Liaison statement
Liaison on IEEE 802.1 TSN projects to the IETF DetNet WG

We would like to inform you about our current projects that might be most
relevant for your ongoing work on enhanced DetNet data plane.

The IEEE P802.1DC “Quality of Service Provision by Network Systems” project
(https://1.ieee802.org/tsn/802-1dc/) specifies procedures, managed objects, and
YANG modules for Quality of Service (QoS) features specified in IEEE Std
802.1Q, such as per-stream filtering and policing, queuing, transmission
selection, flow control and frame preemption, in a network system that is not a
bridge. IEEE Std 802.1Q specifies QoS features for bridges; however, these
features are perfectly applicable to other devices, e.g., end stations,
routers, e.g., DetNet routers. In IEEE Std 802.1Q, the specifications of these
features are scattered, and coupled tightly to the operation of a bridge. IEEE
P802.1DC provides simple reference points to the IEEE Std 802.1Q QoS
specifications that are usable for non-bridge systems, and for managed objects
for these features that are not specific to bridges. A list of TSN QoS features
provided in Table 9-2 in IEEE P802.1DC. IEEE P802.1DC is at IEEE Standards
Association ballot.

The IEEE P802.1Qdv “Enhancements to Cyclic Queuing and Forwarding” project
(https://1.ieee802.org/tsn/802-1qdv/) specifies procedures, protocols and
managed objects to enhance Cyclic Queuing and Forwarding, comprising: a
transmission selection procedure that organizes frames in a traffic class
output queue into logical bins that are output in strict rotation at a constant
frequency; a procedure for storing received frames into bins based on the time
of reception of the frame; a procedure for storing received frames into bins
based on per-flow octet counters; a protocol for determining the phase
relationship between a transmitter’s and a receiver’s bin boundaries in time;
managed objects, Management Information Base (MIB), and YANG modules for
controlling these procedures; and an informative annex to provide guidance for
applying these procedures. This amendment also addresses errors and omissions
in the description of existing IEEE Std 802.1Q functionality. The existing
Cyclic Queuing and Forwarding (CQF) functionality in IEEE Std 802.1Q provides
bounded end-to-end delays, allows simple delay analysis methods, and does not
depend on per-flow state. These properties are critical for scaling up
Time-Sensitive Networking to large networks with a high number of simultaneous
flows, such as service provider networks. This amendment extends the existing
CQF functionality to support long physical links with high delay, processing
delay variations in bridges, non-time-synchronized ingress traffic, and/or
flows with a wider range of latency requirements. These properties enhance the
suitability of CQF for large networks. The time-based bin filling provides for
synchronized time division multiplexing (TDM). The count-based bin filling
(“paternoster”) provides ingress to a TDM domain and provides the QoS between
TDM domains. In addition, count-based bin filling without synchronized clocks
provides very low latency variation, which improves scaling when aggregating
flows. IEEE P802.1Qdv is at Task Group ballot.

We look forward to continued collaboration between our groups.