ARGOS: A GPS Time-Synchronized Network Interface Card based on NetFPGA

Jaime J. Garnica, Victor Moreno, Iván González, Sergio Lopez-Buedo, Javier Aracil

jaime.garnica@uam.es, sergio.lopez-buedo@uam.es High Performance Computing and Networking Group

www.hpcn.es

Universidad Autónoma de Madrid

Abstract

ARGOS: a Network Interface Card featuring transparent time synchronization.

Sister card adds a serial port communication Conventional NIC to the OS. Timestamping features offered by newer Linux

kernels (Wireshark). OneLab2 European Internet testbed. Internet delay and available bandwidth obtained.

2

Table of contents

Introduction Timing solution OneLab2 testbed Experiments and results Conclusions, future work and references

3

Introduction Study of the behavior of communication network. Accurate packet timestamping. Current time protocols: NTP and IEEE 1588. A GPS connected to each board provides tens of

nanosecond accuracy.

4

Table of contents

Introduction

Timing solution• GPS modules• NetFPGA and GPS communication• Packet management and timestamping• Clock error correction

OneLab2 testbed Experiments and results Conclusions, future work and references

5

Timing solution

6

GPS modules• GPS is based on high-precision atomic clocks.• Specialized GPS modules on timing issues.• Widespread use of GPS has dramatically reduced the price of receivers.• GPS time receivers:

• UTC-synchronized.• Pulse Per Second (PPS) signal.• Less than nanosecond accuracy.

• Communication protocols:• NMEA as standard.• Proprietary protocols more completes.

7

NetFPGA and GPS communication• Sister card• Second board connected to NetFPGA through debug connector• Power supply from the PCI bus• Implements a serial port (RS232).

• Connects the NetFPGA and the GPS module.

• MAX3232 level-conversion chip and buffer to drive LVTTL signals through the ribbon cable.• An additional buffer on the adaptor to convert signals to the 2.5V required by the NetFPGA.

8

Packet management and timestampling• The transmission is done by UDP packet burst train sending.• Interpacket and interburst time parameters can be specified.• Received packets are time stamped and saved into a FIFO.• This FIFO is a DP memory, the host can read the packet.• Sent packets are time stamped just before the sending.• Packets contains the two times inside the UDP payload.

9

Clock error correction1. The FPGA clock presents a drift

of more than 6 ns per sec (30 ms per hour aprox.)

Next second error must be expected.

Tuning value: number of ns the count must be fasted/delayed.

tuning(t) = 1 s / expected(t) ns

2. Options:a) expected(t + 1) = error(t): does

not avoid the drift error.

b) expected(t + 1) = drift(t): clock instability persists.

3. expected(t) = drift(t) + error(t): accurate the clock in hundreds of ns. Clock instability peaks.

4. Instability peaks are corrected by adapting drift error every second.

Every second:

drift(t + 1) = drift(t) 1expected(t + 1) = drift(t + 1) + error(t)

10

1

4

3

2b2a

Table of contents

Introduction Timing solution

OneLab2 testbed• Etomic• OneLab2 nodes

Experiments and results Conclusions, future work and references

11

OneLab2 testbed

European open federated laboratory supporting network research for the future Internet.

The proposal was funded as an IST project under the EU FP7 funding program.

It runs and operate PlanetLab Europe [9], federated with PLC.

12

European Traffic Observatory Measurement Infrastructure

ETOMIC Open access, public testbed. Active measurement methods. Fully reconfigurable nodes.

• GPS-synchronized.• DAG cards to ARGOS cards.

More than 30 nodes GPS-sync.• Triangles show ARGOS nodes.

13

OneLab nodes

Advanced Network Measurement Equipment (ANME):• HP Proliant ML370 server.• ARGOS card as NIC.

Kernel typically runs on RedHat or Debian OS. Kernel recompilation to allow ARGOS

timestamping in spite of time-of-the-day.

14

Table of contents

Introduction Timing solution OneLab2 testbed

Experiments and results• LAN• Internet

Conclusions, future work and references

15

Experiments and results

OneLab2/ETOMIC environment Experiment over two UTC-synchronized nodes:

• Sender script: UDP packet burst train sending• Receiver script: timestamp extraction and comparison

16

LAN one way delayBoth nodes inside UAM local network

Minimum delay deviation , few atypical results

17

Internet one way delayExperiment between Spain and Hungary nodes through Internet

18

Table of contents

Introduction Timing solution OneLab2 testbed Experiments and results

Conclusions, future work and references

19

Conclusions (I)

ARGOS provides a highly accurate timestamping solution that enables big Internet measurement testbeds to work.

Project as OneLab2 provides users a testbed with the precision needed to run their experiments between nodes around Europe.

ARGOS is a low-cost solution for these projects. Timestamp is managed using standard

structures inside Linux Kernel.

20

Conclusions (II)

Sister card provides NetFPGA a GPS port, even a serial port to another devices.

Measurements are also useful for companies to know the QoS they are offering.

21

Future work

New version compatible with the existing NetFPGA developments, to be added to the collection of open source projects.

DMA support to allow a higher rate to the communication between the NetFPGA and the host.

22

ARGOS: A GPS Time-Synchronized Network Interface Card based on NetFPGA

Jaime J. Garnica, Victor Moreno, Iván González, Sergio Lopez-Buedo, Javier Aracil

jaime.garnica@uam.es, sergio.lopez-buedo@uam.es High Performance Computing and Networking Group

www.hpcn.es

Universidad Autónoma de Madrid