One-way Delay Measurement Vladimir Smotlacha TF-NGN, October 2002.

Slides:

Advertisements

Similar presentations

A Trajectory-Preserving Synchronization Method for Collaborative Visualization Lewis W.F. Li* Frederick W.B. Li** Rynson W.H. Lau** City University of.

Advertisements

XFEL 2D Pixel Clock and Control System Train Builder Meeting, DESY 22 October 2009 Martin Postranecky, Matt Warren, Matthew Wing.

Tuning and Evaluating TCP End-to-End Performance in LFN Networks P. Cimbál* Measurement was supported by Sven Ubik**

Time Synchronization - using Reference-Broadcast Synchronization

Vladimír Smotlacha, CESNET Accurate Time Transfer over Optical Network 6 th CEF Networks Workshop Prague 13 September 2010.

Kenji SHIMIZU NTT Network Innovation Labs. This work was partially supported by the National Institute of Information and Communications Technology. 1.

pathChirp Efficient Available Bandwidth Estimation

Timo-Pekka Heikkinen TKK Networking laboratory Supervisor: Prof. Raimo Kantola Instructor: Lic. Tech. Marko Luoma “Measuring the performance of an active.

Pathload A measurement tool for end-to-end available bandwidth Manish Jain, Univ-Delaware Constantinos Dovrolis, Univ-Delaware Sigcomm 02.

HIERARCHY REFERENCING TIME SYNCHRONIZATION PROTOCOL Prepared by : Sunny Kr. Lohani, Roll – 16 Sem – 7, Dept. of Comp. Sc. & Engg.

Comp Spring 2003 Delay Jitter Ketan Mayer-Patel.

OWAMP March 10 th 2011, OSG All Hands Meeting, Network Performance Jason Zurawski – Internet2.

Iperf Tutorial Jon Dugan Summer JointTechs 2010, Columbus, OH.

Time and Clock Primary standard = rotation of earth De facto primary standard = atomic clock (1 atomic second = 9,192,631,770 orbital transitions of Cesium.

NTP Time for iThingies A Network Time Protocol app. for iPhone and iPad Presented to TTSO8 on by Chris Douglass 1.

Dale E. Gary Professor, Physics, Center for Solar-Terrestrial Research New Jersey Institute of Technology 1 3/15/2012OVSA Preliminary Design Review Meeting.

Dale E. Gary Professor, Physics, Center for Solar-Terrestrial Research New Jersey Institute of Technology 1 11/7/2011OVSA Technical Design Meeting.

Distributed Systems Fall 2010 Time and synchronization.

Time Synchronization (RBS, Elson et al.) Presenter: Peter Sibley.

Mapping a Network by Latency (and other things) Client connecting to , UDP port.

Available bandwidth measurement as simple as running wget D. Antoniades, M. Athanatos, A. Papadogiannakis, P. Markatos Institute of Computer Science (ICS),

I.1 ii.2 iii.3 iv.4 1+1=. i.1 ii.2 iii.3 iv.4 1+1=

PAM A Measurement Study of Internet Delay Asymmetry Abhinav PathakPurdue University Himabindu PuchaPurdue University Ying ZhangUniversity of Michigan.

1 End-to-End Detection of Shared Bottlenecks Sridhar Machiraju and Weidong Cui Sahara Winter Retreat 2003.

On Efficient On-line Grouping of Flows with Shared Bottlenecks at Loaded Servers by O. Younis and S. Fahmy Department of Computer Sciences, Purdue University.

CS335 Principles of Multimedia Systems Multimedia Over IP Networks -- II Hao Jiang Computer Science Department Boston College Nov. 8, 2007.

I.1 ii.2 iii.3 iv.4 1+1=. i.1 ii.2 iii.3 iv.4 1+1=

Low-Rate TCP Denial of Service Defense Johnny Tsao Petros Efstathopoulos Tutor: Guang Yang UCLA 2003.

Nus.soc.cs5248 Ooi Wei Tsang 1 Intermedia Synchronization Ooi Wei Tsang.

Robert Horn, Agfa Corporation

1 Physical Clocks need for time in distributed systems physical clocks and their problems synchronizing physical clocks u coordinated universal time (UTC)

Jennifer Rexford Fall 2014 (TTh 3:00-4:20 in CS 105) COS 561: Advanced Computer Networks Locations.

Enhanced NTP IETF – TicToc BOF Greg Dowd – Jeremy Bennington –

A Security Analysis of the Network Time Protocol (NTP) Presentation by Tianen Liu.

FlockLab: A Testbed for Distributed, Synchronized Tracing and Proﬁling of Wireless Embedded Systems IPSN 2013 NSLab study group 2013/04/08 Presented by:

Active Measurement tool for the EuQoS project René Serral-Gracià (Universitat Politècnica de Catalunya)

Time of arrival(TOA) Prepared By Sushmita Pal Roll No Dept.-CSE,4 th year.

High Performance Computing & Communication Research Laboratory 12/11/1997 [1] Hyok Kim Performance Analysis of TCP/IP Data.

© 2002, Cisco Systems, Inc. All rights reserved..

GPS based time synchronization of PC hardware Antti Gröhn

1 Clock Synchronization for Wireless Sensor Networks: A Survey Bharath Sundararaman, Ugo Buy, and Ajay D. Kshemkalyani Department of Computer Science University.

OWAMP August 10 th 2010, OSG Site Admin Workshop - Network Performance Jason Zurawski, Internet2.

NTP Network Time Protocol What is NTP and to what extent is it currently useful for Video Occultation Observations? By Dave Gault Presented to 8 th Trans-Tasman.

Vladimír Smotlacha CESNET High-speed Programmable Monitoring Adapter.

10-Jun-2005 OWAMP (One-Way Active Measurement Protocol) Jeff Boote Network Performance Workshop.

Network Time Protocol Objectives Contents to learn how to setup ntp

One-way DelayMeasurement and Accuracy of the Network Time Synchronization Vladimir Smotlacha TF-NGN, April 2002.

Time This powerpoint presentation has been adapted from: 1) sApr20.ppt.

Time Synchronization Protocols in Wireless Sensor Networks.

Physical clock synchronization Question 1. Why is physical clock synchronization important? Question 2. With the price of atomic clocks or GPS coming down,

Network Time Protocol Objectives Contents to learn how to setup ntp

ITIS 3110 IT INFRASTRUCTURE II Tony Kombol. NTP "Does Anybody Really Know What Time It Is?"*  Time keeping is one of most fundamental aspects of computer.

Computer Network Design EEL 6785 Dr. Janusz Zalewski University of Central Florida.

Precision Measurements with the EVERGROW Traffic Observatory Péter Hága István Csabai.

Instrument Control System Seminar, 20 th -24 th October 2014 Time Synchronisation via Ethernet An introduction to IEEE 1588 Andreas Jost.

Time Synchronization in Ad Hoc Networks Kay R¨omer MobiHOC 2001 Speaker : hsiwei.

Distributed Systems Lecture 5 Time and synchronization 1.

Connect communicate collaborate Performance Metrics & Basic Tools Robert Stoy, DFN EGI TF, Madrid September 2013.

Chapter 5 Peer-to-Peer Protocols and Data Link Layer Timing Recovery.

Vladimír Smotlacha, CESNET Alexander Kuna, IPE Time and Frequency Transfer in All-optical Network TNC 2011 Prague 17 May 2011.

ITIS 3110 IT INFRASTRUCTURE II Tony Kombol. NTP "Does Anybody Really Know What Time It Is?"*  Time keeping is one of most fundamental aspects of computer.

iperf a gnu tool for IP networks

Packet Leashes: Defense Against Wormhole Attacks

OWAMP (One-Way Active Measurement Protocol)

Infrastructure II NTP.

Presentation by Wyatt Zacharias

A tool for locating QoS failures on an Internet path

Exercises for Chapter 11: TIME AND GLOBAL STATES

Physical clock synchronization

Logical time (Lamport)

Presentation transcript:

One-way Delay Measurement Vladimir Smotlacha TF-NGN, October 2002

One-way delay sender and receiver evaluate timestamps of packet OWD = Ts - Tr –Tr packet receiving timestamp –Ts packet sending timestamp problem: time in both sites of measurement has to be synchronized

Box Specification Pentium III (450MHz and 860MHz) Linux kernel with nanokernel patch NTP package (4.1.71) Rude/Crude 0.50 PPS connected to serial port

Box Configuration two workstation: traffic generator and receiver RUDE sends UDP stream, CRUDE captures it NTP configuration –setup I and II: server maxpoll 6 –setup IIa:server PPS processing (to evaluate exact OWD)

What was measured Ts - timestamp of packet sending (from CRUDE log) Tr - timestamp of packet receiving (from CRUDE log) Os - offset of sender clock (reported by NTP) Or - offset of receiver clock (reported by NTP) Ps - exact offset of sender clock (from PPS capture log) Pr - exact offset of receiver clock (from PPS capture log)

What was calculated Raw one-way delay obtained from CRUDE log OWD_r = Tr - Ts One-way delay corrected by estimated NTP offsets OWD_n = Tr - Or - (Ts - Os) Exact one-way delay calculated from GPS time OWD_e = Tr - Pr - (Ts - Ps)

OWD Measurement Setup I + II NTP_ A NTP_B | | PPS --> Box_A network Box_B <-- PPS NTP | PPS --> Box_A network Box_B <-- PPS

Results (setup I)

Error of measurement (setup I)

Results (setup II)

Error of measurement (setup II)

Results (setup IIa)

Error of measurement (setup IIa)

OWD Measurement Setup III NTP | \ / | PPS --> Box_A network Box_B <-- PPS GEANT > TELIA <------

Results (setup III) Cesnet -> Heanet (TELIA) red: measured OWD (about 28ms) green:exact OWD (about 37 ms) Heanet -> Cesnet (GEANT) red: measured OWD (about 28ms) green:exact OWD (about 20 ms)

Results (setup III) Cesnet -> Heanet (TELIA) red: measured OWD (about 28ms) green:exact OWD (about 36 ms) red: corrected OWD (about 28ms)

Results (setup III) Heanet -> Cesnet (GEANT) red: measured OWD (about 28ms) green:exact OWD (about 20 ms) red: corrected OWD (about 28ms)

Errors (setup III) Cesnet: error of NTP reported offset Heanet: error of NTP reported offset

Conclusions Max. error is less than round-trip delay between NTP server and client (site of measurement), estimated error is the asymmetry Setup I (local NTP server in each site of measurement) robust, estimated error in the order of 100 us assumed low offset between both NTP servers Setup II (one common NTP server) accuracy depends on NTP server position estimated error less than 1 ms in case of symmetric routing careful setup of ntpd necessary (differs from default ! )

Conclusions (cont.) Setup III (one NTP server, asymmetric routing ) stable asymmetry in OWD can not be detected mean value of measured OWD in both directions is the same estimated error of measurement is one half of the asymmetry

OWD Measurement Setup IV NTP_A network NTP_B | | institute_A network institute_B network | | NTP_A_sec NTP_B_sec | | (PPS --> ) Box_A Box_B ( <-- PPS)