Distributed Broker-Agent Architecture for Multimedia Communications Traversing NAT/Firewall in NGN

The forthcoming Next Generation Network (NGN) is an all IP network. Multimedia communications over IP networks are a type of bundled session communications, which cannot directly traverse Network Address Translations (NATs) and firewalls even in NGN. To solve the problem that the existing traversal methods are not suitable for service providers to set up a real system in NGN, a Distributed Broker-agent Architecture (DBA) is addressed. DBA is secure and realizable for service providers and enterprises because it is easy to set up and does not need to upgrade the existing devices like Firewalls, NATs or endpoint devices of subscribers. DBA is composed of two-layer distributed agents, the server proxies and the client agents, in which all multimedia communications use shared tunnels to carry signaling messages and media data between broker-agents, and the call signaling is encrypted over Security Socket Layer (SSL) to guarantee the security of calling. Moreover, the function model and multiplexed connection messages format of DBA are designed, which lays a basis for the protocol in the future NGN. In addition, a simple implementation based on H.323 verifyies the main function of traversing firewalls and NATs.

Performance Analysis for Multimedia Communication Systems with a Multilayer Queuing Network Model

Software performance evaluation in multimedia communication systems is typically formulated into a multi-layered client-server queuing network(MLCSQN) problem. However, the existing analytical methods to MLCSQN model cannot provide satisfactory solution in terms of accuracy, convergence and consideration of interlocking effects. To this end, this paper proposes a heuristic solving method for MLCSQN model to boost the performance prediction of distributed multimedia software systems. The core concept of this method is referred to as the basic model, which can be further decomposed into two sub-models: client sub-model and server sub-model. The client sub-model calculates think time for server sub-model, and the server sub-model calculates waiting time for client sub-model. Using a breadthfirst traversal from leaf nodes to the root node and vice versa, the basic model is then adapted to MLCSQN, with net sub-models iteratively resolved. Similarly, the interlocking problem is effectively addressed with the help of the basic model. This analytical solver enjoys advantages of fast convergence, independence on specific average value analysis(MVA) methods and eliminating interlocking effects.Numerical experimental results on accuracy and computation efficiency verify its superiority over anchors.

Self Fault-Tolerance of Protocols: A Case Study

The prerequisite for the existing protocols' correctness is that protocols can be normally operated under the normal conditions, rather than dealing with abnormal conditions. In other words, protocols with the fault-tolerance can not be provided when some fault occurs. This paper discusses the self fault-tolerance of protocols. It describes some concepts and methods for achieving self fault-tolerance of protocols. Meanwhile, it provides a case study, investigates a typical protocol that does not satisfy the self fault-tolerance, and gives a new redesign version of this existing protocol using the proposed approach.

Ant Colony Optimization for Multi-Objective Multicast Routing

In the distributed networks,many applications send information from a source node to multiple destination nodes.To support these applications requirements,the paper presents a multi-objective algorithm based on ant colonies to construct a multicast tree for data transmission in a computer network.The proposed algorithm simultaneously optimizes total weight(cost,delay and hop)of the multicast tree.Experimental results prove the proposed algorithm outperforms a recently published Multi-objective Multicast Algorithm specially designed for solving the multicast routing problem.Also,it is able to find a better solution with fast convergence speed and high reliability.

A Recovery Algorithm for Self-Stabilizing Communication Protocols

This paper presents a recovery algorithm for self-stabilizing communication protocols. It first describes some concepts and a formal description method for the algorithm. Then it proposes the algorithm procedures, proves its correctness and analyses its complexity. Finally, it also verifies the availability and efficiency of the algorithm by illustrating an example protocol with multi-processes.

Fairness based channel borrowing strategy in multimedia LEO satellite communications

A novel bandwidth allocation strategy along with a connection admission control technique was proposed to improve the utilization of network resources.It provides the network with better quality-of-service(QoS)guarantees,such as new call blocking probability(CBP)and handoff call drop-ping probability(CDP)in multimedia low earth orbit(LEO)satellite networks.Simulation results show that,compared with other bandwidth allocation schemes,the proposed scheme offers very low call dropping probability for real-time connections while,at the same time,keeping resource utilization high.Finally we discussed the fairness for the borrowed nonreal-time connections under three different channel borrowing methods.

The Algorithms for Achieving Global States and Self-Stabilization for Communication Protocols

This paper discusses the algorithms for achieving global states and self-stabilizationfor communication protocols. It first describes a primary algorithm including its suitability forachieving global states and limitation of self-stabilization for communication protocols, and thenpresents an improved algorithm that can be suitable to achieve global states and can be also usedto self-stabilizing communication protocols. Filially, it gives the proof of correctness and analysis ofcomplexity of the improved algorithm, and verifies its availability and efficiency by illustrating anexample protocol.

Algorithm for Delay-Constrained Minimal Cost Group Multicasting

Group multicast routing algorithms satisfying quality of service requirements of real-time applications are essential for high-speed networks. A heuristic algorithm was presented for group multicast routing with bandwidth and delay constrained. A new metric was designed as a function of available bandwidth and delay of link. And source-specific routing trees for each member were generated in the algorithm by using the metric, which satisfy member′s bandwidth and end-to-end delay requirements. Simulations over random network were carried out to compare the performance of the proposed algorithm with that from literature.Experimental results show that the algorithm performs better in terms of network cost and ability in constructing feasible multicast trees for group members. Moreover,the algorithm can avoid link blocking and enhance the network behavior efficiently.

A Bandwidth Control Method Providing Entrance QoS for Multimedia Communication

With the development of wideband IP network, many new IP-Based multimedia applications appear ceaselessly. The real-time multimedia application requires that the IP network provides QoS. To the end-to-end real-time multimedia communication, the QoS service includes the trunk QoS and the entrance QoS. The trunk QoS has some feasible technologies, such as RSVP and DiffServ. But, the entrance QoS has few technologies at the moment. So, this paper introduces the entrance bandwidth control to get the end-to-end QoS. The design and scheme of bandwidth controller applying to the usual Internet application and real-time media communication is provided in this paper. It distinguishes between the usual 1nternet applications, such as HTTP and FTP, and the real-time multimedia applications, such as Internet telephony and videoconferencing. Then they will be dealt with in different ways in order to satisfy the QoS requirements of different types of services. In this paper, we propose a new bandwidth control method for real-time multimedia communication. The principle, the implementing flow, the control policy and the application scheme are discussed.

A PERFORMANCE EVALUATION INDEX SYSTEM FOR MULTIMEDIA COMMUNICATION NETWORKS AND FORECASTING FOR WEB-BASED NETWORK TRAFFIC

This paper presents a new index system for the performance evaluation and network planning of multimedia communication systems using measurement on actual systems to support several different traffic types. In this index system, we develop an expert system to evaluate the performance of such multimedia communication networks including channel utilization and call blocking probability and packet delay, and apply the network planning methods to optimize the networks and forecast the demand of the growing multimedia communications systems. Two important planning problems for the multimedia communication systems are presented: optimization problem for construction of the world system and forecast problem for increasing traffic demands. We first discuss analysis methods, performance measures for the multimedia communication systems. Then, we describe network planning methods for the multimedia communication systems and give some efficiency network planning methods. Finally, we present some results studied in traffic forecast for the campus network and show the effectiveness of these methods.

Covert voice over internet protocol communications based on spatial model

This paper presents a new spatial steganography model for covert communications over voice over internet protocol(Vo IP), providing a solution to the issue of increasing the capacity of covert Vo IP channels without compromising the imperceptibility of the channels. Drawing from Orthogonal Modulation Theory in communications, the model introduced two concepts, orthogonal data hiding features and data hiding vectors, to covert Vo IP communications. By taking into account the variation characteristics of Vo IP audio streams in the time domain, a hiding vector negotiation mechanism was suggested to achieve dynamic self-adaptive steganography in media streams. Experimental results on Vo IP steganography show that the proposed steganographic method effectively depicted the spatial and temporal characteristics of Vo IP audio streams, and enhanced robustness against detection of steganalysis tools, thereby improving the security of covert Vo IP communications.

A Semantics-Based Approachfor Achieving Self Fault-Tolerance of Protocols

The cooperation of different processes may be lost by mistake when a protocol is executed. The protocol cannot be normally operated under this condition. In this paper,the self fault-tolerance of protocols is discussed, and a semanticsbased approach for achieving self fault-tolerance of protocols is presented. Some main characteristics of self fault-tolerance of protocols concerning liveness, nontermination and infinity are also presented. Meanwhile, the sufficient and necessary conditions for achieving self fault-tolerance of protocols are given. Finally, a typical protocol that does not satisfy the self fault-tolerance is investigated, and a new redesign version of this existing protocol using the proposed approach is given.

Studies on Algorithms for Self-StabilizingCommunication Protocols

in this paper the algorithms for self-stabilizing communication protocols are studied. First some concepts and a formal method for describing theproposed algorithms are described, then an improved algorithm for achieving globalstates is presented. The study shows that the improved algorithm can be appliedto obtain the global states in the case of a loss of cooperation of the different processes in the protocol, which can be used as a recovery point that will be used bythe following recovery procedure. Thus, the improved algorithm can be used toself-stabilize a communication protocol. Meanwhile, a recovery algorithm for selfstabilizing communication protocols is presented. After a failure is detected, allProcesses can eventually know the error. The recovery algorithm uses the contextualinformation exchanged during the progress of the protocol and recorded on the stablememory. The proof of correctness and analysis of complexity for these algorithmshave been made. The availability and efficiency of the algorithms have been verifiedby illustrating the example protocols. Finally, some conclusions and remarks aregiven.