[tor-commits] [torflow/master] Clean up the spec a tad.

[mikeperry at torproject.org]

commit 2d4b7ba817e6c398f5b0137d893d96957ac2adf7
Author: Mike Perry <mikeperry-git at fscked.org>
Date:   Sat Dec 3 18:13:37 2011 -0800

    Clean up the spec a tad.
---
 NetworkScanners/BwAuthority/README.spec.txt |   15 ++++++++-------
 1 files changed, 8 insertions(+), 7 deletions(-)

diff --git a/NetworkScanners/BwAuthority/README.spec.txt b/NetworkScanners/BwAuthority/README.spec.txt
index 5eb0661..a1b732e 100644
--- a/NetworkScanners/BwAuthority/README.spec.txt
+++ b/NetworkScanners/BwAuthority/README.spec.txt
@@ -371,10 +371,6 @@
    The bandwidth authorities measure F_node: the filtered stream
    capacity through a given node (filtering is described in Section 1.6).
 
-   In PID control, we add in this extra failure rate as a damper, to prevent
-   the PID control system from driving nodes to CPU overload. Once nodes
-   begin failing circuits, we want to stop devoting more capacity.
-
    The PID Setpoint, or target for each node is F_avg: the average F_node
    value observed across the entire network.
 
@@ -412,9 +408,9 @@
    hours. Since the bandwidth authorities also take on the order of
    hours to measure a slice of nodes, we do nothing special here.
 
-   For Guard nodes however, clients have minimum rotation rate of 4-6
+   For Guard nodes however, clients try to keep their Guards for 4-6
    weeks. However, on the assumption that they rotate more frequently
-   than this, we set our Guard feedback interval to 2 weeks.
+   than this in practice, we set our Guard feedback interval to 2 weeks.
 
    Guard measurements are also used without feedback whenever new
    measurements are available, to compensate for changes in Guard flag
@@ -428,7 +424,7 @@
    determining when to report a measurement.
 
    The integral component, pid_error_sum is subjected to a decay factor
-   of 20% per interval, to prevent unbounded growth in cases without
+   per each interval, to prevent unbounded growth in cases without
    convergence.
 
    The differential component is a simple delta, calculating by
@@ -521,6 +517,11 @@
        of the circ_error and the original pid_error as the new
        pid_error.
 
+       We use this to prevent the PID control system from driving nodes
+       to CPU overload. Once nodes begin failing circuits, we want to stop
+       devoting additional capacity to them (and decrease it proportional
+       to their failure rate relative to the rest of the network).
+
     "bwauthbestratio=0"
        If absent, the larger of stream bandwidth vs filtered bandwidth
        is used to compute F_node.