This paper presents an adaptive control design for the ABR traffic congestion control in ATM networks. Firstly, we consider a control-based mathematical model to the ABR traffic congestion control problem. Then the feedback pole placement control design is applied to the ATM ABR traffic congestion control problem for the case of known delays. Finally, by using the online plant parameter estimation algorithm and modifying the controller parameters adaptively in real time, a method to treat the case of unknown time-varying delays is proposed. Several design modifications are introduced to solve practical control issues such as bounded command rate constraint, output buffer saturation and bounded values to the plant parameter estimation algorithm. Simulations are implemented to verify the proposed control design. It is shown that while considering these practical control issues, the control method satisfies the requirements of fairness to users, network efficiency, unknown time-varying delays, queue length control and good convergence performance at an acceptable computation effort.

In this paper, we propose a novel traffic engineering architecture for IP networks with MPLS backbones. In this architecture, two link-disjoint label switched paths, namely the primary and secondary paths, are established among every pair of IP routers located at the edges of an MPLS backbone network. As the main building block of this architecture, we propose that primary paths are given higher priority against the secondary paths in the MPLS data plane to cope with the so-called knock-on effect. Inspired by the ABR flow control mechanism in ATM networks, we propose to split traffic between a source-destination pair between the primary and secondary paths using explicit rate feedback from the network. Taking into consideration the performance deteriorating impact of packet reordering in packet-based load balancing schemes, we propose a traffic splitting mechanism that operates on a per-flow basis (i.e., flow-based multipath routing). We show via an extensive simulation study that using flow-based multipath traffic engineering with explicit rate feedback not only provides consistently better throughput than that of a single path but is also void of out-of-order packet delivery.

This paper proposes a stable rate allocation algorithm for ABR service in ATM networks. The main goals in designing this algorithm are to speed up the convergence according to the max-min fairness criterion and to maximize the network utilization while the switch queue length can be properly controlled. Importantly, the set goals should be achieved in a wide range of network conditions without the need for adjusting the algorithm parameters. The algorithm is targeted to work in various networking environments with additional criteria as extended from the work of E-FMMRA (Enhanced Fast Max-Min Rate Allocation) and ERICA+ (Explicit Rate Indication for Congestion Avoidance) . The additional design criteria include the ability to enhance a large number of ABR connections and staggered TCP connections as well as to perform an accurate traffic averaging. The algorithm is analytically proved to be convergent. Simulation results indicate that the proposed algorithm achieves the goals in all evaluated configurations. However, it has some limitations when working in the large-scale network due to its per-connection accounting. It is not recommended to implement the algorithm with a switch that has a small buffer size due to its relatively long averaging interval.

In this paper, we propose a new consolidation algorithm called the Selective Backward Resource Management (BRM) cell Feedback (SBF) algorithm. It achieves a fast response and low consolidation noise by selectively forwarding BRM cell from the most congested branch to the source instead of waiting from all branches. Mathematical models are derived to quantitatively characterize the performance, i.e. the response time and ACR of the source, of SBF and previously proposed algorithms. The interoperation of consolidation algorithms in point-to-multipoint available bit rate (ABR) is investigated. We address response time, consolidation noise and the effect of asymmetrical round trip delay (RTD) from branch point to destinations aspects. All combinations of four different consolidation algorithms are interoperated in both local/metropolitan area network (LAN/MAN) and wide area network (WAN) configuration. By a simulation method, we found that the consolidation algorithm used at the uppermost stream branch point, especially in WAN configuration, plays an important role in determining the performance of the network. However, consolidation algorithm used at the lower stream branch point affects the network performance insignificantly. Hence, in order to achieve a good and effective performance of the consolidation algorithms interoperated network, a fast response with low consolidation noise algorithm should be used at the uppermost stream branch point and a simple and easy to implement algorithm should be used at the lower stream branch point.

The available bit rate (ABR) is an ATM service category that provides an economical support of connections having vague requirements. An ABR session may specify its peak cell rate (PCR) and minimum cell rate (MCR), and available bandwidth is allocated to competing sessions based on the max-min policy. In this paper, we investigate the ABR traffic control from a different point of view: Based on the decentralized bandwidth allocation model studied in [9], we prove that the max-min rate vector is the equilibrium of a certain system of noncooperative optimizations. This interpretation suggests a new framework for ABR traffic control that allows the max-min optimality to be achieved and maintained by end-systems, and not by network switches. Moreover, in the discussion, we consider the constrained version of max-min fairness and develop an efficient algorithm with theoretical justification to determine the optimal rate vector.

In this paper, we first investigate the problems of the existing branch point algorithms for available bit rate (ABR) multicast connections in ATM networks, and then propose various solutions for resolving those problems. By combining these solutions, we also propose a new efficient and scalable branch point algorithm. In the proposed algorithm, each branch point stores the feedback information on a per-branch basis for each virtual connection and only passes BRM cells returning from the farthest destination. Simulation results show that the proposed algorithm can provide a good fairness, a higher efficiency and an excellent scalability, compared with the existing algorithms.

This paper investigates the performance of relative rate (RR) switch algorithms for available bit rate (ABR) flow control in asynchronous transfer mode (ATM) networks. An RR switch can be implemented differently according to the congestion detection and notification methods used. This paper proposes three implementation schemes for an RR switch using various congestion detection and notification methods, and then analyzes the allowed cell rate (ACR) of a source and the queue length at a switch in steady state. The upper and lower bounds for the maximum and minimum queue lengths are also determined for each scheme, respectively, thereby investigating the effects of ABR parameter values on a queue length. Furthermore, a selection method for rate increase factor (RIF) and rate decrease factor (RDF) parameter values is suggested to prevent buffer overflow and underflow.

This letter proposes an efficient implementation method for a binary feedback switch, called EFCI/RELAY, which can reduce the feedback delay of the congestion status of a switch in multiple-hop network environments. At each transit switch, this method relays the EFCI-bit contained in an incoming data cell to the head-of-line cell with a corresponding VC which is waiting for transmission in the output buffer. Simulation results show that the proposed method can achieve a lower queue length while maintaining a higher link utilization.

We propose ATM switching nodes with a feedback rate control scheme, AREX, which does not require a large buffer space and does not deteriorate throughput even in large-scale and high-speed ATM-WANs. The goal of our study is to establish the ATM multi-protocol emulation network ALPEN, which is an ATM-WAN architecture for establishing a backbone for multimedia networks. ALPEN achieves an ATM-WAN which is robust against long propagation delays. It also provides high performance without a large buffer space in an ATM-WAN environment. In ALPEN, each transit node informs the edge nodes only its residual bandwidth ratio. The edge nodes support multiple ATM-layer services by emulating them based on the information notified by transit nodes. Our research has been directed towards achieving high performance ABR (Available Bit Rate) service in an ATM-WAN by using ALPEN. The conventional ABR service requires transit nodes to have relatively high calculation power and large buffer space to overcome the effect of the long propagation delays common in WANs. ALPEN node systems have been developed for trials with actual network traffic. ALPEN with AREX reduces the calculation load of transit nodes for ABR service. That is confirmed by the size of the DSP program created for a test system. ALPEN with AREX is, therefore, able to emulate ABR service with higher performance in ATM-WANs, because ALPEN edge nodes are able to indicate the users allowed by ER (Explicit Rate) feedback. The network throughput, maximum queue length at congestion point, and burst transmission rate are determined by simulation. ALPEN with AREX achieves better performances than the conventional ABR network.

We investigate performance of TCP protocol over ATM networks by using a simulation technique. As the ATM layer, we consider (1) rate-based control of the ABR service class and (2) an EPD (Early Packet Discard) technique applied to the UBR service class and (3) and EPD with per-VC accounting for fairness enhancement applied to the UBR service class. In comparison, we adopt a multi-hop network model where the multiple ATM switches are interconnected. In such a network, unfairness among connections is a possible cause of the problem due to differences of the number of hops and/or the round trip times among connections. Simulation results show that the rate-based control method of ABR achieves highest throughput and best fairness in most circumstances. However, the performance of TCP over ABR is degraded once the cell loss takes place due to the inappropriate control parameter setting. To avoid this performance degradation, we investigate the appropriate parameter set suitable to TCP on ABR service. As a result, parameter tuning can improve the performance of TCP over ABR, but limited. We therefore consider TCP over ABR with EPD enhancement where the EPD technique is incorporated into ABR. We last consider the multimedia network environment, where the VBR traffic exists in the network in addition to the ABR/UBR traffic. By this, we investigate an applicability of the above observations to a more generic model. Through simulation experiments, we find that the similar results can be obtained, but it is also shown that parameters of the rate-based congestion control must be chosen carefully by taking into account the existence of VBR traffic. For this, we discuss the method to determine the appropriate control parameters.

One of the functions that should be provided in ATM LANs is multicast communication. For multicast communication on ATM LANs, the architecture of switch fabric and protocols for signaling have been studied. However, when data communication using a multicast connection such as LAN emulation service is provided, ABR service on a multicast connection (Multicast ABR) is also required. ABR service has been actively discussed in the ATM forum. Unfortunately, the study on flow control mechanism for Multicast ABR is not enough. This paper discusses the suitable flow control mechanism for Multicast ABR and shows its performance.

Rate-based congestion control is a promising scheme as data transfer service in ATM networks, and has been standardized in the ATM Forum. To migrate the existing upper layer protocols to ATM networks, however, further investigation is necessary. In particular, when ABR service class is applied to TCP (Transmission Control Protocol), duality of congestion control schemes in different protocol layers, i.e., conventional window-based congestion control in the Transport layer and ratebased congestion control in the ATM layer, may have a unexpected influence on performance. As an alternative approach for supporting TCP protocol, EPD (Early Packet Discard) has been recently proposed, which adds the function to the UBR (Unspecified Bit Rate) service. It does not have a "duality problem" since EPD only discards cells selectively to improve packet-level performance. In this paper, we exhibit performance of TCP protocol over ATM networks by using a simulation technique. We first compare rate-based control of ABR service and EPD applied to UBR service, and show that rate-control achieves better fairness and higher throughput in most circumstances. However, rate-based control requires careful tuning of control parameters to obtain its effectiveness and a duality problem leads to unexpected degradation of TCP-level performance. By the rate-based congestion control, temporal congestion at the switch is quickly relieved by the rate down of the source terminals. However, our simulation explores that if the parameter set of the rate-based congestion control is not appropriately used, the congestion is also recognized at TCP due to packet drops and TCP unnecessarily throttles its window size. To avoid this sort of the problem, we develop the appropriate parameter set suitable to TCP on ABR service, and point out that some modification of TCP may be necessary for further performance improvement.

This paper investigates Available Bit Rate (ABR) traffic control based on the Explicit Forward Congestion Indication (EFCI). A flow control mechanism is specified for ABR service to control the source rate. Resource Management (RM) cells are used to convey feedback. A source sends a forward RM cell for at least every N cells sent. At the destination, a forward RM cell turns around as a backward RM cell and returns to the source. A data cell has EFCI-bit in its header field. A network element sets EFCI-bit if it is congested. A destination indicates congestion status of networks by using RM cells based on the value of the EFCI-bit of the data cells. A one-bit feedback scheme is used by the ATM Forum. However, indication schemes have also been proposed which use explicit indication of source rate based both on values of the EFCI-bit of data cells and on other information contained in a forward RM cell. We evaluated explicit indication schemes as well as a one-bit scheme by simulation. Simulation study showed explicit cell rate indication gives superior performance than one-bit indication especially for long round trip distances. In this paper, we report the results with brief discussion.

Data communication by using TCP/IP is one of important services on ATM networks. At one approach in traffic control of this service, the dedicated bandwidth for data transfer is not guaranteed and the feedback congestion control to prevent cell loss is performed in the congestion case. However, when a large quantity of data is transferred within a short period, this traffic control cannot be expected to achieve high efficiency. In this case, it is suitable that the dedicated bandwidth is guaranteed by FRP (Fast Reservation Protocol) before the data is transferred. This paper describes that FRP is superior to the feedback congestion control for large size data transmission. Next, it proposes a selectable traffic control which selects adaptively one of the feedback congestion control and FRP.