[Sis-SCPS-INTEREST] New SCPS RI Release on Open Channel Software...

[Feighery, Patrick D.]

Well there is a new release (version 1-1-128) of the SCPS RI on the
open channel software site -
https://www.openchannelsoftware.org/projects/SCPS/.

The following is a quick synopsis of the changes.

	1)  The SCPS RI rate control emission policy is based on a
watch dog timer firing at exactly every 10 msec.  For example, if the
outgoing rate over the RF is 1Mbps, then every time the watchdog timer
expires it will add exactly 1250 bytes (1Mbps/100/8) to the rate
control algorithm.  Unfortunately, if other processes are taxing the
CPU's resources and the timer does not expire at exactly 10 msec
intervals (10.01 or 11.0 msec for example), then the rate control will
be short, resulting in the link being under utilized.  This has been
corrected - we now look at the difference when the watch down timer was
previously fired and take and difference into account.

	2)  While we are on the subject of rate control and CPU
resources.  As I'm sure you all are aware of, the SCPS process tends to
be a CPU hog - to put it mildly...  This was intentional, because the
SCPS RI constantly polls the internal sockets to read packets from the
kernel as soon as possible. This unfortunately means the SCPS reference
implementation will consume all available CPU resources that it can.
This can have some adverse interactions with other processes trying to
consume the CPU's resources.  Now given this, I have added two
compilation flags that can be used to alleviate this issue.  The
configuration option -low_idle=yes will keep the RI from consuming CPU
resources during periods of idle traffic.  The configuration option
-low_cpu=yes can also be included to further reduce CPU resources when
traffic is being processed.  If the -low_cpu option is included then
the -low_idle option must also be include.  The next big question is
"Does this affect performance?"  The real answer is.. maybe and it
depends on the horsepower of the CPU and the data rates involved.  If
data rates are under 10 Mbps, you should be completely safe.  Try it
and see what happens.  Let me know if there are any issues.

	3)  I corrected some minor compilation issues based on the
combination of options used in the --configure script.

Best Regards

	Pat