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Session Date/Time: 16 Mar 2026 03:30

DTN

IETF 125 Session 1 Minutes

Summary

The DTN Working Group held its first session of IETF 125, led by chairs Edward Birrane and Rick Taylor (both participating remotely). The session covered an introduction of the new Area Director (AD), technical presentations on OpenFlow encapsulation over Bundle Protocol (BP), status updates and interoperability results for several working group drafts, and a discussion on the evolving definition of reliability and custody within DTN.

Key Discussion Points

AD Transition

Outgoing AD Eric Vyncke introduced Tommy Pauly as the incoming AD responsible for the DTN working group starting Wednesday of the meeting week.

Encapsulation of OpenFlow over BP

Presenter: Xiaojing Fan

• Problem: OpenFlow traditionally requires stable TCP/IP paths, which are unavailable in DTN environments.
• Proposed Solution: Use the Bundle Protocol (BP) as a transport for OpenFlow control messages, treating OpenFlow PDUs as BP Application Data Units (ADUs).
• Technical Details:
  • Messages are mapped one-to-one (one OpenFlow message per bundle).
  • Communication is bidirectional using stable, unique BP Endpoint IDs (EIDs).
  • Receivers must handle duplicate delivery and re-ordering using transaction IDs and sequence numbers.
  • Experimental verification was performed using the ION-DTN implementation in satellite-to-ground scenarios.
• Discussion: Rick Taylor noted that mapping PDUs directly to ADUs (rather than tunneling IP) is the correct architectural approach for BP.

Sipos All-Topics Update

Presenter: Brian Sipos

• draft-ietf-dtn-bpsec-cose (BPSec COSE Context):
  • Completed Working Group Last Call (WGLC).
  • Underwent successful interoperability testing between two independent implementations.
  • Recent changes include profiling for HKDF algorithms and PKIX profile alignment with CA/Browser Forum.
  • Action: The document is ready for IESG review. A shepherd is needed for the write-up.
• draft-ietf-dtn-eid-pattern (EID Patterns):
  • Provides a framework for patterns on EID schemes (text and binary forms).
  • Recent changes improved terminology, normalization, and binary forms for IPN ranges.
  • Open Issue: Determining interoperability minimums (e.g., matching a minimum of 10 items/intervals).
  • Decision: Known changes and the suggested minimum of 10 should be applied before the document moves to Last Call.
• draft-ietf-dtn-udpcl (UDP Convergence Layer V2):
  • Introduces congestion control and Path MTU discovery for UDP.
  • Added Appendix B to explain congestion control (CC) algorithm selection.
  • Brian Sipos presented experimental results showing successful congestion control using the "Prague" algorithm with ECN markings.
  • Open Issue: Requires IANA assignments for IP multicast.
• draft-ietf-dtn-bp-sand (SAND):
  • Remains stable. It leverages the UDPCL multicast for zero-configuration discovery.
• draft-sipos-dtn-manifest-block (Manifest Block):
  • An individual draft defining a block to record which blocks existed at the time of manifest creation. This is intended to aid security and path auditing.

BTPU Updates

Presenter: Rick Taylor

• draft-ietf-dtn-btpu (Bundle Transfer Protocol - Unidirectional):
  • Designed for lossy, frame-based link layers (e.g., CCSDS, Ethernet) without requiring an IP stack.
  • Major Change: Reverted from descending segment indices back to ascending indices (starting at 0) with an explicit "End" marker for better rate-control flexibility.
  • Metadata was renamed to "Hints" to avoid confusion.
  • Features a rolling "transfer window" for passive synchronization on unidirectional links.
  • Open Question: The current default transfer window size is set to 16. The chair requested feedback on this value from implementers.
• draft-ietf-dtn-btpu-fec (BTPU FEC):
  • Aligned with the changes in the main BTPU document. It leverages the RFC 6363 FEC framework.

Reliability Considerations for DTN Update

Presenter: Edward Birrane

• Discussion focused on distinguishing between "custody transfer" and "reliability."
• Reliability Classes:
  • Class 1: Best effort.
  • Class 2: "Store Until Forward" (the RFC 9171 default).
  • Class 3: Guaranteed custodian (at least one node along the path).
  • Class 4: Redundant/Independent custodians.
• Key Concept: Discussion on whether custody signals should be node-to-node (breaking information hiding) or if they should signal a network-level reliability commitment.

Decisions and Action Items

• draft-ietf-dtn-bpsec-cose: The chairs called for a volunteer to act as the Document Shepherd to move the draft to the IESG.
• draft-ietf-dtn-eid-pattern: Brian Sipos to update the draft with a proposed interoperability minimum (e.g., 10) before entering Last Call.
• draft-ietf-dtn-udpcl: Tommy Pauly (incoming AD) to assist with the pending IANA IP multicast assignment request.

Next Steps

• Further discussion on EID patterns and the BTPU transfer window size will continue on the mailing list.
• The "Reliability Considerations" discussion will be moved to the mailing list to address the proposed reliability classes and the definition of custodial signaling.
• Session 2 (90 minutes) will continue later in the week to cover additional technical topics.

Session Date/Time: 17 Mar 2026 06:00

DTN

IETF 125 - Session B Minutes

Summary

The DTN working group met for a second session at IETF 125 to discuss application protocols (CoAP over BP), security enhancements (SBAM), network management and operations (Echo, ARP, and Peering protocols), convergence layers (Ethernet and QUIC), and the architectural update to RFC 4838. Key highlights included progress on the CoAP over BP draft, the integration of manifest blocks into the SBAM security proposal, and a strong consensus on the need to update the DTN architecture to reflect the evolution of the Bundle Protocol.

Key Discussion Points

1. CoAP over Bundle Protocol

Presenter: Carles Gomez Slides: Sipos all-topics (Covering draft-ietf-dtn-coap-over-bp)

• Updates: Version 02 includes refinements to CoAP block-wise transfer parameters, specifically max_payloads. The default value of 10 (from RFC 9177/6928) may need adjustment for deep space environments vs. terrestrial wireless.
• Security: New content in Section 11 focuses on security requirements for requests/responses. A suggestion from Marco Tiloca to use the padding option from the CORE working group’s cacheable OSCORE draft was discussed as a mitigation for traffic analysis.
• IANA: Requesting a well-known service number in the IPN scheme registry.
• Discussion: Ed Birrane inquired about implementations; Carles Gomez confirmed a public reference implementation led by Ana Calveras (UPC) exists.

2. BPSec Source-added Block Authentication and Monitoring (SBAM)

Presenter: Bhagya Slides: Sipos all-topics (Covering draft-ietf-dtn-bpsec-sbam)

• Mechanism: SBAM provides end-to-end integrity for security operations. It has been redesigned to use draft-ietf-dtn-bpsec-cose manifest blocks for auditing (source-added) and reporting (intermediary-added).
• Key Identifiers: Bhagya raised the need for unique key identifiers in the audit record.
• Discussion: Rick Taylor and Brian Sipos discussed the overlap with draft-ietf-dtn-bpsec-cose. Brian Sipos suggested that reusing BPSec mechanisms (audit pairs) is preferable to creating new structures. Ed Birrane supported the migration to the manifest block design.

3. BP Echo Service

Presenter: Rick Taylor Slides: Sipos all-topics (Covering draft-taylor-dtn-echo)

• Proposal: A simple reflector service for RTT measurement and connectivity verification. It involves swapping source/destination EIDs while preserving timestamps and lifetimes.
• Discussion: Scott Burleigh expressed concern regarding BIB/BCB integrity if the primary block is manipulated during reflection. Rick Taylor clarified that flags can exclude the primary block from the signature for this purpose. Felix Walter suggested differentiating between simple ADU reflection and bundle-level reflection. Erik Nye supported adding a DTN demux column to the IANA registry but cautioned about naming collisions.

4. BP ARP (Address Resolution Protocol)

Presenter: Rick Taylor Slides: Sipos all-topics (Covering draft-taylor-dtn-arp)

• Function: Maps Convergence Layer (CL) adjacencies to EIDs to bootstrap routing and draft-ietf-dtn-bp-sand.
• Addressing: Initially proposed using the "Local Node" address (ipn:!).
• Discussion: Felix Walter suggested using the anycast naming scheme instead of modifying the local-node behavior. Rick Taylor agreed this was a cleaner approach and would explore well-known anycast group IDs.

5. DTN Peering Protocol (DPP)

Presenter: Rick Taylor Slides: Openflow over BP (Note: Presented as "BGP for DTN", covering draft-taylor-dtn-peering)

• Concept: A mechanism for independently administered DTN domains (e.g., NASA and ESA) to share relaying capabilities without surrendering internal routing control.
• Design: Uses gRPC for transport between "speakers" and DNS for identity assertion. It utilizes longest-prefix-matching and specificity scoring for draft-ietf-dtn-eid-pattern.

6. BTPU Updates: Ethernet and QUIC CL

Presenter: Erik Nye Slides: BTPU Updates (Covering draft-ietf-dtn-btpu and related CLs)

• Ethernet: Requests for an EtherType and multicast MAC to support draft-ietf-dtn-btpu directly over Ethernet.
• QUIC CL: Mapping bundle transfers to QUIC streams. Provides reliable and unreliable (via datagrams) delivery.
• Discussion: Season raised security concerns regarding the synchronous nature of QUIC/TLS handshakes in high-latency environments. Erik Nye noted the initial focus is terrestrial relay, but asynchronous keying may be required for deep space.

7. 4838bis Discussion

Presenter: Scott Burleigh Slides: 4838bis Discussion

• Rationale: RFC 4838 (DTN Architecture) is 19 years old. An update is needed to align the architecture with BPv7 and modern DTN operations to prevent confusing new adopters.
• Plan: Retain core concepts (Store-and-Forward, Custody) but revise or remove outdated items and add new concepts like TVR (Temporal Vector Routing) and modern security models.

Decisions and Action Items

• SBAM: The authors will move the discussion regarding Key ID requirements and the use of the extensible security context registry to the mailing list.
• BP Echo: Rick Taylor to refine the draft to address concerns regarding security block manipulation and consider the "simple ADU reflection" vs. "full bundle reflection" use cases.
• BP ARP: Rick Taylor will pivot the addressing scheme from "Local Node" to an anycast-based approach based on feedback from Felix Walter.
• BTPU/Ethernet: The chairs will take the adoption call for the BTPU over Ethernet document to the mailing list.

Next Steps

• Further technical discussion on the QUIC CL security handshake (Season and Erik Nye) to take place on the mailing list.
• Continued coordination on the EID pattern subset required for the Peering Protocol.
• Scott Burleigh to lead the effort on the 4838bis architectural update.

Related Documents

draft-ietf-dtn-bp-sand, draft-ietf-dtn-bpsec-cose, draft-ietf-dtn-bpsec-sbam, draft-ietf-dtn-btpu, draft-ietf-dtn-btpu-fec, draft-ietf-dtn-coap-over-bp, draft-ietf-dtn-eid-pattern, draft-ietf-dtn-udpcl, draft-sipos-dtn-manifest-block, draft-taylor-dtn-arp, draft-taylor-dtn-echo, draft-taylor-dtn-peering