Guest Editors' Introduction: Special Section on Autonomic Network Computing

IN the paper “Slicing Distributed Systems,” Gramoli et al. consider the problem of slicing—the partitioning of nodes into subsets using an one-dimensional attribute—in distributed systems. This problem arises in peer-to-peer networks and other popular distributed systems used in today’s large data centers. Slicing can help autonomic systems shift work dynamically among nodes and react dynamically to nodes dropping from the system or new nodes joining. The paper reviews existing approaches such as sorting and ranking and shows their problems in convergence, resulting in slow adaptation to changed conditions or inaccurate slice assignments in nonstatic networks. The authors introduce Sliver, a simple distributed slicing protocol that samples attribute values from the network and estimates the slice index from the sample. The theoretical results show that Sliver has provably rapid conversion, is robust under stress, and is simple to implement which they also show with simulation results of the new protocol. The paper “Cholla: A Framework for Composing and Coordinating Adaptations in Networked Systems” by Bridges et al. describes Cholla, a software architecture that separates the policy decisions of how and when adaptive components in networked systems react to their environment into separate centralized controllers that are constructed from composable rule sets. A major goal of this work is to develop a controller architecture that can be used for any collection of adaptive networking components, not a specific architecture that has to be implemented for each application-specific configuration or reimplemented each time that configuration changes. To achieve this, controllers are designed to be composable, with each adaptive component in the system contributing logic that together implements the overall functionality of the controller. This logic is implemented as rule sets that describe particular adaptation policies, and allow rule sets that implement linear, heuristic, and fuzzy control policies. Using composable control logic allows the controller to be specialized based not only on the set of adaptive components in the system, but also on the target network architecture and application requirements. This architecture consists of adaptable components, composable adaptation controllers, and a runtime system. In addition to describing the architecture of Cholla, this paper also presents a Linux-based prototype implementation of this architecture that controls and coordinates adaptation policy decisions inside network protocols and multimedia applications. An experimental evaluation of this prototype demonstrates that Cholla’s controller architecture enables component-based construction and customization of adaptation policies in networked systems, and that these policies can effectively control and coordinate adaptation. The paper “An Online Mechanism for BGP Instability Detection and Analysis” by Deshpande et al. proposes an online instability detection architecture for the border gateway protocol (BGP). BGP is one of the core building blocks of the Internet and is used to direct traffic between different subnetworks of the Internet, known as Autonomous Systems (ASs). The stability of BGP is critical to the stability of the Internet, and under stressful conditions such as worm attacks or router failures, BGP’s basic update protocol can result in severe route fluctuations and loss of connectivity for impacted networks for extended periods of time. The proposed architecture can be implemented by individual routers autonomously without the need for central control or centralized data. This allows widespread deployment without the need for modification of standards and also allows partial deployments without the need of large-scale cooperation among networks. The proposed system uses statistical techniques to detect instabilities using the time domain characteristics of BGP update message data and does not need any additional probing. The experimental evaluation using data collected from routers in Europe including data from several anomaly periods show that the system performs well various kinds of instabilities and across different topologies and policies. The paper “An Integrated Planning and Adaptive Resource Management Architecture for Distributed RealTime Embedded Systems” by Shankaran et al. looks at autonomicity issues in an open distributed embedded realtime environment. Such systems which may arise in context such as space control missions have fundamentally different characteristics than traditional embedded systems with controllable inputs. Autonomic operations require a close coordination between the resource planning needs of the IEEE TRANSACTIONS ON COMPUTERS, VOL. 58, NO. 11, NOVEMBER 2009 1441