Lakshman S. Tamil

On optical burst switching and self-similar traffic

In this letter we consider burst switching for very high speed routing in the next generation Internet backbone. In this scenario, Internet protocol (IP) packets to a given destination are collected in bursts at the network edges. We propose a burst assembly mechanism that can reduce the traffic autocorrelation or degree of self-similarity, and at the same time keep the delay due to burst formation limited at the network edges.

Optical routing of asynchronous, variable length packets

We discuss the introduction/implementation of optical IP routers, then we introduce a novel scheduling algorithm incorporating void filling and aimed at optical routing of asynchronous, variable packet length packets. We describe its structure and discuss the complexity issues. Albeit introduced with the purpose of cancelling expensive optical synchronization, we argue that this approach represents the most viable all-optical approach for implementing packets-over-SONET (IP-centric scenario). We also present simulations under self-similar traffic conditions which point to the inefficiency of optical buffering to combat the effects of self-similarity, and we outline alternative strategies for proper buffer dimensioning.

Nondegenerate buffers: an approach for building large optical memories

We describe a new methodology for analyzing optical buffers with nonuniform distribution of the delay lines, the nondegenerate buffers. Coupled with an intelligent scheduling algorithm, it features improved system performance leading to more efficient and larger optical buffers. We demonstrate that the concept under bursty, both time-slotted and asynchronous traffic conditions, can lead to a sizable reduction in buffer depth requirements compared to conventional solutions.

A new scheduling algorithm for asynchronous variable length IP traffic incorporating void filling

We demonstrate that optimum switch performance can be achieved by matching the basic delay line unit in the optical buffer to the degree of self-similarity of the input traffic, in tandem with a scheduling algorithm for void filling.

Routing in all-optical packet switched irregular mesh networks

The performance of packet switching wavelength routed optical networks critically depends on packet contentions at the intermediate routers. This paper shows through simulations that deflection routing is an effective technique for packet switching wavelength routed optical networks with irregular meshed topologies. It is shown that multiple path routing (MPR) as the deflection rule mitigates the blocking of packets substantially in cross-connected all-optical networks leading to a significant reduction in hardware volume and cost of all-optical IP routers. The effectiveness of the blocking reduction critically depends on the network topology, and meshed topologies with a high number of interconnections benefit of the largest gain from deflection routing.

Optical packet switching multiple path routing

Abstract The performance of packet-switching wavelength routed optical networks critically depends on packet contentions at the intermediate routers. This paper shows through simulations that deflection routing is an effective technique for packet-switching wavelength routed optical networks with irregular meshed topologies. It is shown that multiple path routing (MPR) as the deflection rule mitigates the blocking of packets substantially in cross-connected all-optical networks leading to a significant reduction in hardware volume and cost of all-optical IP routers. The effectiveness of the blocking reduction critically depends on the network topology, and meshed topologies with a high number of interconnections benefit of the largest gain from deflection routing.

Asymmetric WDM all-optical packet switched routers

It is shown that asymmetric WDM all-optical routers architectures are the best candidates to reduce hardware volume and cost of all-optical networks. We show that due to the non-uniform network traffic behavior, routers require asymmetric wavelength conversion capabilities and also asymmetric buffering capacity to solve contention. This paper shows that due to the topology, packets may generate traffic bottlenecks produced by a tendency of the routing scheme to send packets with different destinations through preferred paths.

WDM fiber delay line buffer control for optical packet switching

A high-speed optical packet switching node using the WDM all optical switch structure is studied in this paper. Tele-traffic performance of an all-optical IP packet router is simulated under the self-similar (bursty) traffic condition. Four different control algorithms are investigated for the performance and complexity. A simple round-robin algorithm cannot attain an acceptable performance. Finding minimum buffer occupancy and sorting the packets by length are methods used to improve the IP router performance.

Performance of an optical IP router using non-degenerate buffers

We describe optical buffers with non-uniform distribution of the delay lines, so-called nondegenerate buffers. Coupled with an intelligent scheduling algorithm, nondegenerate buffers feature improved system performance leading to more efficient and larger optical buffers for optical IP routers. We demonstrate that the concept under bursty, both time-slotted and asynchronous traffic conditions, can lead to a sizable reduction in buffer depth requirements compared to conventional solutions. The simulations point to the fact that in optical IP routers operating under asynchronous conditions, this would almost be a mandatory solution.

Analysis of all-optical IP routers

The increased data traffic experienced today and the projected increase in the data traffic in the future demand exploration of novel approaches to IP transport such as transport of IP traffic over optics. The bimodal nature of the IP traffic short packets which are typical of transactional-style flows and large packets or bursts which are encountered in the transport of large data blocks requires, design of routers that are capable of routing packets with variable lengths efficiently. In this paper, we discuss the design aspects of such all-optical IP-switches. The broadcast and select architecture is a prime candidate for implementing optical IP routers. Construction of optical routers with buffering, wavelength conversion and multipath routing are considered. The merits and demerits of all these cases and the effect of buffer size, wavelength conversion and multiple-path routing on the blocking probability and probability of packet loss are discussed.