Design of traffic shaper / scheduler for packet switches and DiffServ networks : algorithms and architectures

The convergence of communications, information, commerce and computing are creating a significant demand and opportunity for multimedia and multi-class communication services. In such environments, controlling the network behavior and guaranteeing the user\u27s quality of service is required. A flexible hierarchical sorting architecture which can function either as a traffic shaper or a scheduler according to the requirement of the traffic load is presented to meet the requirement. The core structure can be implemented as a hierarchical traffic shaper which can support a large number of connections with a wide variety of rates and burstiness without the loss of the granularity in cells\u27 conforming departure time. The hierarchical traffic shaper can implement the exact sorting scheme with a substantial reduced memory size by using two stages of timing queues, and with substantial reduction in complexity, without introducing any sorting inaccuracy. By setting a suitable threshold to the length of the departure queue and using a lookahead algorithm, the core structure can be converted to a hierarchical rateadaptive scheduler. Based on the traffic load, it can work as an exact sorting traffic shaper or a Generic Cell Rate Algorithm (GCRA) scheduler. Such a rate-adaptive scheduler can reduce the Cell Transfer Delay and the Maximum Memory Occupancy greatly while keeping the fairness in the bandwidth assignment which is the inherent characteristic of GCRA. By introducing a best-effort queue to accommodate besteffort traffic, the hierarchical sorting architecture can be changed to a near workconserving scheduler. It assigns remaining bandwidth to the best-effort traffic so that it improves the utilization, of the outlink while it guarantees the quality of service requirements of those services which require quality of service guarantees. The inherent flexibility of the hierarchical sorting architecture combined with intelligent algorithms determines its multiple functions. Its implementation not only can manage buffer and bandwidth resources effectively, but also does not require no more than off-the-shelf hardware technology. The correlation of the extra shaping delay and the rate of the connections is revealed, and an improved fair traffic shaping algorithm, Departure Event Driven plus Completing Service Time Resorting algorithm, is presented. The proposed algorithm introduces a resorting process into Departure Event Driven Traffic Shaping Algorithm to resolve the contention of multiple cells which are all eligible for transmission in the traffic shaper. By using the resorting process based on each connection\u27s rate, better fairness and flexibility in the bandwidth assignment for connections with wide range of rates can be given. A Dual Level Leaky Bucket Traffic Shaper(DLLBTS) architecture is proposed to be implemented at the edge nodes of Differentiated Services Networks in order to facilitate the quality of service management process. The proposed architecture can guarantee not only the class-based Service Level Agreement, but also the fair resource sharing among flows belonging to the same class. A simplified DLLBTS architecture is also given, which can achieve the goals of DLLBTS while maintain a very low implementation complexity so that it can be implemented with the current VLSI technology. In summary, the shaping and scheduling algorithms in the high speed packet switches and DiffServ networks are studied, and the intelligent implementation schemes are proposed for them

Machine Learning-Powered Management Architectures for Edge Services in 5G Networks

L'abstract è presente nell'allegato / the abstract is in the attachmen

A survey on the chronological evolution of timestamp schedulers in packet switching networks

The interest in solving the issue of congestion or flow control in network established from the first discovery and increase popularity of the Internet in 1967 or earlier. As the use of the network deployed and the popularity increase, the issue grows and the demand for an optimal or tentative solution becomes obvious. Since that time there has been an intensive effort from the scholars and researchers to solve the congestion control problem. The problem get worse by the engagement of novel traffic with different characteristics for application called realtime applications such as video and voice applications. Another cause of this demand is the user himself. The attempt in solving the congestion problem in network layer was popular in 90’s.This article will demonstrate chronologically how the attempts toward timestamp based scheduling in the packet-switch network have been evolved.Furthermore, the benefit and the drawbacks of using a mechanism will be presented. Also, a brief explanation of the mathematical, conceptual or implementation issue of a mechanism is given. The key success of the scheduler in the market will be highlighted. This paper will stimulate the research thinking to identify the importance and the ability of scheduling in routers to enhance quality of service (QoS) for real time application over other solution in several layers. In addition it will assist the researcher to distinguish the key failure of other proposed mechanisms which have not been implemented in real routers

Design Issues of Reserved Delivery Subnetworks, Doctoral Dissertation, May 2006

The lack of per-flow bandwidth reservation in today\u27s Internet limits the quality of service that an information service provider can provide. This dissertation introduces the reserved delivery subnetwork (RDS), a mechanism that provides consistent quality of service by implementing aggregate bandwidth reservation. A number of design and deployment issues of RDSs are studied. First, the configuration problem of a single-server RDS is formulated as a minimum concave cost network flow problem, which properly reflects the economy of bandwidth aggregation, but is also an NP-hard problem. To make the RDS configuration problem tractable, an efficient approximation heuristic, largest demands first (LDF), is presented and studied. In addition, performance improvements with local search heuristic is investigated. A traditional negative cycle reduction and a new negative bicycle reduction algorithms are applied and evaluated. The study of RDS configuration problems is then extended to multi-server RDSs. The configuration problem can be similarly formulated as the single-server RDS configuration problem; however, the major challenge of multi-server RDS configuration is the optimal server locations. A number of server placement algorithms are evaluated using simulations. The simulation results show that a class of greedy algorithms provide the best solutions. In addition to configuration problem, the dynamic load redistribution mechanism is studied to improve the tolerance to server failures. A configuration algorithm to build redistribution subnetworks is proposed and evaluated to deal with single server failures in a group of servers. Besides the exclusive bandwidth access, there are potentials to further improve end-to-end performance in an RDS because end hosts can utilize the knowledge about the underlying networks to achieve better performance than in the ordinary Internet. These improvements are illustrated with a source traffic regulation technique to resolve the unbalanced bandwidth utilization problem in an RDS. A per-connection and an aggregated regulation algorithm for single-server and multi-server RDSs are presented and studied