Page 103 - ITU-T Focus Group IMT-2020 Deliverables

ITU-T Focus Group IMT-2020 Deliverables 3

6.1.5.2 The Work Scope of Detnet WG

Detnet work covers the overall architecture, data plane technologies, the data plane flow information model,
yang models, problem statement and vertical requirements as needed, etc. The work in the overall
architecture will consist of the data plane, OAM, time synchronization, control plane and manage plane. The
data plane will work on the method to identify the flow and to forward the packets across the multi-hop
deterministic path over the layer 3 network. The data plane flow information model will be used by the
reservation protocol and yang data model. New yang models will be used for device configuration, states
reporting, and advertising the deterministic network elements information to the control plane. Problem
statement work will establish the deployment environment and deterministic network requirements.
Vertical requirements part will analyze the details of the deterministic properties for various services.

6.1.5.3 Standardization activities states of Detnet WG
At present Detnet has four WG drafts, the Problem Statement document states issues that need to be solved,
the Use Cases document describes the usecases which will apply Detnet technologies, the Architecture
document defines the detnet architecture and explores the techniques used for extreme low data loss rates
and bounded latency, the Data Plane document identifies existing IP and MPLS, and other encapsulations
that run over IP and/or MPLS data plane technologies that can be considered as the base line solution for
deterministic networking data plane definition.
The Problem Statement document states that Detnet must propose a new model first to integrate
determinism in IT technology, afterwards, signalling used to establish multi-hop path which meets
deterministic requirements will be specified, and the tagging elements to be used identify the flows need to
be specified as well. Multi-hop path can be end to end from a host to another host, it also can be the
deterministic part of the whole path. To establish the deterministic path, one needs to compute path in
advance. Path computation can be based on the centralized or the distributed. Centralized path computation
can combine with PCE to achieve the global optimization. The draft proposes many aspects that need to be
clarified based on this model, such as how to install path computation on the network entities, how to
establish the path, how to make controller interact with network devices etc.. Distributed path computation
can be an enhancement to RSVP-TE. To enable RSVP-TE function, some issues such as improving CSPF to
compute constrained path, defining flow identification and so on need to be resolved.
The Use Cases document specifies the requirements such as bandwidth and latency to establish multi-hop
deterministic path for diverse industries. Various industry applications are included, such as professional
audio and video, electrical utilities, building automation system, gaming and so on. Using professional audio
and video as an example, when transmitting the professional audio and video on the packet -based network,
it’s required to eliminate congestion by guaranteeing the bandwidth to achieve the uninterrupted stream
playback, to meet the tolerance requirements of audio and video synchronize with bounded latency to make
the sound matched to the movements in the video. For packet-based transport network in cellar radio, the
allocated time that allows is 100us between the remote radio heads and the baseband processing unite, and
the transport loss assume almost zero, because errors can result in a reset of the radio interface, which can
reduce the throughput. To support the mobile services in 5G, the path with deterministic properties in
latency and loss needs to be established.

The Detnet architecture draft proposes three key points, which are reserving the data plane resources for
Detnet flows, creating fixed path for Detnet, and applying replication and elimination at different points for
high packet delivery ratio. The draft emphasises that the Detnet flow can’t exclude the traditional non-Detnet
flow presence, and to support Detnet flows, one doesn’t need to configure the special interface. Detnet uses
QoS parameters such as maximum and minimum end to end latency, and possibility of packet loss under any
assumptions to evaluate the deterministic properties. In the draft, Detnet architecture is composed of an
application plane, a control plane, and a network plane, which echoes the architecture of Software-defined
Networking (SDN). Detnet architecture is presented in Figure 1 below, which is cited from draft-ietf-detnet
architecture. Note that the number of PCE or intermediate node or NIC in the Figure 6.1.5-1 is just for
illustration.

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