工业互联网（IIOT）的实施无疑会产生其挑战的份额，其中最大的是信息技术（IT）和运营技术（OT）网络的融合。当前，这些网络存在于单独的域中 - 设计的网关在每个方向上提供有限的通信。但是，要启用网络物理系统，这些网络需要收敛，从而使用IIOT相互交互。
当前的体系结构控制工厂utomation is hierarchical. Enterprise resource planning (ERP) applications at the highest level provide an integrated management and automation of business core processes, progressing down to manufacturing execution systems (MES) that control the manufacturing process. Programmable logic controller (PLC) systems execute the automation tasks using connected industrial devices like electric drives, sensors, or I/Os, which reside at the lowest level of the hierarchy.
总体而言，这些水平通常被称为“自动金字塔”（图。1），说明顶部的底部和高性能计算机的大量设备。金字塔层说明了层次结构。
1. The Automation Pyramid illustrates the typical assignment of networks to hierarchies.
金字塔中的不同层具有不同的网络要求。尽管较高的层需要高带宽和灵活的网络拓扑，但较低的层需要确定性的行为，并且能够以低数据包延迟变化的恒定间隔运输样品。这导致多个网络并排工作。
The Urge to Converge
A converged network will address several challenges that currently exist in today’s disparate network architecture:
- 更透明：所有层次结构的所有数据都可以访问工厂中的每个元素，而无需转换。
- 较少的网络计划：更灵活的拓扑实现了更轻松的更改。
- 更少的资本支出：减少电缆；减少具有不同协议的网络之间的网关。
- 较少的OPEX：减少网络管理工作。
- More bandwidth:Avoid limitation to one network speed.
- 针对M2M进行了优化：准备与整个工厂中的OPC UA这样的常见数据模型之间进行互处理。
This convergence is provided by time-sensitive networking (TSN). TSN is a set of IEEE 802 sub-standards that, when implemented, enable deterministic communication over Ethernet networks while keeping the benefits of communication in best effort manner, on that same network.
TSN introduces different traffic classes that share the same link. TSN network configuration reserves resources for streams with deterministic time characteristics. TSN, therefore, enables one common network to be implemented that supports multiple communication standards.
Such a network opens the door to several improvements over standard Ethernet. Standard Ethernet communication isn’t time-aware; it distributes the data over the entire bandwidth of the link with packets queued in order for transmission. TSN implements time awareness with scheduled traffic at configured offsets in cyclic intervals. That follows a schedule distributed by a network configuration controller. Further TSN features introduce Filtering and Policing for TSN streams, seamless redundancy, and support for cyclic data transmission, while also providing pre-emption for higher-priority packets.
TSN is defined by a set of IEEE 802.1 standards that specify the implementation（请参阅表）。截至2017年9月，采用了其中四个标准，其余的仍在任务和工作组阶段。
这些标准是通过以太网（IEEE 802.3物理层）和支持星，链，环和混合拓扑结构实现的，并且不仅限于特定的数据速率。工业应用将主要使用100MBIT和1GBIT数据速率。因此，TSN提供了IT和OT网络之间的收敛性。这种融合降低了实施网络的成本，大大降低了所有权和运营成本。
TSN实施
Proper implementation of TSN requires a solution that can provide a low latency and deterministic response at TSN end points and TSN bridges. Many applications solve this challenge by combining a processor and a FPGA connected over a high-speed link such as PCIe. This two-chip solution not only increases occupied board space, power consumption, development time and cost, but also prevents a holistic integrated solution from being developed. Furthermore, segmenting the design between two devices increases the complexity of verification.
To avoid those issues, providers are opting for alternatives such as All Programmable Zynq-7000 and Zynq UltraScale+ MPSoC devices to implement their solutions. These devices, which combine a processing system (PS) and programmable logic (PL) for the implementation of acquisition, control, and processing applications, introduce:
- 接口和控制各种传感器，执行器，电动机和其他应用特定界面的能力。
- The ability to implement complex processing at the edge, e.g., machine learning, sensor fusion, image processing, and real-time analytics.
- 有关网络接口数量的可伸缩性。
- Security and the ability for the device and system to be secure in terms of information assurance, anti-tamper, and trust.
The Zynq devices also support any-to-any interfacing and the ability to couple PS and PL.
Looking deeper at the systems-on-a-chip (SoCs), they incorporateXilinx's1G/100M TSN Subsystem LogiCORE IP, which consists of FPGA logic for MAC, TSN Bridge, and TSN Endpoint. The TSN design with dedicated logic resources guarantees that the timing behavior is strictly deterministic.
Software that runs in the PS is for network synchronization, initialization, and interfacing with network configuration controllers for stream reservation. The software is designed to run on Petalinux and will be published for Yocto builds.
2.这是集成在的时间敏感网络IPXilinx的Zynq-7000和Zynq Ultrascale+ MPSOC。
The LogiCORE IP also has an optional integrated time-aware L2 switch that creates the chain or tree topology required in many industrial applications without allocating another port at an external TSN switch. Seamless Redundancy (P802.1CB) also requires the additional port. With the complete IP（图2），用户可以在合成之前自由配置开关是否应集成。
Once instantiated, the TSN IP core provides individual AXI Streaming ports for each traffic class. Scheduled traffic, reserved traffic, and best effort traffic are supported. The AXI Streaming ports connect to infrastructure that’s introduced byXilinx’s Vivado Design Suite. AXI Lite is used in the configuration of the TSN blocks.
3. Here’s a TSN implementation for evaluation purposes (using the Zynq UltraSCALE+ MPSoC).
用于评估目的的现成实现包括每个流量类别的直接内存访问（DMA）。评估系统（图3）可以用来测试Xilinx组件或与第三方设备或协议分析仪结合使用。
由于PL是灵活的，因此它还提供了更新IP核心作为TSN标准和市场细分特定符合测试的能力。另一方面，具有固定硬件实现的设备（例如自定义ASIC和特定于应用程序的标准产品或ASSP）缺乏沿TSN Evolution引入功能更改的选项。
为了演示行动中的TSN IP核心，Xilinxcreated a demonstration application for both the ZCU102 and ZC702 development boards. Connecting two of these boards（图4）允许传输和接收网络流量，从而验证TSN网络功能。
4. Shown is the TSN evaluation system.
The Industrial Internet Consortium (IIC) offers a TSN testbed (of whichXilinx是一个成员），公司可以通过其中进行供应商的互操作性测试，并测试高性能和关键延迟应用程序。该测试可以正式进行在美国或欧洲的两个永久性测试床上之一。
Conclusion
To enable deployment of the cyber physical systems for Industrie 4.0 and IIoT, there needs to be convergence between IT and OT networks. TSN makes it possible to converge these networks, creating significant advantages in network connectivity, scalability, and cost of deployment and ownership. For more information,click here。
