Subject: [tsvwg] Circuit-breaker -09

From: "Black, David" <[email-masked]>
Date: Mon, 23 Nov 2015 02:00:41 +0000

This is looking good.  The one serious issue here is that the discussion
of the perils of ECN needs to be aligned with the Tunnel Congestion Feedback
draft.

I also would like to see what Bob Briscoe thinks of the changes in -09.

-- Section 1

The first paragraph in Section 1 (Introduction) is a good fit to that
section (it was moved there from Section 6.1), but it should not be the
first paragraph in Section 1.  I would move it down to become the third
paragraph, so that the introduction starts with an introduction to circuit
breakers.

-- Nit (Section 1):

OLD
   The introduction of a congest control in TCP
NEW
   The addition of congestion control to TCP

[at a minimum, "a congest" -> "congestion"]

-- Nit (Section 1.1)

   o  Fast-Trip Circuit Breakers: The relatively short timescale used by
      this form of Circuit Breaker is intended to provide protection for
-->   network traffic of a single non-responsive flow or related group
      of non-responsive flows.

"of a single non-responsive flow" -> "from a single non-responsive flow"
(undo unintended side effect of primary edit to add "non-responsive")

-- Section 4

   o  A Circuit Breaker REQUIRED to define a measurement function to
      measure the level of congestion or loss.  This does not have to
      detect individual packet loss, but MUST specify a way to know that
      packets have been lost/marked from the traffic flow.  If Explicit
      Congestion Notification (ECN) is enabled [RFC3168], an egress
      meter MAY also count the number of ECN congestion marks/event per
      measurement interval, but even if ECN is used, loss MUST still be
      measured, since this better reflects the impact of persistent
      excessive congestion.  In this context, loss represents a reliable
      indication of congestion, as opposed to the finer-grain marking of
      incipient congestion that can be provided via ECN.

"REQUIRED" -> "is REQUIRED" in the first line.

Beyond that, the discussion of ECN in this paragraph needs to be aligned
with the Tunnel Congestion Feedback draft, as that draft uses ECN as part
of a measurement mechanism that could be used to drive a circuit breaker.
I think the Tunnel Congestion Feedback draft should be cited here as an
example of ECN-based measurements that could be used to drive a circuit
breaker if certain things are done to use the measurements correctly.

Thanks,
--David
----------------------------------------------------
David L. Black, Distinguished Engineer
EMC Corporation, 176 South St., Hopkinton, MA  01748
+1 (508) 293-7953             FAX: +1 (508) 293-7786
[email-masked]        Mobile: +1 (978) 394-7754
----------------------------------------------------