R. E. Hughes-Jones

Evaluation of Advanced TCP Stacks on Fast Long-Distance Production Networks

With the growing needs of data intensive science, such as high energy physics, and the need to share data between multiple remote computer and data centers worldwide, the necessity for high network performance to replicate large volumes (TBytes) of data between remote sites in Europe, Japan and the U.S. is imperative. Currently, most production bulk-data replication on the network utilizes multiple parallel standard (Reno based) TCP streams. Optimizing the window sizes and number of parallel stream is time consuming, complex, and varies (in some cases hour by hour) depending on network configurations and loads. We therefore evaluated new advanced TCP stacks that do not require multiple parallel streams while giving good performances on high speed long-distance network paths. In this paper, we report measurements made on real production networks with various TCP implementations on paths with different Round Trip Times (RTT) using both optimal and sub-optimal window sizes.We compared the New Reno TCP with the following stacks: HS-TCP, Fast TCP, S-TCP, HSTCP-LP, H-TCP and Bic-TCP. The analysis will compare and report on the stacks in terms of achievable throughput, impact on RTT, intra- and inter-protocol fairness, stability, as well as the impact of reverse traffic.We also report on some tentative results from tests made on unloaded 10 Gbps paths during SuperComputing 2003.

Photoproduction of ϱ0 and ω on hydrogen at photon energies of 20 to 70 GeV

Abstract We present results on photoproduction of ϱ 0 and ω in the reactions γ p→ π + π − p and γ p→ π + π − π 0 p by tagged photons in the energy ranges 20 to 70 GeV and 20 to 45 GeV, respectively. The production of the ϱ 0 shows dominantly the characteristics of a diffractive process with respect to the E γ and t dependence of the cross section and the spin density matrix. The ϱ 0 photoproduction yields on average over the photon energy range a total cross section of σ ( γ p→ ϱ 0 p) = 9.4±0.1 μ b with an additional systematic error of ±1 μ b, and average slope parameters of the t distribution d σ /d t ≈exp(− b | t | + ct 2 ), of b =9.1±0.1 GeV −2 and c = 3.1 ±±0.2 GeV −4 . The shape of the ϱ 0 peak in the π + π − invariant spectra shows a skewing similar to that observed at lower energies. The photoproduction of ω is also consistent with a diffractive process and has a cross section of σ ( γ p→ ω p) = 1.2± 0.1 μ b with an additional systematic error of ±0.2 μ b. The average slope parameters of the t distribution are b =8.3 ± 1.3 GeV −2 and c = 3.4±2.6 GeV −4 .

The reaction γp → pπ+π−π+π− for photon energies from 25 to 70 GeV

Abstract Measurements of the reaction γ p → p π + π − π + π − are presented, in which π + π − π + π − systems with masses up to 3 GeV are produced from fragmentation of the incident photon. The reaction is dominated by production of the large peak of the ϱ′(1600) meson and, at higher masses ≳2 GeV, y production of jet-like 4 π systems. The ϱ′(1600) meson is produced by a predominantly s -channel helicity conserving mechanism. At higher masses there are also indications of ϱπ peaks, of masses 1.3 GeV (the A 2 meson) and 1.75 GeV, produced with a recoiling π meson by a mechanism consistent with the Deck effect.

Characterization and Evaluation of TCP and UDP-based Transport on Real Networks

StandardTcp (RenoTcp) does not perform well on fast long distance networks, due to its AMD congestion control algorithm. In this paper we consider the effectiveness of various alternatives, in particular with respect to their applicability to a production environment. We then characterize and evaluate the achievable throughput, stability and intra-protocol fairness of differentTcp stacks (Scalable,Hstcp,Htcp, FastTcp, Reno,Bictcp, hstcp-lp andLtcp) and aUdp based application level transport protocol (Udtv2) on both production and testbed networks. The characterization is made with respect to both the transient traffic (entry and exit of different streams) and the steady state traffic on production Academic and Research networks, using paths withRtts differing by a factor of 10. We also report on measurements made with 10 Gbit/secNics with and withoutTcp Offload Engines, on 10 Gbit/s dedicated paths set up forSc2004.RésuméTcp standard (RenoTcp) n’est pas très efficace dans les réseaux à haut débit longue distance en raison de son algorithme de contrôle de congestionAimd. Dans cet article, nous analysons l’efficacité de diverses alternatives, en particulier en fonction de leur possibilité d’application dans un environnement de production. Nous caractérisons et évaluons, dans des réseaux réels et des réseaux de test, le débit que l’on peut atteindre, la stabilité et l’équité intra-protocole de différentes pilesTcp (Scalable,Hstp, htcp, FastTcp, Reno,Bictcp,Hstcp-lp etLtcp) et d’un protocole de transport basé sur udp (udtv2). Cette analyse est menée entenant compte à la fois du trafic transitoire (entrée et sortie de divers flux) et du trafic en régime permanent des réseaux de production académique, avec des chemins dont lesRtt diffèrent d’un facteur 10. Nous présentons aussi des mesures faites avec des cartes d’interfaces à 10 Gbit/s, avec et sans déport deTcp sur la carte, sur des liaisons à 10 Gbit/s mises en place pour SC2004.

Photoproduction of charmed D mesons at γ energies of 40–70 GeV

Inclusive D0 photoproduction is observed in Kπ+π− and K+π−π0. Evidence is presented for an associated (CD) production mechanism. Cross section estimates and limits are given for D and D mesons.

Performance of 1 and 10 Gigabit Ethernet cards with server quality motherboards

System administrators often assume that just by plugging in a Gigabit Ethernet Interface, the system will deliver line rate performance; sadly this is not often the case. The behaviour of various 1 and 10 Gigabit Ethernet Network Interface cards (NICs) has been investigated using server quality motherboards. The latency, throughput, and the activity on the PCI buses and Gigabit Ethernet links were chosen as performance indicators. The tests were performed using two PCs connected back-to-back and sending UDP/IP frames from one to the other. This paper shows the importance of having a good combination of memory and peripheral bus chipset, Ethernet Interface, CPU power, good driver, and operating system designs and proper configuration to achieve and sustain gigabit transfer rates. With these considerations taken into account, and suitably designed hardware, transfers can operate at gigabit and multi-gigabit speeds. Some recommendations are given for high performance data servers.

e+-e− pair creation by 40–150 GeV photons incident near the 〈110〈 axis in a germanium crystal

Experimental results are presented on the pair production from high-energy photons (40–150 GeV) incident on a 0.5 mm Ge single crystal around the 〈110〉 axis. The observed enhancement increases from around 1 at threshold (40 GeV) to 7 at 1 50 GeV for photons aligned with the axis. Also the angilar dependence and the differential e+/e− spectra have been studied. For photons aligned with the axis, the results are in good agreement with calculations based on the constant field approximation.

Observation of the ϱ′(1600) in the channel γp→π+π−p☆

Abstract A dipion enhancement of mass 1.59 GeV and width 0.23 GeV is observed in the channel γp→π + π − p. The spin-parity of the enhancement is consistent with being 1 − .

Enabling network measurement portability through a hierarchy of characteristics

Measurement and prediction of network resources are crucial so that adaptive applications can make use of grid environments. Although a large number of systems and tools have been developed to provide such measurement services, the diversity of grid resources and lack of central control prevent the development of a single monitoring system that can be deployed to answer every applications resource queries for connections between any pair of machines it can use. We propose a standard for representing network entities and measurements of their properties. Our standard enables the exchange of measurements and will allow applications to function even in environments without the particular measurement system for which they were developed. We present an overview of our measurement representation and evaluate its usefulness. We have used the characteristics hierarchy to store and exchange measurement data between several systems, and we discuss its usefulness in comparing the output of several measurement tools.

Radiation from planar channeled 5–55 solGeVc positrons and elctrons

Abstract The emission of radiation from 5 to 55 GeV c planar channeled positrons and electrons passing through a 135 μ thick silicon-crystal has been investigated. The intensity of the channeling-radiation is found to be 10 to 30 times the intensity of normal bremsstrahlung. For channeled electrons no structure is found in the spectrum, whereas strong and sharp peaks are found for positrons. This peak structure is extremely sharp at GeV c and for momenta above 20 GeV c the structure disappears. For a classical description of channeling, but using an anharmonic potential, certain energies are found for which the maximum energy of the channeling radiation is practically independent of transverse energy. The possibility of making a monoenergetic γ-source in the energy range of 10–100 MeV is mentioned.