203169
An evaluation of parallel optimization for OpenSolaris® network stack
Computing is now shifting towards multiprocessing. The fundamental goal of multiprocessing is improved performance through the introduction of additional hardware threads or cores (referred to as “cores” for simplicity). Modern network stacks can exploit parallel cores to allow either message-based parallelism or connection-based parallelism as a means to enhance performance. OpenSolaris has redesigned and parallelized to better utilize additional cores. Three special technologies, named Softring Set, Soft ring and Squeue are introduced in OpenSolaris for stack parallelization. In this paper, we study the OpenSolaris packet receiving process and its core parallelism optimization techniques. Experiment results show that these techniques allow OpenSolaris to achieve better network I/O performance in multiprocessing environments; however, network stack parallelization has also brought extra overheads for system. An effective and efficient network I/O optimization in multiprocessing environments is required to cross all levers of the network stack from network interface to application.
109829156
Metropolitan area network support at Fermilab
Advances in wide area network service offerings, coupled with comparable developments in local area network technology have enabled many research sites to keep their offsite network bandwidth ahead of demand. For most sites, the more difficult and costly aspect of increasing wide area network capacity is the local loop, which connects the facility LAN to the wide area service provider(s). Fermilab, in coordination with neighboring Argonne National Laboratory, has chosen to provide its own local loop access through leasing of dark fiber to nearby network exchange points, and procuring dense wave division multiplexing (DWDM) equipment to provide data channels across those fibers. Installing and managing such optical network infrastructure has broadened the Laboratory's network support responsibilities to include operating network equipment that is located off-site, and is technically much different than classic LAN network equipment. Effectively, the Laboratory has assumed the role of a local service provider. This paper will cover Fermilab's experiences with deploying and supporting a Metropolitan Area Network (MAN) infrastructure to satisfy its offsite networking needs. The benefits and drawbacks of providing and supporting such a service will be discussed.
10630563
Lambda Station: On-Demand Flow Based Routing for Data Intensive Grid Applications Over Multitopology Networks
Lambda Station is an ongoing project of Fermi National Accelerator Laboratory and the California Institute of Technology. The goal of this project is to design, develop and deploy network services for path selection, admission control and flow based forwarding of traffic among data- intensive Grid applications such as are used in High Energy Physics and other communities. Lambda Station deals with the last-mile problem in local area networks, connecting production clusters through a rich array of wide area networks. Selective forwarding of traffic is controlled dynamically at the demand of applications. This paper introduces the motivation of this project, design principles and current status. Integration of Lambda Station client API with the essential Grid middleware such as the dCache/SRM Storage Resource Manager is also described. Finally, the results of applying Lambda Station services to development and production clusters at Fermilab and Caltech over, advanced networks such as DOE's UltraScience Net and NSF's UltraLight is covered.
6103735
Sorting Reordered Packets with Interrupt Coalescing
TCP performs poorly in networks with serious packet reordering. Processing reordered packets in the TCP-layer is costly and inefficient, involving interaction of the sender and receiver. Motivated by the interrupt coalescing mechanism that delivers packets upward for protocol processing in blocks, we propose a new strategy, Sorting Reordered Packets with Interrupt Coalescing (SRPIC), to reduce packet reordering in the receiver. SRPIC works in the network device driver; it makes use of the interrupt coalescing mechanism to sort the reordered packets belonging to the same TCP stream in a block of packets before delivering them upward; each sorted block is internally ordered. Experiments have proven the effectiveness of SRPIC against forward path reordering.
10168770
End-to-end network/application performance troubleshooting methodology
The computing models for HEP experiments are globally distributed and grid-based. Obstacles to good network performance arise from many causes and can be a major impediment to the success of the computing models for HEP experiments. Factors that affect overall network/application performance exist on the hosts themselves (application software, operating system, hardware), in the local area networks that support the end systems, and within the wide area networks. Since the computer and network systems are globally distributed, it can be very difficult to locate and identify the factors that are hurting application performance. In this paper, we present an end-to-end network/application performance troubleshooting methodology developed and in use at Fermilab. The core of our approach is to narrow down the problem scope with a divide and conquer strategy. The overall complex problem is split into two distinct sub-problems: host diagnosis and tuning, and network path analysis. After satisfactorily evaluating, and if necessary resolving, each sub-problem, we conduct end-to-end performance analysis and diagnosis. The paper will discuss tools we use as part of the methodology. The long term objective of the effort is to enable site administrators and end users to conduct much of the troubleshooting themselves, before (or instead of) more » calling upon network and operating system 'wizards,' who are always in short supply. « less
55533633
Building global HEP systems on Kerberos
As an underpinning of AFS and Windows 2000, and as a formally proven security protocol [1] in its own right, Kerberos is ubiquitous among HEP sites. Fermilab and users from other sites have taken advantage of this and built a diversity of distributed applications over Kerberos v5. We present several projects in which this security infrastructure has been leveraged to meet the requirements of geographically dispersed collaborations. These range from straightforward ''Kerberization'' of applications such as database and batch services, to quick tricks like simulating a user-authenticated web service with AFS and the ''file'': schema, to more complex systems. Examples of the latter include experiment control room operations and the Central Analysis Farm (CAF). We present several use cases and their security models, and examine how they attempt to address some of the outstanding problems of secure distributed computing: delegation of the least necessary privilege; establishment of trust between a user and a remote processing facility; credentials for long-queued or long-running processes, and automated processes running without any user's presence; security of remotely-stored credentials; and ability to scale to the numbers of sites, machines and users expected in the collaborations of the coming decade.
120207464
Electron-Nuclear Potential Fields from Hyperfine Structure