Kohei Shiomoto

Dynamic call admission control in ATM networks

The authors present dynamic call admission control using the distribution of the number of cells arriving during the fixed interval. This distribution is estimated from the measured number of cells arriving at the output buffer during the fixed interval and traffic parameters specified by users. Call acceptance is decided on the basis of online evaluation of the upper bound of cell loss probability, derived from the estimated distribution of the number of calls arriving. QOS (quality of service) standards can be guaranteed using this control when there is no estimation error. The control mechanism is effective when the number of call classes is large. It tolerates loose bandwidth enforcement and loose policing control, and dispenses with modeling of the arrival processes. Numerical examples demonstrate the effectiveness of this control, and implementation is also discussed. >

GMPLS-based photonic multilayer router (Hikari router) architecture: an overview of traffic engineering and signaling technology

A new extended signaling and traffic engineering method for the GMPLS-based photonic and electrical multilayer router (Hikari router) is proposed. The method allows dynamic optical network management and photonic signal recovery, such as regeneration, reshaping, etc., to be realized adaptively. Wavelength conversion is also adaptive, which reduces network cost. Multilayer traffic engineering, which yields the dynamic cooperation of IP and photonic layers, is described to provide IP services cost effectively. To realize multilayer traffic engineering, we propose the OSPF extension, which advertises both the number of total wavelengths and the number of unused wavelengths, and the RSVP-TE extension, which minimizes the number of wavelength conversions needed. In addition, this paper proposes a heuristics-based multilayer topology design scheme that uses IP traffic measurements in a generalized multi-protocol label switch (GMPLS). The proposed scheme yields the optical label switch path (OLSP) network topology, that is, OLSP placement, that minimizes network cost, in response to fluctuations in IP traffic demand. In other words, the OLSP network topology is dynamically reconfigured to match IP traffic demand. Networks are reconfigured by the proposed scheme so as to utilize network resources in the most cost effective manner.

Dynamic multilayer routing schemes in GMPLS-based IP+optical networks

This article presents two dynamic multilayer routing policies implemented in the photonic MPLS router developed by NTT for IP+optical generalized MPLS networks. According to IP traffic requests, wavelength paths called lambda label switched paths are set up and released in a distributed manner based on GMPLS routing and signaling protocols. Both dynamic routing policies first try to allocate a newly requested electrical path to an existing optical path that directly connects the source and destination nodes. If such a path is not available, the two policies employ different procedures. Policy 1 tries to find available existing optical paths with two or more hops that connect the source and destination nodes. Policy 2 tries to establish a new one-hop optical path between source and destination nodes. The performances of the two routing policies are evaluated. Simulation results suggest that policy 2 outperforms policy 1 if p is large, where p is the number of packet-switching-capable ports; the reverse is true only if p is small. We observe that p is the key factor in choosing the most appropriate routing policy. We also describe items that need to be standardized in the IETF to effectively achieve multilayer traffic engineering.

A disjoint path selection scheme with shared risk link groups in GMPLS networks

This letter proposes a disjoint path selection scheme for generalized multi-protocol label switching (GMPLS) networks with shared risk link group (SRLG) constraints. It is called the weighted-SRLG (WSRLG) scheme. It treats the number of SRLG members related to a link as part of the link cost when the k-shortest path algorithm is executed. In WSRLG, a link that has many SRLG members is rarely selected as the shortest path. Simulation results show that WSRLG finds more disjoint paths than the conventional k-shortest path algorithm.

Overview of measurement-based connection admission control methods in ATM networks

An overview is given of previously-proposed measurement-based connection admission control (CAC) methods. First we address requirements for CAC methods, and then provide a taxonomy for CAC methods. Measurement-based CAC methods are discussed in detail, classified according to the taxonomy, and compared against each other with respect to the requirements. We conclude that measurement-based CAC methods based on effective bandwidth and bufferless models are promising because they do not require complex hardware and are less dependent on assumptions regarding traffic than methods in which the effect of buffer is considered.

Gradually reconfiguring virtual network topologies based on estimated traffic matrices

Traffic matrix is essential to traffic engineering (TE) methods. Because it is difficult to monitor traffic matrices directly, several methods for estimating them from link loads have been proposed. However, estimated traffic matrix includes estimation errors which degrade the performance of TE significantly. In this paper, we propose a method that reduces estimation errors while reconfiguring the virtual network topology (VNT) by cooperating with the VNT reconfiguration. In our method, the VNT reconfiguration is divided into multiple stages instead of reconfiguring the suitable VNT at once. By dividing the VNT reconfiguration into multiple stages, our traffic matrix estimation method calibrates and reduces the estimation errors in each stage by using information monitored in prior stages. We also investigate the effectiveness of our proposal using simulations. The results show that our method can improve the accuracy of the traffic matrix estimation and achieve an adequate VNT as is the case with the reconfiguration using the actual traffic matrices.

Adaptive Virtual Network Topology Control Based on Attractor Selection

One approach to accommodating traffic on a wavelength-routed optical network is to construct a virtual network topology (VNT) by establishing a set of lightpaths between nodes. To accommodate fluctuating traffic on a VNT, we propose an adaptive VNT control method, which reconfigures VNTs according to traffic conditions on VNTs, in IP over wavelength-routed wavelength-division-multiplexing networks. To achieve adaptability in the VNT control method, we focus on attractor selection, which models behaviors where biological systems adapt to unknown changes in their surrounding environments and recover their conditions. The biological system driven by attractor selection adapts to environmental changes by selecting attractors at which the system condition is preferable. Our VNT control method uses deterministic and stochastic behaviors and controls these two appropriately by simple feedback of the conditions of an IP network. By utilizing stochastic behavior, our new approach adapts to various changes in traffic demand with selecting suitable attractors, which correspond to VNTs in our method, for the current traffic demand. Moreover, to define feedback of the conditions on the IP network, our proposed scheme only uses load information on links, which is easily and directly retrieved and thus achieves quick responses to changes in traffic demand. The simulation results indicate that our VNT control method based on attractor selection quickly and adaptively responds to various changes in traffic demand, and our method adapts to at most twice larger changes in traffic demand than existing heuristic approaches.

A fast and compact longest match prefix look-up method using pointer cache for very long network address

We propose a fast and compact longest match table look-up method for very long network addresses like IP version 6. This method uses two ideas for a routing-table arranged in a tree-structure. The first idea is to make table look-up fast by caching pointers to intermediate nodes in the tree, reducing the number of node traversals. The second idea is to reduce the memory size required for each node in the tree by one-third by eliminating common parts of addresses of adjacent nodes. Evaluating the performance of this method by using actual routing table data of an IP backbone network, we found it was five to ten times faster than a conventional method.

A simple bandwidth management strategy based on measurements of instantaneous virtual path utilization in ATM networks

A new connection admission control method based on actual virtual path traffic measurements is proposed to achieve high bandwidth efficiency for various types of traffic. The proposed method is based on the measurement of instantaneous virtual path utilization, which is defined as the total cell rate of the active virtual channels normalized by the virtual path capacity. A low-pass filter is used to determine the instantaneous virtual path utilization from crude measurements. A smoothing coefficient formula is derived as a function of the peak rate of the virtual channel. The residual bandwidth is derived from the maximum instantaneous utilization observed during a monitoring period. Simulation shows that the proposed method achieves statistical multiplexing gains of up to 80% of the limit possible with optimum control for similar traffic sources. It can be implemented with very simple hardware. The admission decision is simple: the requested bandwidth is compared with the residual bandwidth. This method is therefore well suited for practical asynchronous transfer mode switching systems.

Path computation element (PCE)-based traffic engineering in MPLS and GMPLS networks

This paper describes a new path computation model in Multi-protocol Label Switching (MPLS) and Generalized MPLS (GMPLS) networks. It introduces a path computation element (PCE), which is functionally separate from label switching routers (LSRs). The Path Computation Element (PCE) is an entity that is capable of computing a network path or route based on a network graph, and applying computational constraints. It is applied to intra-area, inter-area, inter-AS, and inter-layer traffic engineering. Then, we describes an PCE-based inter-layer traffic engineering framework. Inter-layer traffic engineering optimizes network resource utilization globally, i.e. taking into account all layers, rather than optimizing resource utilization at each layer independently. This allows better network efficiency to be achieved. We present two inter-layer path control models. One is a cooperation model with PCE and virtual network topology (VNT) manager. The other is higher-layer signaling trigger model. We compares these models in terms of functions of the network manager, node functions, and signaling time. We also discuss PCE standardizations in Internet Engineering Task Force (IETF).