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2005 © SWITCH PERT – Beyond Fat Pipes Simon Leinen.

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Presentation on theme: "2005 © SWITCH PERT – Beyond Fat Pipes Simon Leinen."— Presentation transcript:

1 2005 © SWITCH PERT – Beyond Fat Pipes Simon Leinen

2 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

3 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

4 2005 © SWITCH 4 Example PERT Initiatives: GN2 PERT GN2 “PACE” (formerly known as “SA3”) PERT Oriented towards European projects—including Grids Large virtual team with participants from many NRENs Weekly “Case Manager” duty, rotating between organisations ttp:// (still being built)ttp:// ttp:// (Pilot Knowledge Base)ttp://

5 2005 © SWITCH 5 Example PERT Initiatives: 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 are the two I’m most familiar with…

6 2005 © SWITCH 6 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.

7 2005 © SWITCH 7 DEISAThroughputReduction Issue (2) DEISA Iperf test traffic Normal DFN-GEANT traffic

8 2005 © SWITCH 8 DEISAThroughputReduction Issue Possible Avenues Towards Resolution: Missing QoS configuration on DFN's router to GEANT Try TCP variants that fill the pipe more easily (e.g. BIC, FAST) More measurements (delay/loss/reordering when with bg. traffic?) Is this a practical problem at all?

9 2005 © SWITCH 9 Slow access to Example SWITCH PERT Issue Users at site X observe low download speeds from software distribution site (30-70 kbps)

10 2005 © SWITCH 10 Download Issue (2) First tests from a test host close to X result in good rates (30-40 Mbps) → probably an issue within site X, right? $ wget Resolving, Connecting to[]:80... connected. HTTP request sent, awaiting response... 200 OK Length: 24,265,736 [application/octet-stream] 100%[====================================>] 24,265,736 4.49M/s ETA 00:00 13:44:22 (3.54 MB/s) - `dotnetfx.exe' saved [24265736/24265736]

11 2005 © SWITCH 11 Download Issue (3) However, subsequent tests reproduce rates similar to what the customer observed. $ wget Resolving Connecting to[]:80... connected. HTTP request sent, awaiting response... 200 OK Length: 24,265,736 [application/x-msdownload] 12% [===> ] 2,968,483 7.37K/s ETA 51:32 Further investigation shows that mapping of to actual hosts is highly variable, and the performance of the servers mapped to is even more variable.

12 2005 © SWITCH 12 Download Issue (4) 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.

13 2005 © SWITCH 13 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”

14 2005 © SWITCH 14 How Grid Community Can Benefit Today PERT Knowledgebase (ttp:// Lots of performance-related information In the process of being built 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 New: PERT Consultancy Service Ask PERT for help with future applications/tests (proactive)

15 2005 © SWITCH 15 How the Grid Community can Help PERT Follow the project and provide constructive criticism Volunteer as GN2 PERT Subject Matter Expert (SME) Make the concept known within your communities Bring interesting cases before the PERT

16 2005 © SWITCH 16

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