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What started with the sundial has, thus far, been refined to a level of precision based on atomic resonance: Time. Our obsession with time is evident in this continued scaling down to nanosecond resolution and beyond. But this obsession is not without warrant. Precision and time synchronization are critical in many applications, such as air traffic
Carefully coordinated, reliable, and accurate time synchronization is vital to a wide spectrum of fields—from air and ground traffic control, to buying and selling goods and services, to TV network programming. Ill-gotten time could even lead to the unimaginable and cause DNS caches to expire, leaving the entire Internet to implode on the root servers. Written by the original developer of the Network Time Protocol (NTP), Computer Network Time Synchronization: The Network Time Protocol on Earth and in Space, Second Edition addresses the technological infrastructure of time dissemination, distribution, and synchronization—specifically the architecture, protocols, and algorithms of the NTP. This system has been active in one form or another for almost three decades on the Internet and numerous private networks on the nether side of firewalls. Just about everything today that can be connected to a network wire has support for NTP. This book: Describes the principal components of an NTP client and how it works with redundant servers and diverse network paths Provides an in-depth description of cryptographic and other critical algorithms Presents an overview of the engineering principles guiding network configuration Evaluating historic events that have taken place since computer network timekeeping started almost three decades ago, the author details a number of systems and drivers for current radio, satellites, and telephone modem dissemination and explains how we reckon the time, according to the stars and atoms. The original 16 chapters of the first edition have been rewritten, updated, and enhanced with new material. Four new chapters cover new algorithms and previously uncovered concepts, including timekeeping in space missions. Praise for the first edition: "... For those that need an exhaustive tome on all of the minutiae related to NTP and synchronization, this is the source. ... definitive ... this book should be considered the last word on the topic." —Ben Rothke on Slashdot.org "... the bible of the subject... contains enough information to take you just as far as you want to go....Dr. Mills is the original developer of NTP." —Books On-Line
* In-depth look into all of the aspects of NTP. * Takes the mystery (and fear) out of working with NTP. * Written in an entertaining and multi-faceted voice.
This book presents the latest research results in the area of secure localization for both wireless mobile ad hoc networks and wireless sensor networks. It is suitable as a text for computer science courses in wireless systems and security. It includes implementation studies with mica2 mote sensors. Due to the open spectrum nature of wireless communication, it is subject to attacks and intrusions. Hence the wireless network synchronization needs to be both robust and secure. Furthermore, issues such as energy constraints and mobility make the localization process even more challenging. The book will also interest developers of secure wireless systems.
Network synchronization deals with the distribution of time and frequency across a network of clocks often spread over a wide geographical area. The goal is to align (i.e. synchronize) the time and frequency scales of all clocks, by using the communication capacity of their interconnecting links. Network synchronization plays a central role in digital telecommunications as it determines the quality of most services offered by the network operator. However, the importance of network synchronization is often underestimated and how to solve quality-of-service degradation caused by synchronization difficulties can become problematical to all but a synchronization engineer. * Systematically covers a wide spectrum of both theoretical and practical topics * Features a clear and profound description of synchronous and asynchronous digital multiplexing (PDH, SDH), jitter and timing aspects of SDH networks * Expounds synchronization network principles and implementation issues, clock modelling, time and frequency measurement * Presents recent advances in telecommunications clock characterization and measurement If you are a system engineer, researcher, designer or postgraduate student searching for both the basics and an insight into more advanced areas currently under discussion then you will find Synchronization of Digital Telecommunications Networks an enlightening read. It will also prove to be a valuable sourcebook for senior undergraduates and technical personnel in telecommunications companies.
This book constitutes the refereed proceedings of the 36th Conference on Current Trends in Theory and Practice of Computer Science, SOFSEM 2010, held in Špindleruv Mlýn, Czech Republic, in January 2009. The 53 revised full papers, presented together with 11 invited contributions, were carefully reviewed and selected from 134 submissions. SOFSEM 2010 was organized around the following four tracks: Foundations of computer science, principles of software construction, Data, knowledge, and intelligent systems and Web science.
The complete guide to timing and synchronization in advanced service provider networks and enterprise applications As networks have advanced, so has the need for precise timing and synchronization--including highly accurate phase synchronization. Without it, networks become increasingly vulnerable to outages, data loss events, and inefficiencies that can be notoriously difficult to diagnose. 5G telecom networks have especially stringent requirements, but they also apply to a growing number of enterprise applications in finance, factory automation, IoT, media, and beyond. Synchronizing 5G Mobile Networks is the definitive, comprehensive guide to all aspects of timing and synchronization. Drawing on extensive experience developing and implementing timing and synchronization systems, three leading experts cover standards, protocols, clock design, architecture, solution design, deployment tradeoffs, day-to-day operations, troubleshooting, and more. This book will be valuable to professionals with diverse backgrounds, even those with no timing or synchronization experience. It will be especially useful to engineers and consultants designing or implementing mobile networks; test engineers validating equipment or production solutions; students seeking careers with service providers or in advanced private networks; and technology leaders seeking to understand the growing role of time synchronization. Understand timing and synchronization concepts, goals, sources, and transport Explore timing applications in telecommunications and beyond Build synchronous networks with clocks, timing reference sources, time distribution, and timing signal consumption Review the role of standards development organizations in defining standards for timing and synchronization Drill down into the details of clocks, clock signals, and clock components Review traditional TDM-based techniques for frequency synchronization Explore precision time protocol (PTP) characteristics, features, profiles, and security Master best practices for designing and deploying timing in physical and packet-based networks Thoroughly understand timing metrics and end-to-end time error budgeting Establish accurate timing and synchronization in advanced 5G and LTE networks, including 5G New Radio and RAN environments Manage tradeoffs in synchronizing diverse cell sites, topologies, radio types, and mobile generations Verify, operate, monitor, and troubleshoot timing systems
This book addresses the multiple technical aspects of the distribution of synchronization in new generation telecommunication networks, focusing in particular on synchronous Ethernet and IEEE1588 technologies. Many packet network engineers struggle with understanding the challenges that precise synchronization distribution can impose on networks. The usual “why”, “when” and particularly “how” can cause problems for many engineers. In parallel to this, some other markets have identical synchronization requirements, but with their own design requirements, generating further questions. This book attempts to respond to the different questions by providing background technical information. Invaluable information on state of-the-art packet network synchronization and timing architectures is provided, as well as an unbiased view on the synchronization technologies that have been internationally standardized over recent years, with the aim of providing the average reader (who is not skilled in the art) with a better understanding of this topic. The book focuses specifically on synchronous Ethernet and IEEE 1588 PTP-based technologies, both key developments in the world of synchronization over the last 10 years. The authors address the needs of engineers and technical managers who are struggling with the subject of synchronization and provide an engineering reference for those that need to consider synchronization in NGN. The market applications that are driving the development of packet network synchronization and timing architectures are also discussed. This book provides a wide audience with everything they need to know when researching, implementing, buying and deploying packet synchronization architectures in telecommunication networks.
Thoroughly revised and expanded, this second edition adds sections on MPLS, Security, IPv6, and IP Mobility and presents solutions to the most common configuration problems.
Nowadays, as society has become more interconnected, secure and accurate time-keeping becomes more and more critical for many applications. Computing devices usually use crystal clocks with low precision for local synchronization. These low-quality clocks cause a large drift between machines. The solution to provide precise time synchronization between them is to use a reference clock having an accurate source of time and then disseminate time over a communication network to other devices. One of the protocols that provide time synchronization over packet-switched networks is Network Time Protocol (NTP). Although NTP has operated well for a general-purpose use for many years, both its security and accuracy are ill-suitedfor future challenges. Many security mechanisms rely on time as part of their operation. For example, before using a digital certificate, it is necessary to confirmits time validity. A machine with an inaccurate clock canaccept an expired or revoked certificate.This thesis first provides a background on time synchronization starting with the definition of some fundamental concepts such as the clock model, the problem of clock synchronization, and some notions like accuracy, precision, and stability of clocks. We study the most common time synchronization protocols used in packet-switched networks, and among others NTP.Then,we consider the security of time synchronization by presenting the possible security threats against time synchronization protocols and the security requirements of these protocols. We zoom in the securityof the NTP protocol as described by the standard NTP and other related work that tried to enhance NTP security. We also discuss the importance of having a well-balanced trade-off between security and performance.In our first contribution, we propose to go further in the support of NTP security with Secure Time Synchronization protocol (STS), a new secure authenticated time synchronization protocol suitable for widespread deployments. We describe the operation of STS and prove its design secure with a formal analysis using two security protocol verification tools: Proverif and Tamarin. We present the implementation of STS based on the OpenNTPD project, and evaluate its performance by comparing the STS precision with unauthenticated NTP. We point out the circular dependency between certificate validation and time synchronization. In fact, reliable time synchronization requires cryptographic materials that are valid only over designated time intervals, but time intervals can be only enforced when participating hosts are reliably synchronized. We present a solution for bootstrapping time synchronization based on the Bitcoin blockchain to break this circular dependency.In our second contribution, we propose a method for improving the accuracy of the NTP protocol by taking into account asymmetric transmission delays due to different bandwidth or routing on the forward and backward paths. In fact, asymmetry is quite prevalent in the Internet, which leads to low accuracy ofNTP that relies on the symmetric delay assumption to compute the clock offset. This method builds on using an NTP client synchronized with GPS to measure precisely the one-way transmission delay on the forward and backward path with his time server. In this way, it is possible to calibrate NTP to take into account asymmetry.