J.C. de Oliveira

A performance evaluation study of RPL: Routing Protocol for Low power and Lossy Networks

In this paper, a performance evaluation of the Routing Protocol for Low power and Lossy Networks (RPL) is presented. Detailed simulations are carried out to produce several routing performance metrics using a set of real-life scenarios. A real outdoor network was reproduced in simulation with the help of topology and link quality data. Behaviors of such a network in presence of RPL, their reason and potential areas of further study/improvement are pointed out.

New preemption policies for DiffServ-aware traffic engineering to minimize rerouting in MPLS networks

The preemption policy currently in use in MPLS-enabled commercial routers selects LSPs for preemption based only on their priority and holding time. This can lead to waste of resources and excessive number of rerouting decisions. In this paper, a new preemption policy is proposed and complemented with an adaptive scheme that aims to minimize rerouting. The new policy combines the three main preemption optimization criteria: number of LSPs to be preempted, priority of the LSPs, and preempted bandwidth. Weights can be configured to stress the desired criteria. The new policy is complemented by an adaptive scheme that selects lower priority LSPs that can afford to have their rate reduced. The selected LSPs will fairly reduce their rate in order to accommodate the new high-priority LSP setup request. Performance comparisons of a nonpreemptive approach, a policy currently in use by commercial routers, and our policies are also investigated.

Applicability Study of RPL with Local Repair in Smart Grid Substation Networks

In this paper, a performance evaluation of the Routing Protocol for Low power and Lossy Networks (RPL) in a typical outdoor Smart Grid Substation Network is presented. Detailed simulations are carried out to produce several routing performance metrics using real-life scenarios. The real outdoor network was reproduced in simulation with the help of topology and link quality data gathered from the network over the time. Behaviors of such a network in presence of RPL and local repair mechanism, and potential areas of further study/improvement are pointed out. This study shows, RPL has the desired advantages of bounding control overhead and low delay. It also provides quick repair of local outage of link to root node and path quality fairly close to an optimized shortest path for an outdoor deployment.

Optimal policy for label switched path setup in MPLS networks

An important aspect in designing a multiprotocol label switching (MPLS) network is to determine an initial topology and to adapt it to the traffic load. A topology change in an MPLS network occurs when a new label switched path (LSP) is created between two nodes. The LSP creation involves determining the route of the LSP and the according resource allocation to the path. A fully connected MPLS network can be used to minimize the signaling. The objective of this paper is to determine when an LSP should be created and how often it should be re-dimensioned. An optimal policy to determine and adapt the MPLS network topology based on the traffic load is presented. The problem is formulated as a continuous time Markov decision process with the objective to minimize the costs involving bandwidth, switching, and signaling. These costs represent the trade-off between utilization of network resources and signaling/processing load incurred on the network. The policy performs a filtering control to avoid oscillations which may occur due to highly variable traffic. The new policy has been evaluated by simulation and numerical results show its effectiveness and the according performance improvement. A sub-optimal policy is also presented which is less computationally intensive and complicated.

TEAM: A traffic engineering automated manager for DiffServ-based MPLS networks

In this article an automated manager called traffic engineering automated manager (TEAM) for DiffServ/MPLS networks is introduced, and its design and implementation details are discussed. TEAM is designed for complete automated management of an Internet domain. TEAM is an adaptive manager that provides the required quality of service to the users and reduces the congestion in the network. The former is achieved by reserving bandwidth resources for the requests and the latter by distributing the load efficiently. These goals are achieved by online measurements of the network state. TEAM is composed of a traffic engineering tool (TET), which adaptively manages the bandwidth and routes in the network, a measurement and performance evaluation tool (MPET), which measures important parameters in the network and inputs them to the TET, and a simulation tool (ST), which may be used by TET to consolidate its decisions. These three tools work in synergy to achieve the desired network operation objectives. The experimental results demonstrate the efficiency of TEAM as a network manager in different and unpredictable traffic conditions at the expense of a limited increase in the computational complexity and costs.

Invited A new traffic engineering manager for DiffServ/MPLS networks: design and implementation on an IP QoS Testbed

In a multi-service network, different applications have varying QoS requirements. The IETF has proposed the DiffServ architecture as a scalable solution to provide Quality of Service (QoS) in IP Networks. In order to provide quantitative guarantees and optimization of transmission resources, DiffServ mechanisms should be complemented with efficient traffic engineering (TE) mechanisms, which operate on an aggregate basis across all classes of service. The MultiProtocol Label Switching (MPLS) technology is a suitable method to provide TE, independent of the underlying layer2 technology. Currently, the combined use of Differentiated Services (DiffServ) and MPLS is a promising technique to provide Quality of Service (QoS), while efficiently exploiting network resources. In this paper, TEAM, an automated manager for DiffServ/MPLS networks is introduced and its design. The design and implementation details are discussed.

SPeCRA: a stochastic performance comparison routing algorithm for LSP setup in MPLS networks

A new algorithm for dynamic routing of LSPs is proposed. While off-line algorithms are not suitable due to the necessary a priori knowledge of future LSP setup requests, our proposed algorithm, SPeCRA (stochastic performance comparison routing algorithm), does not assume any specific stochastic traffic model and does not require any knowledge of future demands. Both features are a must for the new Internet traffic. In order to analyze SPeCRAs performance, we compare the ISP rejection ratios of SPeCRA and MIRA (Kar, K. et al., IEEE J. on Selected Areas in Commun., vol.18, no.12, p.2566-79, 2000). SPeCRA is easy to implement. It can be implemented using only simple shortest-hop or shortest-cost algorithms, which are interesting solutions for vendors, and not as computationally heavy as other routing algorithms.

Proactive versus reactive revisited: IPv6 routing for Low Power Lossy Networks

In this paper, we revisit the reactive versus proactive debate, however in the context of Low Power Lossy Networks (LLNs). We investigate the suitability of two protocols: RPL (proactive), standardized by the IETF for use in LLNs, and LOAD-ng (reactive) recently being discussed in the IETF MANET working group as a promising reactive candidate protocol with deployment in LLNs. We provide a detailed and impartial simulation study that is based on two real deployment topologies and realistic traffic profiles provided by the industry. We investigate typical routing requirements, and delve into metrics of interest, such as overhead for multicast traffic, path quality, end-to-end delay for alert traffic, and memory requirements. The results of this study suggest that a proactive protocol, such as RPL, is the best candidate for most deployment scenarios. Our analysis also helped identify areas of concern and provide suggestions for further improvements.

On adaptive timers for improved RPL operation in low-power and lossy sensor networks

In this paper, we propose two adaptive algorithms to control Destination Advertisement Option (DAO) packet emissions in RPL non-storing mode: a centralized, or controlled by the DAG root, and a distributed. We propose new mechanisms to derive the most appropriate value for the DelayDAO Timer, a timer that determines how long a node should wait before transmitting its destination advertisement packet to the DAG root or collection point. We also propose similar mechanism for RPL-storing mode by implementing multiple destination aggregation in a single DAO packet. We show that instead of using a fixed universal timer to control DAO emissions, as recommended in the IETF standard, the use of an adaptive timer at each node allows the network to quickly adjust to topological changes. This is aimed at reducing congestion and packet drops, specially near the DAG root, which also impacts memory and buffer requirements, as well as data delivery delay. This is crucial for networks such as Urban LLNs or Smart Grid AMI networks, whose nodes have very limited resources with regards to energy and buffer space. We show how the proposed mechanisms outperform the default method in RPL with regards to these metrics.

Trend Based Bandwidth Provisioning: An Online Approach for Traffic Engineered Tunnels

In this paper, a novel dynamic bandwidth provisioning scheme for traffic engineered tunnels is proposed. The mechanism uses information from the traffic trend to make resizing decisions and is designed to lower signaling and computational overhead while meeting QoS constraints. The traffic trend is observed using a slope estimator and a memory moderator unit. The slope estimator periodically analyzes traffic for growth and spikes whereas the memory moderator keeps track of traffic history and uses it to influence the update in reservation. Key metrics are identified and detailed analysis is then undertaken to gauge the performance of this approach. Accurate simulations on realistic traffic profiles and topologies show effective resizing and reduction in signaling overhead. A comparison with similar state-of-the-art mechanisms is also discussed.