The developed Explicit Rate flow control mechanism is the result of a balanced trade-off between implementation complexity and link load efficiency. Also, the ABR end-system behavior is implemented on a Network Interface Card. At the same time, a solution is presented to realize ABR in a service multiplexer built around a shared-medium bus. Experimental and simulation results are presented which show the main characteristics of ABR. It is demonstrated that a cost- effective implementation of ABR performs very efficiently.

Evaluation of medium access mechanisms in HFC systems with ATM cell transport

An important element in the performance of the Medium Access and Control (MAC) layer of Hybrid Fiber Coax (HFC) systems are the medium access mechanisms employed: e.g. requests via contention mini-slots, piggybacking requests, request poling, etc. Therefore, the starting point in the design of the MAC of ATM cell based HFC systems, is an evaluation of the candidate mechanisms, which is presented in this paper. Furthermore, it is shown that different traffic types need different ideal MAC mechanisms, or different ideal combinations of them. Several proposals will be given for different traffic classes, and while in standardization and early deployment a lot of attention goes to Internet traffic today, this paper will consider in addition also the very different traffic of ATM terminals, which is rate controlled according to the ATM traffic characteristics.

Probiding GFR Guarantees for TCP/IP Traffic over APON Access Systems

The paper focuses on providing bandwidth guarantees for the Guaranteed Frame Rate (GFR) service category in the context of ATM-based Passive Optical Networks (APONs). Our work builds on the research performed on ATM multiplexers and extends it with the specifics of the APON access system. We study the performance of two known buffer management schemes (DFBA, WFBA), combined with either FIFO or per-VC queueing, when applied on virtual circuits carrying TCP/IP traffic. Our simulation results show that with fairly small buffers at the Optical Network Units, the schemes based on per-VC queueing yield very good performance in large number of cases. The schemes based on FIFO queueing suffer from unfairness, although they do provide bandwidth guarantees in case the GFR bandwidth reservation is kept reasonably small. Tagging helps protecting TCP-like responsive traffic but does not prevent aggressive traffic from grabbing the nonreserved bandwidth. Tagging also increases unfairness.