Showing papers by "Norvald Stol published in 2002"

An optical packet switch design with shared electronic buffering and low bit rate add/drop inputs

Abstract: An optical packet switch design using optical switching and shared electronic buffering is described and analyzed. The electronic buffering and add/drop unit allows random memory access, variable packet length, and aggregation/segregation of low bit rate streams. The design is scalable to a large number of wavelengths, and employs contention resolution by using the wavelength dimension combined with electronic buffering. The number of buffer inputs, i.e. the number of optoelectronic conversions, is minimized. The packet loss and delay performance when using fixed packet length and electronic buffering are investigated by simulation. If the link utilization is moderate, the buffering requirements becomes minimal. If number of wavelengths in the link is increased, the number of buffer inputs can be reduced. With a sufficiently high number of wavelengths, the buffer requirements is minimal, even when the link utilization is high.

Quality of service in optical packet switched DWDM transport networks

Abstract: For support of multimedia applications in Internet, at least four service classes are normally outlined. We expect optical packet switching to be of special interest in terabit capacity networks with a high number of wavelengths. Our analysis shows that when the wavelength dimension is used for contention resolution, and number of wavelengths is 32 or higher, node-delay is negligible. However buffering in optical packet switches is a scarce resource which use should be minimized. Based on the requirement of the future network, and on our packet switch performance analysis, we suggest reducing the number of service classes to two: A normal class (NCT) with medium low packet loss and a low need for buffering, and a high class (HCT) with a minimum of packet loss. Performance of a buffer reservation scheme is analyzed by simulation. Assuming the network of today with 10 % HCT traffic, assigning four buffer inputs to the HCT traffic, a difference in optical packet loss ratio of three orders of magnitude can be obtained. The same difference in optical packet loss ratio can be obtained if 50 % HCT traffic is assumed (network of tomorrow), by assigning a higher number of buffer inputs.

QoS provisioning using traffic shaping and policing in 3rd-generation wireless networks

Abstract: According to the recently presented QoS architecture by 3GPP, a traffic conditioner may be deployed to provide conformance of the negotiated QoS in UMTS The traffic conditioning is performed by traffic shaping or/and policing A framework of traffic conditioning with QoS provisioning in the 3G radio access network is proposed in this paper The main idea of our traffic conditioning approach is to employ traffic shaping at each user equipment (UE) and traffic policing at the RNC The traffic generated at each UE is regulated by a traffic shaper in the form of a token bucket, and the conformance of the traffic is policed at the RNC according to traffic policing policies A system model based on the proposed framework is implemented The simulation results regarding the impact of traffic shaping on packet discarding probability, the tradeoff between probability of non-compliance and shaping delay are also presented in this paper

A study on traffic shaping, policing and conformance deterioration for QoS contracted networks

Abstract: Based on the framework of shaping the traffic at the source node and policing or reshaping the traffic at further node(s), the objective of this paper is to better understand conformance consistency in QoS contracted networks. It has been pointed out in Guerin et al. (2001) that an originally conformant packet may become non-conformant at the egress in the presence of variable packet length, even though the packet is transmitted at a constant bitrate. We refer to this phenomenon by using a terminology conformance deterioration in this paper, and further analyze the probability of conformance deterioration relating to link speed and token rate. We demonstrate that the conformance deterioration could reach up to 11% in the worst case. In order to eliminate conformance deterioration, two measures, enlarging bucket size or reshaping at the policing node, are investigated by simulation. Conformance deterioration for aggregated traffic flows is also studied and compared with the results from an individual traffic flow. Both analytical and simulation results are presented in this paper.