Time-Sensitive Networking is a set of Ethernet sub-standards defined in the IEEE 802.1 TSN Task Group. TSN focuses on creating a convergence between information technology (IT) and industrial operational technology (OT) by extending and adapting existing Ethernet standards.
TSN technology aims to standardize features on OSI-Layer 2 in order that different protocols can share the same infrastructure. The challenge lies in configuring critical and non-critical data traffic so that neither real-time characteristics nor performance is impaired.
2. Meaning
TSN is a standard technology to provide deterministic messaging on standard
Ethernet. TSN technology is centrally managed and delivers guarantees of
delivery and minimized jitter using time scheduling for those real-time
applications that require determinism.
3. TSN:
TSN is an Ethernet standard, not an Internet Protocol standard. The forwarding
decisions made by the TSN bridges use the Ethernet header contents, not the IP
address. The payloads of the Ethernet frames can be anything and are not limited to
Internet Protocol. This means that TSN can be used in any environment and can
carry the payload of any industrial application.
TSN was developed to enable deterministic communication on standard Ethernet.
The market for deterministic communication is using nonstandard technologies or
nonstandard Ethernet.
4. TSN COMPONENTS:
● TSN flow: Term used to describe the time-critical communication between end
devices. Each flow has strict time requirements that the networking devices
honor. Each TSN flow is uniquely identified by the network devices.
● End devices: These are the source and destinations of the TSN flows. The end
devices are running an application that requires deterministic communication.
These are also referred to as talkers and listeners.
● Bridges: Also referred as Ethernet switches. For TSN, these are special bridges
capable of transmitting the Ethernet frames of a TSN flow on a schedule and
receiving Ethernet frames of a TSN flow according to a schedule.
5. ● Central network controller (CNC): For TSN, the CNC acts as a proxy for
the Network (the TSN Bridges and their interconnections) and the control
applications that require deterministic communication.
The CNC defines the schedule on which all TSN frames are transmitted.
The CNC application is provided by the vendor of the TSN bridges. Cisco
has developed a CNC application for controlling its TSN bridges for TSN.
● Centralized user configuration (CUC): An application that communicates
with the CNC and the end devices. The CUC represents the control
applications and the end devices. The CUC makes requests to the CNC for
deterministic communication (TSN flows) with specific requirements for
those flows. The CUC is an application that is vendor specific. Typically the
vendor of the TSN end devices will supply a CUC for those end devices.
6. WHY TSN?
In most cases, traditional Ethernet networks involving automated sectors such as
manufacturing are based on the hierarchical automation pyramid which separates
information technology (IT) from operational technology (OT). IT includes classic
office communication with typical end devices such as printers and personal
computers.
IT is made up of systems, machines and software used for process control and
automation. The two areas are fundamentally different in how they communicate,
with IT dependent on bandwidth and OT focused on high availability. Data traffic at
the IT level is therefore often classified as non-critical while data traffic is
designated (time-) critical at the OT level. As a result, each level uses a particular
communication standard.
7. REAL TIME COMMUNICATION:
Guarantees regarding cycle times and fluctuations in cycle times are prerequisite for
a range of application fields in automation, including, for example, drive, control-,
and conveyor technology. The data transfer times demanded in these application
fields are significantly less than 1 ms. In addition to these applications requiring
“hard” real-time capability, other applications such as process automation
implement “soft” real-time capability with longer cycle times. Nevertheless,
guaranteed latencies are required for these applications as well.
