Introduction of Real-Time Ethernet-Based Standards
Introduction of Real-Time Ethernet- Based Standards
This section will briefly introduce the standard, the standards body history, and the key philosophical and architectural underpinning that distinguishes each standard from the other. This paper does not describe the entire protocol but shines a light on the technological component that simultaneously capitalizes on Ethernet yet distinguishes it from other open standards that also seek to capitalize on Ethernet. Following that, the standards can be compared side by side to uncover the relative strengths of each approach.
As we will see in the review of each respective protocol, there are profound differences in the technical approaches. This creates real separation between the contenders as to which standard is the most valuable and enduring. Some approaches rely on traditional Ethernet protocols and thus have a limited real-time capability and bandwidth, while others reuse the hardware components of the Ethernet and deliver breakthrough performance.
Specifically in the context of real-time deterministic fieldbuses, there are three different approaches that have emerged that allow the standard to deliver determinism on an Ethernet-based infrastructure:
Standard Software / Standard Ethernet
Based on TCP/IP: Protocols are based on standard TCP/IP layers with real-time mechanisms embedded in the top layer. These solutions usually have a limited performance range.
Open Software/ Standard Ethernet
New standard protocols are implemented on top of standard Ethernet layers. These solutions benefit from Ethernet evolution without further investment. However, to deliver the determinism, the standard must include a proprietary software controller at the OSI Layer 3&4 to reserve time on the network, otherwise latency can occur.
Open Software / Modified Ethernet
These solutions effectively create a new standard to take advantage of the existing Ethernet hardware, but require a new protocol and some hardware that guarantees determinism. The software is published freely and in the public domain. The hardware can be as complex as a special switch or as simple as an ASIC that fits into the slave device.
With that as context, each Ethernet standard will be described and assigned to one of these three architectural categories.
Talk to us. We speak industrial data communications.