From: "Rich" 

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   I tried one of my own tools.  With a UDP payload size of 1K I can get =
50% network utilization of a 1GB adapter with 100% CPU utilization.  If = I
increase the payload size to 1025 bytes then I get 4% network = utilization
with around 35% CPU utilization.

Rich

  "Gregg N"  wrote in message =
news:428a3454{at}w3.nls.net...
  We have an application that sends UDP datagrams over gigabit ethernet. =
It=20
  was not achieving the performance we expected, so we ran some tests. =
When=20
  the packet size is 1024 bytes or less, we can send 40,000 packets per=20
  second, or about 312.5 Mbps. Not great, but acceptable. However, with =
packet=20
  sizes greater than 1024 bytes, we could not send more than about 3700=20
  packets per second, or about 28.9 Mbps (note this is on a 1Gb =
interface!).=20
  The process is not CPU bound, so that is not what is causing the =
limitation.

  We verified this using the iperf tool from this location:

  http://www.noc.ucf.edu/Tools/Iperf/default.htm

  which you can try yourself. Use the command

  iperf -u -l 1024 -c dummytarget -i 1 -b 500m -w 256k

  and see what it shows with -l 1024 and -l 1025. You can substitute a =
smaller=20
  value for -b (bandwidth) on a 100 Mb interface.

  Apparently, this has been encountered by others. For example, see

  =
http://groups.google.co.uk/group/comp.protocols.tcp-ip/browse_frm/thread/=
7ec2673b5471490f/409197bb36320ace?hl=3Den&lr=3D&ie=3DUTF-8&oe=
=3DUTF-8&safe=3Doff&rnum=3D1&prev=3D/groups%3Fhl%3Den%26lr%3D=
%26ie%3DUTF-8%26oe%3DUTF-8%26safe%3Doff%26selm%3D2003-01-27-01-42.0%2540c=
hch.demon.co.uk#409197bb36320ace

  and

  =
http://groups.google.co.uk/group/alt.winsock.programming/browse_frm/threa=
d/f05890d2b6b71452/8d8873987d71893b?tvc=3D1&q=3Dalanjmcf+1024&hl=3D=
en#8d8873987d71893b

  and

  http://www.chch.demon.co.uk/wintest/wintest.html

  However, I could not find anything about this on the MS web site. Does =

  anyone have any idea what is causing this?

  Thanks.

  Gregg

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   I tried
one of my own =
tools. =20
With a UDP payload size of 1K I can get 50% network utilization of a 1GB = adapter=20
with 100% CPU utilization.  If I increase the payload size to 1025
= bytes=20
then I get 4% network utilization with around 35% CPU =
utilization.
 
Rich
 

  "Gregg N" <invalid{at}invalid.invalid>">mailto:invalid{at}invalid.invalid">invalid{at}invalid.invalid>
= wrote in=20
  message news:428a3454{at}w3.nls.net...We=
 have=20
  an application that sends UDP datagrams over gigabit ethernet. It =
was not=20
  achieving the performance we expected, so we ran some tests. When =
the=20
  packet size is 1024 bytes or less, we can send 40,000 packets per =
second,=20
  or about 312.5 Mbps. Not great, but acceptable. However, with packet =
sizes=20
  greater than 1024 bytes, we could not send more than about 3700 =
packets=20
  per second, or about 28.9 Mbps (note this is on a 1Gb interface!). =
The=20
  process is not CPU bound, so that is not what is causing the=20
  limitation.We verified this using the iperf tool from this=20
  location:http://www.noc.uc" target="new">http://www.noc.uc=">http://www.noc.ucf.edu/Tools/Iperf/default.htm">http://www.noc.uc=
f.edu/Tools/Iperf/default.htmwhich=20
  you can try yourself. Use the commandiperf -u -l 1024 -c =
dummytarget=20
  -i 1 -b 500m -w 256kand see what it shows with -l 1024 and -l =
1025.=20
  You can substitute a smaller value for -b (bandwidth) on a 100 Mb=20
  interface.Apparently, this has been encountered by
others. For =

  example, seehttp://groups.google.co.uk/group/comp.protocols.tcp-ip/browse_frm=
/thread/7ec2673b5471490f/409197bb36320ace?hl=3Den&amp;lr=3D&amp;i=
e=3DUTF-8&amp;oe=3DUTF-8&amp;safe=3Doff&amp;rnum=3D1&amp;=
prev=3D/groups%3Fhl%3Den%26lr%3D%26ie%3DUTF-8%26oe%3DUTF-8%26safe%3Doff%2=
6selm%3D2003-01-27-01-42.0%2540chch.demon.co.uk#409197bb36320ace">http://=
groups.google.co.uk/group/comp.protocols.tcp-ip/browse_frm/thread/7ec2673=
b5471490f/409197bb36320ace?hl=3Den&amp;lr=3D&amp;ie=3DUTF-8&a=
mp;oe=3DUTF-8&amp;safe=3Doff&amp;rnum=3D1&amp;prev=3D/groups%=
3Fhl%3Den%26lr%3D%26ie%3DUTF-8%26oe%3DUTF-8%26safe%3Doff%26selm%3D2003-01=
-27-01-42.0%2540chch.demon.co.uk#409197bb36320aceand<=
A=20
  =
href=3D"http://groups.google.co.uk/group/alt.winsock.programming/browse_f=
rm/thread/f05890d2b6b71452/8d8873987d71893b?tvc=3D1&amp;q=3Dalanjmcf+=
1024&amp;hl=3Den#8d8873987d71893b">http://groups.google.co.uk/group/a=
lt.winsock.programming/browse_frm/thread/f05890d2b6b71452/8d8873987d71893=
b?tvc=3D1&amp;q=3Dalanjmcf+1024&amp;hl=3Den#8d8873987d71893b<=
BR>andhttp://www.chch" target="new">http://www.chch=">http://www.chch.demon.co.uk/wintest/wintest.html">http://www.chch=
.demon.co.uk/wintest/wintest.htmlHowever,=20
  I could not find anything about this on the MS web site. Does =
anyone have=20
  any idea what is causing=20
this?Thanks.Gregg

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