DOE/MICS Mid-Year Project Report†† Date: February 6, 2002

Project Title:Internet End-to-end Performance Monitoring (IEPM)

Project Type: Base

PI: R. Les Cottrell, PhD††††††††††††††††††††††† Institution: Stanford Linear Accelerator (SLAC)

1.                Executive Summary

In the last half year the IEPM-PingER project has evolved to create the IEPM-BW project to add bandwidth network and application bandwidth monitoring. The popular PingER measurements continue to be supported, and are expanding in coverage, and are vital to the worldwide collaborations of HENP and other disciplines.

Progress with collecting high throughput measurements with IEPM-BW has been excellent, and we are now reliably making continuously available measurements on network and application throughput from SLAC to about 32 remote hosts in 8 countries. Ambitious plans are underway to use the data for prediction and application steering, and research and to tie this in more closely with various Grid and HENP activities.

2.                Current Accomplishments

PingER

The graphs produced by PingER have been improved to make them faster.We have added metrics: duplicate packets, out of order packets, jitter, minimum RTT, and conditional loss probability. We have defined ~ 45 affinity groups, cover 73 countries and have 37 monitoring sites (including all PPDG sites). FNAL have totally revamped the FNAL PingER ping data archive to improve robustness, ensure more reliable collection of data, speed the graphing up and add new facilities.Data has been shared between the SLAC and FNAL archive sites to provide the maximum coverage. We have added an extra 5 monitoring sites (SDSC, LANL, Rice, Milan, Trieste). Operational issues include tracking and working with the contacts formonitoring hosts that are having problems providing data, identifying ping rate limiting or blocking and working with the contacts at the remote sites to get alternative hosts.

We provided PingER ping data to the Network Weather Service (NWS) and Daresbury Lab and worked with them to provide NWS predictions.

Throughput measurements

To understand the factors that affect high network and application throughput for disciplines such as the Grid or High Energy and Nuclear Physics (HENP), we undertook to make measurements of throughput between SLAC and various collaborators with high speed links. This is reported on at http://www-iepm.slac.stanford.edu/monitoring/bulk/index.html for TCP and http://www-iepm.slac.stanford.edu/monitoring/bulk/bbcp.html for file copy/transfer.

QBSS

We worked with Stanislav Shalunov of Internet 2 to understand the QBone Scavenger Service (QBSS) and then built testbeds (with a 10 Mbit/s and a 100Mbit/s bottleneck) to evaluate the utility and performance. This is reported on in http://www-iepm.slac.stanford.edu/monitoring/qbss/measure.html. We found that it is very effective in using the available bandwidth, that it enables the scavenger service to back of quickly (<~ 1 sec) in the face of congestion from higher priority services (e.g. best effort), and that it can reduce the impact on delays for other competing applications with higher priorities. We have written an article on QoS experiences for CENIC which is planned to be published in the next couple of months.

BBCP

The bbcp secure file copy tool that supports large windows and multiple streams has been enhanced to support network measurements. The following features have been added: memory to memory copies as well as disk to disk; periodic reporting of incremental and cumulative throughputs; self-rate-limiting; setting DiffServ Control Point (DSCP) values for QoS testing. A paper entitled Peer-to-Peer Computing for Secure High Performance Data Copying was published at CHEP01 on bbcp by Andy Hanushevsky, Artem Trunov & Les Cottrell.

Passive measurements

We installed and configured the Cisco Netflow to make passive measurements on flows at the SLAC border. We gathered the Netflow records and for large flows (> 10Mbits/s) we validated that passive Netflow throughputs give reasonably good agreement with iperf TCP network throughput measurements. This is documented at http://www.slac.stanford.edu/comp/net/netflow/thru.html

 

SC2001

For SC2001, we proposed and had accepted a demonstration entitled Bandwidth to the World (see http://www-iepm.slac.stanford.edu/monitoring/bulk/sc2001/ ). Briefly the deomstration emulated an HENP tier 0 accelerator site distribution large volumes of data to about 25 collaborator sites. This required getting logon accounts at the remote sites, building tools to run on 3 PCs at SC2001 to send the data, record the throughput, analyse and present the results via the web. We also had to understand and measure the optimum configuration values to use (windows and streams, cpu speeds and OSí etc.), see http://www-iepm.slac.stanford.edu/monitoring/bulk/window-vs-streams.html. We achieved a sustained 1.6Mbits/s over a 2Gbit/s link to 17 sites in 5 countries. Since we were able to congest the link we were also able to demonstrate QBone Scavenger Service (QBSS) working at 2 Gbit/s rates. For the SLAC/FNAL booth itself we put together demonstrations of the IEPM measurement project including RTT to the work (PingER) and higher throughput measurements (IEPM-BW), animated bar charts on top of a world map which now are part of the Atlas of Cyberspace (see http://www.cybergeography.org/atlas/geographic.html).

Bandwidth Measurement Project (IEPM-BW)

Following on from the SC2001 project we extended and ruggedized the infrastructure put in place for the SC2001 bandwidth challenge. We have built a simple database to track the configurations (OS, directory paths, options needed to execute measurement tools, which commands work, contact people and to allow anonymization of the host for reporting purposes) for each host being monitored. In addition to this we have developed a simple problem tracking mechanism. At the end of the current period we have about 28 sites in 8 countries, and are making regular measurements with ping, traceroute, bbcp (both memory to memory and disk to disk), bbftp and pipechar.   We are starting to analyze the data from these measurements. Early results from the IEPM-BW project indicate:
  • Reasonable estimates of throughput can be obtained with 10 second measurements. This is typically much shorter than pipechar measurements.
  • In many cases it is not sufficient to simply increase the window size to achieve high throughput, multiple parallel streams are also critical.
  • Careful attention to window sizes and parallel streams in necessary.
  • Improvements of between 5 and 60 times have been observed for the optimum window and stream settings compared to using a single stream and the default maximum window size.
  • It is also observed that there is an optimum window*number parallel streams beyond which performance does not increase, or may decrease, while, packet loss increases.
  • Throughput can vary by an order of magnitude with time of day or day of week etc.
  • Roughly speaking one needs 1 MHz to provide 1 Mbit/sec on today's CPUs and OSs
  • The bbcp file copy rates from memory to memory are about 60+-20% of the rates.
  • File copy rates disk to disk are typically about 90% of the memory to memory rates, for rates below 60Mbits/s, but can vary depending on disk performance, caching etc. Uncached disk performance typically tops out at between 4 and 8MBytes/sec.
  • In some cases (e.g. SLAC to CERN for Objectivity data compression can improve throughput by over a factor of 2 on a reasonably high performance host (e.g. Sun 336MHz cpus).
  • When running high throughput applications, the RTT for other users can be noticeably increased, e.g. for SLAC to CERN the average increases from about 160 The impact of high throughput applications, on other applications requiring low latency, may be reduced by applying lower than best effort priority (Scavenger Service) to the high throughput applications' packets.
We have created a web site organized to provide easy access to all aspects of this project, see http://www-iepm.slac.stanford.edu/bw/.

Presentations in last 6 month period

3.                Future Accomplishments (next 6 months)

We are in the process of improving the analysis and reporting/graphing/table tools in particular in the areas of robustness, manageabilityand portability. We are also building tools to facilitate and automate the infrastructure management. This includes downloading of code, checking whether measurements are successful, gathering the remote configurations parameters (OS, cpu speed, code versions), understanding disk performance, verifying windows and streams are set correctly. We will measure the impacts of compression, add and understand gridFTP and bandwidth measurement tools such as pathrate, and compare and contrast the various measurements. We will integrate the Netflow measurements with the IEPM-BW measurements and also integrate the PingER analysis and graphical and tabular presentation tools with the IEPM-BW measurements. We also hope to tie together the measurements being made in the UK with the SLAC measurements so they appear more integrated to the user. We will make the IEPM-BW data available to interested, friendly developers and researchers for example for validating data and algorithm applicability, and forecasting. We will document the format of the data, and assist the developers and researchers in the analysis. We will use the IEPM-BW and Netflow measurements to make simple forecasts of the performance, and look at how to tie these into an application such as bbcp. As this work evolves we will collaborate with the NWS project to do more sophisticated forecasting.Following this we will select a representative minimum subset of tools to make measurements with, improve the reporting/graphing/table tools and make the data available via the web. We also hope to deploy a 2nd measurement host in the next 6 months.

4.                Research interactions

We are working with researchers at:

                    LBNL (Guojun Jin) to validate, understand and improve pipechar.

                    U Delaware (Constantinos Dovrolis) to understand, improve and validate pathrate. When it is ready we will plug it into the IEPM-BW infrastructure to make detailed comparisons and determine its area of applicability. When pathload is ready we will work with davrolis on it.

                    CAIDA (Margaret Murray & kc claffy), we will share IEPM-BW data with them to enable further research on the validity of various bandwidth measurement tools

                    We are working with researchers at Rice to evaluate the INCITE multifractal path measurements tools to integrate them into IEPM-BW to gather more extensive measurements for research.

                    UCSB, Rich Wolski, to provide him with data from IEPM-BW and collaborate on the research and development needed to use the measurements for forecasting.

5.                Remarks

As can be seen from the lists of research interactions above, and also from the number of collaborating sites (~30), it is apparent that there is a great deal of interest in this project, since it quickly promises to have network AND application throughput data on a persistent time frame, with measurements made close to the application, and results made available publicly. This is of interest to planners, researchers, Grid applications developers and users, people with high throughput requirements such as the High Energy and Nuclear Physics (HENP) community. Besides participating at SC2001 and in the SC2001 Bandwidth Challenge, we are looking to collaborate with CERN and NIKHEF at the iGrid2002 in Amsterdam in September 2002. The IEPM project is also a formal collaborator with the Particle Physics data Grid (PPDG) and is located at the site of BaBar a major HENP physics experiment, which greatly assists in getting ideas of what features are important to the users, and providing input to the users on what to expect.

The outstanding success of the PingER ping measurement project (over 2000 web hits per day) in providing long term (over 7 years), continuous, publicly available measurements, analysis, also gives credibility to the success of the follow on IEPM-BW project.