LTD: Add Rationale for 10^-7 % Loss Ratio

This expanded item in the Throughput RFC description
explains a choice we made in Release A.
modified:   docs/requirements/vswitchperf_ltd.rst

JIRA: VSPERF-2??  (having trouble with JIRA on 3/26)

Change-Id: Icf5132f55c8b00f99c41439ca644655dfcdf017d
Signed-off-by: Al Morton <acmorton@att.com>
Reviewed-by: Maryam Tahhan <maryam.tahhan@intel.com>
Reviewed-by: Martin Klozik <martinx.klozik@intel.com>
Reviewed-by: Christian Trautman <ctrautma@redhat.com>

diff --git a/docs/requirements/vswitchperf_ltd.rst b/docs/requirements/vswitchperf_ltd.rst
index 8755976..72a93cb 100644 (file)
--- a/docs/requirements/vswitchperf_ltd.rst
+++ b/docs/requirements/vswitchperf_ltd.rst
@@ -959,7 +959,15 @@ largest frames of 9K bytes.
 Types of tests are:
 
 1. Throughput test defines the maximum number of frames per second
-   that can be transmitted without any error.
+   that can be transmitted without any error, or 0% loss ratio.
+   In some Throughput tests (and those tests with long duration),
+   evaluation of an additional frame loss ratio is suggested. The
+   current ratio (10^-7 %) is based on understanding the typical
+   user-to-user packet loss ratio needed for good application
+   performance and recognizing that a single transfer through a
+   vswitch must contribute a tiny fraction of user-to-user loss.
+   Further, the ratio 10^-7 % also recognizes practical limitations
+   when measuring loss ratio.
 
 2. Latency test measures the time required for a frame to travel from
    the originating device through the network to the destination device.