Test Automation solution - Veryx Technologies · iv. Synchronization Network Scalability 3. Performance Testing based on G.8261 Traffic Profiles These tests verify the performance

FROM VERYX TECHNOLOGIES

TIME SYNCHRONIZATION TEST SOLUTION

Copyright © 2002 - 2013 Veryx Technologies Page i

CONTENTS

Introduction............................................................................................................................................................................................. 1

1588v2 Overview .................................................................................................................................................................................. 1

SyncE overview ...................................................................................................................................................................................... 2

VERYX capability ................................................................................................................................................................................... 2

1588v2 Test Coverage ........................................................................................................................................................................ 2

Time Sync Application Test Coverage ....................................................................................................................................... 7

I. MOBILE BACKHAUL .......................................................................................................................................................... 7

II. INDUSTRIAL AUTOMATION ......................................................................................................................................... 8

III. ETHERNET AUDIO/VIDEO NETWORKS ............................................................................................................ 8

Conclusion ................................................................................................................................................................................................ 8

Copyright © 2002 - 2013 Veryx Technologies Page ii

This page has been left blank intentionally

Copyright © 2002 - 2013 Veryx Technologies Page 1

Introduction

With the transport of all telecommunication services over unified and packet switched platforms,

telecommunication networks are evolving into converged packed switched networks. Ethernet is

now gaining prominence in the converged network scenario and playing a crucial role in access,

aggregation and metro networks. The key pre-requisite for completing this evolution is the ability to

distribute frequency and/or timing information which is required by some applications (like mobile

back haul, circuit emulation, etc.).

Though various technologies have been suggested to augment Ethernet for frequency and time

distribution, the two widely deployed methods of synchronization are – 1588v2 (Precision Timing

Protocol) and SyncE (Ethernet Synchronization Message Channel Protocol). This document provides

a brief overview of these synchronization technologies and Veryx capability to verify these

implementations covering following application scenarios: Mobile backhaul, Industrial networks and

Ethernet Audio/Video networks.

1588v2 Overview

IEEE 1588v2 provides a mechanism to synchronize the system clock of distributed nodes in a

system using standardized packet based networks. It also allows all the nodes in the network to

synchronize system-wide in the sub-microsecond range. The nodes (clocks) in the network are

classified based on the synchronization functionality it performs. The various types of clock types

that are components of PTP network are:

Grand Master Clock

Boundary Clock

End-to-End Transparent Clock

Peer-to-Peer Transparent Clock

Ordinary Clock (Client)

The operation of PTP relies on a measurement of the communication path delay between the time

source, referred to as a master, and the receiver, referred to as a slave.


SyncE overview

SyncE is a timing distribution technology over Ethernet physical interfaces specified by ITU-T

recommendations G.8262 and G.8264. The principle of SyncE is that each node in the network is

provided with an Ethernet Equipment Clock (EEC) that synchronizes to the frequency received from

one interface (connected to Primary Reference Clock) and uses the same frequency for all outgoing

interfaces. The same procedure is used by the nodes in the next hop along the synchronization

path until all the nodes are synchronized. In other words, SyncE is a hop-by-hop synchronization

protocol.

VERYX capability

Veryx has extensive knowledge in verifying and validating several 1588v2 and SyncE

implementations as a part of test solution offered to its customers. It has developed a

comprehensive test library for verifying them. These tests are carried out using Veryx’s own as well

as third party tool providers such as Symmetricom, Calnex and Meinberg. The range of tests

available as a part of test library to ascertain the correct behavior of time synchronization

implementation are broadly classified under two different heads – 1588v2 Test Coverage and SyncE

Test Coverage.

1588v2 Test Coverage

1. 1588v2 Functionality Tests

These tests verify time synchronization functionality using IEEE 1588v2 protocol across various

clock types – Grand Master, Boundary, Transparent, Ordinary (slave). The functionality

verification is performed in following four test topologies – Chain Topology, Ring Topology, Star

Topology and Tree Topology which are depicted below:

FIGURE 1 CHAIN TEST TOPOLOGY TO VERIFY 1588V2 FUNCTIONALITY


FIGURE 2 RING TEST TOPOLOGY TO VERIFY 1588V2 FUNCTIONALITY

FIGURE 3 STAR TEST TOPOLOGY TO VERIFY 1588V2 FUNCTIONALITY


FIGURE 4 TREE TEST TOPOLOGY TO VERIFY 1588V2 FUNCTIONALITY

The following functionality are verified in the above mentioned topologies

i. Boundary Clock Functionality

ii. End-to-End Transparent Clock Functionality

iii. Peer-to-Peer Transparent Clock Functionality

iv. BMC (Best Master Clock) Functionality

v. Ordinary (Slave) Clock Synchronization with Master

2. 1588v2 Scalability Tests

These tests verify the ability of the time synchronization functionality to scale for a larger time

synchronization network. This is performed by emulating multiple Master/Ordinary Clocks and

verifying the functionality of Master, Boundary, Transparent and Ordinary Clock. These

scalability tests which are listed below are performed in all the functional test topologies

i. Master Clock Scalability

ii. Boundary Clock Scalability

iii. Transparent Clock Scalability

iv. Synchronization Network Scalability

3. Performance Testing based on G.8261 Traffic Profiles

These tests verify the performance of clock recovery when the network (link between Master

and Slave) is congested with uni-directional traffic and/or bidirectional traffic. The simulated


congestion conforms to Network Traffic Model defined in G.8261. The test cases defined in

G.8261 Appendix VI are used to measure the performance of clock recovery. A sample test

topology used for Performance Testing is depicted below:

FIGURE 5 SAMPLE TEST TOPOLOGY TO MEASURE CLOCK RECOVERY

This test topology introduces congestion between two transparent clocks, anywhere between

Master clock and Slave Clock and then measures the clock recovery. The congestion is created

by generating traffic conforming to G.8261 Traffic Profiles from traffic generator and the packet

delay (1588v2 packets) is measured using the Network Emulator.

4. Clock Accuracy/Quality Tests

These tests verify the accuracy of clock recovery and the quality of recovered clock. The clock

quality and accuracy will be measured using following analysis:

i. Wander Generation Analysis

ii. Wander Tolerance Analysis

iii. Noise Generation Analysis

iv. Noise Tolerance Analysis

v. Noise Transfer Analysis

vi. Transient Response Analysis

vii. Holdover Performance Analysis

viii. Correction field Accuracy Analysis

The sample test topology for measuring the clock accuracy is depicted below:



The accuracy is measured in a time synchronization network using the Network Emulator which

is capable of measuring the Packet Delay Variations. These tests are performed by generating

traffic in the time synchronization network and measuring the Packet Delay Variation using the

Network Emulator. The clock accuracy is measured under various traffic load conditions.

5. 1588v2 Protocol Message Format Verification

These tests verify the 1588v2 message format. This is done by snooping the packet exchanged

between Master and Slave Clocks and between transparent clock devices. The message format

verification is to make sure that the messages are conforming to IEEE 1588 – 2008 standard.

SYNCE TEST COVERAGE

1. SyncE Conformance Test based on ITU-T 8262

These tests verify that the implementation is conforming to ITU-T 8262. This verification will

primarily focus on the ESMC message exchange between EEC devices and the subsequent clock

accuracy measurement. The measurements that are carried out are:

i. Jitter Generation Measurement

ii. Frequency Accuracy Measurement

iii. Wander Generation Measurement

iv. Wander Tolerance Measurement

v. Wander Transfer Measurement

vi. Pull-in Ranges Measurement

vii. Hold-in Ranges Measurement

viii. Pull-out Ranges Measurement

ix. Phase Transient Response Measurement

x. Jitter Tolerance Measurement

The sample test topology for verifying SyncE (G.8262) conformance is depicted below:



2. ESMC Protocol Message Format Verification

These tests will verify the ESMC message format. This is done by snooping the packet

exchanged between EEC emulator and EEC devices. The message format verification is to make

sure that the messages are conforming to ITU-T G.8262 standard.

Time Sync Application Test Coverage

As a part of Time Synchronization Application test, Veryx Test Solution covers following application

scenarios:

i. Mobile Backhaul

ii. Industrial Automation

iii. Ethernet Audio/Video Networks

The test approach adopted for each application is provided below.

I. MOBILE BACKHAUL

With mobile backhaul network transforming to Ethernet/IP based network with LTE/4G, the

challenge faced by network operators is the timing distribution and synchronization in packet

network. These challenges are addressed by industry recognized standards – Synchronous Ethernet

(ITU-T G.8262) and 1588v2 (IEEE 1588 Version 2).

Veryx test solution verifies whether these time synchronization protocols address the challenges

faced by network operators. In other words, the test solution will verify whether the SyncE

implementation is distributing the reference frequency at physical layer between EEC and 1588v2

implementation is distributing the time and frequency across mobile backhaul networks through

Boundary and Transparent Clocks. The test solution is adapted to the deployment scenarios based

on the inputs provided by the customer and the adapted test solution is executed for validating the

customer implementation.


II. INDUSTRIAL AUTOMATION

In traditional industrial automation environment, input sensors, output actuators, and industrial

controllers are distributed over a local area network. Since the traditional environment which use

scan-based and event-triggered control algorithm experience jitter and delay, time based control

methods is preferred. The time based control mechanism need a mechanism for distributing timing

information across the entities in the industrial automation environment and it is provided by

industry recognized standard IEEE 1588 Version 2. Veryx test solution verifies 1588v2

implementation in the industrial automation network from the perspective of following parameters:

Jitter Delays

Accuracy

Latency

This verification will ensure that the time based control mechanism provides the performance

alternative to scan-based and event-triggered mechanisms.

III. ETHERNET AUDIO/VIDEO NETWORKS

With the Ethernet forming the backbone of the emerging Audio/Video networks, it becomes

essential to be able to provide reliable audio and video delivery over such networks. Audio/Video

Bridging (AVB) Task Group worked on this enhancement to deliver time-synchronized, low-latency

audio and video over Ethernet networks. To achieve this, AVB devices periodically exchange timing

information to synchronize their time base reference clock very precisely. The protocol used for

time synchronization is IEEE 802.1AS which is the constrained subset of IEEE 1588 Version 2. Veryx

test solution verifies the delivery of time-synchronized audio/video delivery within AVB network,

covering the following two purposes:

Allowing synchronization of multiple streams

Providing common time base at the source and destination AVB devices

Veryx 1588v2 test solution has been adapted to verify the capability of AVB networks.

Conclusion

Testing for Time synchronization support is a key requirement for the new generation of Ethernet

based networks for supporting LTE/4G mobile backhaul, Industrial networks, AVB for Entertainment

etc. Veryx has proven capabilities for supporting its customers for verifying their 1588v2 and

SyncE implementations used in these applications.


www.veryxtech.com

[email protected]

Veryx Technologies (www.veryxtech.com) is an innovative enterprise providing solutions that enhance product

quality and testing efficiency. Leading equipment vendors, rely on the ATTEST range of products for testing

applications in Access, Carrier Ethernet, Data Center, Edge, Enterprise, Industrial Networking and Security

domains for over a decade. Veryx offers flexible, cost-effective products that enhance the Service Assurance

capabilities of Ethernet Service Providers.

AMERICAS: +1-408-850-1247 | ASIA: +91 (44) 45 67 22 22 | EUROPE: +44-203-371-8691

© 2002-2013 Veryx Technologies. Veryx and Veryx ATTEST are trademarks of Veryx Technologies.

All other trademarks of respective owners are acknowledged.

v1.1/1/2013

http://www.veryxtech.com/

Documents

Test Automation solution - Veryx Technologies · iv. Synchronization Network Scalability 3. Performance Testing based on G.8261 Traffic Profiles These tests verify the performance