Blocking performance analysis on adaptive routing over WDM networks with finite wavelength conversion capability

Analytical blocking probability analysis is important for network design. In this paper, we present an analytical model for the blocking probability analysis on adaptive routing over the WDM networks with finite wavelength conversion capability. Modeling the finite nature of wavelength conversion has been a difficult task. We make use of the idea of segmented route to handle the finite wavelength conversion property. In this approach, a route is divided into a number of segments separated by wavelength converting nodes. We then combine the single-link model and the overflow model to derive the network-wide blocking probability. There are two distinct features in our technique. First, a concept of segmented route is used. Second, link state is considered when calculating the traffic flow. The latter ensures that the analytical results match closely to practical network status. Extensive simulations show that the analytical technique is effective in modeling the blocking probability performance for sparse networks.     

Optical multicast over wavelength-routed WDM networks: A survey

With the rapid development of optical networking technology, it is now a realizable technique to support point-to-multipoint connections directly on the optical layer, giving rise to optical multicast. The topic of optical multicast has attracted much enthusiasm in recent years for the reason that it will not only make full use of the abundant bandwidth provided by optical fibers, but also take full advantage of multicast over the traditional point-to-point connection approach. In this paper, we present a comprehensive review of optical multicast over wavelength-routed WDM networks, covering the development of both data plane and control plane designs. In particular, we provide an up-to-date state-of-the-art review on the multicast routing and wavelength assignment problem. To the best of our knowledge, this is the most thorough and comprehensive review conducted so far on this topic in the literature.     

End-to-end QoS guarantees for a network based on Latency-Rate Max–Min service curve

Recently, a number of studies have been made based on the concept of Route Interference to provide deterministic end-to-end quality of service (QoS) guarantees. Nonetheless, these studies tend to confine to a simple scheduling scheme and study the traffic in a single-class environment or the highest priority traffic in a multi-class environment. This is rather restrictive. In this paper, we propose a new general service scheme to service flows. This scheme is represented by a Latency-Rate Max–Min service curve (LRMMSC). Subsequently, for a network of LRMMSC, we prove the existence of tight bounds on end-to-end queuing delay and buffer size needed for loss-free packet delivery, provided that all flows obey a given source rate condition in the form of their route interference. Our approach has two salient features: (1) the general nature of the concept of service curve enables the service scheme to be implemented by many well-known scheduling disciplines, (2) the general network model adopted with no constraints on the manner of packet queuing makes the results applicable to many complex networks. In addition, we have also derived a concise expression of end-to-end delay bound that depends only on the service offered to the buffers containing the considered flow. This is very useful in practice as the expression is simple and requires minimum amount of information input. Simulation experiments are conducted to verify the LRMMSC model. The analytical and simulation results exhibit close resemblance. In addition, the advantage of LRMMSC scheme in providing maximum end-to-end delay is also demonstrated.     

A hybrid cycle bandwidth allocation scheme with differentiated services support in Ethernet passive optical networks

The Ethernet passive optical network (EPON) has emerged as one of the most promising solutions for next generation broadband access networks. Designing an efficient upstream bandwidth allocation scheme with differentiated services (DiffServ) support is a crucial issue for the successful deployment of EPON, carrying heterogeneous traffic with diverse quality of service (QoS) requirements. In this article, we propose a new hybrid cycle scheme (HCS) for bandwidth allocation with DiffServ support. In this scheme, the high-priority traffic is transmitted in fixed timeslots at fixed positions in a cycle while the medium- and low-priority traffic are transmitted in variable timeslots in an adaptive dynamic cycle. A suitable local buffer management scheme is also proposed to facilitate QoS implementation. We develop a novel feature providing potentially multiple transmission opportunities (M-opportunities) per-cycle for high-priority traffic. This feature is significant in improving delay and delay-variation performance. The HCS provides guaranteed services in a short-cycle scale for delay and jitter sensitive traffic while offering guaranteed throughput in a moderately long-time scale for bandwidth sensitive traffic and at the same time maximizing throughput for non-QoS demanding best-effort traffic. We develop analytical performance analysis on the deterministic delay bound for high-priority traffic and minimum throughput guarantees for both high- and medium-priority traffic. On the other hand, we also conduct detailed simulation experiments. The results show a close agreement between analytical approach and simulation. In addition, the simulation results show that the HCS scheme is able to provide excellent performance in terms of average delay, delay-variation, and throughput as compared with previous approaches.

Modeling of the XOM/XMP application programming interface (API)

With the growing complexity of communication protocols, it is increasingly difficult for application developers to interface the applications to the communication stacks across a number of platforms. A common application program interface (API) is needed for the purpose. The API can effectively conceal the complexities of communication protocols and architecture, making it easier for application development. This article presents the modeling and development of a generic API, XOM and an application-specific API, XMP. XOM API provides a general-purpose data handling mechanism and XMP API provides service primitives to network management protocols. The development is based on object-oriented technology. The attractiveness of object-oriented implementation is its ability to provide encapsulation, reusability and extensibility in the software modules. The benefits and difficulties encountered during the implementation are to be discussed. The experience will be useful for API development     

File recovery by ISO FTAM

File recovery enhances the reliability and robustness of a network file management system. This capability of error detection and recovery is examined in an FTAM implementation. The issues of docket design, checkpoint insertion, recoverability, as well as interface transparency, are discussed in the paper. The impact of the recovery on the end-to-end performance and the effectiveness of the error recovery protocol in the light of failures are also examined by means of performance measurements. The result shows that the advantage gained by error recovery outweighs the protocol overheads incurred in the process.     

Layered-routing approach for solving multicast routing and wavelength assignment problem

We have developed a new layered-routing approach to address the problem of all-optical multicast over wavelength-routed wavelength division multiplexing (WDM) networks. We model the WDM network as a collection of wavelength layers with sparse light- splitting (LS) and wavelength conversion (WC) capabilities. We apply the degree constraint technique to solve the problem. The approach is capable of completing multicast routing and wavelength assignment (MCRWA) in one step. We propose two generic frameworks to facilitate heuristic development. Any heuristic that is derived from either Prim’s or Kruskal’s algorithm can be easily imported to solve the MCRWA problem. One example is given for each framework to demonstrate heuristic development. Extensive simulations were carried out to measure the performance of heuristics developed from the frameworks. The results show that the STRIGENT scheme is suitable for hardware design and it is advisable to deploy light splitters and wavelength converters to the same node for better performance.     

Wavelength assignment with sparse wavelength conversion for optical multicast in WDM networks

This paper addresses the problem of multicast wavelength assignment for sparse wavelength conversion (MWA-SWC) in wavelength-routed wavelength-division-multiplexing (WDM) networks. It aims to optimally allocate the available wavelength for each link of the multicast tree, given a sparse wavelength conversion network and a multicast request. To our knowledge, little research work has been done to address this problem in literature.In this paper, we propose a new technique called MWA-SWC algorithm to solve the problem. The algorithm first maps the multicast tree from the sparse conversion case to the full conversion case by making use of a novel virtual link method to carry out the tree mapping. The method provides a forward mapping to generate an auxiliary tree as well as a reverse mapping to recover the original tree. Applying the auxiliary tree, we propose a dynamic programing algorithm for the wavelength assignment (WA) aiming to minimize the number of wavelength converters (NWC) required. Simulation results show that our new algorithm outperforms both random and greedy algorithms with regard to minimizing the NWC. Testing on various scenarios by varying the number of wavelength conversion nodes in the tree has confirmed the consistency of the performance. The primary use of the MWA-SWC algorithm is for static traffic. However, it can also serve as a baseline for dynamic heuristic algorithms. Typically, the MWA-SWC algorithm will provide great benefit when the number of available wavelengths on each link of the multicast tree is relatively large and the performance advantage is significant.     

Study of signaling effects on Dynamic Traffic Grooming in IP/MPLS over WDM network

Signaling is essential in a practical network for connection establishments. Previous works on Dynamic Traffic Grooming (DTG) did not consider the signaling and related information update. The performance is poor when we incorporate the signaling requirement in previous DTG algorithms. This shows that the effect of signaling cannot be ignored in a practical network. In this paper, we discuss the effect of signaling on DTG, and propose a new technique called DTG-PRL to handle the DTG problem. In DTG-PRL, we divide the DTG into two steps: (1) pre-reserve some lightpaths based on statistical traffic observations and (2) dynamically groom the traffic based on the established virtual topology. We have developed an ILP formulation and a heuristic algorithm for the purpose. The simulation results show that the DTG-PRL outperforms previous DTG algorithms in IP Bandwidth Blocking Probability, Network Resource Utilization, Connection Setup Time and Control Message Efficiency. This demonstrates the usefulness of DTG-PRL in practical networks.     

Network Resource Provisioning for IP over Multi-Granular Optical Networks

In the internet protocol（IP） over multi-granular optical switch network （IP/MG-OXC）, the network node is a typical multilayer switch comprising several layers, the IP packet switching （PXC） layer, wavelength switching （WXC） layer and fiber switching （FXC） layer. This network is capable of both IP layer grooming and wavelength grooming in a hierarchical manner. Resource provisioning in the multi-granular network paradigm is called hierarchical grooming problem. An integer linear programming （ILP） model is proposed to formulate the problem. An iterative heuristic approach is developed for solving the problem in large networks. Case study shows that IP/MG-OXC network is much more extendible and can significantly save the overall network cost as compared with IP over wavelength division multiplexing network.