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Credit-based Flow Control Based on RSVP for RDMA transmission in WAN#

IETF 124 (Montreal) digest Program Core pick Montreal · 1–7 November 2025

Draft Session recording Materials

Jiayuan Hu, Zehua Hu, Tanxin Pi, Yongqing Zhu (China Telecom)

  • Why: The other half of lossless WAN RDMA: instead of notify-and-reroute, backpressure — credit-based flow control (the InfiniBand model) extended across the WAN for cross-AIDC training with elephant flows and extreme concurrency.
  • What: A credit-based flow control mechanism for RDMA traffic in SRv6 tunnels over the WAN, carried by an extended RSVP, aiming to provide high-throughput, zero-packet-loss transmission guarantees (from abstract only).
  • How: Introduces credit grants into RSVP signaling so that senders transmit only against granted credits, giving precise per-flow traffic control across SRv6 tunnels rather than drop-based or ECN-based response.
  • Where applicable: Cross-data-center AI training over SRv6 WAN — a China Telecom carrier scenario. Very early: an individual draft whose current revision (-01, September 2025) has actually expired on Datatracker without a replacement, so momentum is uncertain; treat as a design signal, not a trajectory, and watch whether it is revived or folded into the broader FANTEL work.