With the emergence of voice over IP and other real-time business applications, there is a growing demand for an IP network with high service availability. Unfortunately, in today's Internet, transient failures occur frequently due to faulty interfaces, router crashes, etc., and current IP networks lack the resiliency needed to provide high availability. To enhance availability, we proposed failure inferencing based fast rerouting (FIFR) approach that exploits the existence of a forwarding table per line-card, for lookup efficiency in current routers, to provide fast rerouting similar to MPLS, while adhering to the destination-based forwarding paradigm. In our previous work, we have shown that the FIFR approach can deal with single link failures. In this paper, we extend the FIFR approach to ensure loop-free packet delivery in case of single router failures also, thus mitigating the impact of many scenarios of failures. We demonstrate that the proposed approach not only provides high service availability but also incurs minimal routing overhead.

Abstract — Static broadband wireless networks, due to their ease of deployment, are likely to proliferate in the near future. The major stumbling block, however, is that wireless links are prone to external interference, channel fading, inclement weather, etc. Therefore scalable and reliable routing despite frequent link quality fluctuations is needed for accelerating the growth of these networks. Most of the wireless routing schemes proposed in the literature are less suitable for these networks, as they are designed primarily for mobile ad hoc networks with dynamic and unpredictable topologies. In this paper, we propose a novel link-state-based blacklist-aided forwarding (BAF) approach, that takes advantage of the fact that the nodes and therefore their adjacencies are relatively static, for scalable packet delivery in static wireless networks. Under BAF, each packet carries a blacklist, a minimal set of degraded-quality links encountered along its path, and the next hop is determined based on both its destination and blacklist. BAF provides loop-free delivery of packets to reachable destinations regardless of the number of degraded links in the network. We evaluate the performance of BAF and show that it is not only reliable but also scalable. I.

Dealing with network failures effectively is a major operational challenge for Internet service providers. Commonly deployed link state routing protocols such as OSPF react to link failures through global (i.e., network-wide) link state advertisements and routing table recomputations, causing significant forwarding discontinuity after a failure. The drawback with these protocols is that they need to trade off routing stability and forwarding continuity. To improve failure resiliency without jeopardizing routing stability, we propose a proactive local rerouting based approach called failure insensitive routing (FIR). The proposed approach prepares for failures using interface-specific forwarding, and upon a failure, suppresses the link state advertisement and instead triggers local rerouting using a backwarding table. In this paper, we prove that when no more than one link failure notification is suppressed, FIR always finds a loop-free path to a destination if one such path exists. We also formally analyze routing stability and network availability under both proactive and reactive approaches, and show that FIR provides better stability and availability than OSPF.

Location-based routing significantly reduces routing overheads in mobile ad hoc networks (MANETs) by utilizing position information of mobile nodes in forwarding decisions. A location service is therefore critical to location-based routing, the scalability of which hinges largely on the overheads of such a service. Although several location service schemes have been proposed, most of them focus only on one or two aspects of scalability in their performance evaluations, and a comprehensive comparative study is missing. We first explore the design space of location services and present a taxonomy of existing schemes. We then propose HIGH-GRADE, a new location service scheme that employs a multilevel hierarchical location server structure and a multi-grained location information organization. We develop a uniform theoretical framework to analyze HIGH-GRADE and four other existing schemes in terms of three metrics: location maintenance cost, location query cost, and storage requirement cost. We show that the design of a location service scheme involves tradeoffs among all three of these kinds of overhead. Further, in our theoretical analysis and simulation experiments, HIGH-GRADE demonstrates superior scalability, especially when a localized data traffic pattern is assumed.

Network aware multimedia delivery applications are a class of applications that provide certain level of quality of service (QoS) guarantees to end users while not assuming underlying network resource reservations. These applications guarantee QoS parameters like media object transmission time limit by actively monitoring the available bandwidth of the network and adapting the object to a target size that can be transmitted within a given time limit. A critical problem is how to obtain an accurate enough estimation of available bandwidth while not wasting too much time in bandwidth testing. In this paper, we present an algorithm to determine optimal amount of bandwidth testing given a probabilistic confidence level for network-aware multimedia object retrieval applications. The model treats the bandwidth testing as sampling from an actual bandwidth population. It uses statistical estimation method to quantify the benefit of each new bandwidth-testing sample, which is used to determine the optimal amount of bandwidth testing by balancing the benefit with the cost of each sample. Our implementation and experiments shows the algorithm determines the optimal amount of bandwidth testing effectively with minimum computation overhead.