2005 © SWITCH PERT – Beyond Fat Pipes Simon Leinen

2005 © SWITCH 2 Contents End-to-end performance initiatives and PERT history Example PERT activities: GN2-PACE and SWITCH Lessons learned so far How Grid developers and users can benefit from PERT

2005 © SWITCH 3 End-to-End Performance Initiatives Motivation Observation: Backbone improvements not reflected at end users Frustrations with differentiated-QoS mechanisms Ideas for improvement Education (close the “wizard gap”) Measurement infrastructures – In the network, e.g. GN2-JRA1 – In the hosts, e.g. Web100 Human support infrastructure → PERT

2005 © SWITCH 4 Example PERT Initiatives GN2 “PACE” (formerly known as “SA3”) PERT Oriented towards European projects—including Grids Large virtual team with participants from many NRENs SWITCH PERT Includes support for performance of the “commodity” Internet Small team from our NOC/network engineering group Other NRENs are building PERT groups as well but these two I’m most familiar with…

2005 © SWITCH 5 DEISAThroughputReduction Example GN2 PERT Issue Iperf (single-stream TCP) measurements between the German and French DEISA sites usually achieve 900 Mb/s. DEISA traffic uses Premium IP inside the GEANT backbone. In parallel, there are 2-3 Gb/s throughput tests between Karlsruhe and CERN, using LBE (Less Than Best Effort) inside GEANT. Although there shouldn’t be an impact, DEISA measurements drop to 400 Mb/s during the Karlsruhe/CERN tests.

2005 © SWITCH 6 Slow access to download.microsoft.com Example SWITCH PERT Issue Users at site X observe low download speeds from software distribution site (30-70 kbps) First tests from a test host close to X result in good rates (30-40 Mbps) → probably an issue within site X, right? However, subsequent tests reproduce rates similar to what the customer observed. Further investigation shows that mapping of download.microsoft.com to actual hosts is highly variable, and the performance of the servers mapped to is even more variable. Because SWITCH doesn’t entertain business relationships with Microsoft of its content distributors, suggested that our customer complain to Microsoft (of which they are also a customer). Although technically a PERT failure, customer seems happy.

2005 © SWITCH 7 Lessons Learned So Far It’s hard to establish contacts with the customer It’s easy to “lose” the customer Performance expectations are often unclear Very hard to close an issue – Lack of criteria for problem resolution Should think in terms of bottlenecks rather than “problem locations”

2005 © SWITCH 8 How Grid Developers & Users Can Benefit PERT Knowledgebase ( Lots of performance-related information In the process of being built (try to) Use & contribute! Contact the PERT in case of performance problems If it happens when using GEANT/GN2 After other avenues have been explored (campus system and networking support) Through your NREN or (for groups such as DEISA) directly

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