Nattapong Kitsuwan

Performance of Optical Packet Switches Based on Parametric Wavelength Converters

In an optical packet switch (OPS), input fibers carry multiple wavelengths, each of which carries a packet to one output fiber. As several wavelengths from different inputs could be destined to the same output fiber, one wavelength can be connected and the others remain disconnected, losing the carried packets. Because of the multiple wavelengths available at an output fiber, wavelength conversion in the OPS of the unconnected wavelengths into those available can increase the number of connections. A parametric wavelength converter (PWC) provides multichannel wavelength conversion where wavelengths can be converted to another. A PWC uses a pump wavelength that can be flexibly chosen to define which wavelengths can be converted, defining the so-called wavelength conversion pairs. However, it is unknown which set of pump wavelengths, and therefore the set of connection pairs, should be selected to improve the OPS performance while the number of PWCs in the OPS is reduced. This paper proposes a pump wavelength selection policy for an OPS that uses different pump wavelengths, one for each PWC, within an arbitrarily selected interval. This policy is called a variety-rich (VR) policy. This paper also introduces a non-wavelength-blocking OPS (NWB-OPS) to make full use of PWCs. The switch performance is evaluated through computer simulation. The results show that the proposed policy with different pump wavelengths achieves the highest performance when compared with another of similar complexity. Furthermore, the performance study shows that small sizes of the interval to select a pump wavelength are more beneficial than larger ones.

Independent transient plane design for protection in OpenFlow-based networks

Network protection against link failure is required to allow packets to reach the destination with minimal packet loss when a failure occurs. When a link fails, traffic that attempts to use the failed link is interrupted. Typically, routers in the network discover the failure and find a new route to bypass the failed link. Alternatively, well-known segment protection schemes can also be used to speed up the link recovery time by rerouting packets locally through precalculated protection paths. However, several backup paths have to be prepared for each primary path, making path configuration rather complex and poorly scalable. This paper proposes a design for fast rerouting in an OpenFlow-based network. This new design reduces the number of flow entries and the number of configuration messages needed for network rerouting, which in turn reduces the memory size needed in each switch and the CPU load at the controller. We show empirically and using simulations that our design can reduce the number of flow entries and configuration messages needed by about 60% and 75%, respectively, when compared with an existing OpenFlow-based segment protection design. Furthermore, we implement the proposed design on a pan-European network and show that our design can recover from a link failure in as little as 25 ms.

Experimental End-to-End Demonstration of Shared N:M Dual-Homed Protection in SDN-Controlled Long-Reach PON and Pan-European Core

Seeking reduction of capital and operational costs on next-generation fiber networks is the holy grail of network planning and deployment for all operators worldwide. In particular, efficient deployment strategies of next-generation fiber access networks is of paramount importance to enable wide-scale ubiquitous deployment of high-speed broadband services. Exploiting the large capacity of fiber networks to support heterogeneous services from residential and business users is a promising strategy toward this goal. Long-reach passive optical networks (LR-PON) is one such strategy that also adopts greater sharing of active and passive components, together with consolidation of central offices, to reduce capital and operational expenditures. However, due to its long reach and large split ratio, protection mechanisms become a major consideration when designing an LR-PON, as a single feeder cable cut could disrupt services for several thousand users. In this paper, we demonstrate fast restoration of LR-PON services using a dual-homed shared optical line terminal (OLT) protection mechanism. Our end-to-end testbed connects our optical access broadband laboratory operating on custom built LR-PON ONU and OLT field programmable gate array prototypes with a Europe-wide testbed core network. We use a software-defined network control plane to manage the dual-homed N:M protection switching and traffic reroute in the core and achieve access protection and end-to-end services restoration times of 40 and 80 ms, respectively.

Recursive Parametric Wavelength Conversion Scheme for Optical Packet Switch

This paper proposes a scheme to increase possible patterns of wavelength-conversion for an optical packet switch (OPS) with parametric wavelength converters (PWCs) by obtaining additional converted wavelengths using the existing resources. It is called a recursive parametric wavelength conversion (RPWC) scheme. A PWC uses a pump wavelength to define the original and converted wavelengths, called wavelength conversion pairs. None of conversion pairs from any PWCs can sometime support the request, although some wavelengths at the requested output fiber are available. Therefore, packet loss occurs and several conversion pairs are wasteful. In RPWC, unused conversion pairs are used to create additional conversion pairs. The OPS allows each wavelength to be converted using combination of unused conversion pairs using more than one PWC, instead of using only a single PWC as in a conventional scheme. Simulation results show that RPWC achieves lower packet loss rate than the conventional scheme, under both uniform and non-uniform traffic. To show the feasibility of RPWC, we develop a prototype of an optical switch with RPWC and demonstrate it in experiment.

A Novel Protection Design for OpenFlow-Based Networks

Network protection against link failure is required to allow packets to reach the destination with minimal packet loss when the failure occurs. When a link fails, traffic that attempts using the failed link is interrupted. Typically, routers in the network discover the failure and find a new route to bypass the failed link. Alternative well-known segment protection schemes can also be used to speed up the link recovery time, by re-routing packets locally through pre-calculated protection paths. However, several backup paths have to be prepared for each primary path, making path configuration rather complex and poorly scalable. In this paper, we propose a network protection mechanism aiming at reducing the complexity of the path configuration process, based on OpenFlow. The performance of the proposed design is compared to that of an existing OpenFlow-based segment protection mechanism. Results show that our design can reduce by about 60% the number of flow entries and by 75% the number of configuration messages, leading to a substantial reduction in memory and CPU usage on each OpenFlow switch.

Performance of a routing and wavelength assignment scheme for an optical-carrier-reusable ring network

This study investigates a heuristic routing and wavelength assignment (RWA) scheme for an optical-carrier-reusable ring network. This network has two unique features. First, only one light source, called the multi-carrier light source, is required which eases the difficulty of controlling many light source devices. Second, optical carriers are reused in order to improve the efficiency of wavelength usage. Given the target of wavelength-resource-efficient channel establishment, performance of the heuristic RWA scheme is evaluated. To realise efficient wavelength usage, the authors formulate the RWA problem as an integer linear programming (ILP) problem of obtaining the minimum number of required wavelengths for given requests. With the ILP approach, the calculation process is not tractable in practical time. The heuristic RWA scheme introduced in this study solves the RWA problem. This scheme consists of two algorithms. Channel routes are obtained by the routing algorithm, and the wavelength assignment algorithm is then performed to assign a wavelength to each route. Moreover, two candidates, considering the shortest path and considering the avoidance of wavelength conversion, for the routing algorithm are examined. Numerical results show that the first candidate is more suitable in terms of reducing the number of required wavelengths than the second candidate.

A routing and wavelength assignment scheme in multi-carrier-distributed optical mesh networks with wavelength reuse

This paper proposes a routing and wavelength assignment (RWA) scheme that minimizes the number of required wavelengths for wavelength-reusable multi-carrier-distributed (WRMD) mesh networks. These networks have two unique features. First, only one light source, called the multi-carrier light source (MCLS), is required, which eases the difficulty of controlling many light source devices. Second, optical carriers are reused to improve the efficiency of wavelength usage. Since there are differences between the WRMD network and the conventional network, an efficient RWA scheme for the WRMD network is needed for wavelength-resource-efficient lightpath establishment. To realize efficient wavelength usage, we first formulate the RWA problem as an integer linear programming (ILP) problem of obtaining the minimum number of required wavelengths to satisfy the given requests. For large-scale networks, the ILP approach is not practical solution times. A heuristic RWA scheme is introduced in this paper to solve the RWA problem. Simulation results show that the proposed heuristic scheme with two carrier regenerations for the WRMD network approaches the near-optimum number of wavelengths. In addition, the optimum placement of the MCLS node is shown to reduce the number of required wavelengths for lightpath establishment, and achieve the optimum number of wavelengths.

Performance of dynamic pump-wavelength selection for optical packet switch with chained parametric wavelength conversion

This paper proposes a scheme for pump-wavelength selection in an optical packet switch (OPS) with parametric wavelength converters (PWCs). In this scheme, pump wavelengths can be dynamically changed in all time slots, and more than one PWC is allowed to convert a wavelength in a chained manner. The objective of this scheme is to minimize the packet loss rates of the OPS. This scheme is called dynamic pump-wavelength selection with chained parametric wavelength conversion (DPS-C). DPS-C selects the pump wavelength for each PWC so as to maximize the number of successful requests, which refer to packets that wish to be forwarded to their requested output fibers. A PWC, which has the advantage of multiple wavelength conversion, uses a pump wavelength that can be flexibly chosen to define which wavelengths can be converted from/to. The set of original and converted wavelengths, where the pump wavelength is set in the middle of the two wavelengths, is called the conversion pair. Each PWC supports several conversion pairs. The OPS allows each wavelength to be converted using combinations of available conversion pairs, which are not used by any requests, from more than one PWC. A simulation shows that DPS-C outperforms the conventional scheme in terms of packet loss rates in both uniform and nonuniform traffic patterns.

A pump wavelength assignment scheme for optical packet switch with parametric wavelength converters

This paper proposes a scheme to optimize the number of different colored light sources under the acceptable packet loss rate. It reduces the number of different colored light sources up to 50%.

Optical Packet Switch Based on Dynamic Pump Wavelength Selection

This paper proposes an optical packet switch with parametric wavelength converters (PWCs), where the pump wavelengths are dynamically changed in every time slot. It is called the dynamic pump wavelength selection (DPS) switch. A PWC, which performs multiple wavelength conversion, uses a pump wavelength that can be flexibly chosen to define which wavelengths can be converted. To enhance switch performance, the DPS switch employs a matching scheme, which sets connections between input and output ports, in combination with dynamic pump wavelength selection; a conventional switch, on the other hand, performs matching with a given set of pump wavelengths that are configured in a static manner. The dynamic pump wavelength selection is used to select the pump wavelength for each PWC to maximize the number of wavelength conversion pairs supported. Numerical results from a simulation show that the DPS switch provides lower blocking rates than the conventional switch with pump wavelengths assigned statically, under both uniform and non-uniform traffic.