Shorewall users - May 2010 - IFB0 throughput 3-4% lower than expected

I have two boxes for the purpose of testing traffic control and
my knowledge thereof (which is at the inkling stage).  The boxes are
connected by 100Mbit ethernet cards via a switch.

For egress traffic via eth0 I achieve a throughput that is close to the
specified CEILing, particularly for values above 1mbit.  Ingress traffic
does not seem so well behaved.  Above about 1mbit rates achieved are
about 3-4% less than the CEILing.  Has this been your experience or am
I missing something?

Regards

Fog_Watch.


Shorewall 4.4.2.1

# egrep -v ''^#'' tcdevices 
1:eth0	- 20mbit		
2:ifb0	- 20mbit classify eth0

# egrep -v ''^#'' tcclasses 
1 2 100kbit 5000kbit 1 default
2:20 - 100kbit 5000kbit	1 default

# egrep -v ''^#'' tcrules   
2:T 192.168.3.21/32 192.168.3.27/32 tcp	- 5001

# egrep -v ''^#'' tcfilters 
2:20 192.168.3.27/32 192.168.3.21/32 tcp 5001

The egress demonstration below indicates that throughput was 5.02mbit as
averaged over 20 seconds, in comparison to the 5mbit asked for.
# iperf -c mr-cool -i4 -t20 -p 5001
------------------------------------------------------------
Client connecting to mr-cool, TCP port 5001
TCP window size: 16.0 KByte (default)
------------------------------------------------------------
[  3] local 192.168.3.21 port 60537 connected with 192.168.3.27 port
5001 [ ID] Interval       Transfer     Bandwidth
[  3]  0.0- 4.0 sec  2.49 MBytes  5.23 Mbits/sec
[ ID] Interval       Transfer     Bandwidth
[  3]  4.0- 8.0 sec  2.46 MBytes  5.16 Mbits/sec
[ ID] Interval       Transfer     Bandwidth
[  3]  8.0-12.0 sec  2.27 MBytes  4.75 Mbits/sec
[ ID] Interval       Transfer     Bandwidth
[  3] 12.0-16.0 sec  2.43 MBytes  5.10 Mbits/sec
[ ID] Interval       Transfer     Bandwidth
[  3] 16.0-20.0 sec  2.36 MBytes  4.95 Mbits/sec
[ ID] Interval       Transfer     Bandwidth
[  3]  0.0-20.1 sec  12.0 MBytes  5.02 Mbits/sec

This ingress demonstration indicates that throughput was 4.77mbit as
averaged over 20 seconds, in comparison to the 5mbit asked for.
# iperf -c mr-clever -i 4 -t20 -p 5001
------------------------------------------------------------
Client connecting to mr-clever, TCP port 5001
TCP window size: 16.0 KByte (default)
------------------------------------------------------------
[  3] local 192.168.3.27 port 44702 connected with 192.168.3.21 port
5001 [ ID] Interval       Transfer     Bandwidth
[  3]  0.0- 4.0 sec  2.30 MBytes  4.82 Mbits/sec
[ ID] Interval       Transfer     Bandwidth
[  3]  4.0- 8.0 sec  2.27 MBytes  4.77 Mbits/sec
[ ID] Interval       Transfer     Bandwidth
[  3]  8.0-12.0 sec  2.33 MBytes  4.88 Mbits/sec
[ ID] Interval       Transfer     Bandwidth
[  3] 12.0-16.0 sec  2.25 MBytes  4.72 Mbits/sec
[ ID] Interval       Transfer     Bandwidth
[  3] 16.0-20.0 sec  2.25 MBytes  4.72 Mbits/sec
[ ID] Interval       Transfer     Bandwidth
[  3]  0.0-20.0 sec  11.4 MBytes  4.77 Mbits/sec

Dump attached.

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On 5/29/10 12:47 AM, Fog_Watch wrote:
> I have two boxes for the purpose of testing traffic control and
> my knowledge thereof (which is at the inkling stage).  The boxes are
> connected by 100Mbit ethernet cards via a switch.
> 
> For egress traffic via eth0 I achieve a throughput that is close to the
> specified CEILing, particularly for values above 1mbit.  Ingress traffic
> does not seem so well behaved.  Above about 1mbit rates achieved are
> about 3-4% less than the CEILing.  Has this been your experience or am
> I missing something?
I see nothing in the generated TC configuration that would explain the
difference.

-Tom
-- 
Tom Eastep        \ When I die, I want to go like my Grandfather who
Shoreline,         \ died peacefully in his sleep. Not screaming like
Washington, USA     \ all of the passengers in his car
http://shorewall.net \________________________________________________



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