RFC 8985

The RACK-TLP Loss Detection Algorithm for TCP, February 2021

File formats:

icon for HTML icon for text file icon for v3pdf icon for XML
Y. Cheng
N. Cardwell
N. Dukkipati
P. Jha
tcpm (tsv)

Cite this RFC: TXT  |  XML

DOI:  10.17487/RFC8985

Discuss this RFC: Send questions or comments to tcpm@ietf.org

Other actions: Submit Errata  |  Find IPR Disclosures from the IETF


This document presents the RACK-TLP loss detection algorithm for TCP. RACK-TLP uses per-segment transmit timestamps and selective acknowledgments (SACKs) and has two parts. Recent Acknowledgment (RACK) starts fast recovery quickly using time-based inferences derived from acknowledgment (ACK) feedback, and Tail Loss Probe (TLP) leverages RACK and sends a probe packet to trigger ACK feedback to avoid retransmission timeout (RTO) events. Compared to the widely used duplicate acknowledgment (DupAck) threshold approach, RACK-TLP detects losses more efficiently when there are application-limited flights of data, lost retransmissions, or data packet reordering events. It is intended to be an alternative to the DupAck threshold approach.

For the definition of Status, see RFC 2026.

For the definition of Stream, see RFC 8729.