[Detnet] New Liaison Statement, "LS on 3GPP 5G System acting as a Detnet node"

[Liaison Statement Management Tool <[e-mail]>]

Title: LS on 3GPP 5G System acting as a Detnet node
Submission Date: 2022-10-25
URL of the IETF Web page: https://datatracker.ietf.org/liaison/1800/
Please reply by 2022-12-30
From: Susanna Kooistra <[e-mail]>
To: Lou Berger <[e-mail]>,János Farkas <[e-mail]>
Cc: János Farkas <[e-mail]>,Lou Berger <[e-mail]>,John Scudder <[e-mail]>,Andrew Alston <[e-mail]>,Alvaro Retana <[e-mail]>,Deterministic Networking Discussion List <[e-mail]>
Response Contacts: Lionel Morand <[e-mail]>,Susanna Kooistra <[e-mail]>
Technical Contacts: 
Purpose: For comment

Body: 1. Overall Description:
3GPP SA2 is working on extensions to the 5G System Time Sensitive Communications (TSC) framework for the support of IETF’s DetNet deterministic networking framework in a Study Item titled “Extensions to the TSC Framework to support DetNet” as documented in SP-211633. 

With respect to IETF DetNet specifications, the study makes the following assumptions:
	
- The study considers 5GS (5G system) acting as a DetNet node in the DetNet domain. 
- The study only considers the IP case, MPLS is not in the scope.
- The study considers the DetNet forwarding sub-layer related functions that are applicable to the 5GS. For the IP case according to RFC 8939 section 1, no service sub-layer function needs to be defined.

The 5GS DetNet node has interfaces towards the fixed network (N6 interface in 5GS) and on each User Equipment (UE) in the user plane. It is able to forward IP packets between any of its interfaces. It is connected to the DetNet Controller for centralized configuration. The 5GS DetNet node exposes information about its interfaces and neighbour nodes to the Controller. The 5GS DetNet node receives DetNet configuration including flow identification and QoS requirements from the DetNet Controller.

The 3GPP SA2 would like to ask IETF DetNet WG guidance on the following points:

A)	DetNet YANG data model currently only includes end-to-end QoS requirements for the DetNet flow such as max-latency and max-loss. On the other hand, the 5G DetNet node needs to be aware of the max-latency and max-loss requirements specific to the node. 

1. Is there any work chartered in the IETF to determine the node specific traffic requirements?

2. One approach considered in 3GPP has been to extend the DetNet YANG data model in such a way that it can contain the node specific requirements as well. Would this approach be very specific to 3GPP and 5GS DetNet node in which case it would be appropriate for the 3GPP to standardize the required YANG model extension, or would this be of more general interest for IETF DetNet deployments so that the standardization should take place in the IETF? Where possible 3GPP prefers a generic approach defined by IETF.

B)	3GPP is considering to specify to the possibility for reporting the 5GS node, interface and neighbor information to DetNet controller to help build up the network topology information. The reported information may include the DetNet node ID, the list of interfaces (including their IP address and prefix), and when applicable, the list of neighbouring nodes and other information. Has IETF any feedback on 3GPP DetNet exposing its  interface and IP configuration information as defined in RFCs 8343 and 8344 respectively, and on potentially exposing  route information from 5GS Detnet Note as defined in RFC 8349? Does IETF Detnet plan to recommend  any specific protocols between Detnet Nodes for topology discovery (similar to LLDP in Layer 2 TSN Networks ) or is it meant to be subject to deployments?

Is there any other information (e.g. Detnet Node capabilities) that is required by DetNet to be reported to the DetNet controller?

Please Note that 3GPP is going to do the normative work in Q1 2023 about 5G System Time-Sensitive Communications (TSC) framework for the support of IETF’s DetNet and thus would need IETF guidance (in Q4 2022) about whether IETF plans to do further work on these aspects in 2023.

2. Actions:
To IETF "Deterministic Networking (detnet)" WG:

ACTION: SA2 kindly asks IETF "Deterministic Networking (detnet)" WG to take the above information into account and to provide any feedback.

3. Date of Next TSG-SA WG2 Meetings:

             DATES 	          LOCATION	     CTRY
SA2#153e    October, 10-14th 	  Elbonia	     Any (e-meeting)
SA2#154	    November, 14-18th	  To be determine    To be determined
Attachments:

    SP-211633_was_SP-211596_was_SP-211311_rev02_rm
    https://www.ietf.org/lib/dt/documents/LIAISON/liaison-2022-10-25-3gpp-tsgsa-sa2-detnet-ls-on-3gpp-5g-system-acting-as-a-detnet-node-attachment-1.docx

    SP-211633_was_SP-211596_was_SP-211311_rev02_clean
    https://www.ietf.org/lib/dt/documents/LIAISON/liaison-2022-10-25-3gpp-tsgsa-sa2-detnet-ls-on-3gpp-5g-system-acting-as-a-detnet-node-attachment-2.docx

    S2-2207432 was 6103r09
    https://www.ietf.org/lib/dt/documents/LIAISON/liaison-2022-10-25-3gpp-tsgsa-sa2-detnet-ls-on-3gpp-5g-system-acting-as-a-detnet-node-attachment-3.docx