Delay performance of some scheduling strategies in an input queuing ATM switch with multiclass bursty traffic

Considers an N×N nonblocking, space division, input queuing ATM cell switch, and a class of Markovian models for cell arrivals on each of its inputs. The traffic at each input comprises geometrically distributed bursts of cells, each burst destined for a particular output. The inputs differ in the burstiness of the offered traffic, with burstiness being characterized in terms of the average burst length. We analyze burst delays where some inputs receive traffic with low burstiness and others receive traffic with higher burstiness. Three policies for head-of-the-line contention resolution are studied: two static priority policies [shorter-expected-burst-length-first (SEBF), longer-expected-burst-length-first (LEBF)] and random selection (RS). Direct queuing analysis is used to obtain approximations for asymptotic (as N→∞) high and low priority mean burst delays with the priority policies. Simulation is used for obtaining mean burst delays for finite N and for the random selection policy. As the traffic burstiness increases, the asymptotic analysis can serve as a good approximation only for large switch sizes. Qualitative performance comparisons based on the asymptotic analysis are, however, found to continue to hold for finite switch sizes. It is found that the SEBF policy yields the best delay performance over a wide range of loads, while RS lies in between. SEBF drastically reduces the delay of the less bursty traffic while only slightly increasing the delay of the more bursty traffic. LEBF causes severe degradation in the delay of less bursty traffic, while only marginally improving the delays of the more bursty traffic. RS can be an adequate compromise if there is no prior knowledge of input traffic burstiness

Delay Performance of Some Scheduling Strategies in an Input Queuing ATM Switch with Multiclass Bursty Traffic

We consider an N x N nonblocking, space division,input queuing asynchronous transfer mode (ATM) cell switch,and a class of Markovian models for cell arrivals on each of its inputs. The trafRc at each input comprises geometrically distributed bursts of cells, each burst destined for a particular output. The inputs differ in the bursthsesa of the offered traffic,with bumtiness being characterized in terms of the average burst length. We analyze burst delays in the situation in which some inputs receive traf6c with low burstiness and others receive traffic with higher burstiness. Three policies for head-of-the-line contention resolution are studied: two static priority policies [viz,, shorter-expected-burst-length-first (SEBF), longer-expected- burst-length-first (LEBF)] and random selection (RS). Direct queuing analysis is used to obtain approximations for asymptotic (as IV -+ cc) high and low priority mean burst delays with the priority policies. Simulation is used for obtaining mean burst delays for finite N and for the random selection policy. Numerical results show that as the traffic burstineas increases, the asymptotic analysis can serve as a good approximation ordy for large switch sizes. Qualitative performance comparisons based on the asymptotic analysis are, however, found to continue to hold for finite switch sizes. It is found that the SEBF policy yields the best delay performance over a tide range of loads, while RS lies in between. SEBF drastically reduces the delay of the less bursty traffic (e.g., distributed computing traffic) while only slightly increasing the delay of the more bursty traffic e.g., variable bit rate (VBR) video. LEBF causes severe degradation in the delay of less bursty traffic, while only marginally improving the delays of the more bursty traflic. RS can be an adequate compromise if there is no prior knowledge of input traffic burstiness

Design and analysis of a scalable terabit multicast packet switch : architecture and scheduling algorithms

Internet growth and success not only open a primary route of information exchange for millions of people around the world, but also create unprecedented demand for core network capacity. Existing switches/routers, due to the bottleneck from either switch architecture or arbitration complexity, can reach a capacity on the order of gigabits per second, but few of them are scalable to large capacity of terabits per second. In this dissertation, we propose three novel switch architectures with cooperated scheduling algorithms to design a terabit backbone switch/router which is able to deliver large capacity, multicasting, and high performance along with Quality of Service (QoS). Our switch designs benefit from unique features of modular switch architecture and distributed resource allocation scheme. Switch I is a unique and modular design characterized by input and output link sharing. Link sharing resolves output contention and eliminates speedup requirement for central switch fabric. Hence, the switch architecture is scalable to any large size. We propose a distributed round robin (RR) scheduling algorithm which provides fairness and has very low arbitration complexity. Switch I can achieve good performance under uniform traffic. However, Switch I does not perform well for non-uniform traffic. Switch II, as a modified switch design, employs link sharing as well as a token ring to pursue a solution to overcome the drawback of Switch 1. We propose a round robin prioritized link reservation (RR+POLR) algorithm which results in an improved performance especially under non-uniform traffic. However, RR+POLR algorithm is not flexible enough to adapt to the input traffic. In Switch II, the link reservation rate has a great impact on switch performance. Finally, Switch III is proposed as an enhanced switch design using link sharing and dual round robin rings. Packet forwarding is based on link reservation. We propose a queue occupancy based dynamic link reservation (QOBDLR) algorithm which can adapt to the input traffic to provide a fast and fair link resource allocation. QOBDLR algorithm is a distributed resource allocation scheme in the sense that dynamic link reservation is carried out according to local available information. Arbitration complexity is very low. Compared to the output queued (OQ) switch which is known to offer the best performance under any traffic pattern, Switch III not only achieves performance as good as the OQ switch, but also overcomes speedup problem which seriously limits the OQ switch to be a scalable switch design. Hence, Switch III would be a good choice for high performance, scalable, large-capacity core switches

Queue Distribution of Real Time Transportation of Voice over Ip

Electrical Engineerin