Service composition is an efficient way to implement a service of complex business process. In service composition, service selection considering multiple QoS objectives is a challenge. Existing methods mainly utilize fitness function or constraint technique to convert multiple objectives service composition problems to single objective ones. These methods take effect with priori knowledge of problem's solution space. Besides, only one solution can be obtained in each execution of one existing method. Users can hardly acquire evenly distributed solutions with acceptable computation cost. In this paper, we propose a lightweight particle swarm optimization service selection algorithm using approximate distance and external archive mechanisms. Simulation results demonstrate that the proposed algorithm is more effective and efficient than the compared algorithm for multi-objective service composition problems.

The most important thing of service composition (SC) is to select optimal candidate service instances compliant with non-functional requirements (e.g. QoS and load balance constraints). Particle swarm optimization (PSO) is known as an effective and efficient algorithm, which is widely used in this process. However, the premature convergence and diversity loss of PSO may result in suboptimal solutions. In this paper, we propose an accurate sub-swarms particle swarm optimization (ASPSO) algorithm which locates optimal solutions by using sub-swarms searching grid cells in which the density of feasible solutions is high. Simulation results demonstrate that the proposed algorithm improves the accuracy of the standard PSO algorithm in service composition.

Network virtualization provides a powerful tool to allow multiple networks, each customized to a specific purpose, to run on a shared substrate. However, a big challenge is how to map multiple virtual networks onto specific nodes and links in the shared substrate network, known as virtual network embedding problem. Previous works in virtual network embedding can be decomposed to two classes: two-stage virtual network embedding and one-stage virtual network embedding. In this paper, by pruning the topology of virtual network using k-core decomposition, a hybrid virtual network embedding algorithm is proposed to leverage the respective advantage of the two kinds of algorithm simultaneously in the mapping process. In addition, a time-oriented scheduling policy is introduced to improve the mapping performance. We conduct extensive simulations and the results show that the proposed algorithm obtains more revenue in the long-term run.

Aligning different ontologies from similar (or same) domains is an active field of current research. There are various solutions which process and analyze lexical, structural or semantic information to align ontologies. However, there are few solutions that focus on interpreting the concepts that entities are presented with and using them in relation to the semantics implied in an ontology. In this paper, the prototype (OACLAI) is presented to tackle this by combining lexical analysis with consequences from reasoners which reflect the semantics implied in an ontology. We evaluate OACLAI over the four real ontologies and compare it against the seven solutions. The experiments show that the accuracy of OACLAI is higher than those of others on average.

Service composition constructs composite applications with different services to fulfill numerous service requirements. Different users have various QoS demands for composite services. In this paper, we present a service composition model considering not only multiple QoS constraints but also load balance factors. Moreover, a service selection algorithm based on niching technique and particle swarm optimization (PSO) is proposed for the service composition problem. It supports optimization problems with any kinds of constraints and objective functions. Simulation results show the proposed algorithm is effective and efficient for service composition under any circumstances.

IP multimedia subsystem (IMS) is over IP network architecture, but mobile IP cannot directly support session mobility controlled by session initiation protocol-based signaling. The long signaling delay for session reestablishment in application layer always results in session interruptions during the handoff. Therefore, handoff poses a challenge for quality of service (QoS) maintenance in IMS that targets to offer real-time multimedia applications over wireless mobile networks. The existing approaches to solve this problem depend on the advance resource reservation and the optimization of handoff control. Unfortunately, big cost of the advance resource reservation in neighboring domains is a major problem that leads to a serious signaling load and a waste of wireless bandwidth. To solve this issue, we present an enhanced IMS handoff mechanism (EHM) based on user mobility prediction to save network resources by avoiding multiple useless advance reservations. In addition, to support the heterogeneous access networks in IMS domain, EHM evolves a network selective scheme to utilize the network resources more efficiently. The architecture of EHM and the advance QoS negotiation signaling are also presented. We model the cost, the handoff delay and the session blocking probability for EHM and the previous work. Analytical and simulation results show that EHM can enhance the handoff performance, such as reducing resource reservation cost greatly, decreasing session reestablishment delay and making good use of multiple access network resources.

To determine the potential signaling traffic reductions, the session establishment procedures are investigated. The investigation shows that, the S-CSCF (Serving Call Session Control Function) is the major bottleneck in IMS (IP Multimedia Subsystem) and the existing 3GPP (the 3rd Generation Partnership Project) Service Triggering Algorithm (3GPP STA) increases largely the end to end session setup delay. To reduce the session setup delay and improve the system performance, a new Group based Service Triggering Algorithm (GSTA) is proposed. And then the modeling of 3GPP STA and GSTA are presented. Theoretical analysis and simulation results show that, GSTA can efficiently reduce the signaling traffic load of the S-CSCF, increase the throughput of the system and considerably reduce the session setup delay, improve IMS network quality of service.

In the service invocation mechanism of current IMS (IP multimedia system) network, the serving-call session control function (S-CSCF) invokes each application server (AS) sequentially to perform user's service profile. This mechanism makes SIP request be forwarded excessively among the S-CSCF and application servers (ASs), so it is easy to result in the heavy load of the S-CSCF entity and long call set-up delay. Service capability interaction manager (SCIM) is an entity providing service invoking capability and service interaction management, which is out of standards at present. This paper proposes a novel distributed SCIM (DSCIM) service invocation mechanism within IMS service provision architecture. It aims at reducing the call set-up delay in IMS service layer along with decreasing the load of the S-CSCF entity by invoking each AS consecutively without signaling being forwarded back to the S-CSCF. We model the service invocation mechanisms through Jackson network and the simulations of different scenarios verify that DSCIM service invocation mechanism can effectively reduce call set-up delay of the network and decrease the load level of the S-CSCF.

This paper introduced cmpSCTP, a transport layer solution for concurrent multi-path transfer that modifies the standard Stream Control Transmission Protocol (SCTP). The cmpSCTP aims at exploiting SCTP's multi-homing capability by selecting several best paths among multiple available network interfaces to improve data transfer rate to the same multi-homed device. Through the use of path monitoring and packet allotment techniques, cmpSCTP tries to transmit given amount of packets at corresponding path as its ability. At the same time, cmpSCTP updates the transmission strategy based on the real-time information of all of paths. Using cmpSCTP's flexible path management capability, we may switch the flow between multiple paths automatically to realize seamless path handover. Extensive simulations under different scenarios using OPNET verified that cmpSCTP can effectively enhance transmission efficiency and highlighted the superiority of cmpSCTP against the other SCTP's extension implementations under performance indexes such as throughput, handover latency, packet delay, and packet loss.

Multi-path transferring on the different paths with diverse delays would cause reordering and so unnecessary retransmission which eventually degrades the throughput of connections considerably. To address this issue, we first presented an optimal fragmentation strategy that should be held to avoid unnecessary retransmission/recovery timeouts events in TCP or SCTP due to reordering. Then, we introduced an analytical framework for the optimal fragmentation strategy of real-time traffic. Specifically, this paper formulates optimal traffic fragmentation as a constrained optimization problem using deterministic network calculus and derives its closed-form solution by our proposed progressive water-filling algorithm. Compared with previous work, the proposed scheme is simpler to implement and enforce.

Most fault localization techniques are based on time windows. The sizes of time windows impact on the accuracy of fault localization greatly. This paper takes weighted bipartite graph as fault propagation model and proposes a heuristic fault localization approach based on sliding window with preprocessing mechanism (SWPM) to alleviate the shortcomings. First, SWPM defines the concept of symptom extension ratio and partitions observed symptoms into three segments: analyzed segment, analyzing segment, preprocessing segment. Then it determines the most probable fault set through incrementally computing Bayesian suspected degree (BSD) of the three segments and combining their results. Simulations show that the algorithm can reduce the impacts on the accuracy affected by improper window sizes. The algorithm which has a polynomial computational complexity can be applied to large scale communication network.

In order to meet the requirements of complicated mobility management in future mobility applications, multi-layers and multi-protocols mobility management schemes should be used. Mobile IP and SIP are protocols used as mobility management protocol in network layer and application layer, respectively. AAA is the foundation of network application deployment. When performing AAA operations in Mobile IP and SIP independently, it is very inefficient. We propose an optimized scheme, named OIRPMSA. In this scheme, through cooperation of Mobile IP and SIP when performing AAA operations, times of round trips are reduced. Analysis indicates that this scheme can reduce signaling cost, time delay and improve system performance significantly. Key words: Mobile IP,SIP,AAA, mobility management.