Abstract—This paper examines the network interdomain routing information exchanged between backbone service providers at the major U.S. public Internet exchange points. Internet routing instability, or the rapid fluctuation of network reachability information, is an important problem currently facing the Internet engineering community. High levels of network instability can lead to packet loss, increased network latency and time to convergence. At the extreme, high levels of routing instability have led to the loss of internal connectivity in wide-area, national networks. In this paper, we describe several unexpected trends in routing instability, and examine a number of anomalies and pathologies observed in the exchange of inter-domain routing information. The analysis in this paper is based on data collected from BGP routing messages generated by border routers at five of the Internet core’s public exchange points during a nine month period. We show that the volume of these routing updates is several orders of magnitude more than expected and that the majority of this routing information is redundant, or pathological. Furthermore, our analysis reveals several unexpected trends and ill-behaved systematic properties in Internet routing. We finally posit a number of explanations for these anomalies and evaluate their potential impact on the Internet infrastructure. Index Terms—Communication system, communication system routing, computer network, Internet, routing, stability.

We explore the use of end-to-end multicast traffic as measurement probes to infer network-internal characteristics. We have developed in an earlier paper [2] a Maximum Likelihood Estimator for packet loss rates on individual links based on losses observed by multicast receivers. This technique exploits the inherent correlation between such observations to infer the performance of paths between branch points in the multicast tree spanning the probe source and its receivers. We evaluate through analysis and simulation the accuracy of our estimator under a variety of network conditions. In particular, we report on the error between inferred loss rates and actual loss rates as we vary the network topology, propagation delay, packet drop policy, background traffic mix, and probe traffic type. In all but one case, estimated losses and probe losses agree to within 2 percent on average. We feel this accuracy is enough to reliably identify congested links in a wide-area internetwork. Keywords---Internet performance, end-to-end measurements, Maximum Likelihood Estimator, tomography I.

In this paper, we consider the problem of how to represent the locations of Internet hosts in a Cartesian coordinate system to facilitate estimate of the network distance between two arbitrary Internet hosts. We envision an infrastructure that consists of beacon nodes and provides the service of estimating network distance between two hosts without direct delay measurement. We show that the principal component analysis (PCA) technique can e#ectively extract topological information from delay measurements between beacon hosts. Based on PCA, we devise a transformation method that projects the distance data space into a new coordinate system of (much) smaller dimensions. The transformation retains as much topological information as possible and yet enables end hosts to easily determine their locations in the coordinate system. The resulting new coordinate system is termed as the Internet Coordinate System (ICS). As compared to existing work (e.g., IDMaps [1] and GNP [2]), ICS incurs smaller computation overhead in calculating the coordinates of hosts and smaller measurement overhead (required for end hosts to measure their distances to beacon hosts). Finally, we show via experimentation with real-life data sets that ICS is robust and accurate, regardless of the number of beacon nodes (as long as it exceeds certain threshold) and the complexity of network topology.

Many network attacks forge the source address in their IP packets to block traceback. Recently, research activity has focused on packet-tracing mechanisms to counter this deception. Unfortunately, these mechanisms are either too expensive or ineffective against distributed attacks where traffic comes from multiple directions, and the volume in each direction is small. We believe that the fundamental solution to the problem of source address forging is to validate source addresses throughout the network. We have developed a source address filtering protocol that establishes and maintains valid incoming interface information on source addresses at each router, thus allowing all packets carrying improper source addresses to be immediately identified. Our protocol works correctly in the presence of asymmetric routing. We will describe the protocol that gathers the information to validate source addresses and use simulation to demonstrate that it is effective and has reasonable costs.

Many peer-to-peer distributed applications can benefit from accurate predictions of Internet path performance. Existing approaches either 1) achieve high accuracy for sophisticated path properties, but adopt an unscalable centralized approach, or 2) are lightweight and decentralized, but work only for latency prediction. In this paper, we present the design and implementation of iPlane Nano, a library for delivering Internet path information to peer-to-peer applications. iPlane Nano is itself a peer-to-peer application, and scales to a large number of end hosts with little centralized infrastructure and with a low cost of participation. The key enabling idea underlying iPlane Nano is a compact model of Internet routing. Our model can accurately predict end-to-end PoP-level paths, latencies, and loss rates between arbitrary hosts on the Internet, with 70 % of AS paths predicted exactly in our evaluation set. Yet our model can be stored in less than 7MB and updated with approximately 1MB/day. Our evaluation of iPlane Nano shows that it can provide significant performance improvements for large-scale applications. For example, iPlane Nano yields near-optimal download performance for both small and large files in a P2P content delivery system. 1

We present in this paper an analytical model for the calculation of network load and drop probabilities in a TCP/IP network with general topology. First we formulate our model as a nonlinear complementarity problem. Then we transform the model into two equivalent formulations: fixed point formulation and nonlinear programming formulation. These equivalent formulations provide efficient computational procedures for the solution of our model. Furthermore, with the help of the fixed point formulation we are able to prove the existence of a solution. Our model has the main advantage of not requiring the pre-definition of bottleneck links. The model also takes into account the receiver congestion window limitation. Our approach can be used for TCP/IP networks with drop tail buggers as well as for TCP/IP networks with active queue management buggers. We solve the problem for some network examples and we show how the distribution of load varies with network parameters. The distribution of load is sometimes counter-intuitive which cannot be detected by other models making prior assumptions on the locations of bottlenecks.

this paper, we present a more re ned and quanti able understanding of the marginal utility of performing wide-area measurements. We focus on problems in Internet topology discovery, namely, discovering the set of nodes and links which comprise the Internet backbone, discovering the degree distribution of these nodes, and classifying nodes according to their role. We provide a model for how the discovery process scales as the number of measurements and measurement sites increase and validate this model against a set of ########### run across the Internet from 17 measurement sites run to 60,000 destinations. We characterize the topology in terms of nodes, links, node degree distribution, and distribution of end-to-end ows using statistical and information-theoretic techniques

In this paper , we present a new approach to construct multicast trees in MPLS networks. This approach utilizes MPLS LSPs between multicast tree branching node routers in order to reduce forwarding states and enhance scalability. In our approach only routers that are acting as multicast tree branching node for a group need to keep forwarding state for that group. All other non-branching node routers simply forward data packets over tra#c engineered unicast routes using MPLS LSPs. We can deduce that our approach can be largely deployed because it uses for multicast tra#c the same unicast MPLS forwarding scheme.

Unlike traditional routing schemes that route all traffic along a single path, multipath routing strategies split the traffic among several paths in order to ease congestion. It has been widely recognized that multipath routing can be fundamentally more efficient than the traditional approach of routing along single paths. Yet, in contrast to the single-path routing approach, most studies in the context of multipath routing focused on heuristic methods. We demonstrate the significant advantage of optimal (or near optimal) solutions. Hence, we investigate multipath routing adopting a rigorous (theoretical) approach. We formalize problems that incorporate two major requirements of multipath routing. Then, we establish the intractability of these problems in terms of computational complexity. Finally, we establish efficient solutions with proven performance guarantees.

Grid users may wish to have fine-grained control of quality of service (QoS) guarantees in a network in order to allow timely data transfer in a distributed application environment. We present a discussion of the issues and problems involved, with some critical analysis. We propose possible solutions by making reference to and analysing existing work. Also, we describe the mechanisms being proposed as part of a work-in-progress (being conducted by the authors) that uses a peer-to-peer approach to micro-manage network capacity allocations at the edge of the network, at end-sites, in a multi-domain scenario. Scheduling controllers at the end-sites are employed, which are subject to local administrative controls and have flexibility in resource allocation based on user requests for network capacity. We highlight the issues in scaling such systems to large numbers of users and the issues concerning the interfaces available to applications and end-users for accessing such services.