Superposed ATM cell streams have burstiness and strong autocorrelation properties. This paper investigates traffic measurement-based modeling method for superposed ATM cell streams. We develop a new measurement method based on monitoring both the waiting time distribution in a monitoring queue and the autocorrelation of cell interarrival times. Through the monitoring queue, we directly observe the queueing effect of superposed cell flows on ATM multiplexers. The measured traffic is modeled as the two-state MMPP. With the measured traffic, we estimate the cell loss probability in ATM multiplexers from the MMPP/D/1/K queue. Our method successfully works with homogeneous and heterogeneous superposition of traffic sources including voice, data, and video. These results can be applied to the evaluation of ATM multiplexers, traffic engineering, and network performance monitoring.

Since ATM network is a connection-oriented network, the operation for connectionless service is required for data service in it. There are many ways to support connectionless service in ATM network. They are ATM LAN Emulation, Classical IP and ARP over ATM, Indirect approach, Direct approach, and IP switch. It is known that Direct approach is suited for public network. The connectionless server supports connectionless service in Direct approach. There have been presented two kinds of methods, that is, streaming forwarding method and reassembly forwarding method, to forward the frames in the connectionless server. Reassembly forwarding method can work well with AAL5 which has better efficient characteristics than AAL3/4 in terms of easy use and fewer overheads. This paper proposes an algorithm that can decrease the loss of frame by a proposed buffer management working with AAL5. This paper also investigates the structure of the proposed connectionless server and its performance with the one of the conventional connectionless server through simulations. The proposed connectionless server shows a less frame loss and transfer delay than that of the conventional connectionless server.

This paper proposes a new access control scheme called multiple round-robin matching protocol (MRM) for high-speed packet-switched WDM LAN. The architecture is based on a broadcast-and-select star network, where each node has an arbitrary number of fast tunable transceivers. Our scheduling algorithm is simple to implement and can overcome data channel and receiver collision by using a round-robin priority. Simulations demonstrate improved mean delay characteristics with a small number of transceivers at each node.

This paper proposes a new MAC scheme for ATM based Passive Optical Network (APON) which follows the ITU-T recommendation G.983.1. MAC schemes for APON mostly adopt single-side scheduling in which only OLT (Optical Line Termination) schedules upstream access order for ONUs (Optical Network Units) that inform cell arrival information to OLT. In this paper, we propose a MAC scheme called double-side scheduling protocol (DSP) in which both OLT and ONU participate in scheduling process. Through the computer simulation we find out that the CDV (cell delay variation) performance of the real-time service can be improved remarkably using fewer overhead slots than that of the MAC schemes adopting CDV control algorithm. For the proposed MAC scheme, we present grant field format, minislot format, divided slot format, and scheduling algorithm.

Asynchronous Transfer Mode (ATM) switching system is expected to handle various kinds of media (such as motion video, computer data, and voice), and traffic control becomes essential to satisfy various quality requirements and to maintain efficient utilization of system resources. Priority control is one possible solution for realizing such a traffic control. In priority control, cells from various media are scheduled for transmission with different priority according to the quality class to which they belong. In this paper, we propose a new priority control method in which cells from various media are stored in their own buffer, we call it class buffer, and priority assignments are carried out based on the number of cells in each class buffer and the delay time. The number of cells in each class buffer is maintained using the counter circuit. The delay time of the cell is checked by the timer circuit for cell group, each of which consists of cells arriving during a periodical time interval. For simulation model, we consider three kinds of traffic; video, computer data, and voice, of which quality requirements are quite different. We show performance results in terms of the cell delay and the cell loss probability in our method through simulation.

This paper proposes a new scheduling algorithm named TWFQ (Two-phased Weighted Fair Queueing) not only to maintain the fair utilization of available bandwidth but also to improve the performance of CDV and cell loss probability. The TWFQ algorithm makes use of the cell inter-arrival time of each connection for determining the cell service order among connections, which contributes to get a small CDV. To achieve low cell loss probability, the TWFQ allows connections, which suffer from the more bursty input traffic, to send the cell with more opportunities by using two scheduling phases. Through simulations, we show that the proposed algorithm achieves good performance in terms of CDV and cell loss probability, while other performance criteria are preserved in an acceptable level.

In this paper there suggested is a bifurcated (or multiple) input-queued ATM switch in which a buffer for each input port is divided into multiple (m) buffer blocks, i. e. , bifurcated buffers, for enhancement of the limited throughput of the ordinary input-queued switch using a single FIFO. As the contention/arbitration rule for the bifurcated input-queued switching scheme, free and restricted contention rules are come up with and discussed. The free rule allows an input port to switch up to m cells at the cost of internal speedup. With the restricted rule, on the other hand, an input port can switch no more than one cell in a time slot so that the switch operates at the same speed as the external link speed. The throughput bound for the bifurcated input-queued switch is analyzed for both rules through the generalization of the analysis by Karol et al. The throughput bound approaches to 1.0 as m becomes large enough, irrespective of the contention/arbitration rule.

A circuit emulation technique in the ATM network becomes necessary to guarantee user requirements similar to QOS grade offered by STM network where small bit error rates and constant delay times are offered. The Head-Of-Line method or other priority control schemes may be considered to provide such service in the ATM network, while it is known to give too inferior quality to non-circuit emulation service traffic. In this paper, we propose a new method called a periodical bandwidth allocation method for the circuit emulation technique. The cells of circuit emulation service traffic are transmitted periodically in our proposal. A periodical interval is determined from both the length of limit delay time of circuit emulation traffic in each switching node and the number of cell arrivals during the limit delay time. To evaluate our method, we consider three kinds of arrival patterns (the best case, the moderate case, and the worst case) for the circuit emulation traffic and a two-state MMPP for modeling the non-circuit emulation traffic. We show performance results in terms of the cell loss probability and the mean delay time in our proposal through analytic and simulation approaches.

This paper proposes a new algorithm named WGF (Weight-Gap First) scheduling. It not only supports the maximum throughput of a cell, but also provides the fairness of a terminal in HDR. The WG-based new scheduling algorithm is determined by served data of mobile terminals to guarantee requested data rate. WGs are renewed at each timeslot to improve throughput and fairness. Simulations confirm the better performance of the proposed algorithm in terms of throughput and fairness.

An ATM buffer management scheme with logically separated buffers is proposed to guarantee various Quality of Services such as CBR, rt-VBR, nrt-VBR, ABR, and UBR and to make efficient use of system resources in ATM switching systems. By assigning proper priorities based on the count indicator (CI) and the time indicator (TI), respectively, the scheme can afford ABR services without cell loss and real-time services with controllable delay.

This paper proposes three MAC protocols over APON to provide residential and small business customers with multimedia services. The proposed protocols support the frame structure of ITU-T recommendation G.983.1 and also provide diverse ATM service classes such as CBR, rtVBR, nrtVBR, ABR, and UBR traffics. Each service is allocated on the basis of priority. Especially, for allocating CBR and rtVBR services, each protocol uses different cell arrival timing information which is achieved with specific coding and ranging procedure. Focusing the difference of cell arrival timing information, we will investigate the performance of proposed protocols. For the proposed MAC protocols, we present grant field format, minislot format, and bandwidth allocation algorithm. Computer simulation shows the performance of the proposed protocols in terms of CDV and delay, comparing with the normal FIFO protocol.

A hybrid CDMA/TDMA, a combination of CDMA and TDMA, is proposed as a MAC protocol for wireless ATM networks. TDMA offers the ability to integrate different types of services in a flexible way by the use of multiple slots per frame, while CDMA allows multiple users to transmit simultaneously using their own codes. To reduce the multiple access interference in each slot, the channel access is controlled by an access permission probability or a round robin method. A shared code scheme is adopted to utilize the given code resource efficiently. The results of simulation show that the proposed scheme gives better performance than the JCP algorithm.

This paper proposes a novel MAC scheme over APON based on the cell arrival timing information to provide residential and small business customers with multimedia services. The proposed scheme supports the frame format of ITU-T recommendation G.983 and also provides diverse ATM service classes such as CBR, rtVBR, nrtVBR, ABR, and UBR traffics. Each service is allocated on the basis of priority and cell arrival timing information. Especially, the CBR and rtVBR services, which are sensitive to delay and CDV, are allocated with higher priority and more exact arrival timing resolution which is achieved with specific coding and ranging procedure. For the proposed MAC scheme, we present grant field format, minislot format, and bandwidth allocation algorithm. Computer simulation results show that the performance of the proposed scheme is significantly improved in terms of CDV and delay time in case of CBR and rtVBR services, comparing with the normal FIFO scheme.

Wavelength converters are usually used for improving the performance of WDM optical networks. From the viewpoint of network economics and current technologies, the wavelength converters with a limited conversion range are necessary to be used sparsely in real applications. However, there have been little efforts for developing wavelength assignment algorithm that achieves a guaranteed high performance with either limited or sparse wavelength conversion. In this paper, we propose a new wavelength assignment algorithm that can be applied to both sparse and limited wavelength conversion. Through the results of simulation program, we show that the proposed algorithm outperforms other ones presented until now.

This paper proposes three-phased traffic conditioner (3PTC) to be installed at edge routers in Differentiated Services (DiffServ) networks. 3PTC ensures that Assured Service (AS) flows are supplied with the throughput assurance, which stems from alleviating the impact of the size of TCP reserved rate, UDP/TCP interaction, Round Trip Time (RTT) and number of microflows. 3PTC is composed of token bucket phase, writing probability (WP) calculation phase and queue management phase. Computer simulation results show that 3PTC guarantees throughput assurance and provides end users with expected service levels.

In this paper, we propose a new fair queueing algorithm to improve cell delay variation (CDV) for real-time service categories and to make efficient use of system resources for multimedia traffic in high speed ATM networks. The proposed algorithm is called the delay variation-based fair queueing (DVFQ) algorithm, which is based on per-VC queueing to improve CDV and fairness for each VC of real-time services such as CBR and rt-VBR. In DVFQ algorithm, we define two fairness indexes, which indicate the degree of the fairness of CDV at the rate of each VC, and the degree of impartially sharing the bandwidth between the scheduled cells for each VC. The simulation results for both heavily and lightly loaded conditions show that DVFQ algorithm provides better performances in terms of the CDV, the CDV fairness, and the service fairness than those of FCFS for real-time service.

The handoff of in Mobile IP causes packet sequence disruption during packet forwarding procedure, which may result in degradation of network performance in higher layer protocol. In this paper, we investigate the impact of handoff on out-of-sequence packets in Mobile IP with Route-Optimization extension. To evaluate the handoff procedure, we use the unstable time period (UTP) when the packet sequence could be mis-ordered. The results show that the UTP mainly depends on queuing delay of old Foreign Agent (FA) and link capacity between old FA and new FA. Further, we propose that the priority queuing for the astray packets in the old FA can increase Mobile IP performance during handoff procedure by reducing the UTP.

In an effort to reduce switch cost, we present the optimum numbers of tunable wavelength converters (TWCs) and internal wavelengths required for contention resolution of asynchronous and variable length packets, in the optical packet switch (OPS) with the shared fiber delay line (FDL) buffer. To optimize TWCs and internal wavelengths related to OPS design cost, we proposed a scheduling algorithm for the limited TWCs and internal wavelengths. For three TWC alternatives (not shared, partially shared, and fully shared cases), the optimum numbers of TWCs and internal wavelengths to guarantee minimum packet loss are evaluated to prevent resource waste. Under a given load, TWCs and internal wavelengths could be significantly reduced, guaranteeing the same packet loss as the performance of an OPS with full TWCs and internal wavelengths.