A protocol supporting distributed group and QoS management

Object replication is a technique to enhance fault tolerance and high availability. Group communication is a useful mechanism guaranteeing the consistency among replicated objects. We propose a generic group communication framework that allows transparent plug-in of various group communication protocols with no modification of existing CORBA. For this, we extend the Open Communications Interface (OCI) to support interoperability, reusability of existing group communication, and independency on ORB and OS. The proposed scheme is composed of group membership, group IOR, and group multicast. Experimental results show that group object invocation using the proposed scheme performs substantially better than group object invocations using IIOP as the number of members in a group increases.

In hasty growth of communication, security plays a central role in maintaining confidentiality of data in group communication. Keeping the data intended for the group in confidential manner is the most important security feature need to be sustained for the group communication. An efficient group key management mechanism named as Hybrid Broadcast Group Management Protocol (HBGMP) is devised based on the Reverse Function (RF) and Chinese Remainder Theorem (CRT). The distinctive security among the subgroups is ensured by the reverse function and the session ID of each subgroup is calculated by employing Chinese remainder theorem. By contraption, the Session ID using Chinese Remainder Theorem, with which a cohort of n users requires Sub Group Service Provider (SGSP) to do O (n/m) computation for communication and the storage cost are diminished by diverting the computing load of the Group Service Provider (GSP) into the SGSP. The significance of this protocol is the group member needs to store only two different values during the entire life span and also the rekey message is broadcasted which brings down the communication cost to O(1). The protocol is defined generally for any applications in hybrid architecture. The proposed architecture using CRT and Reverse function is scalable for hefty sized dynamically changing group.

Group communication protocols discussed so far can be adopted for only a small group from the processing and communication overhead point of view. In this paper, we discuss how to provide a large-scale reliable group communication among several hundreds entities interconnected by a high-speed one-channel network. A group of entities is partitioned into disjoint subgroups named component clusters interconnected by gateways. The group communication protocol is executed in each component cluster and the gateways forward messages from a component cluster to the others. There exists only one gateway between every two different component clusters in order to prevent the proliferation and indefinite circulation of messages. By this protocol, the processing time and the length of messages of each entity can be reduced because each component cluster is smaller than the group.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

The increasing mobility of Internet users and the growing need to collaborate with staff travelling on business belong to the key characteristics of the future Internet. Mobile collaborative applications require novel schemes for group communication that actively support collaborations in wireless scenarios. An intrinsic problem of collaborations in wireless scenarios is the temporary connection loss with the group due to user mobility and network issues. Existing group communication protocols do not sufficiently support this situation. In this paper, we present a new peer-to-peer group communication protocol, called Moversight, that was specifically designed to support closed group cooperation in mobile environments with varying churn rates. It applies a new group communication paradigm, called mobile optimistic virtual synchrony, to handle churn-related peer failures. It enhances the virtual synchrony paradigm for mobile scenarios. The paper introduces the paradigm and describes the main protocol features of Moversight. Finally we present simulation results to demonstrate the applicability of the protocol.

If a groupware system is to be effectively used, especially over a wide area network such as the Internet, where the quality of networking and computing resources are unpredictable, it should allow clients to tolerate client, link, and server failures. In particular, clients should be able to join groups and transfer groups' current state in the presence of most client and link failures. In order to reduce usage overhead, disconnected clients should also be able to rejoin groups without having to restart from scratch. Furthermore, lock management and group membership should tolerate transient failures in the system. We introduce the notion of stateful group communication, which frees clients of administrative management of shared application state and allows fault tolerant group join, state transfer, and rejoin. Stateful group communication is incorporated in Corona, a general purpose, group communication service provider. In order to allow groups to tolerate transient failures, Corona also provides locks with grace period and group membership notification services that are based on client connection status. We present and discuss Corona's fault tolerant services.

The bicycling recently has gained a lot of popularity in many applications, such as transportation, recreation, and exercise. Bikers may ride in different speeds due to their body strengthes and bike performance such that group members using smart phones form two-tier vehicular long-thin networks along the common cycling path, which consist of a 3G/3.5G high-tier interface and an IEEE 802.11-based low-tier interface. In this paper, we design a Google Android and Maps-based solution for cycling group communications. On the handset side, an Android program is developed for group member localization, communication, and transmission. In addition, the augmented reality interface is integrated to show the biker information on real-time camera views of smart phones. On the web side, a biker community site is built for the biker interaction, grouping, and dedicated album. To provide efficient group communications and reduce the transmission delay, ad-hoc communications are adopted to locally exchange data among bikers. Also, a dynamic grouping mechanism has been designed to maintain the stable member connectivity in ad-hoc environments. Furthermore, the gateway selection in a group has taken the similar mobility pattern of members into account for minimizing 3G/3.5G communications.

The problem of short-term channel failure in transmission of real-time video streams in Wi-Fi networks is considered. An overview of existing solutions to this problem has shown that there is currently no effective solution that could be successfully applied in real equipment. Also discussed is the transfer of real-time video streams over the Wi-Fi network using the random access method to several recipients in the context of short-term channel failures for some of them. Using the standard algorithm of FIFO queuing in the conditions of short-term channel failure, leads to the problem of blocking the queue with the main packet, resulting in the quality of transmission of video streams decreases for recipients with poor quality of connections, and for recipients whose connection quality remained unchanged. To solve this problem a new algorithm for queuing is developed. The application of this discipline avoids a decrease in the quality of the transmission of video streams to recipients for whom the quality of the connections has not deteriorated, as well as to reduce the decrease in the quality of the transfer of video streams to recipients who have been refused channel.

In this paper we study dynamic protocol updates (DPU), which consist in replacing, without interruption, a given protocol during execution. We focus especially on group communication protocols. The paper proposes a methodology to conveniently describe which protocols are correctly replaced by a given DPU algorithm. More precisely, our methodology characterizes DPU algorithms by a set of inference rules. To validate our approach, we illustrate our methodology with a new DPU algorithm.

Mobile agent group concept is a versatile software paradigm capable of providing group task execution flexibility and collaborative adaptability in various application fields of distributed networked systems. However, as the size of these fields is rapidly increasing, improving the performance of the agent group communication in Internet-scale infrastructures should be reconsidered to be suitable for their scale. For this purpose, some appropriate inter-agent group communication protocols are required in distributed agent-based systems. Causal order delivery to a broadcast group is a very important issue for these systems. However, the existing message delivery protocols for mobile agent groups may not satisfy this important requirement. This paper presents a new causally ordered group communication protocol for mobile agent groups to consider weaker message ordering consistency than atomic broadcast semantics while ensuring reliability even with the assumption of unreliable networks for exchanging messages to agent groups and agent mobility. The simulation results show the proposed protocol performs better than the existing atomic broadcast protocol in terms of the total message delivery latency.

Heterogeneous real-time spatial data management is a very active research domain nowadays. We are talking about a real-time spatial big data that process a large amount of heterogeneous data accessed simultaneously by two types of transactions update transactions and user transactions. In these applications, it is desirable to execute transactions within their deadlines using a real-time spatial data. But the real-time spatial big data can be overloaded and many transactions may miss their deadlines, or real-time spatial data can be violated. To address these problems, we proposed, as a first contribution, a new architecture called feedback control scheduling architecture for real-time spatial big data (FCSA-RTSBD) (Hamdi et al., 2015). Then, we propose, as a second contribution, two-shadow speculative concurrency control (SCC-2S) with priority and imprecise computation (SCC-2S-P-IC). Finally, a simulation study is shown to prove that our contributions can achieve a significant performance improvement using the TPC-DS (TPC, 2014) benchmark.

The processing power of today's computers is relatively ineffective unless they can be efficiently interconnected, both locally and globally. On the horizon is the asynchronous transfer mode (ATM) which addresses the switching paradigm for broadband technologies. ATM allocates the total network bandwidth and time to bring multimedia services to the user. Thus, the future of the LAN is ensured. It is the technology for connecting global data bases, world-wide information sources, and data/video/voice communication just to mention a few. The ability to communicate anywhere, anytime has permeated the workplace and personal lives of people. Local Area Networks provide this ability, both as the medium for linking the office/work environment and as a gateway to the world.

First, a business framework for operational support systems (OSS) in communications networks is defined, in the particular case where a satellite link is present. It is shown that the constraints added by the satellite link are the need to minimise management traffic while at the same time policing QoS parameters such as delay and delay variation. Secondly, the use of trace packets is used to estimate end-to-end QoS parameters of delay and delay variation. It is shown that the use of trace packets has advantages in terms of management traffic when the satellite link (or any network link) becomes congested. Contrary to intuition, the accuracy of estimation improves with increasing congestion for the same overhead, which makes the use of trace packets suited to satellite links where overhead is expensive and there is minimal processing power at remote networks. Simulation in OPNET is used to demonstrate QoS parameter measurements using trace packets and the effectiveness of the technique with Poisson and self-similar traffic flows. It is shown that a switch from direct sampling to trace packets is beneficial at utilisations of 0.3 - 0.7, depending on traffic type.

Increasing use of distributed systems, with the corresponding decentralization, stimulates the need for structuring activities around groups of participants, for reasons of consistency, user-friendliness, performance and dependability. Although there is a significant number of group communication protocols in the literature, they are penetrating too slowly in operating systems technology. Two important reasons are: the literal interpretation generally made of the end-to-end argument, and the lack of a layer mapping end-user needs (management of replication, competition, cooperation and group membership) into what is generally provided by the communication layer: agreement and order properties.The paper discusses both problems, proposing ways for structuring systems and defining building blocks for group-oriented activity, using concepts like object groups. It suggests that the group concept should pervade the whole architecture, from network multicasting, to group communications and management. Emerging technology will help materialize these concepts.

Replicated services can be implemented as process groups. Member processes use group communication protocols to communicate amongst themselves and group membership protocols to determine what processes are in the group. These protocols can provide various levels of consistency between members. The author investigates weak consistency protocols that guarantee that messages are delivered to all members, but do not guarantee when. He reports on a new family of communication protocols, an associated group membership mechanism, and current progress in evaluating their efficiency and utility for real applications. >

In many secure application scenarios, establishing a temporary group without revealing group member information is difficult but desirable. Secure group communication can significantly reduce the computation and communication overhead. Traditional group key management schemes are based on a hierarchical tree. Any network entity who wants to set up a group needs to know the keys of the other group members, i.e., the group key establishment must be done before starting the group communication. As a result, the group needs the group formation beforehand. In this paper, we propose a secure grouping scheme providing anonymity for group members to outsiders. Our approach is based on Attribute Based Encryption (ABE) schemes. In our scheme, each network entity is assigned with a set of attributes. Each group is identified by a logical combination of attributes, i.e., the group access policies. The presented solution has an advantage that there is no need for any prior knowledge of other group members. Instead, the sender just needs to focus on the group access policies. Our scheme further preserves the group formation policies by using a gradual exposure method on attributes. Compared to existing hidden-policy schemes, our solution can greatly reduce the computation and communication overhead.