Modern networking applications replicate data and services widely, leading to a need for location-independent routing---the ability to route queries to objects using names independent of the objects' physical locations. Two important properties of such a routing infrastructure are routing locality and rapid adaptation to arriving and departing nodes. We show how these two properties can be efficiently achieved for certain network topologies. To do this, we present a new distributed algorithm that can solve the nearest-neighbor problem for these networks. We describe our solution in the context of Tapestry, an overlay network infrastructure that employs techniques proposed by Plaxton et al. [24].

Abstract — Over the Internet today, computing and communications environments are significantly more complex and chaotic than classical distributed systems, lacking any centralized organization or hierarchical control. There has been much interest in emerging Peer-to-Peer (P2P) network overlays because they provide a good substrate for creating large-scale data sharing, content distribution and application-level multicast applications. These P2P networks try to provide a long list of features such as: selection of nearby peers, redundant storage, efficient search/location of data items, data permanence or guarantees, hierarchical naming, trust and authentication, and, anonymity. P2P networks potentially offer an efficient routing architecture that is self-organizing, massively scalable, and robust in the wide-area, combining fault tolerance, load balancing and explicit notion of locality. In this paper, we present a survey and comparison of various Structured and Unstructured P2P networks. We categorize the various schemes into these two groups in the design spectrum and discuss the application-level network performance of each group.

A central problem for structured peer-to-peer networks is topology maintenance, that is, how to properly update neighbor variables when nodes join and leave the network, possibly concurrently. In this paper, we first present a protocol that maintains a ring, the basis of several structured peer-to-peer networks. We then present a protocol that maintains Ranch, a topology consisting of multiple rings. The protocols handle both joins and leaves concurrently and actively (i.e., neighbor variables are updated once a join or a leave occurs). We use an assertional method to prove the correctness of the protocols, that is, we first identify a global invariant for a protocol and then show that every action of the protocol preserves the invariant. The protocols are simple and the proofs are rigorous and explicit.

This paper presents a general methodology for building messagepassing peer-to-peer systems capable of performing prefix search for arbitrary user-defined names. Our methodology allows to achieve even load distribution, high fault-tolerance, and low-congestion concurrent query execution. This is the first known peer-to-peer system for prefix search with such properties. The essence of this methodology is a plug and play paradigm for designing a peer-to-peer system as a modular composition of arbitrary concurrent data structures.

In a system proposed by Plaxton, Rajaraman and Richa (PRR), the expected cost of accessing a replicated object was proved to be asymptotically optimal for a static set of nodes and pre-existence of consistent and optimal neighbor tables in nodes [9]. To implement PRR’s hypercube routing scheme in a dynamic, distributed environment, such as the Internet, various protocols are needed (for node joining, leaving, table optimization, and failure recovery). In this paper, we first present a conceptual foundation, called C-set trees, for protocol design and reasoning about consistency. We then present the detailed specification of a join protocol. In our protocol, only nodes that are joining need to keep extra state information about the join process. We present a rigorous proof that the join protocol generates consistent neighbor tables for an arbitrary number of concurrent joins. The crux of our proof is based upon induction on a C-set tree. Our join protocol can also be used for building consistent neighbor tables for a set of nodes at network initialization time. Lastly, we present both analytic and simulation results on the communication cost of a join in our protocol.

In this paper, we give sequential and distributed dynamic data structures for finding nearest neighbors in certain growth restricted metrics.

A central problem for structured peer-topeer networks is topology maintenance, that is, how to properly update neighbor variables when nodes join or leave the network, possibly concurrently. In this paper, we consider the maintenance of the ring topology, the basis of several peer-to-peer networks, in the fault-free environment. We design, and prove the correctness of, protocols that maintain a bidirectional ring under both joins and leaves. Our protocols update neighbor variables once a membership change occurs. We prove the correctness of our protocols using an assertional proof method, that is, we first identify a global invariant for a protocol and then show that every action of the protocol preserves the invariant. Our protocols are simple and our proofs are rigorous and explicit.

A naming service is in charge of locating a mobile agent in a distributed system given its name. Three critical characteristics of a naming service are: fault tolerance, scalability, and efficient name resolution. Most naming services provide support for efficient name resolution but do not address fault tolerance or scalability issues. Conversely, distributed hash-table approaches to naming provide fault tolerance and scalability albeit at a sacrificed name resolution performance. We introduce a Fault-Tolerant Home-Based Naming Service (FHNS) that is robust and scalable yet enabling efficient name resolution.

Building overlay network tools for locating information in a manner that exhibits localityawareness is crucial for the viability of large internets. It means that costs are proportional to the actual distance of interacting parties, and in many cases, that load may be contained locally. This paper presents a step-by-step decomposition of several locality-aware networks, that support distributed content-based location services. It explains their common principles and their variations with simple and clear analysis.

Building self-maintaining overlay networks for locating information in a manner that exhibits locality-awareness is crucial for the viability of large internets. It means that costs are proportional to the actual distance of interacting parties, and in many cases, that load may be contained locally. This survey paper describes several locality-aware networks that support distributed content-based location services. It explains their common principles and their variations with simple and clear intuition on analysis.