Date of Award

Spring 2011

Project Type

Thesis

Program or Major

Computer Science

Degree Name

Master of Science

First Advisor

Radim Barto

Abstract

Precision Time Protocol (PTP) is a high precision time synchronization protocol designed to operate over a local area network. PTP, often referred to as 1588, is defined by the IEEE Standard 1588(TM)-2008. The protocol theoretically allows synchronization at the nanosecond level. New devices with support for 1588 are emerging into the market, but there have been few studies on real 1588 devices. Our research was broken into two parts: Phase 1 and Phase 2. Phase 1 studied performance of the protocol in an environment where two 1588 devices are connected via a network in which impairments that are typically observed in real networks are introduced and non-1588 devices are present. Measuring the Pulse-Per-Second (PPS) clock outputs of the 1588 boards, we were able to calculate the standard deviation and the mean synchronization error of the 1588 clocks. When we applied latency via network emulators and traffic generators between the 1588 connections, we found that 1588 boards were unable to maintain high accuracy time synchronization under variable and asymmetric latency. The results provide valuable insight into the real-world accuracy and robustness because it is rare that a network will contain neither variable or asymmetric latency. In Phase 2 we studied the impact of latency and high-bandwidth background traffic on 1588 clock synchronization when connected through 1588 and non-1588 aware switches. We found that 1588 aware switches provide higher precision time synchronization in small networks; but in large networks where congestion is present 1588 aware switches were unable to maintain high accuracy clock synchronization without prioritization. Our results also show that having cut-through Enterprise Ethernet switches connected to high congestion endpoints with priorities enabled is adequate for maintaining sub-microsecond synchronization performance.

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