Cross-layer enhancement of Web servers dedicated to small devices

De nos jours, les systèmes embarqués sont de plus en plus nombreux et ont un besoin grandissant d'accessibilité. Au lieu d'utiliser des protocoles dédiés, imposant l'utilisation de logiciels clients et serveurs, nous soutenons que l'utilisation de serveurs Web sur ces cibles en augmente l'accessibilité ainsi que la maintenabilité et facilite le développement. Ainsi, tout le monde peut accéder et configurer un routeur, un capteur de terrain ou un système domotique depuis n'importe quel ordinateur ou PDA, via un simple navigateur Web. En utilisant les technologies modernes du Web telles qu'AJAX, des applications interactives peuvent être servies. Cependant, cette solution est techniquement difficile à mettre en oeuvre à cause des limitations matérielles des systèmes embarqués ciblés (souvent un CPU à quelques MHz et seulement quelques kilo-octets de RAM), comparées à la lourdeur des serveurs Web classiques (et des protocoles du Web). Dans ce rapport, nous présentons tout d'abord une analyse transversale des protocoles TCP/IP lorsqu'utilisés pour servir des applications Web dynamiques. Nous testons des serveurs Web embarqués existants et analysons leurs performances. A partir de cette analyse, nous proposons de nouvelles solutions pour concevoir des serveurs Web efficaces et peu consommateurs de mémoire. Nous avons implémenté toutes nos propositions, engendrant un nouveau serveur Web embarqué, capable de servir efficacement des applications Web dynamiques avec une consommation en RAM de moins d'un kilo-octet, sans aucun système sous-jacent

Efficient layering for high speed communication: the MPI over Fast Messages (FM) experience

We describe our experience of designing, implementing, and evaluating two generations of high performance communication libraries, Fast Messages (FM) for Myrinet. In FM 1, we designed a simple interface and provided guarantees of reliable and in-order delivery, and flow control. While this was a significant improvement over previous systems, it was not enough. Layering MPI atop FM 1 showed that only about 35 % of the FM 1 bandwidth could be delivered to higher level communication APIs. Our second generation communication layer, FM 2, addresses the identified problems, providing gather-scatter, interlayer scheduling, receiver flow control, as well as some convenient API features which simplify programming. FM 2 can deliver 55–95 % to higher level APIs such as MPI. This is especially impressive as the absolute bandwidths delivered have increased over fourfold to 90 MB/s. We describe general issues encountered in matching two communication layers, and our solutions as embodied in FM 2

Full TCP/IP for 8-Bit architectures

We describe two small and portable TCP/IP implementations fulfilling the subset of RFC1122 requirements needed for full host-to-host interoperability. Our TCP/IP implementations do not sacrifice any of TCP's mechanisms such as urgent data or congestion control. They support IP fragment reassembly and the number of multiple simultaneous connections is limited only by the available RAM. Despite being small and simple, our implementations do not require their peers to have complex, full-size stacks, but can communicate with peers running a similarly light-weight stack. The code size is on the order of 10 kilobytes and RAM usage can be configured to be as low as a few hundred bytes

Hyperscsi : Design and development of a new protocol for storage networking

Ph.DDOCTOR OF PHILOSOPH

Effects of Communication Protocol Stack Offload on Parallel Performance in Clusters

The primary research objective of this dissertation is to demonstrate that the effects of communication protocol stack offload (CPSO) on application execution time can be attributed to the following two complementary sources. First, the application-specific computation may be executed concurrently with the asynchronous communication performed by the communication protocol stack offload engine. Second, the protocol stack processing can be accelerated or decelerated by the offload engine. These two types of performance effects can be quantified with the use of the degree of overlapping Do and degree of acceleration Daccs. The composite communication speedup metrics S_comm(Do, Daccs) can be used in order to quantify the combined effects of the protocol stack offload. This dissertation thesis is validated empirically. The degree of overlapping Do, the degree of acceleration Daccs, and the communication speedup Scomm characteristic of the system configurations under test are derived in the course of experiments performed for the system configurations of interest. It is shown that the proposed metrics adequately describe the effects of the protocol stack offload on the application execution time. Additionally, a set of analytical models of the networking subsystem of a PC-based cluster node is developed. As a result of the modeling, the metrics Do, Daccs, and Scomm are obtained. The models are evaluated as to their complexity and precision by comparing the modeling results with the measured values of Do, Daccs, and Scomm. The primary contributions of this dissertation research are as follows. First, the metric Daccs and Scomm are introduced in order to complement the Do metric in its use for evaluation of the effects of optimizations in the networking subsystem on parallel performance in clusters. The metrics are shown to adequately describe CPSO performance effects. Second, a method for assessing performance effects of CPSO scenarios on application performance is developed and presented. Third, a set of analytical models of cluster node networking subsystems with CPSO capability is developed and characterised as to their complexity and precision of the prediction of the Do and Daccs metrics