Subject: [tcpm] [Technical Errata Reported] RFC8312 (5907)

From: RFC Errata System <[email-masked]>
Date: Wed, 13 Nov 2019 18:07:10 -0800 (PST)

The following errata report has been submitted for RFC8312,
"CUBIC for Fast Long-Distance Networks".

--------------------------------------
You may review the report below and at:
https://www.rfc-editor.org/errata/eid5907

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Type: Technical
Reported by: Elliott Ecton <[email-masked]>

Section: 5.1

Original Text
-------------
 +--------+----------+-----------+------------+-----------+----------+
   |   Loss |  Average |   Average |      CUBIC |     CUBIC |    CUBIC |
   | Rate P |    TCP W |   HSTCP W |   (C=0.04) |   (C=0.4) |    (C=4) |
   +--------+----------+-----------+------------+-----------+----------+
   |  10^-2 |       12 |        12 |         12 |        12 |       12 |
   |  10^-3 |       38 |        38 |         38 |        38 |       59 |
   |  10^-4 |      120 |       263 |        120 |       187 |      333 |
   |  10^-5 |      379 |      1795 |        593 |      1054 |     1874 |
   |  10^-6 |     1200 |     12279 |       3332 |      5926 |    10538 |
   |  10^-7 |     3795 |     83981 |      18740 |     33325 |    59261 |
   |  10^-8 |    12000 |    574356 |     105383 |    187400 |   333250 |
   +--------+----------+-----------+------------+-----------+----------+

                                  Table 1

Corrected Text
--------------
 +--------+----------+-----------+------------+-----------+----------+
   |   Loss |  Average |   Average |      CUBIC |     CUBIC |    CUBIC |
   | Rate P |    TCP W |   HSTCP W |   (C=0.04) |   (C=0.4) |    (C=4) |
   +--------+----------+-----------+------------+-----------+----------+
   |  10^-2 |       12 |        12 |          3 |         6 |       11 |
   |  10^-3 |       38 |        38 |         19 |        33 |       59 |
   |  10^-4 |      120 |       263 |        120 |       187 |      333 |
   |  10^-5 |      379 |      1795 |        593 |      1054 |     1874 |
   |  10^-6 |     1200 |     12279 |       3332 |      5926 |    10538 |
   |  10^-7 |     3795 |     83981 |      18740 |     33325 |    59261 |
   |  10^-8 |    12000 |    574356 |     105383 |    187400 |   333250 |
   +--------+----------+-----------+------------+-----------+----------+

                                  Table 1

Notes
-----
The CUBIC average window sizes for 10^2 and 10^3 are incorrect in the original text using expression 6.

Instructions:
-------------
This erratum is currently posted as "Reported". If necessary, please
use "Reply All" to discuss whether it should be verified or
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can log in to change the status and edit the report, if necessary. 

--------------------------------------
RFC8312 (draft-ietf-tcpm-cubic-07)
--------------------------------------
Title               : CUBIC for Fast Long-Distance Networks
Publication Date    : February 2018
Author(s)           : I. Rhee, L. Xu, S. Ha, A. Zimmermann, L. Eggert, R. Scheffenegger
Category            : INFORMATIONAL
Source              : TCP Maintenance and Minor Extensions
Area                : Transport
Stream              : IETF
Verifying Party     : IESG

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From: Neal Cardwell <[email-masked]>
Date: Thu, 14 Nov 2019 12:53:14 -0500

> "CUBIC for Fast Long-Distance Networks".

I strongly suspect that the original text is correct.

Note that the proposed edit would cause the average congestion window
size of CUBIC to be below that of "TCP W", the Reno [RFC5681] window,
in the cases with loss rates of 10^-2 and 10^-3. But as mentioned in
section 4.2. "TCP-Friendly Region", where the native CUBIC curve
computation produces a target congestion window that is lower than the
congestion window Reno would use, the CUBIC algorithm instead uses the
Reno target congestion window. So the average congestion window size
of CUBIC should not be below that of Reno. I believe that is why in
the original table the average congestion window for "TCP W" and CUBIC
match in cases with loss rates of 10^-2 and 10^-3 and with CUBIC using
C=0.04 or C=0.4.

Are there tests or simulations showing CUBIC achieving a lower
congestion window in these cases with loss rates of 10^-2 and 10^-3?

best,
neal

---

From: Neal Cardwell <[email-masked]>
Date: Fri, 15 Nov 2019 14:54:11 -0500

> congestion window in these cases with loss rates of 10^-2 and 10^-3?

I got a bounce from my "reply-all". It seems there was a typo in the
e-mail address of the report, and it should have been:
  Elliott Ecton <[email-masked]>
...rather than:
  Elliott Ecton <[email-masked]>

I am following up to make sure the [email-masked] address
has the reply and the thread has the correct e-mail address.

best,
neal