DetNet Guangshuo Chen Internet-Draft Yuyin Ma Intended status: Informational Liang Wang Ying Zhou Expires: 22 May 2024 22 November 2023 Deterministic Networks - Navigating Precision in Communication draft-chen-detnet-automation-00 Abstract This document offers a comprehensive overview of deterministic networks, elucidating their significance, key characteristics, and the challenges they address in comparison to non-deterministic counterparts. With a focus on Time-Sensitive Networking (TSN) and Precision Time Protocol (PTP), the technological aspects are explored, encompassing synchronization mechanisms, traffic shaping, and security considerations. Real-world applications in industrial automation, control systems, and multimedia streaming underscore the practical relevance of deterministic networks. The document emphasizes the importance of precise time synchronization, security measures, and collaboration within the networking community. Through acknowledgments, the collaborative efforts of the Deterministic Networking (DetNet) Working Group, authors of relevant standards, and the broader community are recognized, highlighting the collective dedication to advancing deterministic networking technologies. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on 22 May 2024. Copyright Notice Copyright (c) 2023 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/ license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components Chen, et al. Expires 22 May 2024 [Page 1] Internet-Draft Detnet Automation November 2023 extracted from this document must include Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License. Table of Contents 1. Introduction 2. Terminology 3. Problem Statement 4. Technologies and Standards 4.1. Time-Sensitive Networking (TSN) 4.1.1. Overview 4.1.2. Key Components 4.1.3. Synchronization Mechanisms 4.1.4. Traffic Shaping and Scheduling 4.1.5. Quality of Service (QoS) in TSN 4.2. Precision Time Protocol (PTP) 4.2.1. Overview 4.2.2. PTP Message Types 4.2.3. Grandmaster Clock 4.2.4. Best Practices for PTP Deployment 5. Security Considerations 6. IANA Considerations 7. Acknowledgments 8. References 8.1. Normative References 8.2. Informative References Authors' Addresses 1. Introduction Deterministic networks play a pivotal role in meeting the evolving demands of modern communication systems, especially in scenarios where precise timing, low-latency, and high reliability are paramount. This chapter provides an introductory overview of deterministic networks, outlining their significance, key characteristics, and the fundamental challenges they aim to address. Chen, et al. Expires 22 May 2024 [Page 2] Internet-Draft Detnet Automation November 2023 2. Terminology This chapter establishes a set of terms and definitions to facilitate a clear understanding of the concepts discussed throughout this document. The terminology presented here aims to provide a common language for discussing deterministic networks and related technologies. 2.1. Deterministic Network A deterministic network refers to a communication infrastructure where the behavior and performance are predictable and consistent. In such networks, the timing and order of events can be precisely determined, allowing for reliable and deterministic communication. 2.2. Time-Sensitive Networking (TSN) Time-Sensitive Networking (TSN) is a set of IEEE standards designed to enhance Ethernet networks' capabilities to meet the stringent requirements of deterministic communication. TSN introduces mechanisms such as time synchronization, traffic shaping, and scheduling to ensure predictable and low-latency communication. 2.3. Precision Time Protocol (PTP) Precision Time Protocol (PTP), defined in IEEE 1588, is a protocol used to synchronize clocks across a network with high accuracy. PTP is a key component in achieving precise time synchronization within deterministic networks, ensuring coordinated timing across devices. Chen, et al. Expires 22 May 2024 [Page 3] Internet-Draft Detnet Automation November 2023 3. Problem Statement The traditional Internet architecture, while robust and widely adopted, faces challenges when it comes to meeting the stringent requirements of applications and services that demand deterministic behavior. This chapter outlines the key problems addressed by deterministic networks and provides insights into the limitations of non-deterministic networks. 3.1. Network Congestion and Variable Delays In non-deterministic networks, congestion and variable delays are common occurrences due to the shared nature of network resources. As a result, applications with strict timing constraints, such as real-time control systems and industrial automation, may experience performance degradation and unpredictable communication delays. 3.2. Unpredictable Event Handling Non-deterministic networks may struggle with the unpredictable handling of events, leading to difficulties in ensuring timely and synchronized communication. In applications where precise coordination is crucial, such as distributed control systems, unpredictable event handling can introduce uncertainties and compromise system reliability. 3.3. Lack of Precise Time Synchronization Precise time synchronization is a fundamental requirement for deterministic communication. Non-deterministic networks often lack mechanisms to ensure consistent and accurate time synchronization across devices. This limitation hinders the ability to coordinate actions and events with high precision. Chen, et al. Expires 22 May 2024 [Page 4] Internet-Draft Detnet Automation November 2023 4. Technologies and Standards 4.1. Time-Sensitive Networking (TSN) 4.1.1. Overview Time-Sensitive Networking (TSN) is a set of IEEE standards designed to enhance the capabilities of standard Ethernet networks to meet the stringent requirements of deterministic communication. TSN enables precise timing, low-latency communication, and reliability in scenarios where time synchronization and deterministic behavior are critical. 4.1.2. Key Components TSN comprises several key components that collectively contribute to deterministic networking. These include Time-Aware Shaper (TAS), Stream Reservation Protocol (SRP), and Frame Preemption, among others. Each component plays a crucial role in shaping network traffic, ensuring predictable delivery and minimizing latency. 4.1.3. Synchronization Mechanisms Achieving accurate time synchronization is fundamental to deterministic networks. TSN leverages synchronization mechanisms such as IEEE 802.1AS, which defines the time synchronization protocol for TSN networks. This ensures that all devices within the TSN domain operate on a shared and precise timeline. 4.1.4. Traffic Shaping and Scheduling TSN introduces advanced traffic shaping and scheduling mechanisms to prioritize critical traffic and ensure timely delivery. The TimeAware Shaper (TAS) enables the allocation of bandwidth and schedules transmission times for specific streams, preventing contention and guaranteeing determinism. Chen, et al. Expires 22 May 2024 [Page 5] Internet-Draft Detnet Automation November 2023 4.1.5. Quality of Service (QoS) in TSN Quality of Service (QoS) mechanisms in TSN go beyond traditional Ethernet, providing the ability to differentiate between various traffic classes. TSN supports multiple priority levels, allowing critical traffic to receive preferential treatment and ensuring that latency-sensitive applications meet their requirements. 4.2. Precision Time Protocol (PTP) 4.2.1. Overview Precision Time Protocol (PTP), defined in IEEE 1588, is a crucial component in achieving precise time synchronization within deterministic networks. PTP is specifically designed to synchronize clocks across a network with high accuracy, making it an essential building block for applications demanding sub-microsecond synchronization. 4.2.2. PTP Message Types PTP relies on different message types to exchange timing information among network devices. These include Announce, Sync, Follow-Up, and Delay_Req/Resp messages. The coordinated exchange of these messages ensures that clocks across the network are aligned with minimal deviation. 4.2.3. Grandmaster Clock In a PTP-enabled network, the Grandmaster Clock serves as the primary time reference. It is the device with the most accurate clock, and its time is distributed to other devices in the network. Selection of the Grandmaster Clock is crucial to maintaining synchronization accuracy. 4.2.4. Best Practices for PTP Deployment Successful deployment of PTP requires careful consideration of network topology, hardware capabilities, and environmental factors. Best practices include selecting a reliable Grandmaster Clock, optimizing network paths, and ensuring proper configuration to minimize synchronization errors and achieve optimal performance. Chen, et al. Expires 22 May 2024 [Page 6] Internet-Draft Detnet Automation November 2023 5. Security Considerations This document does not contain any security considerations. 6. IANA Considerations This document makes no IANA requests. 7. Acknowledgements The creation of this document has been a collaborative effort, and we extend our gratitude to individuals and organizations whose contributions and insights have enriched the content and quality of this work. Chen, et al. Expires 22 May 2024 [Page 7] Internet-Draft Detnet Automation November 2023 8. References This chapter provides a comprehensive list of references that readers can consult for further exploration of deterministic networks, Time-Sensitive Networking (TSN), Precision Time Protocol (PTP), and related topics. References are categorized into normative references, which are essential for understanding and implementing the concepts discussed, and informative references, which offer additional insights and perspectives. 8.1. Normative References [IEEE 802.1Q] - "IEEE Standard for Local and metropolitan area networks -- Bridges and Bridged Networks -- Amendment 28: Stream Reservation Protocol (SRP) Enhancements and Performance Improvements" This IEEE standard defines enhancements to the Stream Reservation Protocol (SRP), a crucial component of Time-Sensitive Networking (TSN). 8.2. Informative References [IETF Journal - Deterministic Networking] This informative reference provides an in-depth exploration of deterministic networking, including use cases, challenges, and emerging trends. It serves as a valuable resource for readers seeking a broader perspective on the topic. Chen, et al. Expires 22 May 2024 [Page 8] Internet-Draft Detnet Automation November 2023 [TSN Task Group - IEEE-SA] The Time-Sensitive Networking (TSN) Task Group within the IEEE-SA website offers additional documents, presentations, and resources related to TSN standards development and advancements. [PTP - Best Practices Guide] This informative guide offers best practices for deploying Precision Time Protocol (PTP) in various network environments. It provides practical insights into ensuring accurate time synchronization. Readers are encouraged to refer to the cited documents for a deeper understanding of deterministic networks and related technologies. Authors' Addresses Guangshuo Chen BeiJing JiaoTong University Haidian District, Beijing Email: 17733652726@163.com Yuyin Ma BeiJing JiaoTong University Haidian District, Beijing Email: mayuyin@bjtu.edu.cn Liang Wang BeiJing JiaoTong University Haidian District, Beijing Email: wangliang1@bjtu.edu.cn Ying Zhou BeiJing JiaoTong University Haidian District, Beijing Email: 22110019@bjtu.edu.cn Chen, et al. Expires 22 May 2024 [Page 9]