An Adaptive Policy Management Approach to BGP Convergence

The Border Gateway Protocol (BGP) is the current inter-domain routing protocol used to exchange reachability information between Autonomous Systems (ASes) in the Internet. BGP supports policy-based routing which allows each AS to independently adopt a set of local policies that specify which routes it accepts and advertises from/to other networks, as well as which route it prefers when more than one route becomes available. However, independently chosen local policies may cause global conflicts, which result in protocol divergence. In this paper, we propose a new algorithm, called Adaptive Policy Management Scheme (APMS), to resolve policy conflicts in a distributed manner. Akin to distributed feedback control systems, each AS independently classifies the state of the network as either conflict-free or potentially-conflicting by observing its local history only (namely, route flaps). Based on the degree of measured conflicts (policy conflict-avoidance vs. -control mode), each AS dynamically adjusts its own path preferences—increasing its preference for observably stable paths over flapping paths. APMS also includes a mechanism to distinguish route flaps due to topology changes, so as not to confuse them with those due to policy conflicts. A correctness and convergence analysis of APMS based on the substability property of chosen paths is presented. Implementation in the SSF network simulator is performed, and simulation results for different performance metrics are presented. The metrics capture the dynamic performance (in terms of instantaneous throughput, delay, routing load, etc.) of APMS and other competing solutions, thus exposing the often neglected aspects of performance.National Science Foundation (ANI-0095988, EIA-0202067, ITR ANI-0205294

QoS routing in ad-hoc networks using GA and multi-objective optimization

Much work has been done on routing in Ad-hoc networks, but the proposed routing solutions only deal with the best effort data traffic. Connections with Quality of Service (QoS) requirements, such as voice channels with delay and bandwidth constraints, are not supported. The QoS routing has been receiving increasingly intensive attention, but searching for the shortest path with many metrics is an NP-complete problem. For this reason, approximated solutions and heuristic algorithms should be developed for multi-path constraints QoS routing. Also, the routing methods should be adaptive, flexible, and intelligent. In this paper, we use Genetic Algorithms (GAs) and multi-objective optimization for QoS routing in Ad-hoc Networks. In order to reduce the search space of GA, we implemented a search space reduction algorithm, which reduces the search space for GAMAN (GA-based routing algorithm for Mobile Ad-hoc Networks) to find a new route. We evaluate the performance of GAMAN by computer simulations and show that GAMAN has better behaviour than GLBR (Genetic Load Balancing Routing).Peer ReviewedPostprint (published version

Reliable Interdomain Routing Through Multiple Complementary Routing Processes

The Internet inter-domain routing protocol, BGP, experiences frequent routing disruptions such as transient routing loops or loss of connectivity. The goal of this paper is to address this issue while preserving BGP’s benefits in terms of operational maturity and flexibility in accommodating diverse policies. In realizing this goal, we apply to inter-domain routing a common concept in the design of highly reliable systems, namely, the use of redundancy, which we introduce in a manner that maximizes compatibility with the existing BGP protocol. The basic idea is to run several, mostly unchanged BGP processes that compute complementary routes, so that in the presence of network instabilities a working path remains available to any destination. The paper outlines the design of this approach and compares it to previously proposed alternatives. The benefits of the scheme are demonstrated using actual BGP data and realistic simulations

Distributed Path Computation without Transient Loops: An Intermediate Variables Approach

Paths with loops, even transient ones, pose significant stability problems in networks. As a result, much effort has been devoted over the past thirty years to designing distributed algorithms capable of avoiding loops. We present a new algorithm, Distributed path computation with Intermediate Variables (DIV), that guarantees that no loops, transient or steady-state, can ever form. DIV’s novelty is in that it is not restricted to shortest paths, can easily handle arbitrary sequences of changes and updates, and provably outperforms earlier approaches in several key metrics. In addition, when used with distance-vector style path computation algorithms, DIV also prevents counting-to-infinity; hence further improving convergence. The paper introduces DIV and its key properties. Simulation quantifying its performance gains are also presented

Survey of Consistent Network Updates

Computer networks have become a critical infrastructure. Designing dependable computer networks however is challenging, as such networks should not only meet strict requirements in terms of correctness, availability, and performance, but they should also be flexible enough to support fast updates, e.g., due to a change in the security policy, an increasing traffic demand, or a failure. The advent of Software-Defined Networks (SDNs) promises to provide such flexiblities, allowing to update networks in a fine-grained manner, also enabling a more online traffic engineering. In this paper, we present a structured survey of mechanisms and protocols to update computer networks in a fast and consistent manner. In particular, we identify and discuss the different desirable update consistency properties a network should provide, the algorithmic techniques which are needed to meet these consistency properties, their implications on the speed and costs at which updates can be performed. We also discuss the relationship of consistent network update problems to classic algorithmic optimization problems. While our survey is mainly motivated by the advent of Software-Defined Networks (SDNs), the fundamental underlying problems are not new, and we also provide a historical perspective of the subject