Measuring ECN, presented by Geoff Huston at IETF 122
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APNIC Chief Scientist, Geoff Huston, presented on 'Measuring ECN' at IETF 122 held in Bangkok, Thailand from 15 to 21 March 2025.
Measuring ECN, presented by Geoff Huston at IETF 122
- 1. Measuring ECN Geoff Huston Chief Scientist, APNIC
- 2. Loss-Based Congestion Control ? Most of today’s network traffic uses an extremely simple algorithm that avoids networks collapsing under extreme overload: ? Continually increase the amount of data being pushed into the network ? Until a network queue overloads and the sender detects the consequent packet loss ? Halve the sending rate and do it again!
- 3. Refinements ? Change the congestion avoidance inflation algorithm ? Try to detect the difference between isolated damage packet loss and queue overload loss ? Better understand the relationship between network buffers and protocol performance
- 4. Is there a “better” way? Trigger the congestion response at the onset of queue formation rather than at the point of catastrophic queue collapse
- 5. BBR ? Detect queue formation through pulsed testing and delay sensitivity
- 6. Or get the router to help! May 1990!
- 7. Or get the router to help! January 1999!
- 8. Or get the router to help! January 1999!
- 9. Or get the router to help! September 2001!
- 10. Then … Crickets!
- 12. ECN Control Loop ? A router “marks” IP packets at the onset of queue formation with a bit signal ? The Receiver echoes this bit up into the transport protocol reverse flow ? The sender reduces its sending window size (and notifies the receiver that it was performed this window reduction) IP TCP
- 13. ECN Control Loop ? A router “marks” IP packets at the onset of queue formation with a bit signal ? The Receiver echoes this bit up into the transport protocol reverse flow ? The sender reduces its sending window size (and notifies the receiver that it was performed this window reduction) IP TCP
- 14. IP Header Version IHL Total Length Flags Identification Fragment Offset Time To Live Source Address Destination Address Options Padding Protocol Header Checksum Type of Service Precedence 0 1 2 3 4 5 6 7 D T R 0 0 Version Traffic Class Flow Label Payload Length Next Header Hop Limit Source Address Destination Address ECN Bits 0 0 – Non-ECN Capable Transport 0 1 – ECN Capable TransporT 1 0 - ECN Capable Transport 1 1 – Congestion Experienced
- 15. TCP TCP Destination Port Source Port Sequence Number Acknowledgment Number Data offset F I N S Y N U R G A C K P S H R S T Window Checksum Urgent Pointer Padding TCP Options TCP Data E C E C W R ECE – receiver back to sender – CE received CWR – sender to receiver – Congestion Window Reduced SYN+ECE+CWR – ECN capable on session start SYN+ACK+ECE – ECN capable response
- 16. ECN Measures Packet Count (by remote IP addresses) for Feb/March 2025 0. IP Sources 303,545,388 1. IP ECT 6,815,753 (2.45% of sources) 2. IP CE 1,098,965 (16.12% of ECT sources)
- 17. ECN Measures Packet Count (by remote IP addresses) 0. IP Sources 303,545,388 1. IP ECT 6,815,753 (2.45% of sources) 2. IP CE 1,098,965 (16.12% of ECT sources) 3. TCP ECN Opt 7,478,207 (2.46% of sources) 4. TCP ECE (Rec’d) 20,862 (0.27% of TCP sources) 5. TCP CWR (Rec’d) 335,209 (4.48% of TCP sources)
- 18. IP ECT by Country
- 19. TCP ECN Option by Country
- 20. Country Table
- 21. Thanks!