Meeting on ATLAS Remote Farms. Copenhagen 11 May 2004

1
Networking for ATLAS Remote Farms
Richard Hughes-Jones The University of Manchester

DataGrid WP7 Dante Tests on the GÉANT
Core End-2-End Measurements from the 4th Year
VLBI Project at Manchester New TCP stacks the
effect on throughput Some Simple Network Tests
CERN-Manchester
2
DataGrid WP7 Dante Tests on the GÉANT Core

• Set-up
• Supermicro PC in
• London GEANT PoP
• Amsterdam GEANT PoP
• Smartbits in
• London GEANT PoP
• Frankfurt GEANT PoP
• Long link UK-SE-DE2-IT-CH-FR-BE-NL
• Short Link UK-FR-BE-NL

3
Tests GÉANT Core UDP throughput

• UDP Throughput
• London-Amsterdam
• Available BW to packet on wire
• Then 1/t
• Wire rate 998 Mbit/s for packets gt 1400 bytes
• Packet Loss
• None for large packets
• Dips in BW lined to packet loss
• SysKonnect NIC int. per packet
• CPU load important

4
Tests GÉANT Core Packet re-ordering

• Effect of Packet size
• London-Amsterdam
• Packets at 10 µs line speed
• 10,000 sent
• Packet Loss 0.1
• Re-order Distribution

5
Tests GÉANT Core Packet re-ordering

• Effect of LBE background
• Amsterdam-London
• BE Test flow
• Packets at 10 µs line speed
• 10,000 sent
• Packet Loss 0.1
• Re-order Distributions

6
Tests GÉANT Core Packet Jitter

• Amsterdam-London
• BE Test flow
• Packet spacing 80 µs

• BE Test flow Background 60 BE 1.4Gbit 40
  LBE 780Mbit

• IPPremium Test flow

• IPPremium Test flow Background

7
Tests GÉANT Core 1-way Delay

• Amsterdam-London
• IPPremium Test flow
• Packet spacing 80 µs

• BE Test flow Background 60 BE 1.4Gbit 40
  LBE 780Mbit

• BE Test flow Background 60 BE 1.4Gbit 40
  LBE 780Mbit

8
VLBI Project Test Topology
SURFnet
Manchester
JIVE Dwingaloo
Jodrell
SuperJANET4
Adam Mathews Steve OToole Univ of Manchester
9
VLBI Project Throughput

• Manchester to Dwingeloo
• 2.0G Hz Xeon 1.2 GHz PIII
• Re-ordering vs Offered Load

10
VLBI Project Jitter 1-way Delay

• 1472 byte Packets man -gt JIVE
• FWHM 22 µs (B2B 3 µs )

11
VLBI Project Packet Loss Long Range Effects?

• Aggregated Variance Method
• Divide time series length N into blocks of size m
• Calc mean of each section Xm(k) k 1 N/m
• Calc variance VXm of these Xm(k)
• Vary m size of the blocks
• Plot on log-log fit slope ß
• Hurst parameter H ß 2H -2
• Measureß -0.355 which gives H 0.822
• H 1 no long range dependence

12
Traffic Flows

• Manchester NetNorthWest - SuperJANET Access
  links
• Two 1 Gbit/s

• Access linksSJ4 to GÉANT GÉANT to
  SurfNet

13
High Performance TCP DataTAG

• Different TCP stacks tested on the DataTAG
  Network
• 128 ms round trip time
• Drop 1 in 106
• High-Speed
• Rapid recovery
• Scalable
• Very fast recovery
• Standard
• Recovery would take 10 mins

14
High Performance TCP MB-NG

• Drop 1 in 25,000
• Rtt 6.2 ms
• Recover in 1.6 s

• Standard HighSpeed Scalable

15
Some Network Tests

• TCP Request Response

16
Lab Test TCP Request-Response Histograms

• PC router PC
• BE Test flow
• Request spacing 0 µs

• Request spacing 10 ms

17
Man-CERN TCP Request-Response Latency

• DataTAG PC backup link
• BE Tests
• Request spacing 0 µs
• Win size 2.5Mbytes
• Compare with UDP latency
• Large differences
• Rtt of 20 msdelaybw 2.5 Mbytes
• 1Mbyte data 690 pkts ? interesting bursts !

18
Man-CERN UDP Throughput Packet Loss

• DataTAG PC backup link
• BE Tests
• Throughput
• Packet loss

19
Traffic Flows

• Manchester NetNorthWest - SuperJANET Access
  links
• Link to PC in M/c

• Access links
• 1 GE Man to NNW
• Total Man to NNW
• NNW to SuperJANET4

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21
VLBI Project Packet Loss Is it Poisson?

• Divide time series of packets into 1000 slices of
  50 packets
• Total lost packets 1410
• Average number / slice 1.4
• Calc Poisson Probability P(n, µ) µ n e -µ
  n!
• Curves close but not exact
• Could be more than 1 process

22
Traffic QoS Classes on GÉANT Backbone
Max Throughput on 2.5 G PoS

• Normal Traffic
• Radio Astronomy Data
• Less Than Best Effort
• 2.0 Gbit/s

• Normal Traffic
• Less Than Best Effort
• 2.0 Gbit/s

• Normal Traffic
• Radio Astronomy Data
• 500 Mbit/s

• Normal Traffic

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Some Measurements made during ER2002