Search

The advent of the edge computing network paradigm places the computational and storage resources away from the data centers and closer to the edge of the network largely comprising the heterogeneous IoT devices collecting huge volumes of data. This paradigm has led to considerable improvement in network latency and bandwidth usage over the traditional cloud-centric paradigm. However, the next generation networks continue to be stymied by their inability to achieve adaptive, energy-efficient, timely data transfer in a dynamic and failure-prone environment—the very optimization challenges that are dealt with by biological networks as a consequence of millions of years of evolution. The transcriptional regulatory network (TRN) is a biological network whose innate topological robustness is a function of its underlying graph topology. In this article, we survey these properties of TRN and the metrics derived therefrom that lend themselves to the design of smart networking protocols and architectures.We then reviewa body of literature on bio-inspired networking solutions that leverage the stated properties of TRN. Finally, we present a vision for specific aspects of TRNs that may inspire future research directions in the fields of large-scale social and communication networks. [ABSTRACT FROM AUTHOR]

We study the interaction of the programming construct "new," which generates statically scoped names, with communication via messages on channels. This interaction is crucial in security protocols, which are the main motivating examples for our work; it also appears in other programming-language contexts. We define the applied pi calculus, a simple, general extension of the pi calculus in which values can be formed from names via the application of built-in functions, subject to equations, and be sent as messages. (In contrast, the pure pi calculus lacks built-in functions; its only messages are atomic names.)We develop semantics and proof techniques for this extended language and apply them in reasoning about security protocols. This article essentially subsumes the conference paper that introduced the applied pi calculus in 2001. It fills gaps, incorporates improvements, and further explains and studies the applied pi calculus. Since 2001, the applied pi calculus has been the basis for much further work, described in many research publications and sometimes embodied in useful software, such as the tool ProVerif, which relies on the applied pi calculus to support the specification and automatic analysis of security protocols. Although this article does not aim to be a complete review of the subject, it benefits from that further work and provides better foundations for some of it. In particular, the applied pi calculus has evolved through its implementation in ProVerif, and the present definition reflects that evolution. [ABSTRACT FROM AUTHOR]

Low-power wireless communication is a central building block of cyber-physical systems and the Internet of Things. Conventional low-power wireless protocols make avoiding packet collisions a cornerstone design choice. The concept of synchronous transmissions challenges this view. As collisions are not necessarily destructive, under specific circumstances, commodity low-power wireless radios are often able to receive useful information even in the presence of superimposed signals from different transmitters. We survey the growing number of protocols that exploit synchronous transmissions for higher robustness and deficiency as well as unprecedented functionality and versatility compared to conventional designs. The illustration of protocols based on synchronous transmissions is cast in a conceptional framework we establish, with the goal of highlighting differences and similarities among the proposed solutions. We conclude this article with a discussion on open questions and challenges in this research field. [ABSTRACT FROM AUTHOR]

Peer-to-peer systems rely on a scalable overlay network that enables efficient routing between its members. Hypercubic topologies facilitate such operations while each node only needs to connect to a small number of other nodes. In contrast to static communication networks, peer-to-peer networks allow nodes to adapt their neighbor set over time in order to react to join and leave events and failures. This article shows how to maintain such networks in a robust manner. Concretely, we present a distributed and self-stabilizing algorithm that constructs a (slightly extended) skip graph, SKIP+, in polylogarithmic time from any given initial state in which the overlay network is still weakly connected. This is an exponential improvement compared to previously known self-stabilizing algorithms for overlay networks. In addition, our algorithm handles individual joins and leaves locally and efficiently. [ABSTRACT FROM AUTHOR]

Blockchain technology can be extensively applied in diverse services, including online micro-payments, supply chain tracking, digital forensics, health-care record sharing, and insurance payments. Extending the technology to the Internet of things (IoT), we can obtain a verifiable and traceable IoT network. Emerging research in IoT applications exploits blockchain technology to record transaction data, optimize current system performance, or construct next-generation systems, which can provide additional security, automatic transaction management, decentralized platforms, offline-to-online data verification, and so on. In this article, we conduct a systematic survey of the key components of IoT blockchain and examine a number of popular blockchain applications. In particular, we first give an architecture overview of popular IoT-blockchain systems by analyzing their network structures and protocols. Then, we discuss variant consensus protocols for IoT blockchains, and make comparisons among different consensus algorithms. Finally, we analyze the traffic model for P2P and blockchain systems and provide several metrics. We also provide a suitable traffic model for IoT-blockchain systems to illustrate network traffic distribution. [ABSTRACT FROM AUTHOR]

Perfectly reliable message transmission (PRMT) is one of the fundamental problems in distributed computing. It allows a sender to reliably transmit a message to a receiver in an unreliable network, even in the presence of a computationally unbounded adversary. In this article, we study the inherent trade-off between the three important parameters of the PRMT protocols, namely, the network connectivity (n), the round complexity (r), and the communication complexity by considering the following generic question (which can be considered as the holy grail problem) in the context of the PRMT protocols. Given an n-connected network, a message of size l (to be reliably communicated) and a limit c for the total communication allowed between the sender and the receiver, what is the minimum number of communication rounds required by a PRMT protocol to send the message, such that the communication complexity of the protocol is O(c)? We answer this interesting question by deriving a nontrivial lower bound on the round complexity. Moreover, we show that the lower bound is tight in the amortized sense, by designing a PRMT protocol whose round complexity matches the lower bound. The lower bound is the first of its kind, that simultaneously captures the inherent tradeoff between the three important parameters of a PRMT protocol. [ABSTRACT FROM AUTHOR]

In this article, we show that keeping track of history enables significant improvements in the communication complexity of dynamic network protocols. We present a communication optimal maintenance of a spanning tree in a dynamic network. The amortized (on the number of topological changes) message complexity is O(V), where V is the number of nodes in the network. The message size used by the algorithm is O(log ∣ID∣) where ∣ID∣ is the size of the name space of the nodes. Typically, log ∣ID∣ = O(log V). Previous algorithms that adapt to dynamic networks involved Ω(E) messages per topological change-inherently paying for re-computation of the tree from scratch. Spanning trees are essential components in many distributed algorithms. Some examples include broadcast (dissemination of messages to all network nodes), multicast, reset (general adaptation of static algorithms to dynamic networks), routing, termination detection, and more. Thus, our efficient maintenance of a spanning tree implies the improvement of algorithms for these tasks. Our results are obtained using a novel technique to save communication. A node uses information received in the past in order to deduce present information from the fact that certain messages were NOT sent by the node's neighbor. This technique is one of our main contributions. [ABSTRACT FROM AUTHOR]

A fundamental problem of distributed computing is that of simulating a secure broadcast channel, within the setting of a point-to-point network. This problem is known as Byzantine Agreement (or Generals) and has been the focus of much research. Lamport et al. [1982] showed that in order to achieve Byzantine Agreement in the plain model, more than two thirds of the participating parties must be honest. They further showed that by augmenting the network with a public-key infrastructure for digital signatures, it is possible to obtain protocols that are secure for any number of corrupted parties. The problem in this augmented model is called "authenticated Byzantine Agreement". In this article, we consider the question of concurrent, parallel and sequential composition of authenticated Byzantine Agreement protocols with a single common setup. We present surprising impossibility results showing that: (1) Authenticated Byzantine Agreement protocols that remain secure under parallel or concurrent composition (even for just two executions) and tolerate a third or more corrupted parties, do not exist. (2) Deterministic authenticated Byzantine Agreement protocols that run for r rounds and tolerate a third or more corrupted parties, can remain secure for at most 2r -- 1 sequential executions. In contrast, we present randomized protocols for authenticated Byzantine Agreement that remain secure under sequential composition, for any polynomial number of executions. We exhibit two such protocols. In the first protocol, an honest majority is required. In the second protocol, any number of parties may be corrupted; however, the complexity of the protocol is in the order of 2n ·n! for n parties. In order to have this polynomial in the security parameter k (used for the signature scheme in the protocol), this requires the overall number of parties to be limited to O(log k/ log log k). The above results are achieved due to a new protocol for authenticated Byzantine Generals for three parties that can tolerate any number of faulty parties and composes sequentially. Finally, we show that when the model is further augmented so that in each session, all the participating parties receive a common session identifier that is unique to that session, then any polynomial number of authenticated Byzantine agreement protocols can be concurrently executed, while tolerating any number of corrupted parties. [ABSTRACT FROM AUTHOR]

There has been considerable recent interest in probabilistic packet marking schemes for the problem of tracing a sequence of network packets back to an anonymous source. An important consideration for such schemes is the number of packet header bits that need to be allocated to the marking protocol. Let b denote this value. All previous schemes belong to a class of protocols for which b must be at least log n, where n is the number of bits used to represent the path of the packets. In this article, we introduce a new marking technique for tracing a sequence of packets sent along the same path. This new technique is effective even when b =1. In other words, the sequence of packets can be traced back to their source using only a single bit in the packet header. With this scheme, the number of packets required to reconstruct the path is O(22n), but we also show that Ω(2n) packets are required for any protocol where b =1. We also study the trade-off between b and the number of packets required. We provide a protocol and a lower bound that together demonstrate that for the optimal protocol, the number of packets required (roughly) increases exponentially with n, but decreases doubly exponentially with b. The protocol we introduce is simple enough to be useful in practice. We also study the case where the packets are sent along k different paths. For this case, we demonstrate that any protocol must use at least log(2k -1) header bits. We also provide a protocol that requires log(2k +1)header bits in some restricted scenarios. This protocol introduces a new coding technique that may be of independent interest. [ABSTRACT FROM AUTHOR]

We study and further develop two language-based techniques for analyzing security protocols. One is based on a typed process calculus; the other, on untyped logic programs. Both focus on secrecy properties. We contribute to these two techniques, in particular by extending the former with a flexible, generic treatment of many cryptographic operations. We also establish an equivalence between the two techniques. [ABSTRACT FROM AUTHOR]

Presents a study which showed how methods of automated reasoning can be used to prove properties of network routing protocols. Correctness of the asynchronous distributed Bellman-Ford protocol as specified in the Internet Engineering Task Force Routing Information Protocol standard; Verification of networking standards; Approaches to verifying algorithms; Characteristics of routing protocol used in the Internet.

Describes a multilink multisource model of the Transmission Control Protocol (TCP) Vegas congestion control mechanism. Background on TCP; Objective of Vegas; Interpretation of the Vegas algorithm; Examination of the phenomenon of persistent congestion.

Presents information on a study which examined an on-line problem that is motivated by the networking problem of dynamically adjusting delays of acknowledgments in the Transmission Control Protocol. Usefulness of applying packet arrival time prediction to the problem; Description of the algorithms.

Presents information on a study which showed that a crashing network protocol that works over unreliable links can be driven to arbitrary global states. Intuition behind the main theorem; Characterization of computer aided machining; Designing correct protocols that are resilient to crashes; Applications of the findings; Conclusions.

Underwater wireless sensor networks (UWSNs) will pave the way for a new era of underwater monitoring and actuation applications. The envisioned landscape of UWSN applications will help us learn more about our oceans, as well as about what lies beneath them. They are expected to change the current reality where no more than 5% of the volume of the oceans has been observed by humans. However, to enable large deployments of UWSNs, networking solutions toward efficient and reliable underwater data collection need to be investigated and proposed. In this context, the use of topology control algorithms for a suit-able, autonomous, and on-the-fly organization of the UWSN topology might mitigate the undesired effects of underwater wireless communications and consequently improve the performance of networking services and protocols designed for UWSNs. This article presents and discusses the intrinsic properties, potentials, and current research challenges of topology control in underwater sensor networks. We propose to classify topology control algorithms based on the principal methodology used to change the network topology. They can be categorized in three major groups: power control, wireless interface mode management, and mobility assisted-based techniques. Using the proposed classification, we survey the current state of the art and present an in-depth discussion of topology control solutions designed for UWSNs. [ABSTRACT FROM AUTHOR]

Byzantine Fault Tolerant (BFT) protocols have the ability to work correctly even when up to a threshold f of system servers are compromised. This makes them appealing for the construction of critical systems connected to the Internet, which are constantly a target for cyber attacks. BFT protocols differ based on the kind of application, deployment settings, performance, access control mechanisms, number of servers in the system, and protocol implementation. The large number of protocols present in the literature and their differences make it difficult for a system builder to choose the solution that best satisfies the requirements of the system that he wants to build. In particular, the main difference among BFT protocols lies in their system models: server-side versus client-side. In the server-side model each client relies on the system to consistently order and replicate updates, while in the client-side model each client actively participates in the protocol. In this article, we classify BFT protocols as server-side or client-side. We analyze the trade-offs between the two models, describe systems that use these models and the trade-offs they choose, highlight the research gaps, and provide guidelines to system builders in order to choose the solution that best satisfies their needs. [ABSTRACT FROM AUTHOR]

Computer network protocols define the rules in which two entities communicate over a network of unique hosts. Many protocol specifications are unknown, unavailable, or minimally documented, which prevents thorough analysis of the protocol for security purposes. For example, modern botnets often use undocumented and unique application-layer communication protocols to maintain command and control over numerous distributed hosts. Inferring the specification of closed protocols has numerous advantages, such as intelligent deep packet inspection, enhanced intrusion detection system algorithms for communications, and integration with legacy software packages. Themultitude of closed protocols coupled with existing time-intensive reverse engineering methodologies has spawned investigation into automated approaches for reverse engineering of closed protocols. This article summarizes and organizes previously presented automatic protocol reverse engineering tools by approach. Approaches that focus on reverse engineering the finite state machine of a target protocol are separated from those that focus on reverse engineering the protocol format. [ABSTRACT FROM AUTHOR]

Several Peer-to-Peer (P2P) protocols and applications have been developed to allow file distribution/sharing, video and music streaming, and data and information dissemination. These P2P systems are regularly used by a large number of users, both in desktop and mobile environments, and they generate a remarkable portion of the overall Internet traffic. However, many common P2P protocols and applications were designed neglecting the energy problem. In fact, they often require always-on devices in order to work properly, thus producing significant energy waste. The problem is even more relevant in the mobile context, since the battery lifetime of mobile devices is limited. Therefore, energy efficiency in P2P systems is a highly debated topic in the literature. New P2P approaches--more energy efficient than traditional client/server solutions--have been proposed. In addition, several improvements to existing P2P protocols have been introduced to reduce their energy consumption. In this article, we present a general taxonomy to classify state-of-the-art approaches to the energy problem in P2P systems and applications. Then, we survey themain solutions available in the literature, focusing on three relevant classes of P2P systems and applications: file sharing/distribution, content streaming, and epidemics. Furthermore, we outline open issues and provide future research guidelines for each class of P2P systems. [ABSTRACT FROM AUTHOR]

This article explains the full reconfigurable multidecree Paxos (or multi-Paxos) protocol. Paxos is by no means a simple protocol, even though it is based on relatively simple invariants. We provide pseudocode and explain it guided by invariants. We initially avoid optimizations that complicate comprehension. Next we discuss liveness, list various optimizations that make the protocol practical, and present variants of the protocol. [ABSTRACT FROM AUTHOR]

Key management is required for basic security services of confidentiality, integrity, and data source authentication. Wireless sensor networks (WSNs) are a challenging environment to provide such services due to the resource constraints and the increased likelihood of nodes to be captured. Various key management techniques were proposed that trade off resilience to node capture and overhead in terms of communication and memory. We identify the main factors influencing the design space of key management protocols for sensor networks and describe representative protocols that trade off the number of links established, communication overhead, and resilience to node capture. These trade-offs are due to using direct, pathbased, or multipath-based communication to establish secure links. We propose a new multipath protocol relying on an encoding scheme tailored for WSNs and analyze the effects of key pre-distribution on multipath key establishment. We provide extensive simulations to understand the trade-offs between resilience to node compromise and communication overhead under numerous network scenarios. This comparison highlights the tradeoffs between these vastly different key management schemes. For the newer class of key management schemes--multipath based--we quantify experimentally the additional communication overhead required for extra paths and the improvement in resilience from using these paths. [ABSTRACT FROM AUTHOR]

In a wireless world, users can establish ad hoc virtual connections between devices that are unhampered by cables. This process is known as spontaneous device association. A wide range of interactive protocols and techniques have been demonstrated in both research and practice, predominantly with a focus on security aspects. In this article, we survey spontaneous device association with respect to the user interaction it involves. We use a novel taxonomy to structure the survey with respect to the different conceptual models and types of user action employed for device association. Within this framework, we provide an in-depth survey of existing techniques discussing their individual characteristics, benefits, and issues. [ABSTRACT FROM AUTHOR]

Networking research often relies on simulation in order to test and evaluate new ideas. An important requirement of this process is that results must be reproducible so that other researchers can replicate, validate, and extend existing work. We look at the landscape of simulators for research in peer-to-peer (P2P) networks by conducting a survey of a combined total of over 280 papers from before and after 2007 (the year of the last survey in this area), and comment on the large quantity of research using bespoke, closedsource simulators. We propose a set of criteria that P2P simulators should meet, and poll the P2P research community for their agreement. We aim to drive the community towards performing their experiments on simulators that allow for others to validate their results [ABSTRACT FROM AUTHOR]

The University of Canterbury Although system virtualization is not a new paradigm, the way in which it is used in modern system architectures provides a powerful platform for system building, the advantages of which have only been realized in recent years, as a result of the rapid deployment of commodity hardware and software systems. In principle, virtualization involves the use of an encapsulating software layer (Hypervisor or Virtual Machine Monitor) which surrounds or underlies an operating system and provides the same inputs, outputs, and behavior that would be expected from an actual physical device. This abstraction means that an ideal Virtual Machine Monitor provides an environment to the software equivalent to the host system, but which is decoupled from the hardware state. Because a virtual machine is not dependent on the state of the physical hardware, multiple virtual machines may be installed on a single set of hardware. The decoupling of physical and logical states gives virtualization inherent security benefits. However, the design, implementation, and deployment of virtualization technology have also opened up novel threats and security issues which, while not particular to system virtualization, take on new forms in relation to it. Reverse engineering becomes easier due to introspection capabilities, as encryption keys, security algorithms, low-level protection, intrusion detection, or antidebugging measures can become more easily compromised. Furthermore, associated technologies such as virtual routing and networking can create challenging issues for security, intrusion control, and associated forensic processes. We explain the security considerations and some associated methodologies by which security breaches can occur, and offer recommendations for how virtualized environments can best be protected. Finally, we offer a set of generalized recommendations that can be applied to achieve secure virtualized implementations. [ABSTRACT FROM AUTHOR]

Recent advances in wireless communications and sensor technologies have enabled the development of low-cost wireless sensor networks (WSNs) for a wide range of applications. Medium access control (MAC) protocols play a crucial role in WSNs by enabling the sharing of scarce wireless bandwidth efficiently and fairly. This article provides a survey of the literature on MAC protocols for WSNs. We first briefly describe the unique features of WSNs. We then review representative MAC protocols from the following four categories: contention-based protocols, contention-free (scheduled-based) protocols, hybrid protocols, and preamble sampling protocols. Our discussions focus on the background, main features, operation procedures, major design issues, and the advantages and disadvantages of these protocols. We also present an analysis of the inherent and desirable features of the protocols, and the key challenges of MAC technology for WSNs. Finally, we present our view on future research directions for WSN MAC protocols in a reader-friendly way using illustrative diagrams. [ABSTRACT FROM AUTHOR]

The Stream Control Transmission Protocol (SCTP) is a relatively recent general-purpose transport layer protocol for IP networks that has been introduced as a complement to the well-established TCP and UDP transport protocols. Although initially conceived for the transport of PSTN signaling messages over IP networks, the introduction of key features in SCTP, such as multihoming and multistreaming, has spurred considerable research interest surrounding SCTP and its applicability to different networking scenarios. This article aims to provide a detailed survey of one of these new features-multihoming-which, as it is shown, is the subject of evaluation in more than half of all published SCTP-related articles. To this end, the article first summarizes and organizes SCTP-related research conducted so far by developing a four-dimensional taxonomy reflecting the (1) protocol feature examined, (2) application area, (3) network environment, and (4) study approach. Over 430 SCTP-related publications have been analyzed and classified according to the proposed taxonomy. As a result, a clear perspective on this research area in the decade since the first protocol standardization in 2000 is given, covering both current and future research trends. On continuation, a detailed survey of the SCTP multihoming feature is provided, examining possible applications of multihoming, such as robustness, handover support, and loadsharing. [ABSTRACT FROM AUTHOR]

Most routing protocols guarantee convergence to a stable routing state. That is, in the absence of topology or configuration changes, each router will eventually find a stable route to any destination. However, this is not the case for policy-based routing protocols, for example, the BGP protocol used as a de facto standard for interdomain routing. The interaction of not-so-complex BGP configurations can cause permanent oscillations of routing. Several models and algorithms have been proposed in the literature to study routing oscillations. This article surveys state-of-the-art contributions in this field, with a special emphasis on algorithmic and combinatorial aspects. [ABSTRACT FROM AUTHOR]

Wireless self-organizing networks (WSONs) have attracted considerable attention from the network research community; however, the key for their success is the rigorous validation of the properties of the network protocols. Applications of risk or those demanding precision (like alert-based systems) require a rigorous and reliable validation of deployed network protocols. While the main goal is to ensure the reliability of the protocols, validation techniques also allow the establishment of their correctness regarding the related protocols' requirements. Nevertheless, even if different communities have carried out intensive research activities on the validation domain, WSONs still raise new issues for and challenging constraints to these communities. We thus, advocate the use of complementary techniques coming from different research communities to efficiently address the validation of WSON protocols. The goal of this tutorial is to present a comprehensive review of the literature on protocol engineering techniques and to discuss difficulties imposed by the characteristics of WSONs on the protocol engineering community. Following the formal and nonformal classification of techniques, we provide a discussion about components and similarities of existing protocol validation approaches. We also investigate how to take advantage of such similarities to obtain complementary techniques and outline new challenges. [ABSTRACT FROM AUTHOR]

The past two decades have seen a growing interest in methods for anonymous communication on the Internet, both from the academic community and the general public. Several system designs have been proposed in the literature, of which a number have been implemented and are used by diverse groups, such as journalists, human rights workers, the military, and ordinary citizens, to protect their identities on the Internet. In this work, we survey the previous research done to design, develop, and deploy systems for enabling private and anonymous communication on the Internet. We identify and describe the major concepts and technologies in the field, including mixes and mix networks, onion routing, and Dining Cryptographers networks. We will also review powerful traffic analysis attacks that have motivated improvements and variations on many of these anonymity protocols made since their introduction. Finally, we will summarize some of the major open problems in anonymous communication research and discuss possible directions for future work in the field. [ABSTRACT FROM AUTHOR]

The article reviews the most popular peer-to-peer key management protocols for mobile ad hoc networks (MANETs). The protocols are subdivided into groups based on their design strategy or main characteristic. The article discusses and provides comments on the strategy of each group separately. The discussions give insight into open research problems in the area of pairwise key management. [ABSTRACT FROM AUTHOR]

This survey covers rollback-recovery techniques that do not require special language constructs. In the first part of the survey we classify rollback-recovery protocols into checkpoint-based and log-based. Checkpoint-based protocols rely solely on checkpointing for system state restoration. Checkpointing can be coordinated, uncoordinated, or communication-induced. Log-baaed protocols combine checkpointing with logging of nondeterministic events, encoded in tuples called determinants. Depending on how determinants are logged, log-based protocols can be pessimistic, optimistic, or causal. Throughout the survey, we highlight the research issues that are at the core of rollback-recovery and present the solutions that currently address them. We also compare the performance of different rollback-recovery protocols with respect to a series of desirable properties and discuss the issues that arise in the practical implementations of these protocols. [ABSTRACT FROM AUTHOR]

Transmission Control Protocol (TCP) is the most commonly used transport protocol on the Internet. All indications assure that mobile computers and their wireless communication links will be an integral part of the future internetworks. In this paper, we present how regular TCP is well tuned to react to packet loss in wired networks. We then define mobility and the problems associated with it. We discuss why regular TCP is not suitable for mobile hosts and their wireless links by providing simulation results that demonstrate the effect of the high bit error rates of the wireless link on TCP performance. We discuss and illustrate the problems caused by the mobility of hosts using a graph tracing packets between fixed and mobile hosts. We then present a survey of the research done to improve the performance of TCP over mobile wireless networks. We classify the proposed solutions into three categories: link layer, end-to-end and split. We discuss the intuition behind each solution and present example protocols of each category. We discuss the protocols functionality, their strengths and weaknesses. We also provide a comparison of the different approaches in the same category and on the category level. We conclude this survey with a recommendation of the features that need to be satisfied in a standard mobile. TCP protocol. [ABSTRACT FROM AUTHOR]

Transport layer protocols provide for end-to-end communication between two or more hosts. This paper presents a tutorial on transport layer concepts and terminology, and a survey of transport layer services and protocols. The transport layer protocol TCP is used as a reference point, and compared and contrasted with nineteen other protocols designed over the past two decades. The service and protocol features of twelve of the most important protocols are summarized in both text and tables. [ABSTRACT FROM AUTHOR]

Introduces local area networks (LAN) and discusses the performance degradation of LAN at high speeds. Presentation of proposed LAN schemes designed to operate at high data rates; Identification of characteristics in LAN medium access protocols.

During the past ten years, the field of multiple-access communication has developed into a major area of both practical and theoretical interest within the field of computer communications. The multiple-access problem arises from the necessity of sharing a single communication channel among a community of distributed users. The distributed algorithm used by the stations to share the channel is known as the multiple-access protocol. In this paper we examine the multiple-access problem and various approaches to its resolution. In this survey we first define the multiple-access problem and then present the underlying issues and difficulties in achieving multiple-access communication. A taxonomy for multiple-access protocols is then developed in order to characterize common approaches and to provide a framework within which these protocols can be compared and contrasted. Different proposed protocols are then described and discussed, and aspects of their performance are examined. The use of multiple-access protocols for "real- time" or "time-constrained" communication applications, such as voice transmission, is examined next. Issues in time-constrained communication are identified, and recent work in the design of time-constrained multiple-access protocols is surveyed. [ABSTRACT FROM AUTHOR]

The rapidly evolving field of local network technology has produced a steady stream of local network products in recent years. The IEEE 802 standards that are now taking shape, because of their complexity, do little to narrow the range of alternative technical approaches and at the same time encourage more vendors into the field. The purpose of this paper is to present a systematic, organized overview of the alternative architectures for and design approaches to local networks. The key elements that determine the cost and performance of a local network are its topology, transmission medium, and medium access control protocol. Transmission media include twisted pair, baseband and broadband coaxial cable, and optical fiber. Topologies include bus, tree, and ring. Medium access control protocols include CSMA/CD, token bus, token ring, register insertion, and slotted ring. Each of these areas is examined in detail, comparisons are drawn between competing technologies, and the current status of standards is reported. [ABSTRACT FROM AUTHOR]

During the last ten years, many computer networks have been designed, implemented, and put into service in the United States, Canada, Europe, Japan, and elsewhere. From the experience obtained with these networks, certain key design principles have begun to emerge, principles that can be used to design new computer networks in a more structured way than has traditionally been the case. Chief among these principles is the notion of structuring a network as a hierarchy of layers, each one built upon the previous one. This paper is a tutorial about such network hierarchies, using the Reference Model of Open Systems Interconnection developed by the International Organization for Standardization as a guide. Numerous examples are given to illustrate the principles. [ABSTRACT FROM AUTHOR]

The recovery subsystem of an experimental data management system is described and evaluated. The transaction concept allows application programs to commit, abort, or partially undo their effects. The DO-UNDO-REDO protocol allows new recoverable types and operations to be added to the recovery system. Application programs can record data in the transaction log to facilitate application-specific recovery. Transaction undo and redo are based on records kept in a transaction log. The checkpoint mechanism is based on differential files (shadows). The recovery log is recorded on disk rather than tape. [ABSTRACT FROM AUTHOR]

There is increasing growth in the number of computer networks in use and in the kinds of distributed computing applications available on these networks. This increase, together with concern about privacy, security, and integrity of information exchange, has created considerable interest in the use of encryption to protect information in the networks. This survey is directed at the reader who is knowledgeable about various network designs and who now wishes to consider incorporating encryption methods into these designs. It is also directed at developers of encryption algorithms who wish to understand the characteristics of such algorithms useful in network applications. Key management, network encryption protocols, digital signatures, and the utility of conventional-or public-key encryption methods are each discussed. A case study of how encryption was integrated into an actual network, the Arpanet, illustrates many issues present in the design of a network encryption facility. [ABSTRACT FROM AUTHOR]

In this article we present a comprehensive survey of various approaches for the verification of cache coherence protocols based on state enumeration, (symbolic) model checking, and symbolic state models. Since these techniques search the state space of the protocol exhaustively, the amount of memory required to manipulate the state information and the verification time grow very fast with the number of processors and the complexity of the protocol mechanisms. To be successful for systems of arbitrary complexity, a verification technique must solve this so-called state space explosion problem. The emphasis of our discussion is on the underlying theory in each method of handling the state space explosion problem, and formulating and checking the safety properties (e.g., data consistency) and the liveness properties (absence of deadlock and livelock). We compare the efficiency and discuss the limitations of each technique in terms of memory and computation time. Also, we discuss issues of generality, applicability, automaticity, and amenity for existing tools in each class of methods. No method is truly superior because each method has its own strengths and weaknesses. Finally, refinements that can further reduce the verification time and/or the memory requirement are also discussed. [ABSTRACT FROM AUTHOR]

Interoperability is the ability of two or more software components to cooperate despite differences in language, interface and execution platform. It is a scalable form of reusability, being concerned with the reuse of server resources by clients whose accessing mechanisms may be plug-incompatible with sockets of the server. Plug compatibility arises most literally with electrical appliances that require both static compatibility of shape and dynamic compatibility of voltage and frequency. If there is no direct match, interoperability of electrical appliances can be achieved by adapters and transformers. The client-server software paradigm is a plug and socket paradigm with static compatibility specified by types and dynamic compatibility by protocols. As with electrical appliances, incompatibility of software plugs and sockets can be mediated by adapters. Static compatibility between calling and called procedures in strongly typed languages can be determined by type checking. Type compatibility guarantees that the plug of the caller fits the socket of the server but not that the service provided is that expected by the caller. But some of the most powerful systems of interoperation are typeless. Interface definition languages with static type-compatibility protocols promote safety and efficiency, but the complexity and implementation cost of typed systems for interoperation is unacceptably high in today's technology.

Interoperability among components of large-scale, distributed systems is the ability to exchange services and data with one another. It is based on agreements between requesters and providers on information including message passing protocols, procedural names, error codes and argument types. Semantic interoperability ensures that these exchanges make sense. It sees that the requester and the provider have a common understanding of the meanings of requested services and data. For example, an application that requests customer data must agree on what a "customer" is, with the application that provides it. Semantic interoperability is based on certain agreements like algorithms for computing requested values, the expected side effects of a requested procedure or the source of requested data elements. The article also indicate the difficulty in achieving semantic interoperability and suggests ways by which commercial repository technology can provide the beginning to help to make semantic interoperability easier.

The advances in IPTV (Internet Protocol Television) technology enable a new user-centric and interactive TV model, in which context-awareness is promising in making the user's interaction with the TV dynamic and transparent. Our research interest is how to achieve TV service personalization applying context-awareness to the NGN IPTV architecture. In this article we present the different existing contributions that employ context-awareness to allow interactive services. Some of these contributions directly focus on TV, while others are proposed for specific NGN services. We present a technical analysis for these solutions and give some guidelines for future deployment of personalized IPTV services. [ABSTRACT FROM AUTHOR]