Based on time, resource reservation, and policy enforcement by distributed shapers [RFC 2475
], Deterministic Networking (DetNet) provides the capability to carry specified unicast or multicast data streams for real-time applications with extremely low data loss rates and bounded latency so as to support time-sensitive and mission-critical applications on a converged enterprise infrastructure.
DetNet aims at eliminating packet loss for a committed bandwidth, while ensuring a worst-case end-to-end latency, regardless of the network conditions and across technologies. By leveraging lower layer (Layer 2 (L2) and below) capabilities, Layer 3 (L3) can exploit the use of a service layer, steering over multiple technologies and using media independent signaling to provide high reliability, precise time delivery, and rate enforcement. DetNet can be seen as a set of new Quality of Service (QoS) guarantees of worst-case delivery. IP networks become more deterministic when the effects of statistical multiplexing (jitter and collision loss) are mostly eliminated. This requires a tight control of the physical resources to maintain the amount of traffic within the physical capabilities of the underlying technology, e.g., by using time-shared resources (bandwidth and buffers) per circuit, by shaping or scheduling the packets at every hop, or by using a combination of these techniques.
Key attributes of DetNet include:
time synchronization on all the nodes,
multi-technology path with co-channel interference minimization,
frame preemption and guard time mechanisms to ensure a worst-case delay, and
new traffic shapers, both within and at the edge, to protect the network.
Wireless operates on a shared medium, and transmissions cannot be guaranteed to be fully deterministic due to uncontrolled interferences, including self-induced multipath fading. The term RAW stands for "Reliable and Available Wireless" and refers to the mechanisms aimed for providing high reliability and availability for IP connectivity over a wireless medium. Making wireless reliable and available is even more challenging than it is with wires, due to the numerous causes of loss in transmission that add up to the congestion losses and due to the delays caused by overbooked shared resources.
The wireless and wired media are fundamentally different at the physical level. While the generic Problem Statement in [RFC 8557
] for DetNet applies to the wired as well as the wireless medium, the methods to achieve RAW necessarily differ from those used to support Time-Sensitive Networking over wires, e.g., due to the wireless radio channel specifics.
So far, open standards for DetNet have prevalently been focused on wired media, with Audio Video Bridging (AVB) and Time-Sensitive Networking (TSN) at the IEEE and DetNet [RFC 8655
] at the IETF. However, wires cannot be used in several cases, including mobile or rotating devices, rehabilitated industrial buildings, wearable or in-body sensory devices, vehicle automation, and multiplayer gaming.
Purpose-built wireless technologies such as [ISA100
], which incorporates IPv6, were developed and deployed to cope with the lack of open standards, but they yield a high cost in Operational Expenditure (OPEX) and Capital Expenditure (CAPEX) and are limited to very few industries, e.g., process control, concert instruments, or racing.
This is now changing (as detailed in [RAW-TECHNOS
IMT-2020 has recognized Ultra-Reliable Low Latency Communication (URLLC) as a key functionality for the upcoming 5G.
IEEE 802.11 has identified a set of real applications [IEEE80211RTA], which may use the IEEE802.11 standards. They typically emphasize strict end-to-end delay requirements.
The IETF has produced an IPv6 stack for IEEE Std. 802.15.4 Time-Slotted Channel Hopping (TSCH) and an architecture [RFC 9030] that enables RAW on a shared MAC.
Experiments have already been conducted with IEEE802.1 TSN over IEEE802.11be [IEEE80211BE
]. This mode enables time synchronization and time-aware scheduling (trigger based access mode) to support TSN flows.
This document extends the "[Deterministic Networking Use Cases
]" document [RFC 8578
] and describes several additional use cases that require "reliable/predictable and available" flows over wireless links and possibly complex multi-hop paths called "Tracks". This is covered mainly by the "Wireless for Industrial Applications" (Section 5
of RFC 8578
) use case, as the "Cellular Radio" (Section 6
of RFC 8578
) is mostly dedicated to the (wired) link part of a Radio Access Network (RAN). Whereas, while the "Wireless for Industrial Applications" use case certainly covers an area of interest for RAW, it is limited to IPv6 over the TSCH mode of IEEE 802.15.4e (6TiSCH), and thus, its scope is narrower than the use cases described next in this document.