Cell Delay Variation Research Articles

A survey of straightforward statistical multiplexing models for ATM networks

Connection Acceptance Control (CAC) is probably the most important function in the preventive congestion control strategy to be implemented in ATM networks. The CAC function must decide, on the basis of the traffic descriptors provided by an incoming connection, whether the new call can be accepted or not. A key factor in the access decision is the behaviour of the superposition of ATM VCs in a switch output buffer, and in particular the cell loss probability resulting from accepting the connection. Many models have been proposed in the literature in order to investigate this issue. In this paper, we present a survey of the queuing models used to estimate the cell loss probability in ATM networks with straightforward statistical multiplexing. The CAC policy under consideration is based on the so-called Worst Case Traffic allocation corresponding to the traffic descriptor parameters submitted by a VC: itspeak cell rate, cell delay variation tolerance, sustainable cell rate, andintrinsic burst tolerance parameters, when applicable. We plan to investigate the practical application of these models to the problem of CAC; in particular, the important issues of accuracy of the available models, their range of validity and their complexity deserve more attention than they have received up to now. The present survey stands as a first step in that direction.

CDV tolerance for mapping cellsbetween ATM andphysical layers

For a customer premise node with multiple terminal equipment, a multiconnection shaper is required to regulate cells toward the customer loop such that they will be treated as conforming by the enforcer at the public user network interface. However, when setting the arguments of the enforcing algorithm (e.g. generic cell rate algorithm), the cell delay variation (CDV) between shaper and enforcer must be taken into consideration. The authors calculate the CDVs for mapping cells between the ATM layer and the physical layer at the shaper and enforcer.

Bandwidth-dependent scheduling algorithm tolimit cell delay variation for CBR traffic inATM networks

A multiplexing control scheme is proposed for limiting the cell delay variation (CDV) caused by multiplexing of constant bit rate (CBR) traffic in asynchronous transfer mode (ATM) networks. The control scheme is based on a bandwidth-dependent scheduling algorithm. The limitation of the CDV is proved.

A transparent MAC method for bandwidth sharing and CDV control at the ATM layer of passive optical networks

In the quest for a way to bring local loop costs down and make B-ISDN affordable to small traffic customers, the passive optical networks (PONs) in combination with ATM (APONs) have been investigated extensively. To achieve the required medium sharing on a time division multiplexing (TDMA) basis, an arbitration mechanism is required in the upstream direction. The resulting multiplexing and concentration, though it is the source of significant savings, it has been plagued by the penalty of high distortion of the traffic profiles at the exit of the PON. The preventive congestion control method of ATM is rather intolerant of such distortions in the multiplexing stages. Arbitration methods which are either semistatic or based on number of arrivals per reservation period, cause very high cell delay variation (CDV). The cell clustering introduced by the arbitration method cannot be distinguished from peak rate violations of the contract by the policing unit. The result is either unwarranted rejections of conforming cells or unacceptably low utilization. The scheme presented herewith maintains a CDV behavior comparable to that of a common centralized FIFO multiplexer. It relies on a meticulous recording of the arrival timing of cells enabling a subsequent allocation of slots which produces almost the same output (and CDV) as the centralized FLFO multiplexer. A compact coding of the timing information restricts bandwidth waste for control information to the size found in other similar protocols. The most important feature is that the scheme is amenable to easy hardware implementation and does not require any call related information.

Cell multiplexing in ATM networks

Formulates, analyzes, and compares several connection multiplexing algorithms for a multiplexer residing in the equivalent terminal of the asynchronous transfer mode (ATM) layer at the user premise. The primary goal is to find an algorithm that efficiently combats the cell delay variation (CDV) introduced by the multiplexer. Several performance criteria are examined, one of which is unique to ATM networks. This one is the proportion of arriving cells that do not conform to the traffic contract of the connection. The conformance is being tracked by a generic cell rate algorithm (GCRA) recommended (but not mandatory) by CCITT. Other criteria are the classical buffer requirements and the cell delay. Service fairness among connections is also evaluated with respect to each performance criterion. The impact of the following five multiplexing policies on the performance criteria are evaluated for constant bit rate (CBR) traffic sources. The policies are first in, first out (FIFO), round robin (RR), least time to reach bound (LTRB), most behind expected arrival (MBEA), and golden ratio (GR). Extensive numerical examples reveal that there is no single policy that is best across all criteria. With respect to cell conformance, most behind expected arrival (MBEA) emerges as the preferred one. FIFO is best with respect to cell delay, except for high utilizations where RR dominates. The LTRB is marginally better than all other policies with respect to buffer requirements.

Protocols to accommodate asynchronous transfer mode cells in satellite TDMA links

AbstractTo deyelop the broadband integrated services digital network (B‐ISDN) service on a national scale and to handle various media in a unified way economically from ‐ an early stage, it will be effective to construct a system combining the satellite link into the terrestrial communication network. the TDMA system is adequate as the transmission system in the satellite link in such a system which can contain efficiently users distributed over a country.When the satellite TDMA link, which is a synchronous system, and the terrestrial network, based on the asynchronous transfer mode (ATM), are to be connected, the deterioration of the ATM transmission quality such as the cell delay variation, is a serious problem. Then there must be a compensation method for the delay variation which can cope with the asynchronous transfer. In such a transformation between ATM and TDMA, it is required that the maximum delay variation should be kept below the specified value, the burstiness of the transferred cell sequence should not be increased, and the satellite link with limited network resources should efficiently be utilized.This paper assumes that the time‐stamp method, which is considered in the ground network, is applied to the satellite link as a method for the delay variation 38 compensation and summarizes the problems in the application. Then the cell‐numbering method is proposed and the performance is evaluated to solve the problems.

Traffic control at terminal equipment in ATM networks using cryptographic techniques

The usage parameter control (UPC) function, which monitors and controls user traffic to protect network resources from both malicious and unintentional misbehaviour, is an important task for ATM networks in performing congestion control procedures. The scheme performing the UPC function is usually called a ‘control scheme’ or ‘policing scheme’. No matter what scheme is employed, the cell delay variation (CDV) that comes before the scheme makes it difficult to police user traffic accurately as long as it is located at the edge node of the public network 1–10. In this paper, we propose an architecture where the network can perform the UPC function at a user's terminal equipment, in order to overcome the CDV problem. With this feature, the network can control user traffic more accurately. Applying cryptographic techniques, we also propose a signalling protocol to support this architecture.

The split‐switching network (SSN): A high‐performance multicast ATM switch

AbstractThis paper proposes a new high‐performance multicast ATM switch architecture. The switch, called the split‐switching network (SSN), is based on banyan networks. The SSN achieves multicasting in a way that is non‐typical for banyan‐based switches: copying and routeing of multicast cells are carried out simultaneously and within the same fabric. Thus, cells are copied only when needed as they traverse the switch towards the appropriate output ports. The SSN consists of successive spliting stages, and buffering is provided in front of each stage. The SSN is non‐blocking with complexity of order Nlog2/2N for a switch of size N, and is characterized by distributed and parallel control. The throughput‐delay performance of the SSN is shown to be similar to that of a non‐blocking output‐buffering switch under different mixtures of unicast/multicast traffic. In particular, the SSN achieves a maximum throughput of 100 per cent and the cell delay and delay variation remain small for loads just below the maximum throughput.

Methodology for derivation of network resources to support video-related services in ATM-based private wide-area networks

The statistical mode of operation of asynchronous-transfer-mode (ATM) networks can lead to congestion which, in turn, leads to a degradation in the quality of service (QOS) of calls. Normally, congestion manifests itself by overflow in the input or output controllers of switches. An outstanding research issue relating to ATM networks, therefore, is resource management; i.e. determining the optimum network resources, in terms of link bandwidth and buffer capacity in switches, that are required for a call which guarantees a defined QOS, even under high-network-loading conditions. The two most important QOS parameters associated with a cell are cell-loss rate and cell-delay variation. In practice, the parameters are interrelated and make conflicting demands on the available resources. Video services, for example, are sensitive to both parameters and hence it is necessary to consider the combined parameters when allocating resources for such services. The paper describes a new method for deriving the optimum resources required for video-related services in an ATM-based private network to guarantee specific QOS requirements.

Clock recovery and reconstruction of PAL pictures for MPEG coded streams transported over ATM networks

The problem of clock recovery for an MPEG audio/video decoder, when the MPEG stream is transmitted over an ATM network and the decoded signal is to be converted to a PAL/NTSC format, is addressed. The presence of ATM cell delay variation represents a jitter source for the reconstruction of the main presentation reference signals associated with the coded streams. Since the PAL/NTSC synchronization signals are obtained from these signals, care must be taken to avoid visible artifacts in the displayed images, typically hue changes. It is shown that the clock recovery design, based on consumer quality video display requirements, is not more complex than ordinary PLLs used in transmission systems, while the buffer size requirements can be certainly contained within acceptable limits.

A discrete time queueing model to study the cell delay variation in an ATM network

This paper studies two different physical situations that are important to dimension User Parameter Function mechanisms and the buffers needed at the ATM Adaptation Layer: 1. (i)the cell delay variations a Constant Bit Rate traffic is subject to when mixed with Variable Bit Rate traffic in an ATM network, 2. (ii)the cell loss rate when a Worst Case Traffic is multiplexed with Variable Bit Rate sources. The model we use is a queueing system in which the arrival process is a special class of discrete time batch Markovian arrival process (D-BMAP): the superposition of periodic and Variable Bit Rate traffic. An exact solution of this model in a realistic situation is not possible due to computing time and memory requirements. An approximate solution is obtained through spectral decomposition and using asymptotic analysis.

Analysis of cell clumping caused by ATM network GFC protocols

Two GFC (Generic Flow Control) protocols are currently under study within the CCITT, namely the BT/NTT proposal and the Australian proposal. In this paper, their basic operating principles are recalled. Then, since it has been recognized in earlier studies that cell delay variation, or more precisely cell clumping, has a major impact on peak cell rate control performed in the usage parameter control, a method for quantifying the magnitude of cell clumping in a cell stream is proposed. This method is subsequently applied for evaluating the magnitude of cell clumping introduced by the above GFC protocols. Although they provide for three priority levels, the analysis is carried out for one priority level only. Under the assumption that each traffic source transmits at its peak cell rate and that a cell spacing device is implemented in each terminal, simulation results show that both GFC mechanisms are similar in terms of cell clumping.

Effect of video synchronisation in an ATM multiplexer

Video services sharing an ATM network can be made either synchronous to each other at video frame level or asynchronous. Frame synchronised video results in larger cell loss than asynchronous video, especially for head-and-shoulders pictures. Use of 20-30 ATM cell size buffers with maximum delays of 55-82 mu s are sufficient enough to bridge the gap, without causing significant cell delay variations for both methods. >

Evaluation of UPC functions for peak cell rate enforcement

AbstractA number of Usage Parameter Control (UPC) functions are compared with respect to their ability to detect violation of the negotiated traffic contract. The traffic contract parameters in this study are the peak cell rate and the maximum cell delay variation (CDV). In order to take cell delay variation into account, tolerances must be introduced in the UPC functions. This simulation study investigates how this affects their ability to detect contract violation. None of the window mechanisms studied have been found capable of detecting all types of contract violation.

Orwell

Orwell is a high speed media access protocol which is used in the dual-ring Orwell Torus Local Area Network (LAN). It supports guaranteed bandwidth per service queue per terminal, with up to four types of service queue. These are assigned (in order of decreasing priority) to constant high bit-rate connections, i.e., greater than 1.5 Mbit/s; constant low bit-rate connections; variable bit-rate video; and data. Signalling and data are multiplexed into one queue, with signalling having the higher priority. A Torus LAN can extend to about 4 km with 125 terminals while meeting 500 microseconds maximum cell delay variation for constant high bit-rate connections. The diameter of the network can be further expanded through the use of both the Orwell Link Multiplexor to provide guaranteed bandwidth per service queue on point-to-point links, and a multi-ring Orwell Torus with up to 8 rings used as a backbone network for the interconnection of LANs. This paper describes the Orwell Ring access protocol, the Orwell Torus and Orwell Link Multiplexor. Some simulation results are also discussed which have led to conclusions on how traffic should be shaped in each terminal prior to transmission over the Orwell Torus.

Bursty ATM user traffic allowed by a jitter tolerant leaky bucket and its impact on link utilization

AbstractIn a network based on the asynchronous transfer mode (ATM), quality of service requirements have to be met even in the presence of users who send traffic as bursty as the policing device allows. For peak cell rate policing with a jitter tolerant leaky bucket, a periodic maximally bursty traffic pattern allowed by the leaky bucket is derived. The impact of this kind of bursty user traffic on the cell loss performance of the remaining sources is investigated by introducing, solving and applying the queueing model Geo(n) + P/D/1/K, where P stands for ‘periodic’. Taking bursty user traffic into account, it is shown that the maximal jitter or cell delay variation allocated to the user and tolerated by the leaky bucket is an important parameter for link utilization. The results help to answer the question under which conditions a shaping function is needed in conjunction with the usage parameter control function.

Cell delay variation smoothing methods for atm‐based sdh signal transport system

AbstractIf the synchronous digital hierarchy (SDH) signal is converted into asynchronous transfer mode (ATM) cells to be transmitted through the ATM transport network, the efficiency of the operation/management/maintenance of the network will be improved in addition to maintaining the economy and reliability of the network. This is one of the advantages of the ATM transport network.This paper considers the system where SDH signal is transported by ATM technique. The delay variation produced in the ATM transport network is evaluated. Then the buffer readout control and the required buffer capacity are discussed. The order of processing between the delay variation smoothing function and other required functions in the proposed system is analyzed.

Spacing cells protects and enhances utilization of ATM network links

It is shown that peak cell rate policing can be combined with fast reservation protocols for achieving statistical multiplexing in asynchronous transfer mode (ATM) networks. A cell spacer-controller architecture which smooths out cell clusters according to the original period both at the user network interface (UNI) and at network node interface (NNI) is proposed. A performance evaluation of the spacer-controller is presented. The evaluation involves modeling the spacer-controller, dimensioning a virtual scheduling algorithm, and the impact on cell delay variation (CDV). It is shown that large CDVs may induce severe degradation in the accuracy of usage parameter control/network parameter control mechanisms. >

Traffic control in asynchronous transfer mode

The definition of traffic descriptors is discussed, and cell delay variation (CDV) that complicates usage parameter control (UPC) is analyzed. A generic flow control protocol that facilitates UPC is described. It is based on the asynchronous transfer mode ring (ATMR) protocol. The ATMR-GFC protocol achieves the guarantee of bandwidth by a cyclic reset scheme. Bandwidth calculation methods for connection admission control are reviewed from the viewpoint of different time scales. Both a real-time and offline calculation method are discussed. A combined method taking advantage of both methods is proposed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>