Kemal Bengi

Efficient QoS support in a slotted multihop WDM metro ring

A novel distributed access protocol for a slotted wavelength-division-multiplexing (WDM) metro ring employing all-optical packet switching and supporting quality-of-service (QoS) classes is presented and analyzed. Since we assume that there are more nodes than available wavelengths in the network, we obtain a scalable multihop WDM ring as underlying network architecture. By dividing each channel into several time slots and further applying destination release and slot reuse, data packets can be efficiently transmitted and received in a statistically multiplexed manner. In our architecture, each node is equipped with one tunable transmitter and one fixed-tuned receiver. Furthermore, as we generally consider so-called a posteriori access strategies, different packet selection schemes are proposed and compared. An analytical model based on the semi-Markov process methodology is developed to quantify the performance of one of these schemes. As a key element of the protocol, an efficient QoS support access mechanism is proposed and its performance is evaluated. The new QoS control scheme adopts a frame-based slot reservation strategy including connection setup and termination, which only slightly increases the signaling and node processing overhead. Thus, an efficient hybrid protocol combining connectionless and connection-oriented packet transmissions is proposed.

QoS support and fairness control in a slotted packet-switched WDM metro ring network

In this paper, a novel distributed medium access protocol for a time-slotted WDM metro ring employing all-optical packet switching and supporting QoS classes directly in the optical layer is presented and analyzed. Since we assume much more nodes than available wavelengths in the network, we obtain a scalable multi-hop WDM ring. In our architecture, each node is equipped with one tunable: transmitter and one fixed-tuned receiver. The new QoS control scheme adopts a frame-based slot reservation strategy including connection set-up and release, thus efficiently combining connection-less and connection-oriented services. Furthermore, a fairness control scheme, named M(ultiple)-ATMR, guaranteeing fairness for best-effort traffic through a credit-based mechanism is proposed.

Access protocols for an efficient and fair packet-switched IP-over-WDM metro network

This paper proposes novel distributed medium access protocols for a time-slotted WDM metro ring employing optical packet switching and supporting variable-length data packets such as IP datagrams directly in the optical layer. A scalable multi-hop WDM ring is considered, where much more nodes than available wavelengths may be accommodated in the network. In the underlying control-channel based architecture, each node is equipped with three transmitters (two fixed-tuned and one tunable) and two fixed-tuned receivers. The new access control scheme relies on a frame-based slot reservation strategy including reservation of successive slots for data packets longer than the given slot size, and immediate access for packets shorter than the slot length. Thus, a highly efficient IP-over-WDM metro network with simple receiver hardware is obtained.

Performance of Single-Hop WDM LANs Supporting Real-Time Services

Optical wavelength division multiplexing (WDM) local area networks are capable of fulfilling the enormous bandwidth demands of present and future applications. Up to now, the WDM LAN world is primarily dominated by the passive-star coupler (PSC) based architectures, for which many medium access control (MAC) protocols have been proposed. However, an arrayed waveguide grating multiplexer (AWGM)-based single-hop WDM network seems to be a very promising alternative. One of the most critical issues in designing next generation photonic LANs is the support of real-time services for applications with different time constraints. In this paper, different basic access protocols for the PSC as well as AWGM-based single-hop WDM LANs are considered and their performance in supporting real-time traffic is analyzed by means of extensive computer simulations. For evaluation of real-time performance, packet drop rates and deadline missing rates are taken as performance measures. Furthermore, new real-time message scheduling schemes are proposed which improve the performance of protocols accommodating mixed traffic. They can be differentiated between message scheduling at the source nodes’ transmit queues and scheduling based upon control information from a control channel. It is shown that both types of priority scheduling significantly improve the overall real-time performance.

Access protocols for an efficient optical packet-switched metropolitan area ring network supporting IP datagrams

Novel distributed medium access protocols for a time-slotted WDM metro ring employing optical packet switching and supporting variable-length data packets such as IP datagrams directly in the optical layer are proposed in this paper. In the underlying control-channel based network architecture, much more nodes than available wavelengths may be accommodated and each node is equipped with three transmitters (two fixed-tuned and one tunable) and two fixed-tuned receivers. The new access control scheme relies on a frame-based slot reservation strategy including reservation of successive slots for data packets longer than the given slot size, and immediate access for packets shorter than the slot length. Thus, an efficient EP-over-WDM metro network with simple receiver hardware is obtained.

An Analytical Model for a Slotted WDM Metro Ring with A-Posteriori Access

In this paper, an analytical model based on the semi-Markov theory is developed to quantify the performance of a distributed access protocol for a slotted WDM metro ring employing all-optical packet switching and based on an a-posteriori packet selection strategy. In our architecture, each node is equipped with one tunable transmitter and one fixed-tuned receiver. Furthermore, as we generally consider a-posteriori access strategies, different packet selection schemes are compared by simulations.

CONRAD: a novel medium access control protocol for WDM local lightwave networks enabling efficient convergence of real-time and data services

This paper proposes a new medium access control (MAC) protocol named CONRAD (CONvergence of Real-time And Data services) for a passive-star based single-hop WDM local lightwave network which efficiently supports services with tight delay constraints, i.e. real-time traffic, and best-effort services, i.e. data traffic, directly in the optical layer. The integration of both service types in a packet-switched environment is primarily achieved by combining two different reservation schemes on the control channel, instead of applying conventional priority strategies or circuit-switched approaches. Thereby, a significant improvement of the access delay balance between real-time and data transmission may be obtained, while the system achieves high throughputs.

An optical packet-switched IP-over-WDM metro ring network

Novel distributed medium access protocols for a time-slotted WDM metro ring employing optical packet switching and supporting variable-length data packets, such as IP datagrams, directly in the optical layer are proposed. A scalable multi-hop WDM ring is considered since we assume many more nodes than available wavelengths in the network. In the underlying control-channel based architecture, each node is equipped with three transmitters (two fixed-tuned and one tunable) and two fixed-tuned receivers. The new access control scheme relies on a frame-based slot reservation strategy including reservation of successive slots for data packets longer than the given slot size, and immediate access for packets shorter than the slot length. Thus, a highly efficient IP-over-WDM metro network with simple receiver hardware is obtained.

A novel scalable optical packet compression/decompression scheme

A novel optical packet compression/decompression scheme is proposed allowing for high compression rates and large packet sizes thereby reducing the rate conversion latency. Extensive simulations are performed in order to investigate the feasibility of the proposed scheme. An OSNR of more than 22 dB is estimated for very large packets.

An Overview on Technologies for Access Nodes in Ultra-Fast OTDM Photonic Networks

In this paper, photonic technologies for the realization of high-capacity optical time-division multiplexed (OTDM) local and metropolitan area networks (LANs and MANs) are addressed including all-optical techniques such as ultra short pulse generation, all-optical clock recovery, optical multiplexing/demultiplexing, and optical packet compression/decompression. Furthermore, the new trends in high-speed electronics, data processing and optical interconnects are analyzed enabling the avoidance of the electronic processing bottleneck. By the use of both, high-speed electronics for implementing functions of higher complexity with higher level of parallelism and all-optical techniques for the realization of simple ultra fast (> 40 Gbit/s) medium access functions, a hybrid medium access node capable of handling high data rates can be designed.