Markdown Version | Session Recording

Session Date/Time: 27 Jul 2022 14:00

RAW Session Minutes

Summary

The Reliable and Available Wireless (RAW) working group met to discuss the status of its various drafts, including the LDACS informational document, the RAW Architecture document, and the Use Cases document. Key discussions revolved around demonstrating working group consensus for the LDACS draft's publication, clarifying the scope and terminology of the RAW Architecture, and exploring new developments in Wi-Fi reliability (IEEE 802.11be) and multi-domain RAW scenarios. A significant technical discussion also took place regarding the application of Forward Error Correction (FEC) at the IP datagram level to enhance reliability over wireless links, and the broader challenge of adapting transport protocols to fully leverage deterministic networks.

Key Discussion Points

• LDACS Document Status (draft-ietf-raw-ldacs):

  • Niels ten Oever presented updates, emphasizing the document's intent to inform the IETF about LDACS (a Layer 2 technology for aeronautical IP transition) and seek council, rather than to standardize LDACS itself.
  • Significant IESG feedback questioned the document's relevance to IETF/RAW and noted a perceived lack of working group discussion.
  • LDACS is an ICAO-standardized Layer 2 technology that encapsulates IPv6 (UDP). It supports seamless handovers and employs PMIPv6 for local mobility and LISP for FCI multi-link mobility.
  • Link-layer security mechanisms (mutual authentication, key establishment, integrity/authenticity protection) are defined, with confidentiality for specific traffic.
  • Standards referenced in the document are behind a paywall but can be provided for review.
  • A poll indicated a significant number of participants (25 out of 39) had read the document.
  • It was noted that similar "informational" documents on other wireless technologies (e.g., 5G ULL, TSN) may emerge as valid inputs to RAW's work.

• Architecture Document (draft-ietf-raw-architecture):

  • Pascal Thubert presented the architecture, defining RAW as an Observe, Decide, Act (UDA) loop to adapt to dynamic wireless conditions. The document is intended to scope the working group's efforts.
  • The architecture is split into a conceptual "Architecture" document and a more practical "Framework" document.
  • RAW is positioned within the DetNet ecosystem, adding functions, particularly in the control plane (e.g., a "RAW Control Sublayer" with a Packet Stream Controller - PSC).
  • A key point of clarification was that RAW's role is to control or signal desired lower-layer behaviors (e.g., abstract ARQ requests) rather than performing these actions itself. The document needs to be updated to clearly reflect this distinction.
  • Requests were made for more detailed diagrams (signaling sequence, data/control flow) to illustrate interactions in "pure RAW" and "RAW+DetNet" scenarios.
  • Concerns were raised about potentially inventing new terminology for concepts already existing in the IETF.
  • The discussion affirmed that RAW's scope, as per its charter, is focused on the traditional reactive control (UDA loop), with advanced concepts like machine learning/predictive modeling requiring potential rechartering.

• Wi-Fi Update (IEEE 802.11):

  • Jerome Ori provided an update on IEEE 802.11 developments relevant to reliability.
  • 802.11be (Wi-Fi 7): Includes Multi-Link Operation (MLO) for increased reliability by using two links (e.g., 5GHz and 2.4/6GHz) to a single Access Point (AP). Multi-AP MLO was deferred to future generations.
  • Uplink OFDMA: Allows APs to schedule uplink traffic from multiple stations, enhancing reliability for scheduled sessions.
  • New Study Groups (SGs):
    • Ambient Power (AMP) SG: Explores energy harvesting, with potential implications for coexistence if it introduces noise.
    • Artificial Intelligence/Machine Learning (AIML) SG: Examines how ML can optimize Wi-Fi performance and reliability through coordination and data exchange between APs and stations.
    • Ultra High Reliability SG: Directly relevant to RAW, it will work on items such as multi-AP MLO and other high-reliability aspects of Wi-Fi.

• RAW Multi-Domain Extension (draft-ietf-raw-multi-domain-ext):

  • Carlos J. Bernardos presented the motivation for addressing multi-domain scenarios in RAW, covering different technology or administrative domains.
  • The draft aims to identify gaps in existing DetNet inter-PCE solutions and explore the need for inter-PSC coordination or APIs.
  • The chair indicated that RAW should primarily build upon DetNet's multi-domain work, adapting it for wireless contexts.

• Transports over RAW/DetNet:

  • Bob Moskowitz proposed applying Forward Error Correction (FEC) at the IP datagram level to enhance reliability over unreliable wireless links, using existing technologies like Reed-Solomon and potentially SCHC for encoding/fragmentation.
  • Marie-José Montpetit highlighted extensive prior work in the IETF Network Coding Research Group and transport area RFCs, noting Reed-Solomon's limitations for large/long data and potential IPR issues with some solutions. She stressed the need for on-the-fly decoding solutions.
  • The discussion emphasized that FEC and reliability are often transport layer functions, prompting a debate on the appropriate layering for these capabilities within the DetNet service model.
  • A fundamental open question was raised: how should transport protocols (like TCP) interact with or be designed for deterministic networks (RAW/DetNet) to avoid negating the underlying reliability and predictability guarantees? This involves considering whether to "educate" existing TCP implementations or explore new transport protocols.
  • It was broadly agreed that RAW's role would be to define the desired services from a transport layer, which can then be addressed by the Transport Area.

Decisions and Action Items

• LDACS Document (draft-ietf-raw-ldacs):
  • Action Item: All working group members are requested to send explicit comments and/or statements of support for the document to the mailing list to demonstrate consensus to the IESG.
  • Action Item: Authors to consider integrating more contextual information and explicit cross-references to RAW's use cases and technologies documents within the LDACS draft to clarify its relevance.
• Architecture Document (draft-ietf-raw-architecture):
  • Action Item: Authors to refine the document's text to clearly differentiate RAW's role in controlling lower-layer functions (e.g., ARQ) from the actual implementation of those functions by the lower layers.
  • Action Item: Collaborators are encouraged to assist Pascal Thubert by suggesting specific text edits and providing example diagrams (signaling sequence, data/control flow) to enhance clarity.
• Transport over RAW/DetNet:
  • Action Item: Participants interested in FEC over RAW/DetNet are encouraged to research existing IETF work on network coding and FEC (especially in the Transport Area and Network Coding Research Group) to inform future proposals suitable for wireless error patterns.

Next Steps

• Continue active discussions on the LDACS, Architecture, Multi-Domain, and Use Cases drafts via the mailing list and upcoming interim meetings.
• Call for Volunteers: The working group needs volunteers to begin drafting the Gap Analysis document, which will evaluate existing IETF technologies and identify gaps for RAW.
• IETF participants are encouraged to engage with the newly formed IEEE 802.11 Ultra High Reliability Study Group, given its direct relevance to RAW's objectives.
• The working group will continue to monitor and potentially engage with the Transport Area regarding suitable transport protocols for deterministic networks.