Selcuk Cevher

Trade-off analysis of Multi Topology Routing based IP fast reroute mechanisms

To seamlessly support real-time services such as voice and video over next generation IP networks, routers must continue their forwarding tasks in case of link/node failures by limiting the service disruption time to sub-100 ms. IETF Routing Area Working Group (RTGWG) has been working on standardizing IP Fast Reroute (IPFRR) methods with a complete alternate path coverage. In this paper, a trade-off analysis of Multi Topology Routing (MTR) based IPFRR technologies targeting full coverage, namely Multiple Routing Configurations (MRC) and Maximally Redundant Trees (MRT), are presented. We implemented a comprehensive analysis tool to evaluate the performance of MRC and MRT mechanisms on various synthetic network topologies. The performance results show that MRTs alternative path lengths are not scalable with respect to the network size and density while the alternative path lengths of MRC only slightly change as the network size and density vary. We believe that this is an important scalability result providing a guidance in the selection of MTR-based IPFRR mechanism for improving the availability in ISP networks.

An integrated soft handoff approach to IP fast reroute in wireless mobile networks

This paper presents an integrated approach to IP fast reroute (IPFRR) of both unicast and multicast paths in wireless mobile networks. A distinct feature of the proposed approach is that, instead of modifying existing routing protocols, it employs a soft handoff technique, i.e., temporarily installs pre-computed Loop Free Alternative Paths (LFAPs) until the co-existing routing protocol converges to new routes. The proposed approach builds on our previously proposed IPFRR technology and uses the concept of pre-computed LFAPs not only for local but also for remote link failures within a certain neighborhood to achieve full alternative path coverage for a single link failure. This papers contributions include: i) bandwidth efficient fast failure detection by integrating two novel mechanisms, namely probing and link quality prediction, ii) a novel method for calculating LFAPs, iii) a framework for switching seamlessly between LFAPs and OSPF paths, iv) a multicast fast reroute mechanism, and v) implementation in eXtensible Open Router Platform (XORP). We also present a generic framework for handling multiple simultaneous failures in the integrated IPFRR. The performance evaluation has been performed in both indoor and outdoor environments with real 802.11 radio links. The results confirm that our IPFRR technology consistently provides significant convergence time improvement during a single link failure event.

Performance evaluation of Multiple Routing Configurations

Routers in IP networks, which were initially designed to carry data services only, need special protocols to seamlessly carry real-time services such as voice and video. As one of the leading activities in this context, IETF RTGWG working group has been working on standardizing IP Fast Re- Route (IPFRR) protocols which provide a complete alternate path coverage against network component failures. Multiple Routing Configurations (MRC) is a Multi Topology Routing (MTR) based IPFRR technology targeting a complete coverage. In this paper, we evaluated the performance of virtual topology construction mechanism of MRC on various realistic network topologies. The performance results show that the minimum number of virtual topologies required by MRC to provide full alternate path coverage and the alternate path lengths depend on the link density and other structural properties of network topologies.

Multicast Planning for Mission-Critical Networks

In this paper, considering user vicinity information, maximum tolerable unwanted traffic, and routing overhead, we introduce a new two-stage multicast group planning technique which has many applications in tactical networks (TN) used in the future battlefield networks (FBN). We formally define channelization problem with respect to no false exclusion and minimum false inclusion requirements. We address: (i) selection of the number of multicast groups, (ii) adaptation of the mapping algorithms to the networks with different characteristics, and (Hi) reduction of the computational complexity of the mapping algorithms. Our approach results in scalable group configurations based on the availability of resources in the network. Simulation results show that it is cost-effective and generates multicast groups of smaller sizes, which are easier to maintain especially in mobile ad hoc networks (MANETs), than other greedy approaches for the same amount of unwanted traffic per user.

An automated topological analysis of Multiple Routing Configurations

Topological changes in IP networks may significantly influence the performance of networking algorithms, which therefore should be carefully evaluated using a large topology pool with diverse characteristics. In this paper, we present an automated topology generation and analysis tool to perform an elaborate topological dependency analysis of a Multi Topology Routing based IP Fast Re-Route technology, namely Multiple Routing Configurations. Our tool is used to generate 11, 500 topologies with diverse properties by selectively varying the parameters of the existing topology generation models. Through its extensive topological diversity and in-depth analysis capabilities, we discover a significant correlation, such that MRC requires higher number of virtual topologies to provide full alternate path coverage if a network tends to have a higher number of hub nodes. The discovery of such a correlation demonstrates the effectiveness of our tool in evaluating the performance of networking algorithms. Inspired by this correlation, we propose an extension to MRC reducing its operational complexity.

Network Planning for Multicast Using Partitioned Virtual User Domains

We introduce a new network planning approach for management of multicast communications in large data dissemination networks. Our approach, addressing Channelization Problem, considers both the common user interests and geographical dependencies while evaluating multicast configurations. We first perform Global Similarity Classificationto partition users into virtual domains based on their characteristics within the same geographical vicinity. Second, based on the resource availability of a given network, Localized Multicast Updatemechanism is used to evaluate the benefits of forming a new multicast group and the cost of the management overhead. We evaluate the performance of the proposed approach using our simulation software. Preliminary results show that, using two-stage planning, the performance of our approach is at least 40% better than the existing greedy approaches.

Enhancing Multiple Routing Configurations through systematic analysis of topological characteristics

Summary Previous studies show that topological characteristics in IP networks significantly influence the performance of networking algorithms, which therefore should be systematically analyzed using diverse topologies prior to their deployments. In this paper, we present an elaborate topological dependency analysis of a multi-topology routing-based IP fast re-route technology, namely, Multiple Routing Configurations (MRC), using a large topology pool with diverse properties. Through an extensive analysis using our automated topological analysis tool, we discover a significant correlation between the performance of MRC and topological characteristics. MRC needs to construct a higher number of virtual topologies to provide full alternate path coverage if a network topology tends to have more hub nodes, whose degree is much higher than the rest of the network. Inspired by our topological analysis results, we propose a new heuristic algorithm enhancing MRC. Numerical experiments demonstrate that our heuristic significantly improves the performance of MRC confirming the effectiveness of the systematic analysis of topological characteristics. Copyright

Interest-aware and bandwidth-efficient multicast group planning

In multicast group planning in tactical networks (TNs), one of the most important challenges is to maximize the efficient use of network and end-user resources. Hence, multicast groups should be planned cleverly such that the total shared link capacity in a multicast distribution tree is increased and the reception of unwanted traffic at receiver nodes is reduced to a maximum extent. In this paper, we propose a technique to generate a group configuration by estimating the link capacity shared by any two users in a shortest-path multicast tree to improve the branching characteristics such as height and breadth of the tree while reducing the unwanted traffic by considering overlapping user interests. A two-tier information dissemination system architecture for TNs, where a central planner controls many dissemination executives, is a typical application for multicast group planning techniques. We provide simulation results showing that, compared to existing group planning techniques, our approach generates multicast trees with improved branching characteristics while keeping the unwanted traffic within acceptable limits.

Multi topology routing based failure protection for software defined 5G networks

The continuous increase in data traffic, heterogeneous access networks, and the diversity in the Quality of Service (QoS) requirements of the applications is expected to significantly increase the management complexity of 5G networks. Software Defined Networking provides an effective management architecture enabling more efficient utilization of 5G network resources. In this paper, a novel failure recovery technique, which quickly re-routes the disrupted traffic to alternate routes in case of link/node failures in the core network, is proposed to support the stringent QoS requirements of software defined 5G networks (SD5G). Experimental results show that our approach provides an efficient solution for fast failure recovery in SD5G.

Multiple Routing Configurations for Fast Re-route in Software Defined Networks

Real-time services in IP networks require a fast switching of disrupted traffic to alternate paths in case of link/node failures to satisfy their stringent Quality of Service requirements. Multi Topology Routing (MTR) based IP Fast Re-route (IPFRR) technologies rely on virtual topologies to seamlessly forward the IP packets during network failures by activating the proactively computed alternate routes which avoid the failed component. Multiple Routing Configurations (MRC) is a widely studied MTR based IPFRR technique which provide full protection against network failures. In this paper, a new MRC-based fast re-route technique for Software Defined Networks (SDN) is proposed. Our experimental results show that our approach considerably reduces the recovery time from network failures compared to the reactive Shortest Path First (SPF) routing.