Sang Bae Lee

Modeling and call admission control algorithm of variable bit rate video in ATM networks

The authors propose a new method for the modeling and call admission control (CAC) of variable bit rate video source, which come to the front of ATM networks as hot issues nowadays. First, the modeling of video source is accomplished using the three-state Markov chains including the effects of scene change at which the bit rate of video source is abruptly increased. Also, using two AR models, they improve the defects which an AR model has in modeling a video source. In addition, they represent the analytical model of a video source so that a network manager can acquire the information which is very important in managing the entire networks. CAC is accomplished using the previously defined analytical model. A routing manager calculates the cell loss probability of a chosen VP where a new call is connected so that the routing manager decides whether this new call is accepted or not. This calculation is accomplished through the GB/D/1-S queuing system. Using BIA (bandwidth increasing algorithm), they check whether the calls rejected by the routing manager could be accepted if possible. Finally, the applicable procedures to suitable allocate bandwidth to each VP on a link are presented in detail. >

Internet traffic measurement and analysis in a high speed network environment: Workload and flow characteristics

A study on Internet traffic characterization is essential in designing the next generation Internet. In this paper we characterize the aggregated Internet traffic based on the traffic logs captured from a high speed Internet access network environment. First, we constructed an Internet traffic measurement and analysis system in high-speed Internet access network environment. Then, we analyzed the captured traffic in two ways. First, we analyze general Internet traffic characteristics. In this analysis, we present general workload characteristics of Internet traffic at each communication protocol layers. We also scrutinize how the behavior of upper layer protocols affects the characteristic of IP packet size. To be more precise in characterizing the aggregated Internet traffic, we analyze the captured traffic according to Internet flow model and show its general characteristics and derive analytic models describing the random variables associated with Internet flow size. In this analysis, we found that Internet flow consists of few packets, especially over 45% flows are composed of only one packet and its size is small and last only a few milliseconds. Even if Internet flows are small in size, most of Internet traffic is carried by small number of long-lived flows or big-sized flows. We also found that Internet flow size follows log-normal distribution which shows burstiness over a wide range of time scales. This is a sharp contrast to commonly made modeling choices that exponential assumptions dominate and show only short-range dependence and it has very close relationship with the self-similarity of the aggregated traffic.

Hierarchical performance management using OAM MIB in ATM networks

As the network grows bigger and faster, the demand for reliable and rapid network monitoring and control is on the increase. For efficient network performance management, the network manager should be able to not only acquire the overall network status information with minimum management traffic, but also immediately figure out the faulty network elements. We propose a hierarchical performance management scheme with operation and maintenance (OAM) management information base (MIB) by using the SNMP management protocol. With this MIB we can remotely monitor each connection and pinpoint the location of a performance problem.

A method of gathering end-to-end management information

Asynchronous transfer mode (ATM) network management is an urgent issue for the fast and successful proliferation of ATM networks. Especially, performance management of ATM virtual connections is urgently required because a different quality of service should be guaranteed on each connection. In most cases, the customers virtual connections traverse multiple subnetworks, therefore, performance information related to specific user connection is distributed in the networks. This makes performance management of ATM network more difficult. In order to obtain this distributed performance information with current ATM-related management information bases (MIBs), interactions among managers and frequent polling of switches are inevitable. This frequent polling and manager to manager interactions may cause management traffic and data retrieval time to increase. In this article, we propose a performance management method using OAM MIB. The MIB is a set of managed objects which have the information provided by OAM (Operation Administration and Maintenance) cells. The basic concept and structure of the MIB are similar to the RMON MIB. By using the OAM MIB, management traffic and manager to manager interactions are much reduced. In our model, customer network management system (NMS) accesses the MIB via M1/M2 reference points of the ATM Forum management architecture with simple network management protocol (SNMP).

OAM MIB: an end-to-end performance management solution for ATM

Current network management needs an end-to-end overview of various connections rather than the information that is purely local to the individual devices. The typical manager-centric polling approach, however, is not adequate to understand network-wide behavior of a large-scale broadband network. We propose a new management information base (MIB) approach, called operation, administration, and maintenance (OAM) MIB. The MIB provides a network manager with dynamic end-to-end management information by utilizing special standard ATM cells. The MIB makes end-to-end management feasible while it reduces management-related traffic and manager-to-manager interactions. In our model, a customer network management system accesses the MIB through M1/M2 reference points of the ATM Forum management architecture with simple network management protocol (SNMP).

Dynamic bandwidth management for VBR MPEG traffic using ATM OAM cell

In this paper, we design a model which connects the ATM OAM and the function of traffic control. To implement this model, we propose a scheme that combines the ATM OAM and the bandwidth allocation control. Especially, we design this scheme for the VBR MPEG traffic. In this scheme, a source sends information of frame types and sizes using OAM cells. These OAM cells are F5 flow performance management cells. The layer management function allocates the bandwidth dynamically on the basis of this information. Because MPEG frames have different sizes and importance, our algorithm uses the cell discarding scheme which considers priority. The proposed algorithm has low error in allocating bandwidth compared with prediction algorithms.

A flexible communication architecture to support multimedia services in high speed network

There have been research works on supporting QoS (Quality of Service) in a distributed multimedia systems. These researches can be categorized as following; system platform, real-time operating system, transport protocol, communication architecture. In distributed multimedia environment, QoS must be guaranteed in end systems, but much less progress has been made in addressing this problem. As the processing power of end systems increases, most of the bottleneck occurs in communication protocol, especially transport protocol. To meet an end-to-end QoS, overall QoS architectures must be integrated. In this paper, we propose a new QoS architecture and control mechanisms (group control, and flow control) to guarantee an end-to-end QoS for distributed multimedia services. We also verify proposed architecture by applying them to a multimedia conferencing system in LAN.

A protocol machine configurator for highly flexible transport protocol

The concepts of functional decomposition and selective functionality for the high speed transport protocol have been proposed; along these lines, we implement a protocol machine configurator (PMC) that can configure a protocol machine to be adaptive in the given environment (for multimedia application). For efficiency and flexibility, the operation of this PMC is divided into two steps: protocol function (PF) selection, and mechanism selection. In the PF selection step, PFs, which are required for supporting a certain transport protocol service class, are added to an active function set (AFS) which is the set of the enabled PFs. In the mechanism selection step, only one mechanism in the multi-mechanism protocol function (MMPF), which has multiple mechanisms, is selected to satisfy the quality of service (QoS) requirements such as the delay bound and error tolerance level per media type. By dividing the configuration of the protocol machine into steps, the PMC can determine definitely which PF is to be selected according to the transport protocol service class and determine flexibly which mechanism in each MMPF is to be selected by the QoS limits. Eventually, the PMC can adaptively configure the protocol machine per connection with the selected PFs and mechanisms.

QoS restoration using a disjoint path group in ATM networks

A QoS restoration scheme for VP-based ATM networks is proposed and its related characteristics are evaluated. The proposed scheme is a state-independent restoration scheme using a disjoint path group. A VP assignment and capacity planning problem using a disjoint path group are formulated. When a failure occurs, failed working VP are switched to protection paths with the same QoS level using a simple and fast restoration algorithm. The simulated restoration characteristics of the proposed algorithm are presented. A scheme of excess capacity assignment to a protection path for dynamic traffic demands is also presented and analyzed.

Loop-expanding fast restoration

In this presentation, we introduce a fast restoration scheme against a link or node failure. Specifically, we apply this scheme to VP (Virtual Path) restoration in ATM (Asynchronous Transfer Mode) networks. Proposed restoration scheme operates on VP-based ATM network. This scheme is a distributed algorithm performed concurrently by network nodes neighboring failed node or link. When a node or link fails, restoration is performed according to the pre-assigned local, regional, and end-to-end restoration scheme. For this, we assigned a restoration level to each network nodes and VPs, respectively. Also, we devise and construct a VP loop, and fast restoration is performed along this loop. This loop is expanded when a failure occurs, and this expanded loop is used for the restoration of the failed VP connection. We define the required VP loop architecture, restoration messages, and restoration procedures. Proposed algorithm is simulated and compared with general flooding restoration scheme. Results show that the proposed loop-expanding restoration scheme can achieve fast restoration goal with a lower burden to network.