Usage Parameter Control Function Research Articles

Design of a multiple leaky buckets shaper

Asynchronous Transfer Mode (ATM) has been considered as the future trend for the information transfer in Broadband Integrated Services Digital Network (B-ISDN). ATM networks provide a guaranteed Quality of Service (QoS) for a variety of applications. One of the important QoS attributes is Cell Delay Variation (CDV). CDV measures how much delay variation will appear in cell transmission times. Call Admission Control (CAC) and Usage Parameter Control (UPC) are two main functions for achieving traffic control in ATM networks. The UPC scheme monitors and controls traffic in order to determine whether the established connections conform to the predefined parameters or not. For a real source operating at predefined parameters, some delay variation will occur in cell transmission times. CDV Tolerance (CDVT) controls the amount of acceptable deviation. Two classes of UPC methods have been proposed in the past to deal with CDV: one is to design an UPC method considering the worst traffic at User-Network Interface (UNI); the other is using a shaper for each connection of each link to accommodate CDV. In this paper, we propose a new shaper architecture to implement the UPC function that will eliminate CDV introduced between Terminal Equipment (TE) and the edge node of public networks. Our new shaper can follow multiple Generic Cell Rate Algorithm (GCRA) rules and consider all the traffic parameters. Furthermore, we use a simple method to reduce the memory requirement in the shaper. Insufficient memory might lead to incorrect cell departure in previous shapers. Simulation results show the performance is quite good and as expected.

Experimental validation of an ATM traffic control framework in the EXPLOIT testbed

AbstractThis paper deals with the experimental investigation of a preventive traffic control framework for ATM networks as implemented in the EXPLOIT Testbed. This framework comprises a Usage Parameter Control (UPC) function and a Connection Admission Control (CAC) function. The obtained measurement results are complemented and compared with simulation studies and analytical results. For several On/Off traffic types it is shown that the implemented UPC function enforces both the Peak Cell Rate (PCR) and the Sustainable Cell Rate (SCR) simultaneously. By measuring the cell loss ratio as a function of the number of multiplexed sources, admission boundaries for a given network performance objective can be found and compared with the implemented CAC function based on the convolution algorithm. It appears that network performance objectives can be guaranteed, while exploiting most of the possible multiplexing gain in a network with small buffers like the EXPLOIT Testbed. Finally, it is shown that the two co‐operating functions constitute a traffic control framework which is robust against traffic contract violations as well as worst case traffic utilising the contracted UPC function tolerances maximally at both the cell level and the burst level.

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.

Usage parameter control employing a tagging method

In asynchronous transfer mode (ATM) networks, each user requests a call setup with the traffic descriptor which describes its own traffic characteristics. Since network resource control is carried out by this traffic descriptor, it would be necessary that the traffic generation is monitored by the network, which is the so-called usage parameter control (UPC). In this paper, three methods are evaluated analytically for implementing the UPC function: a discarding method, a tagging method, and a hybrid method. The last method is proposed anew in the paper and the comparative results for the three methods are offered from a viewpoint of performance of the cell multiplexer when the output traffic from UPC is superposed.

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.

Modeling and performance comparison of policing mechanisms for ATM networks

Asynchronous transfer mode (ATM) networks, as proposed by CCITT as the solution for the future broadband ISDN, will provide high flexibility with respect to the varying bandwidth requirements of the different services. They will also support variable bit rates within a connection. The packetized information transfer, without flow control between the user and the network, in combination with the asynchronous multiplexing principle, results in a need to control the individual cell stream during the entire duration of the calls to ensure an acceptable quality of service for all coexisting calls sharing the same network resources. This kind of control will be provided by introducing a policing or usage parameter control function. Basic design objectives and requirements for such a function are described. These requirements serve as a basis for the comparison of some of the mechanisms proposed so far, namely the leaky bucket, the jumping window, the triggered jumping window, the moving window, and the exponentially weighted moving average mechanisms. >