The introduction of networks providing Internet-like services such as the Open Computer Network (OCN) by NTT and others like it will lead to higher level demands by users. For example, users will be asking for higher quality, greater functionality, and lower charges for high-speed, high-throughput data transfer. To respond effectively to the wishes of sophisticated and varied users, technological development must be pursued from the user's point of view. For this reason, research and development is being performed on middleware to open up network functions and make it possible for the user and network to cooperate with each other. This paper discusses the development of major technologies for achieving an enhanced internetworking that should become a catalyst for the future multimedia network, and presents a future vision for the network.

In the future Internet, hierarchically classified Quality of Service (QOS) controls will be effective because various connections requiring different QOS are mixed. However, even in such an environment, among the same class connections, performance protection to harmful impact from the other connections and quality differentiation between connections will be required furthermore. In this paper, from this point of view, we focus on the active connections succession time (age of active connections) as a new dimensional criterion for buffer controls. To be concrete, the packet discarding control of congested router's buffer based on active connections is proposed. Moreover, its performance is evaluated through TCP/IP level simulation from the viewpoint of file transfer time. Conventional Internet can be regarded as the environment where only one class traffic exists (unit class environment). The proposed control scheme can provide powerful differentiation capability to avoid the performance disruption of total connections even in the conventional Internet.

Optical switching networks to transport vast amounts of information are important for B-ISDN services. Wavelength division multiplexing (WDM) is emerging as the dominant technology for future optical networks. A large capacity photonic ATM switch architecture using WDM technology is proposed in this paper. The proposed switch is suitable for WDM optical ATM networks, that is, an input and an output of the switch are wavelength division multiplexed. The basic switch module of the proposed switch has a simple architecture, and reduces the amount of a buffer hardware by introducing the WDM concept.

The Non-stop Service-Enhanceable Software (NOSES) platform was developed as part of our overall plan to establish a communications software platform that can be customized for use by various communications systems, such as STM, ATM and IN. The developed NOSES techniques are call-recovery restart, system file update, and on-line partial file modification, so called "Plug-in"; they were achieved by using dynamic program modification. A system-file update inevitably affects calls in service, despite efforts to save in-service calls by copying the call data from the old file to the new one. We therefore developed a different approach: Plug-in modification. This paper evaluates the applicability of the plug-in mechanism of the NOSES platform. Plug-in is a dynamic partial-file modification technique that does not affect calls in service in a communication switching system. In order to apply plug-in program modification widely, the static and dynamic properties of the modified software must be considered. Therefore, an applicability judgement matrix is introduced. The evaluated applicability of plug-in based on case studies and field data was about 60% for service feature additions and modifications. Thus, plug-in is effective for file maintenance of switching systems from the viewpoint of quick provisioning of new service features and bug fixes.

DQRUMA (Distributed-Queueing Request Update Multiple Access) protocol has been proposed as an access protocol for the wireless ATM Local Area Networks. DQRUMA protocol is useful to transmit fixed-length packets (e. g. ATM cells). However, it cannot be applied to multimedia environment because it does not include any access control policy for multimedia traffic. In the paper, we propose a slot assignment scheme of DQRUMA protocol in wireless ATM LAN which supports integrated multimedia traffic with different service requirements. In this scheme we can allocate network resources according to the service requirements of each medium because the base station assigns Transmit-Permission flexibly according to the features of each medium.

The optical ATM transport networks are the key technology for B-ISDN which integrates wide variety of communication services. In a photonic ATM switch, electronically operated switching control drastically limits the total throughput. With this bottleneck of the control speed of the switch compared to the cell transmission speed, if the unit of switching operation can be made longer, the system throughput will be improved. This paper proposes the optical backbone network configuration to obtain traffic concentrating effect to construct a large switching unit called a multi-cell. In the backbone network applied the concept of virtual path set (VPS), a multi-cell is constructed by cells from all of ATM switches in a regional network connected with each own's cross connect. The multi-cell format in the case of two different network models is investigated in this paper. The average delay and average idle cells per multi-cell in the multi-cell MUX of an optical cross connect are evaluated by computer simulation as the performance of the multi-cell transfer scheme in the backbone network. Simulation results show that the multi-cell transfer scheme can be operated efficiently with traffic load of more than 0.5. This paper also proposes the configuration of multiplexing and demultiplexing module to assemble and disassemble the multi-cell.

The self-healing capability against network failure is one of indispensable features for the B-ISDN infrastructure. One problem in realizing such self-healing backbone network is the inefficient utilization of the large spare capacity designed for the failure-restoration purpose since it will be used only in the failure time that does not occur frequently. "Pool-capacity" is the concept that allows some VPs (virtual paths) to efficiently utilize this spare capacity part. Although the total capacity can be saved by using the "Pool Capacity," it is paid by less reliability of VPs caused by the emerging influence of indirect-failure. Thus, this influence of indirect-failure has to be considered in the capacity designing process so that network-designers can trade off the saving of capacity with the reliability level of VPs in their self-healing networks. In this paper, Damage Rate:DR which is the index to indicate the level of the influence caused by indirect-failure is defined and the pool-capacity design scheme with DR consideration is proposed. By the proposed scheme, the self-healing network with different cost (pool-capacity) can be designed according to the reliability level of VPs.

In reliable multicast communications, lost information due to packet loss should be re-multicasted. NAK-based retransmission scheme is said to be effective for scalable reliable multicast communications because it can avoid implosion of control packets. When the source sends packets faster than receiver's ability, packet loss due to buffer overflow occurs constantly at corresponding receivers. With this constant packet loss, implosion of control packets degrades total throughput seriously even in the case of NAK-based retransmission scheme. In order to prevent this kind of constant packet loss at receivers, flow control scheme should be implemented for reliable multicast communications. In the paper, we propose a new flow control scheme suitable for NAK-based retransmission scheme. From the viewpoint of flow control, receiving a NAK indicates that transmission rate is too high. However, in multicast communications, multiple NAKs may be generated for a corresponding packet. If the transmission rate is decreased simly by receiving a NAK, the rate may be decreased excessively. In the paper, logging information of transmission rate stored at the sender is proposed to be effective to prevent the transmission rate. Performance evaluation by computer simulation shows that the proposed scheme notably improves throughput performance compared with the case of no flow control.

For the realization of the very high-speed data transmission over wide area network, the HIPPI-ATM conversion for connecting two remote HIPPI end systems is specified by ANSI. Since the credit scheme is adopted for the flow control on the ATM part in the specification, the propagation delay influences the remarkable transfer throughput degradation with the longer distance between end systems. In this paper, two priority types of HIPPI bursts are proposed, which include the flag indicating the priority, high priority or low priority. We propose the hybrid scheme that the credit scheme is adopted only for sending the high priority HIPPI bursts and the source can send low priority HIPPI bursts without reserving buffers in the receiver. In order to confirm the effectiveness of the proposed scheme, we show the characteristics of transfer performance and low priority bursts loss ratio v. s. transmission distance by simulation. Furthermore, we introduce the implemental example of the proposed scheme in the MPEG video transmission application, and show it's good performance.

Optical switching networks to transport vast amounts of information are important for B-ISDN services. The wavelength division multiplexing (WDM) is emerging as the dominant technology for future optical networks. This paper proposes a large capacity photonic ATM switch architecture using WDM technology. The switch consists of two stages. The first stage is a space switch and the second stage is a wavelength switch. The proposed switch is suitable for WDM optical ATM networks, that is, an input and an output of the switch are wavelength-division-multiplexed. The switch can provide very large ATM cell switching capacity, for instance, 10Tbit/s, with reasonable complexity. The main switch module of the proposed switch has a simple architecture, and reduces the amount of a buffer hardware by introducing the WDM concept.

One of the objectives of ABR traffic control is a fair allocation of transmission rate to every connection. Algorithms which have been proposed can achieve the fair allocation of transmission rate in persistent traffic, even though the connections have different number of hops. In bursty traffic, however, the transmission rate during the burst period, called average burst throughput, may become degraded when the number of hops increases. In this paper, we evaluate the average burst throughput characteristics of ERICA switch algorithm and investigate the effect of the number of hops. We propose a new bandwidth allocation method which can improve the performance degradation by taking the number of hops into account. The effectiveness of our method is evaluated by computer simulation.

Recent studies on traffic measurement analysis in the various networks (LAN, MAN, WAN) have shown that packet traffic exhibits Self-Similarity. The packet traffic represents some behavior quite different from what it has been assumed. Some papers reported that Self-Similarity degrades the network performance, such as buffer overflow and network congestion. Thus, we need new network control scheme considering Self-Similar properties. The control scheme requires high-speed calculation method of Hurst Parameter. In this paper, we propose high-speed calculation method of Hurst Parameter based on the Variance-Time Plot method, and show its performance. Furthermore, we try to apply this method to the simple network control, in order to show effectiveness of the network control with Self-Similarity.

In server load balancing where replicated servers are dispersed geographically and accesses from clients are distributed to replicated servers, a way of distributing the accesses from clients to an adequate server plays an important role from the viewpoint of load balancing. In the paper, we propose a new network paradigm for server load balancing using active anycast. In active anycast, an end user only sends its request to group of servers using an anycast address. When this request arrives at an active router, it selects an adequate server from the viewpoint of load balancing and changes the anycast address of a packet to the unicast address of the selected server. The decision which server is the best one from the viewpoint of server load balancing is made by an active router rather than an end user, so active anycast is a network-initiated method. Simulation results show that active anycast can accomplish efficient server load balancing, even when a small part of routers are equipped with active network technology.

The message level performance of error controls in data communication on ATM network is analyzed. Three layers, "a cell"(a unit of transmission), "a block"(a unit of error controls) and "a message"(a unit of transmission of user level) are considered. The error controls treated in this paper are GBN (Go-Back-N) and FEC+GBN. The cell loss process is assumed to be the two state Markov chain considering the cell loss process in ATM networks. Numerical results show that (1) the improvement of the message forwarding delay is saturated in some environments when the interface rate becomes high, (2) FEC is efficient when the burstiness of the cell loss process is small, the message length is large and the interface rate is high.

In this paper, we evaluate the performance of flow control mechanisms for reliable multicast under several retransmission approaches in terms of scalability. The mechanisms examined are a window-based flow control mechanism for ACK-based retransmission approaches and a rate-based flow control mechanism for NAK-based retransmission approaches. Our simulation results show that the NAK-based flow control mechanism has better scalability and higher throughput than the ACK-based flow control mechanism, and the delay incurred by a NAK suppression mechanism does not affect the performance of multicast flow control.

In the paper, we propose a congestion control scheme for reliable multicast communication which enables TCP fairness and prevents a drop-to-zero problem. The proposed congestion control scheme is rate-based one based on NAKs from receivers and cooperatively works with a flow control scheme. The congestion control scheme consists of two components of a rate-based controller and a selection mechanism of a representative. The rate-based controller runs between the sender and the representative and achieves TCP fairness and fast response to losses at the representative. The selection mechanism of the representative allows the sender to select the representative in a scalable manner, in which the sender makes use of NAKs from receivers to select it. In the paper, we also propose the switchover mechanism of the flow and congestion control schemes which enables the sender to use either of them adaptively based on network situations. When the network is congested, the congestion control scheme works to share network resources fairly with competing TCP flows. Otherwise, the flow control scheme works to adapt the transmission rate to the slowest receiver. We verify the performance of our proposed schemes by using computer simulation.

This paper presents a performance evaluation of NAK-based reliable multicast communication protocols operating in an environment where end-to-end delay are heterogeneous. In the case of heterogeneous delay, performance of a timer-based retransmission control scheme may become worse. We show that a counter-based retransmission control scheme works well in the case of heterogeneous transmission delay. We also compare two NAK-based protocols and show that a NAK-multicasting protocol outperforms a NAK-unicasting protocol from the viewpoint of scalability even when delays are heterogeneous.

A highly reliable network which can restore itself from network failures is one important concept for the future high capacity broadband network. In such self-healing network, flooding based failure-restoration algorithm is used to locate new routes and then to reroute failure traffic to that routes automatically when network failures such as link or node failures occur. Since the speed of this algorithm is degraded by the large amount of restoration messages produced by the process, such large volume messages should be reduced. In this paper, the scheme will be proposed, which reduces the large volume messages and efficiently selects alternative routes. In this scheme, the Message Wall will be used to filter useless restoration messages at the tandem nodes and Multi-Message Selecting method will be used to rapidly select a group of link-disjointed alternative routes from the feasible ones in each Flooding Wave sequence. The simulation results show that restoration messages are dramatically reduced and adequate alternative routes can be quickly found out.