Sat. Dec 3rd, 2022

To say that the most popular technology in the field of industrial communication, it must be none other than TSN. In fact, TSN (Time Sensitive Network) time-sensitive network is a new but not unfamiliar technology. So what kind of network is TSN? Why is TSN considered a unified standard for future industrial communications? Will TSN replace all types of real-time industrial Ethernet today? …

Faced with these questions, Lao Shi from CE China and Lao Song from B&R started an inquisitive dialogue, hoping to give you a comprehensive and correct understanding of TSN.

interlocutor

Dialogue transcript

Lao Shi: TSN means time-sensitive network, what does time-sensitive mean? Are other networks not time sensitive? Are there metrics?

Lao Song

To be honest, when I first introduced TSN at the B&R headquarters in 2016, I didn’t think it seemed like a technology in the field of industrial automation, because industrial networks such as PROFINET, POWERLINK, and EtherCAT can already achieve relatively high real-time indicators. And it seems that there are very few cases where the current 100μS can not be solved. The industrial network speaks of “Determistic”, that is, deterministic network, because the control is based on “isochronous synchronization”, and the industrial field has already achieved “time sensitivity”. Therefore, personally, I felt that the word was a network developed by IT people who did not understand the industry, because the original description of TSN was to give Ethernet the “deterministic” and “real-time” transmission capabilities. This is because the standard Ethernet The Internet does not have this capability, but real-time Ethernet has this capability.

So, where is the crux of the problem? The most critical purpose of TSN is data transmission on the “same” network, that is, periodic control communication requirements and aperiodic data transmission in the same network are the core demands of TSN.

Because the current IT and OT integration process will encounter very big problems, that is, periodic data and aperiodic data often need to be transmitted through two networks, therefore, you will find that each controller has two network ports , a real-time Ethernet, a standard Ethernet, the general real-time network is used for machine and system control, and the standard network is used for the transmission of management-level information.

Usually, the QoS (Quality of Service) indicators for measuring the network include cycle period, delay, and jitter. Generally speaking, hard real-time will be refreshed at the level of hundreds of microseconds, and the jitter is controlled at the level of dozens of nS. Latency is in microseconds. There is no special official definition of real-time, because the application scenarios are different.

Lao Shi: One of the features of TSN is its high real-time performance. Don’t our previous fieldbuses and real-time Ethernet also have this feature? Does it also have an advantage in real-time compared to these TSNs?

Lao Song

Although the key requirement of TSN lies in the transmission of the “same” network, the scheduling mechanism also allows to obtain high real-time responsiveness after the design of the R&D personnel. At present, the TSN of the Gigabit Ethernet developed by B&R has tested the jitter in 50nS (jitter usually describes the worst case), the fastest cycle that can be achieved is at the level of 10μS. Therefore, for the existing industrial control, the real-time performance of TSN is completely guaranteed.

Compared with the current mainstream real-time Ethernet, the performance is obviously higher than that of TSN. According to the test data of B&R headquarters, the overall performance is 18 times higher.

Lao Shi: How does TSN achieve time sensitivity? Is it a modification of the standard Ethernet standard?

Lao Song

TSN itself is a series of standards. It includes three key standards of clock synchronization, data scheduling and network configuration. TSN only refers to the standard of the data link layer. It must be clarified that it can use IEEE802.3 Ethernet Or the IEEE802.3cg standard network to implement the physical layer, while the data link layer uses a bridge network and different data flow scheduling strategies, that is, Shaper-shapers, such as CBS credit-based shapers, Qbv-time awareness Shaper TAS, CQF – Periodic Queuing and Forwarding, ATS – Asynchronous Transfer Shaper. If you want to understand this, you have to understand how the Ethernet itself is transmitted, and then understand that TSN mainly designs the policy scheduling mechanism in the place of Transmit Selection.

15 Questions to “Go to the Roots” TSN – Let you understand why industrial interconnection needs TSN?

Lao Shi: TSN has become more and more popular in the industry in the past two years. Where does this TSN come from? Is it unique to our industry? Are other industries also called TSN? Who in the world is leading this standard?

Lao Song

SN does not originate from the industrial world. TSN was first used in the field of audio and video transmission, and later in the automotive field, it established IEEE802.1Q work in 2012, and it was already a matter of 2015 when it arrived in the industry, and the IEEE802.1 TSN working group was established.

15 Questions to “Go to the Roots” TSN – Let you understand why industrial interconnection needs TSN?

Generally known as AVB-Audio Video Bridge in the automotive industry, it is composed of IEEE802.1Qav, IEEE802.1AS and IEEE802.1Qat (already used as the basic standard of IEEE802.1Q).

There are also a large number of time-sensitive network applications in the aerospace field, which can be called AS6802, and in the industrial field, IEC and IEEE cooperate to set up the IEC 60802 working group to implement the interoperability standard formulation of TSN networks.

The current TSN promotion organization is Avnu, including IIC and OPC UA Foundation, which have also joined the work to promote this technology. They will work with major Shaper manufacturers to promote the development of TSN technology.

Lao Shi: TSN is going to become a standard Ethernet protocol in the future, and it is more advanced than the previous standard Ethernet protocol. Does that mean that the Ethernet protocols used in civil, commercial and industrial use will become TSN in the future?

Lao Song

TSN is a VLAN technology, namely Vitural Local Area Network, which obviously defines that it is a local area network and a virtual local area network. It does not necessarily become a standard for all commercial and civilian use, TSN domain and non-TSN domain. The difference is the VLAN ID, that is, when entering the TSN network, it will be tagged with a VLAN tag by the switch, and then transmitted in the network with the help of the TSN mechanism, but when leaving the TSN network, the VLAN tag will be removed, and it can also become a Standard Ethernet frames are transmitted. Therefore, TSN switches will work with normal switches without problems.

Therefore, it is not necessary for commercial or civilian networks to become TSN networks. It all depends on the needs of the application itself, especially economic indicators. Therefore, if there are no special real-time requirements, it is not necessary. At present, the TSN network seems to The focus is on industrial-grade IoT applications.

Lao Shi: Why has TSN suddenly attracted the attention of so many people in the industry in the past two years? Does it solve any problems that cannot be solved now?

Lao Song

The reason for the popularity of TSN is that a large number of IoT applications are required, because you have to consider the same network transmission problem of periodic and aperiodic data, and the demand for bandwidth is greater than before.

As you can see in this diagram, several scenarios are depicted:

(1) Audio and video synchronization: In fact, if you watch CCTV, you will see that the announcer’s mouth and voice will be out of synchronization – this is also a quality problem, because the audio and video are not synchronized, or like the speakers in the grand theater , you think if they can’t achieve synchronization, there will be repeated sounds, which is also a problem of data transmission quality.

(2) ADAS. Compared with traditional cars, ADAS will require multiple lidars (such as three front and rear), including safety systems. These more sensors will bring greater bandwidth requirements than before.

(3) AR/VR, machine vision: More use of these technologies in industrial scenarios will increase the demand for bandwidth.

Therefore, TSN has practical requirements. As connections become more extensive, larger network capacity transmission capabilities are required.

Lao Shi: Since the Ethernet network with time-sensitive features has so many advantages, why was it not considered to be time-sensitive when the earlier standard Ethernet was introduced? Why add time sensitivity now? Is it because it was not thought of before, or the original technology cannot be realized, or the cost is too high and other reasons?

Lao Song

When Volkswagen came to China to invest in building an automobile factory in the 1990s, China’s highways were just beginning, including many old communities now without enough parking spaces. Who would have expected cars to be so popular today?

In the same way, when you don’t need the technology, you don’t really have the motivation to develop such a technology, because if no one uses it, the R&D investment is meaningless, so any technology will take time to become popular. , and, for now, TSN has not yet reached the time when it really broke out, because the demand for interconnection has only begun in recent years, and a large number of factories are actually still in the stage of stand-alone production. Therefore, TSN is now in the stage of preparing for a rainy day, because the application of big data is only starting locally, rather than entering an explosive period.

Of course, you are right. To implement a network like TSN does require a lot of technical investment, because its complexity exceeds that of the existing network, just like clock synchronization has more reliability requirements than IEEE1588, scheduling The mechanism is also more diverse and flexible. These all require chip processing, including Gigabit Ethernet processing chips, transmission cables, switching chips, etc. These are all costs, and only when faced with huge market opportunities will chip manufacturers have the motivation to invest in research and development. .

Lao Shi: So far, what are the latest developments in TSN related product development, test beds, and supported manufacturers?

Lao Song

At present, TSN has several important test bed promoters, one is LNI in Germany, which is the test bed organized by Industry 4.0, the other is the test bed organized by IIC, and the other is the test bed organized by Huawei ECC. All three organizations actively participated in the construction of Testbed.

At present, mainstream automation manufacturers have released their own TSN products or test products. For example, B&R released TSN products at SPS in 2017, while SIEMENS released Profinet over TSN products at Hannover Fair in 2018. In 2019, Mitsubishi released CC- Link IE TSN products. Manufacturers such as Huawei, TTTech, CISCO, MOXA, and Hessman have also released TSN switch products.

In the field of chips, manufacturers such as NXP, XILINX, Intel, and AD have all released chipsets that support TSN.

Lao Shi: Although TSN has been hot in the past two years, almost everyone is optimistic and supported, so why is it still rare in actual products, or it has not been mass-produced and sold, and there is almost no formal industrial application, where is it mainly stuck? When is it expected that TSN will actually start to be applied?

Lao Song

It seems that you are more anxious than the user. However, industrial products generally have a long life cycle, just like CAN bus and Modbus are still in use. In fact, it is not as slow as you think. Compared with the past bus from In terms of concept, local application, and large-scale mature application, the development of TSN is relatively fast, because you need to know that the TSN industry-oriented working group was established at the end of 2015, and the Shaper launch meeting was held in September 2016. Therefore, You can see so many companies launching products in 2018, which is pretty fast.

In 2019, TSN, including B&R and Mitsubishi, which are now known, will have mass-produced products. Industrial products will not be updated as fast as mobile phones. I haven’t bought Huawei’s P20 Mate Pro yet. The product life cycle is generally more than 15 years, because a machine tool may be used for more than 20 years.

Therefore, in fact, the development of TSN has been very fast.

Lao Shi: To implement TSN in a communication network, what equipment is required to form or support it? Will TSN be more expensive to implement than other networks?

Lao Song

TSN is a VLAN, so many of its implementations are at the software level. It needs a switch that handles this clock synchronization and scheduling mechanism. Of course, for the controller, it needs the chip support of TSN. I have no consideration for the specific chip cost. However, the law of development of things is common, and the cost must be a process of continuous decline, because a large number of applications can reduce the cost.

Lao Shi: Now I see that foreign manufacturers have released TSN products one after another, but domestic manufacturers have not yet. How can we develop a TSN master or slave or I/O? Are the costs high?

Lao Song

This is not entirely the case. Huawei has already taken the lead in this regard, and their TSN switches have also been developed, but it seems that they have not yet entered the batch stage, because Huawei will consider more scenarios. Therefore, in In terms of shapers, there will be some designs of our own. Recently, I wrote about the shaper of TSN, and I also consulted two experts from Huawei. In addition, MOXA also launched TSN switch products, as well as some universities, research institutes, Enterprises have also launched TSN-related technical test products, which have not yet been officially released.

At present, TSN technology development boards are provided by XILINX, as well as TSN solutions jointly launched by TTTech and Intel, and chip manufacturers NXP, AD, etc. have also launched TSN development and test chips and test boards.

Lao Shi: Now real-time Ethernet and fieldbus are widely used in the field of control, especially in the field of motion control. Will TSN replace these protocols? What is the relationship between TSN and these real-time networks?

Lao Song

It needs to be emphasized again that TSN is the second layer of the ISO/OSI architecture, which means that the current TSN can appear in various forms. In fact, Ethernet itself is also in this development process. For example, Profinet is Profibus over Ethernet, and POWERLINK is CANopen over Ethernet, then there will be scenarios such as Profinet over TSN and CC-Link IE TSN, which are often designed to maintain the continuity of application layer software to ensure the availability of existing equipment investments, while B&R is OPC UA over TSN will be selected. The original POWERLINK CANopen application layer will gradually turn to OPC UA, and the continuity of a software application must be maintained. This is also the process of maintaining the application layer and gradually turning to TSN for a long period of time.

It must be emphasized that for any industrial application, maintaining the stability and inheritance of technology is a necessary consideration. Therefore, the upgrade of technology must be as smooth as possible. The same is true for users, which is the guarantee of investment security. Therefore, TSN will certainly not replace the existing network in the short term, but in a longer time, TSN will become the basic network architecture.

The ISO/OSI model is very interesting, that is, it enables each layer to be independently designed, including the physical layer, the current IEEE802.3 can continue to be used, of course, it can also be used such as PoE (Power on Ethernet), SPE (Single Pair Ethernet-IEEE802.3cg ) of the physical layer.

Lao Shi: Now another communication technology, 5G, has also arrived. 5G is also characterized by low latency and high bandwidth, and the most applications of 5G may be in the industry, so will TSN and 5G be a competitive relationship?

Lao Song

5G also has scenarios for ULL (Ultra Lower Latency). However, 5G is a wireless network. Applications in the industrial field, especially those similar to motion control, should not adopt 5G. However, the determination of the network in IIoT-based applications 5G can be used in areas where the performance assessment is affordable. In addition, TSN will also have standards for wireless scenarios.

Therefore, evaluating the application prospects of the technology mainly depends on the scenario – they will certainly not be competitive, but complementary.

Lao Shi: Regarding TSN, some people think that it is “big thunder and little rain”. What is the latest development of the TSN standard? What issues still need to be addressed to accelerate progress? Now that technology is developing so fast, will TSN be replaced by new communication technology in the middle?

Lao Song

In fact, the core driving force of any technology is “economy”, and technology promotion must have an acceptance process, and the market needs to be cultivated. Therefore, it is obviously impossible for TSN to have a large number of applications in the short term. Think about the field bus from the beginning. It actually took 30 years to develop to the peak. If you look at the development of the entire industry, TSN has developed at a very fast speed from 2015 to today.

As for whether TSN will be replaced by new communication technologies in the middle, this question is more interesting. In theory, everything is possible. However, any technology comes from demand. If there is no essential change in demand, then there will be no essential change in technology. If demand is the unity of the network, then whether it is TSN or a new technology, it is the same Technology implementation path, and communication technology cannot exist independently of chips and industrial control. Therefore, there will only be an upgrade of TSN, and it is difficult to have an independent technology to replace it.

The development of technology has its inevitability. Since everyone sees the technical requirements after 10 years and develops TSN, it will continue to develop for a long time.

As for what will happen in a longer time, such as 30 years, I think most people can’t pay attention, because at this time, if you are keen to observe the needs of the network in 30 years, and then develop the technology that will be used in 30 years. , your company will not survive that time.

Lao Shi: If TSN is popularized in various fields in the future, will it realize the so-called Industrial Internet of Things Internet of Everything?

Lao Song

This is worth looking forward to. TSN is committed to this. However, whether everything must be interconnected by TSN, that is not necessarily because there are too many technologies in this world. Just like the 5G mentioned just now, human beings are interesting because of their diversity. It is also worth exploring because there are unknowns. It does not matter whether TSN can realize the Internet of Everything, it is just a technology, and it is not necessary to give it such a significant meaning, just like Bill. Gates said, “We always overestimate what can be done in one or two years, and underestimate what can be done in five or ten years” – in the short term, TSN does not seem to have reached the stage of widespread use, but In the long run, TSN will have a dominant position in the automotive and industrial Internet fields, but its best partner is OPC UA. The combination of the two will make it possible for the industry to unify the world.

Of course, in the industrial world, the creation of value depends not only on network technology, but also on the pursuit of customer value, including the application value of software and human creativity. Tools for the Value Creation Process – For industrial companies, value still comes from solving problems for customers, and TSN will help us.

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