Liaison statement
Response to 3GPP SA2 LS on 3GPP 5G System acting as a DetNet node

The Internet Engineering Task Force (IETF) Deterministic Networking (DetNet)
Working Group (WG) appreciates your efforts in support of our technology. We
also thank you for your liaison statement
https://datatracker.ietf.org/liaison/1800/ informing us about the completion of
your Study Item on “Extensions to the TSC Framework to support DetNet”.

Please find below our considerations on your question items:

A)
Please note that in general, it is enough to provide the end-to-end delay
requirement in the YANG configuration. An SDN controller can perform the delay
engineering task and perform the appropriate configuration of the networking
nodes without informing them about their delay budget. The configuration of the
networking nodes by the SDN controller may also include configuration that is
beyond the DetNet YANG configuration, e.g., other IETF YANG or IEEE 802.1 TSN
YANG-specific configuration, which may affect the delay within that specific
node.

1.
For the above, there is no ongoing work in the DetNet WG to specify per-node
traffic requirements such as delay budget and we are not aware of any such work
in any other IETF WG.

2.
It is understood that a 5G System acting as a DetNet node is a special case for
which node-specific requirements would be beneficial. 5G-specific YANG
extensions could be specified with the involvement of the appropriate experts
in either of our organizations. Please note that IETF is contribution driven.
Thus, contributions would be required to start and conduct the specification of
the necessary YANG extensions. The DetNet Working Group would welcome such
contributions.

B)
DetNet does not specify the method to be used for topology discovery from the
multiple possibilities, e.g., based on Neighbor Discovery or from OSPF or IS-IS
routing protocols. Please note that in the case of an SDN approach, explicit
routing information may be provided by an SDN controller to the network nodes.
While not needed for all SDN use cases, network nodes can provide both explicit
and dynamic routing information to an SDN controller (e.g., according to RFC
8349).

We look forward to continued collaboration between our organizations.