Pedro Pedroso

Integrating GMPLS in the OBS Networks Control Plane

The GMPLS set of protocols have been consolidated as the model for building up a Control Plane for WCS (Wavelength Circuit Switched Networks). GMPLS, which is an extension of the MPLS model adopted in IP networks to introduce traffic engineering, constrained routing and connection oriented facilities, includes extensions to introduce these facilities also to circuit switched networks like SDH and WDM networks. Now, adapting GMPLS to optical networks providing statistical multiplexing capabilities like Optical Burst Switching (OBS) networks means close the cycle, since we are coming back to the origins, a packet switched network. In this paper we first discuss the main characteristics of OBS networks and compare them with those of IP and WDM networks, then based on these characteristics we analyze the potential new requirements of building up a Control Plane for OBS networks, and finally we suggest how to integrate GMPLS the OBS control plane.

An interoperable GMPLS/OBS Control Plane: RSVP and OSPF extensions proposal

The GMPLS/OBS Control Plane is a bold research topic. Optical Burst Switching (OBS) networks need to be capable to be rapidly reconfigured with the aim of achieving an efficient use of bandwidth, low latency and high degree of transparency. The OBS Control Plane is just a packet switched network requiring a high control complexity. The demands are clear but a well-defined control plane is still an open issue. As one of excellent candidate control plane for most of network scenarios, Generalized Multi-Protocol Label Switching (GMPLS) is being taken as a reference to design such OBS Control Plane. In this paper we first describe the proposal for the interoperable GMPLS/OBS Control Plane and then based on such architecture we propose and analyze some GMPLS protocol extensions that must be done to integrate it properly into OBS networks.

A performance survey on deflection routing techniques for OBS networks

In this paper, we present a survey comparing different deflection routing based techniques applied to optical burst switching (OBS) networks. For such study we consider the E-OBS architecture proposed in [1] which is an advantageous solution for OBS networks since routing decision can be taken freely inside the network without constraints on the length of the path. Under this environment, several effective routing strategies proposed in the literature are applied, namely deflection routing, reflection routing, reflection-deflection routing and multi-topology routing. The aim of this study is to analyse all these techniques considering both asynchronous and synchronous burst arrivals and compare their benefits. Moreover, we focus on a quasi-synchronous burst arrival case (with bursts not perfectly aligned) and analyse the trade-off between performance and alignment.

Virtual topology design in OBS networks

The problem of burst losses in OBS networks has an impact on the service quality perceived by end users. In order to guarantee certain level of Service Quality (QoS) in terms of burst losses, wavelength resources have to be dimensioned properly. In this paper, we address the problem of the Virtual Topology (VT) design that concerns the establishment of explicit routing paths and the allocation of wavelengths in network links to support connections with QoS guarantees in the OBS network. We consider the GMPLS control plane as an overlying technology which facilitates the establishment of VT on top of physical network topology.

Joint Routing and Wavelength Allocation Subject to Absolute QoS Constraints in OBS Networks

From the network layer perspective, the problem of burst losses is one of the most challenging problems which restrain the development of optical burst switching (OBS) networks. Indeed, OBS is a buffer-less technology and the consequent lack of guarantees for data delivery may affect significantly the quality of service (QoS) perceived by end users. To overcome these obstacles, dedicated network mechanisms and design methods are required for QoS provisioning in the network. With this end in view, in this paper, we present a traffic engineering (TE) approach to support the end-to-end traffic delivery with absolute QoS guarantees, in terms of burst losses, in an OBS network. We focus on the establishment of explicit routing paths and minimum allocation of wavelength resources in network links under the requirement that certain absolute level of burst loss probability for a given set of traffic demands is guaranteed. In this paper, we call such an off-line problem the virtual topology (VT) design problem. Since the VT design problem is NP-complete, as an alternative to the mixed integer linear programming formulation, we develop a local search heuristic algorithm to solve it. Moreover, we focus on a dynamic OBS network scenario, where the offered traffic is subject to a change. In this context, we propose an on-line VT maintenance mechanism that is responsible for traffic admission control and adaptation of the VT to traffic changes. Eventually, proposed algorithms and mechanisms for the TE-driven end-to-end QoS approach are verified both numerically and by means of network simulations for a number of network scenarios.

Dynamic Compact Multicast Routing on Power-Law Graphs

Compact routing schemes address the fundamental tradeoff between the memory space required to store the routing table entries and the length of the routing paths that these schemes produce. This paper introduces the first known nameindependent, leaf-initiated dynamic compact routing scheme that allows the distribution of traffic from any source to any set of leaf nodes along a multicast routing path that defines a distribution tree. By means of the proposed scheme, a multicast distribution tree dynamically evolves according to the arrival of leaf-initiated join/leave requests. To evaluate the performance we consider the following metrics: the stretch of the produced routing paths, the size and the number of routing table entries, and the communication cost. The results obtained by simulation on synthetic power law graphs (modeling the Internet topology) show that our scheme can successfully handle leaf-initiated dynamic setup of multicast distribution trees. Two reference multicast routing schemes (the Shortest Path Tree and the Steiner Tree algorithm) are used to compare the performance of the proposed scheme. While increasing the communication cost compared to the Shortest Path Tree, the proposed scheme achieves considerable reduction of the routing table size compared to both reference schemes. Moreover, the stretch of the resulting multicast routing paths show limited deterioration compared to the minimum value obtained with Steiner Trees.

A GMPLS/OBS network architecture enabling QoS-aware end-to-end burst transport

This paper introduces a Generalized Multi-Protocol Label Switching (GMPLS)-enabled Optical Burst Switched (OBS) network architecture featuring end-to-end QoS-aware burst transport services. The proposed GMPLS/OBS architecture guarantees specific burst loss probability requirements, independently of the offered network load. This is achieved through the configuration of burst Label Switched Paths (LSPs) over the network which are set-up at the GMPLS control plane level only, while it is the OBS node controller the responsible for eventually committing data plane resources upon burst arrival. In such a way, statistical multiplexing feature is preserved and, at the same time, the end-user QoS demands are met by tightly dimensioning the LSPs. A Mixed Integer Linear Programming (MILP) model is devised to provide the optimal burst LSPs dimensioning according to the offered network load and QoS requirements. Moreover, GMPLS-driven capacity reconfigurations are dynamically triggered whenever unfavorable network conditions are detected. The performance of the proposed architecture is extensively assessed on several network scenarios. Future work on the topic is finally outlined.

AnyTraffic Routing Algorithm for Label-Based Forwarding

The high capacity provided by packet-switched networks is supporting the proliferation of bandwidth intensive multimedia applications which require multicasting capability. As a consequence on todays networks, unicast and multicast traffic compete for shared resources where a router must maintain both unicast and multicast forwarding states. Pursuing a forwarding state reduction, in this paper we introduce the novel concept of AnyTraffic data group which consists of a group of nodes receiving both unicast and multicast traffic over the same single minimum-cost network entity. A novel heuristic algorithm is specifically defined to accommodate such data group and has been compared with the standard shortest path (SP) algorithm - the optimal case for unicast routing - and a classical Steiner tree (ST) heuristic algorithm - the optimal case for multicast routing. Exhaustive experiments have been performed to validate the proposed algorithm.

Adaptive burst admission and forwarding in OBS networks

This paper addresses the problem of controlling the performance of optical burst switching (OBS) networks in presence of non-stationary traffic demands. We propose a joint burst admission control and forwarding mechanism that operates in core nodes. This mechanism dynamically adapts its behaviour according to the feedback messages received from other nodes. By not forwarding certain bursts not complying with given requirements, an admission control is implicitly made. Moreover, by forwarding bursts to appropriately selected nodes, traffic balancing is achieved. The advantageous effects of the proposed mechanism can additionally be amplified by granting extra offset time to the burst. The benefits provided by this mechanism are supported by numerical results.

AnyTraffic Labeled Routing

This paper investigates routing algorithms that compute paths along which combined unicast and multicast traffic can be forwarded altogether, i.e., over the same path. For this purpose, the concept of AnyTraffic group is introduced that defines a set of nodes capable to process both unicast and multicast traffic received from the same (AnyTraffic) tree. The resulting scheme is referred to as AnyTraffic routing. This paper defines a heuristic algorithm to accommodate the AnyTraffic group and to find the proper set of branch nodes of the tree. The algorithm supports dynamic changes of the leaf node set during multicast session lifetime by adapting the corresponding tree upon deterioration threshold detection. Studies are performed for both static and dynamic traffic scenarios to i) determine the dependencies of the algorithm (node degree, clustering coefficient and group size); and ii) evaluate its performance under dynamic conditions. Initial results show that the AnyTraffic algorithm can successfully handle dynamic requests while achieving considerable reduction of forwarding state consumption with small increase in bandwidth utilization compared to the Steiner Tree algorithm.