Takafumi Chujo

A distributed restoration algorithm for multiple-link and node failures of transport networks

Fast restoration of broadband optical fiber networks from multiple-link and node failures, as well as single-link failures, is addressed. A distributed restoration algorithm based on message flooding is described. The algorithm is an extension of a previously proposed algorithm for single-link failure. It restores the network from multiple-link and node failures, using multidestination flooding and path route monitoring. Computer simulation of the algorithm verified that it can find alternate paths within 0.5 s, whenever the message processing delay at a node is 5 ms.<<ETX>>

Peer-to-peer traffic in metro networks: analysis, modeling, and policies

We report studies on peer-to-peer (P2P) traffic analysis, modeling, and evaluation of policies for the management P2P traffic in metropolitan networks. We conducted crawler-based measurement and analysis of P2P traffic using Gnutella. Based on the empirical parameters obtained through the measurement, known modeling techniques of P2P peers and contents, and GeoPoint, a geomapping technology, we built a P2P traffic simulator using J-Sim, a Java-based network simulation tool. The simulator is scenario-driven, allowing its user to customize network settings and service environment to examine the behavior of P2P traffic. With the P2P simulator, we were able to recreate a spatio-temporal traffic pattern characteristic to P2P services observed in August 2002. We then evaluated three different P2P traffic management policies, showing that traffic localization using a peer selection policy at super peers is possible, containing P2P traffic to the local metropolitan network as much as 40%.

Providing scalable support for multiple QoS guarantees: architecture and mechanisms

This paper presents architecture and mechanisms to support multiple QoS under the DiffServ paradigm. On the data plane, we present a node architecture based on the virtual time reference system (VTRS), which is a unifying scheduling framework for scalable support of the guaranteed service. The key building block of our node architecture is the core-stateless virtual clock (CSVC) scheduling algorithm, which, in terms of providing delay guarantee, has the same expressive power as a stateful weighted fair queueing (WFQ) scheduler. Based on the CSVC scheduler, we design a node architecture that is capable of supporting integrated transport of the guaranteed service (GS), the premium service (PS), the assured service (AS), and the traditional best-effort (BE) service. On the control plane, we present a BE architecture to provide flexible resource allocation and QoS provisioning. Simulation results demonstrate that our architecture and mechanisms can provide scalable and flexible transport of integrated traffic of the GS, the PS, the AS, and the BE services.

CORBA-based network operation system architecture

The scope of network management systems has been expanding rapidly, from simple network element management systems to integrated management systems that include network management and service management. Since the telecommunications world has become an open market, sales competition has intensified. Accordingly, a flexible, extendable, and reusable network management system is required. A distributed object-oriented environment meets these requirements, and CORBA (Common Object Request Broker Architecture) is a promising candidate as a distributed environment. An integrated management system should provide management capabilities that are independent from management protocols and from the location of Managed Objects (MOs) which represent managed resources. The system should also be able to execute multiple management operations (multiple management scenarios) concurrently. In this paper, we describe a technique of introducing an interface for each MO, called a Proxy MO, that encapsulates the management protocols and locations of the MOs and which are concurrently controlled in the CORBA environment. This technique provides a flexible, extendable, and reusable network management system.

Application of Service Delivery Platform for Supply Chain Management

This paper examines how utilization of Service Delivery Platform (SDP) technology can potentially address some of the key issues facing the existing retail supply chain management (SCM). Existing SCM issues are identified and an analysis of the key functionality requirements for SDPs is described. Meeting these requirements ensures that SDP can provide a collaborative platform for a supply chain with improved end-to-end visibility. Thus the supply chain can better respond to market changes, particularly advantageous in todays demand-driven market.

An Algorithm for Available Bandwidth Measurement

In this paper, we present an algorithm for available bandwidth measurement of a path between two hosts as well as some preliminary simulation results. The measurement algorithm is based on active probing with two techniques we have developed: variable speed probing and zoom-in/zoomout. Compared with previous work, the algorithm has the advantage of low overhead and fast convergence because it relies on the detection of traffic trends (with variable speed probing) rather than any specific properties of probing samples. The measurement can self-adapt to any bandwidth ranges (with zoomout) and respond to accuracy requirements (with zoom-in). Therefore, no knowledge about the bottleneck bandwidth of the measured path is required. We are currently experimenting with self-similar traffic over a real network environment to gain more experience and to further validate and improve the measurement techniques.

A Line Termination Circuit for Burst-Mode Digital Subscriber Loop Transmission

This paper describes a line termination circuit for burst-mode bidirectional digital subscriber loop transmission. It incorporates the most advanced LSI technology to obtain compactness, low cost, and high reliability. Two CMOS LSIs have been developed; one is a line termination LSI (LT) and another is a circuit termination LSI (CT). LT LSI adopts a novel RC active filter-type equalizer and decision feedback bridged tap equalizer suitable for incorporation in LSI and provides high performance. By using these LSIs, a line termination circuit realizes a reach of over 5 km at 88 kbit/s bidirectional digital transmission. This paper describes each LSI and shows total performance characteristics in detail.

A core-stateless buffer management mechanism for differentiated services Internet

The IETF differentiated services (DiffServ) framework achieves scalability by moving complexity out of the core of the network into edge routers which process fewer number of flows. Previously, an end-to-end service called the premium service (PS) has been proposed under the DiffServ model to provide coarse grained guaranteed rate service. This paper presents a buffer management mechanism based on simple FIFO scheduling to support integrated transport of the PS and the traditional best effort (BE) service. A key feature in our buffer management is to perform selective packet discarding from an embedded queue at a shared buffer. We show that such a buffer management mechanism is capable of achieving the following objectives: (1) a core router does not maintain any state information for any flow (i.e., stateless); (2) the bandwidth for an PS flow is guaranteed (in conjunction with a bandwidth broker (BB) for admission control). Simulation results demonstrate that our buffer management mechanism can achieve integrated transport of the PS and the BE services.

Modeling of self-healing managed object for TMN

In high capacity optical fiber networks, fast restoration from catastrophic failure is increasingly more important. A fast restoration self-healing algorithm and an optimized network design method are illustrated. The proposed telecommunications managment network (TMN) is analyzed from the standpoint of implementing the self-healing algorithm. A design and an effective implementation scheme of the self-healing in accordance with TMN are proposed.<<ETX>>

Active misconfiguration detection in Ethernet networks based on analysis of end-to-end anomalies

This paper addresses the detection of duplexity mismatch (DM) of media access devices in Ethernet networks. From the broad spectrum of sources we surveyed, including logging data from real networks, it appears that DM is surprisingly common and very severe. We show how DM introduces degenerative traffic anomalies capable of drastically reducing flow throughput. We, then, propose a novel detection algorithm based on end-to-end active probing. Our investigation is complemented by the implementation of a SW prototype. Extensive experimental evaluation is conducted in a real-world production LAN. The achieved results are encouraging and show that our prototype can be a very useful tool. Our evaluation attained a high success rate of misconfiguration detection: 99.72%. False positive and false negative rates are extremely contained: 0.00% and 0.28%, respectively. Therefore, our prototype appears to be a robust and reliable detection instrument from which network administrators and field engineers can benefit.