Liaison statement
LS/r on work items related to deterministic networking and deterministic communication service in ITU-T SG13 (IEEE 802.1-LS71)

This LS answers the liaison statements from IEEE 802.1 on deterministic
networking and deterministic communication.

This liaison statement answers IEEE 802.1-LS71 and LS66.
ITU-T Study Group 13 (SG13) would like to thank IEEE 802.1 for sharing
information related to collaboration on deterministic communication between
IEEE, IETF and 3GPP, as well as specific technical considerations on
deterministic networking and deterministic communication service related work
items in SG13.

In Q6/13, basic telecommunications operators are specifying common frameworks
and functional architectures in support of heterogeneous deterministic
networking technologies (for example, TSN and 5G). It may benefit the
integration of heterogeneous technologies. The academic organizations are
studying different deterministic networking techniques and related mechanisms.

Based on your request on editorial corrections indicated in IEEE 802.1-LS71,
Question 6 of SG13 (Q6/13) have agreed to adopt the following actions:

• In Y.3120, IEEE Std 802.1Q-2022 will be added in the bibliography as [b-IEEE
TSN] IEEE 802.1 Time-Sensitive Networking Task Group,
https://www.ieee802.org/1/tsn.

• In Y.3121, the term “central network configuration” will be revised as
“Centralized Network Configuration” in clause 4 (abbreviations and acronyms),
and accordingly the outdated TSN bibliography item will be replaced with
“[b-IEEE TSN] IEEE 802.1 Time-Sensitive Networking Task Group,
https://www.ieee802.org/1/tsn”.

For work items you are concerned with in IEEE 802.1-LS66, the following is the
latest information.

Y.det-qos-reqts-lan has been approved and published as Y.3121. The term
“gateway” is replaced with “interworking module” already. The context of Y.3121
is across multiple heterogeneous technology domains. Multiple TSN domains are
not the case, so it is out of the scope. If the networking technologies under
the common IEEE 802 architecture can work without interworking module, it is
also out of the scope. Interworking module is optional, only used when needed.
For 5G and TSN integration, DS-TT (Device side TSN Translator) and NW-TT
(Network side TSN Translator) can be regarded as “interworking module”, which
support interworking across two heterogeneous technology domains, e.g., 5G and
TSN.

Y.IMT2020-jg-lsn and Y.IMT2020-fa-lg-lsn have been approved and published as
Y.3118 and Y.3120, respectively. According to the comments, the following
modifications have been made on these two Recommendations:

• The term ‘large scale network’ was redefined as ‘A network or a set of
interconnected networks, with diameter of 16 or larger, in which the numbers of
flows and nodes are proportional to the diameter of the network’ in order to
reflect the proportional relationship between the diameter and other essential
parameters.

• The term ‘domain’ was elaborated not to be confused with the term
‘aggregation domain (AD)’ that was redefined as ‘A maximal set of the
interfaces of the consecutive relay nodes in the path, travelled by a flow, in
which the ‘flow membership’ of the flow aggregate the flow belongs to is
unaltered’.

Also, it was already stated that the TSN has both synchronous and asynchronous
solutions, e.g. in Y.3113 “The asynchronous traffic shaping (ATS) [b-IEEE
802.1Qcr] technique presented in TSN employs a node with an output port with
IRs for each input port, and a strict priority class-based FIFO system side by
side [b-Specht].”

The concern regarding the difficulty of accurate timestamping in Y.3118 is
indeed valuable, and greatly appreciated. It is expected to be mitigated soon
with the advancement of hardware technology, however, currently most of the
vendors support 1-step PTP, which requires timestamping-on-the-fly on 1Gbps
interfaces (e.g. Allied Telesis). Considering the timestamping in Y.3118 can be
done upon packet entrance to a network, not when departing from a source,
accurate timestamping will be able to be executed in 10 Gbps in near future.

Q6/13 is anticipated to cooperate closely with leading standardization
organizations (i.e., IEEE, IETF and 3GPP) to obtain the latest standard
progress and jointly promote deterministic networking technologies and services.