Guannan Qu

Contention-tolerant crossbar packet switches

We propose an innovative agile crossbar switch architecture called contention-tolerant crossbar, denoted by CTC(N). Unlike the conventional crossbar and the crossbar with crosspoint buffers, which require complex hardware resolvers to grant one out of multiple output requests, CTC(N) can tolerate output contentions by a pipelining mechanism, with pipeline stages implemented as buffers in input ports. These buffers are used to decouple the scheduling task into N independent parts in such a way that N schedulers are located in N input ports, and they operate independently and in parallel. Without using arbiters and/or crosspoint buffers that require additional chip area, the CTC(N) switch is more scalable than existing crossbars. We analyze the throughput of CTC(N) switch, and find 63% throughput bottleneck. For achieving 100%, we consider two approaches: using internal speedup and using space multiplexing without internal speedup. We prove that 100% throughput can be achieved with internal speedup 2 or using two layers of CTC(N) fabric mathematically. Our simulation results validate our theoretical analysis. Copyright

Switch-Centric Data Center Network Structures Based on Hypergraphs and Combinatorial Block Designs

Fat trees are considered suitable structures for data center interconnection networking. Such structures are rigid, and hard to scale up and scale out. A good data center network structure should have high scalability, efficient switch utilization, and high reliability. In this paper we present a class of data center network structures based on hypergraph theory and combinatorial block design theory. We show that our data center network structures are more flexible and scalable than fat trees. Using switches of the same size, our data center network structures can connect more nodes than fat trees, and it is possible to construct different structures with tradeoffs among inter-cluster communication capacity, reliability, the number of switches used, and the number of connected nodes.

Designing fully distributed scheduling algorithms for contention-tolerant crossbar switches

We recently proposed an innovative agile crossbar switch architecture called contention-tolerant crossbar (CTC(N)) switch, which can tolerate output contentions by a pipelining mechanism, with pipeline stages implemented as buffers in the input ports. These buffers are used to decouple the scheduling task into N independent parts in such a way that N schedulers are located in the N input ports, and they operate independently and in parallel without using any arbiter. In this paper, we present a simple fully distributed scheduling algorithm scheme and show its effectiveness by simulations.

Contention-Tolerant Crossbar Packet Switches without and with Speedup

We propose an innovative agile crossbar switch architecture called contention-tolerant crossbar, denoted by CTC(N). Unlike the conventional crossbar and the crossbar with crosspoint buffers, which require complex hardware resolvers to grant one out of multiple output requests, CTC(N) can tolerate output contentions by a pipelining mechanism, with pipeline stages implemented as buffers in input ports. These buffers are used to decouple the scheduling task into N independent parts in such a way that

Queueing Analysis of Multi-Layer Contention-Tolerant Crossbar Switch

N

A high-performance switch architecture based on mesh of trees

schedulers are located in N input ports, and they operate independently and in parallel. Without using arbiters and/or crosspoint buffers that require additional chip area, the CTC(N) switch is more scalable than existing crossbars. We analyze the throughput of CTC(N) switch without and with internal speedup by building a queuing model. We show that, under Bernoulli i.i.d. uniform traffic, CTC(N) without internal speedup has worst-case throughput of 63%, and CTC(N) achieves 100% throughput with internal speedup 2. Our simulation results validate our theoretical analysis.

Performance of CTC(N) Switch under Various Traffic Models

We recently proposed Contention-Tolerant Crossbar (CTC(N)) and multi-layer CTC(N) (MCTC(N)) switch architectures. By developing queueing network model of CTC(N) for tagged output, we proved that MCTC(N) achieves steady state with the layer number k ≥ 2 under Bernoulli i.i.d. uniform traffic. In this letter, we extend the queueing network model for evaluating the mean cell number in each input queue and mean waiting time of MCTC(N) working in steady state under the Bernoulli i.i.d. uniform traffic. This model is validated by simulation results.

ETBAC-Based Model in Media Oriented System Transport Network

SUMMARY With emergence of various new Internet-enabled devices, such as tablet PCs or smart phones along with their own applications, the traffic growth rate is getting faster and faster these days and demands more communication bandwidth at even faster rate than before. To accommodate this ever-increasing network traffic, even faster Internet routers are required. To respond for these needs, we propose a new mesh of trees based switch architecture, called MOTS(N) switch. In addition, we also propose two more variations of MOTS(N) to further improve it. MOTS(N) is inspired by crossbar with crosspoint buffers. It forms a binary tree for each output line, where each gridpoint buffer ‡ is a leaf node and each internal node is 2-in 1-out merge buffer § emulating FIFO queues. Because of this FIFO characteristic of internal buffers, MOTS(N) ensures QoS like FIFO output-queued switch. The root node of the tree for each output line is the only component connected to the output port where each cell is transmitted to output port without any contention. To limit the number of buffers in MOTS(N) switch, we present one of its improved (practical) variations, IMOTS(N) switch, as well. For IMOTS(N) switch architecture, sizes of the buffers in the fabric are limited by a certain amount. As a downside of IMOTS(N), however, every cell should go through log 2N + 1 number of buffers in the fabric to be transmitted to the designated output line. Therefore, for even further improvement, IMOTS(N) with cut-through, denoted as IMOTS-CT(N), is also proposed in this paper. In IMOTS-CT(N) switch, the cells can cut through one or more empty buffers to be transferred from inputs to outputs with simple 1 or 2 bit signal exchanges between buffers. We analyze the throughput of MOTS(N), IMOTS(N), and IMOTS-CT(N) switches and show that they can achieve 100% throughput under Bernoulli independent and identically distributed uniform traffic. Our quantitative simulation results validate the theoretical analysis. Copyright

A new class of data center network structures

In previous papers, we introduced and analyzed an innovative agile crossbar switch architecture called contention-tolerant crossbar, denoted as CTC(N), only under Bernoulli i.i.d. uniform traffic model. The CTC(N) switch achieves about 63% throughput without any internal speedup and 100% throughput with either speedup of 2 or 2 CTC(N) fabrics operating in parallel. In this paper we evaluate the throughput and mean cell delay of CTC(N) switch under four different traffic models. By simulation, quantitative results are presented, evaluated and compared to traditional crossbar switches.

DiaCTC ( N ): An Improved Contention-Tolerant Crossbar Switch

With the development of network communicationtechnology, combination between network and automotiveelectronics industry has more and more extensively. The mainpoints on performance evaluation for this kind of multi-functionnetwork are bandwidth, resource utilization, security andreliability. Through the analysis of automotive electronicsnetwork topology and characteristic information transmissionpattern, we found that it will encounter many problems withtraditional network combination. One of them is the multi-nodesproblem. When multi nodes start at the same time, the networkwill cause congestion in the start-up period during the operationprocess. It will lead to the stagnation of network and reduce thesystem stability and security and reliability. In this paper, inorder to solve above problem, we propose a node-basedresolution strategy ETBAC (Embedding Task-based AccessControl) Model. This is an access control policy modeling byusing the top priority method HLF (Highest-level-First) toschedule the nodes in the media-oriented system network. Weuse CANoe 2640N to establish our network environment, andour implementation experiences connect it with other nodes, and through its real-time monitoring to record the network boottime. Experiments in our test demonstrate that this strategy canavoid network congestion problems effectively and accelerateset-up time during network booting.