There have been may debates about the feasibility of providing guaranteed quality of service (QoS) when network traffic travels beyond the enterprise domain and into the vast unknown of the Internet. Many mechanisms have been proposed to bring QoS to TCP/IP and the Internet (RSVP, DiffServ, 802.1p). However, until these techniques and the equipment to support them become ubiquitous, most enterprises will rely on local prioritization of the traffic to obtain the best performance for mission-critical and time-sensitive applications. This paper explores prioritizing critical TCP/IP traffic using a multi-queue buffer management strategy that becomes biased against random low-priority flows and remains biased while congestion exists in the network. This biasing implies a degree of unfairness but proves to be more advantageous to the overall throughput of the network than strategies that attempt to be fair. Only two classes of service are considered, where TCP connections are assigned to these classes and mapped to two underlying queues with round-robin scheduling and shared memory. In addition to improving the throughput, cell losses are minimized for the class of service (queue) with the higher priority.

A code division multiple access (CDMA) wireless network is simulated to analyze errors, determine impact on services and provide an upper bound on the number of active channels. The simulation emphasizes the encoder, decoder/correlator, and a threshold detector; but assumes a resultant Gaussian function for the "air interface" noise. Since the characteristics of a wireless environment vary significantly, we examine, as a whole, the errors on the received signal without accounting for specific error contributions from power, fading, propagation, interference from other users, and other factors in such an environment. The CDMA encoder uses the 64 Walsh codes that are specified in the draft Wideband CDMA Air Interface Compatibility Standard for 1.85 to 1.99 GHz PCS Applications. We use a digitized actual speech database to test for the intelligibility of the voice service over such a CDMA air interface. Therefore, we are able to learn about the nature of the errors inherent in such a frequency spreading technique and also determine an upper bound on the simultaneous active channels that would preserve the quality of service (QOS).

The performance of the FDDI token ring and IEEE 802.6 DQDB protocols are compared using discrete event simulation models. A metropolitan area network (MAN) of 100 km and with 50 stations was modeled. A 100 Mbps channel is used for both networks with a traffic model with large (1 kbyte) low priority packets and smaller (100 byte) high priority packets. The delay and fairness characteristics of both networks are analyzed. The simulations show that FDDI has advantages in fairness and maximum capacity, while DQDB offers lower delay at all except very heavy loads and has a stronger priority mechanism.>

The author concentrate on the provision of isochronous services to users via the existing IEEE 802.6 framework using Q.931 as the signalling protocol for providing call control functions. They present possible scenarios of isochronous service provisioning via the IEEE 802.6 network. Real time performance for call setup procedures is simulated and analyzed with different priority schemes for transferring signalling messages. The results show that using a prioritized queue arbitrated (QA) bandwidth to send signalling messages greatly reduces call setup delay. Call setup delays are determined using both Poisson-type and bursty type data traffic models. The positioning of the bandwidth manager, the virtual channel identifier (VCI) server and the Q.931 signalling termination is shown to influence call setup performance.>

Two candidate protocols for the generic flow control of the broadband integrated services digital network (B-ISDN) are currently being considered by the Accredited Standards Committee T1 (ASC T1). One proposal advocates the use of a distributed queue dual bus (DQDB)-like mechanism with a three level priority scheme. The other proposal is based on a slotted ring with control terminal equipment (C-TE), assigning periodic credit authorizations to the transmitting stations. This paper analyzes the performance behavior of the two protocols according to traffic scenarios and boundary conditions defined by the International Telephone and Telegraph Consultative Committee (CCITT) and T1.>