Liaison statement
New liaison to ITU-T SG13

Dear Colleagues,

 The Internet Engineering Task Force (IETF) Deterministic Networking (DetNet)
 Working Group (WG) appreciates your liaison statement informing us about your
 work. We would like to take the opportunity to inform you about our work and
 share some of our observations on the work referenced in your Liaison
 https://datatracker.ietf.org/liaison/1753/.

 For those not familiar with the IETF DetNet WG, a description of its charter
 cand be found at https://datatracker.ietf.org/wg/detnet/about/. The WG defines
 technology for Internet Protocol (IP) and Multiprotocol Label Switching (MPLS)
 networks to achieve bounded latency, including upper and lower bound, i.e.,
 bounded packet delay variation (sometimes referred to as jitter), bounded
 loss, and high availability/reliability. The DetNet WG collaborates with the
 IEEE 802.1 Time-Sensitive Networking (TSN) Task Group (TG) to define a common
 architecture for both Layer 2 and Layer 3.

 As a Layer 3 routed technology, one of the benefits of DetNet is that it
 provides desired deterministic characteristics at a larger scale than TSN. We
 would also like to point out that the way of working in the WG is
 evolutionary, from addressing more tractable problems towards more complex
 problems. We would like to inform you that the first phase of DetNet standards
 is mature, the majority have been published, see:
 https://datatracker.ietf.org/wg/detnet/documents/.  Considering your interest
 on large scale networks, we note the WG has already begun work on addressing
 larger scale networks. For example, see
 https://datatracker.ietf.org/meeting/interim-2021-detnet-01/session/detnet and
 https://datatracker.ietf.org/meeting/112/session/detnet.

 Upon reading your documents, we think that DetNet has technology solution
 components for many of the requirements you describe in your documents.
 However, we note that DetNet work appears to not be reflected  in either ITU-T
 Y.3113 or the Draft Recommendations attached to your liaison. Draft
 Recommendation ITU-T Y.IMT2020-jg-lsn references the use of the time-stamping
 function of RTP, UDP and TCP, implying the use case is IP packets, whereas the
 statement in this Draft (and ITU-T Y.3113) says, "Routing and upper layer
 functions lie outside the scope of this Recommendation". It is not clear if
 this solution is targeted to IP networks. As we have explained above, the
 DetNet WG is chartered by the IETF to provide bounded latency solutions for IP
 networks.

 The definition of domain (3.2.2 in ITU-T Y.3113 and ITU-T Y.IMT2020-fa-lg-lsn)
 cites RFC 8655, "Deterministic Networking Architecture". However, this
 definition of domain is different than RFC 8655, which focuses on the
 capabilities of the nodes, not their administrator. The definition of "large
 scale" in the provided documents is  "16 or more relay nodes". It is not clear
 where the number 16 is derived as a definition of a large-scale network.
 Please note that the DetNet WG defined solutions have no specific node count
 limitations and are support networks with more than 16 hops.

 We note that ITU-T Y.IMT2020-jg-lsn relies on a solution published in a
 Journal, and timestamping each packet of data flows. We suggest consulting
 IETF experts in the Timing over IP Connection and Transfer of Clock (tictoc)
 WG. We also note other relevant work in ITU-T SG15/Q13, IEEE 1588, IEEE 802.3,
 and IEEE 802.1.

As the IETF's Liaison statement to ITU-T-TSAG
(https://datatracker.ietf.org/liaison/1677/) expressed, if the intent of this
work covers IETF technologies, requirements or proposals, it is requested for
solution work to be discussed in IETF before any work in other SDOs. The
success of standardization efforts is dependent on collaboration among the
SDOs, as opposed to duplication of efforts and multiple diverging solutions,
which will not benefit the industry.

 The DetNet WG is interested in addressing the needs of the industry. If there
 are specific questions about DetNet or certain aspects that you consider as
 gaps to meet your requirements, we encourage your participants to bring those
 questions and discussion points directly to the DetNet WG. We are also always
 open to organize meetings for discussions about DetNet. We look forward to
 seeing DetNet being adopted by your members to support your specifications and
 we welcome all interested parties to join our efforts.