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Network Performance 1GB ports

 
 
Personne
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Posts: n/a
 
      11-13-2009
Hi,

I have a Cisco 2960 with 2 x 1 GB ports. I have plugged a computer on
each port. and run a netperf (http://www.osnms.com/2008/07/network-
performance-monitor-using-netperf/) between my 2 computers, and I'm
very surprise and disappointed by the performance I get

Info:
Nothing else is connected to the switch (expect the power )
The 2 x 1GB ports are configured to 1000 Full Duplex
The 2 computers NIC are configured to 1000 Full Duplex
The 2 cables I use are Cat5e

The speed I get is only 60Mbytes/sec (or 480 Mbits/s) compare to the
theoretical speed of a 1 GB port 125MBytes/s

Why is this ?

 
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Mark Huizer
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      11-13-2009
The wise Personne enlightened me with:
> Hi,
>
> I have a Cisco 2960 with 2 x 1 GB ports. I have plugged a computer on
> each port. and run a netperf (http://www.osnms.com/2008/07/network-
> performance-monitor-using-netperf/) between my 2 computers, and I'm
> very surprise and disappointed by the performance I get
>
> The speed I get is only 60Mbytes/sec (or 480 Mbits/s) compare to the
> theoretical speed of a 1 GB port 125MBytes/s
>
> Why is this ?


What performance do you get when you connect the two PC's directly with
a cross cable? What network cards do you have? Did you try with jumbo
frames?

The performance limit doesn't have to be in the Cisco, and theoretical
speeds are sometimes just that: theoretical.
I would expect that you need decent PC's and decent network cards to
fill 1Gb. And for real usage (where the PC has to use disk etc) I wonder
if you can get anywhere near that.

Mark
 
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Personne
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Posts: n/a
 
      11-13-2009
Mark,

I did already this test before your post, and you are correct it
doesn't come from the CIsco Switch. With a crosscable (5e) between my
2 computers (not servers) I get the same speed rate (around 50 and 60
MBytes/s)
I know TCP/IP has some overhead but 52% is really a lot.
- Could be a driver issue
- I haven't tried yet Jumbo Frame (I'm not even sure I have the option
in my Windows drivers)
- Netperf doesn't use disk, it is a RAM-RAM test, so no disk overhead.


On Nov 13, 10:04*am, Mark Huizer <xaa
(E-Mail Removed)> wrote:
> The wise Personne enlightened me with:
>
> > Hi,

>
> > I have a Cisco 2960 with 2 x 1 GB ports. I have plugged a computer on
> > each port. and run a netperf (http://www.osnms.com/2008/07/network-
> > performance-monitor-using-netperf/) between my 2 computers, and I'm
> > very surprise and disappointed by the performance I get

>
> > The speed I get is only 60Mbytes/sec (or 480 Mbits/s) compare to the
> > theoretical speed of a 1 GB port 125MBytes/s

>
> > Why is this ?

>
> What performance do you get when you connect the two PC's directly with
> a cross cable? What network cards do you have? Did you try with jumbo
> frames?
>
> The performance limit doesn't have to be in the Cisco, and theoretical
> speeds are sometimes just that: theoretical.
> I would expect that you need decent PC's and decent network cards to
> fill 1Gb. And for real usage (where the PC has to use disk etc) I wonder
> if you can get anywhere near that.
>
> Mark


 
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Mark Huizer
Guest
Posts: n/a
 
      11-13-2009
The wise Personne enlightened me with:
> Mark,
>
> I did already this test before your post, and you are correct it
> doesn't come from the CIsco Switch. With a crosscable (5e) between my
> 2 computers (not servers) I get the same speed rate (around 50 and 60
> MBytes/s)
> I know TCP/IP has some overhead but 52% is really a lot.
> - Could be a driver issue
> - I haven't tried yet Jumbo Frame (I'm not even sure I have the option
> in my Windows drivers)
> - Netperf doesn't use disk, it is a RAM-RAM test, so no disk overhead.
>


I know it's a RAM to RAM test, that's why I said that a 'real life case'
probably would be even worse.
TCP/IP doesn't have to be a problem, and you can account for that in
your test. Not sure what you are testing precisely with netperf, but the
parameters you are using can have enough impact on your measurements. I
normally use iperf, I don't know netperf, but it might have the same
options. You'll see different measurements for e.g. udp vs tcp, since
udp is connectionless so no problems with window sizes. If you are using
tcp, play around with the window size/buffer size, and see the
difference.
You might play with smaller/bigger sizes, you'll see a big difference.

And I'm not entirely sure where PC hardware is nowadays. Can't tell you
the max bandwidth of memory, PCI busses, etc. And you will see a big
difference between using an el cheapo NIC and a topline NIC that does
all kinds of offloading, because it will do stuff in hardware that your
CPU doesn't have to worry about anymore.

And to stress that again: don't expect to get anywhere near Gbit speed
in real life usage with standard pc hardware. It's just not realistic.

Mark
 
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Personne
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Posts: n/a
 
      11-13-2009
Mark,
"And to stress that again: don't expect to get anywhere near Gbit
speed in real life usage with standard pc hardware. It's just not
realistic."

I'm not expecting to get a real 1GB connection, but I'm surprise to
get only 50% of the theoretical number on a 1GB connection.
When I use a 100M connection (with cross cable or with a switch) I get
88% of the 100MB bandwidth.

Thanks,
Personne

On Nov 13, 11:53*am, Mark Huizer <xaa
(E-Mail Removed)> wrote:
> The wise Personne enlightened me with:
>
> > Mark,

>
> > I did already this test before your post, and you are correct it
> > doesn't come from the CIsco Switch. With a crosscable (5e) between my
> > 2 computers (not servers) I get the same speed rate (around 50 and 60
> > MBytes/s)
> > I know TCP/IP has some overhead but 52% is really a lot.
> > - Could be a driver issue
> > - I haven't tried yet Jumbo Frame (I'm not even sure I have the option
> > in my Windows drivers)
> > - Netperf doesn't use disk, it is a RAM-RAM test, so no disk overhead.

>
> I know it's a RAM to RAM test, that's why I said that a 'real life case'
> probably would be even worse.
> TCP/IP doesn't have to be a problem, and you can account for that in
> your test. Not sure what you are testing precisely with netperf, but the
> parameters you are using can have enough impact on your measurements. I
> normally use iperf, I don't know netperf, but it might have the same
> options. You'll see different measurements for e.g. udp vs tcp, since
> udp is connectionless so no problems with window sizes. If you are using
> tcp, play around with the window size/buffer size, and see the
> difference.
> You might play with smaller/bigger sizes, you'll see a big difference.
>
> And I'm not entirely sure where PC hardware is nowadays. Can't tell you
> the max bandwidth of memory, PCI busses, etc. And you will see a big
> difference between using an el cheapo NIC and a topline NIC that does
> all kinds of offloading, because it will do stuff in hardware that your
> CPU doesn't have to worry about anymore.
>
> And to stress that again: don't expect to get anywhere near Gbit speed
> in real life usage with standard pc hardware. It's just not realistic.
>
> Mark


 
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Rob
Guest
Posts: n/a
 
      11-13-2009
Personne <(E-Mail Removed)> wrote:
> Mark,
> "And to stress that again: don't expect to get anywhere near Gbit
> speed in real life usage with standard pc hardware. It's just not
> realistic."
>
> I'm not expecting to get a real 1GB connection, but I'm surprise to
> get only 50% of the theoretical number on a 1GB connection.
> When I use a 100M connection (with cross cable or with a switch) I get
> 88% of the 100MB bandwidth.


That is because the limit is not some percentage of the full bandwidth,
but an absolute number. You are not hitting the limit of bus speed,
cpu speed, memory speed etc. with your 100 Mbit network.

I have done similar tests between Linux systems and got a little higher
rates (600 Mbit if I remember correctly) but also not 1 Gbit.
But I wasn't as surprised as you seem to be.

(I was testing the troughput of a 3com Layer-3 switch when compared to a
cisco router)
 
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Thrill5
Guest
Posts: n/a
 
      11-14-2009
Getting 500Mb/s+ throughput on a standard PC is pretty good. Now you
should know why servers cost so much, all parts of the architecture are
optimized for throughput.

The reason you only get 88% on a 100MB/s connection is because you can't
actually use 100% of the bandwidth. The counters don't count the ethernet
frame, plus there is a a required inter-frame gap between ethernet frames.


"Personne" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
Mark,
"And to stress that again: don't expect to get anywhere near Gbit
speed in real life usage with standard pc hardware. It's just not
realistic."

I'm not expecting to get a real 1GB connection, but I'm surprise to
get only 50% of the theoretical number on a 1GB connection.
When I use a 100M connection (with cross cable or with a switch) I get
88% of the 100MB bandwidth.

Thanks,
Personne

On Nov 13, 11:53 am, Mark Huizer <xaa
(E-Mail Removed)> wrote:
> The wise Personne enlightened me with:
>
> > Mark,

>
> > I did already this test before your post, and you are correct it
> > doesn't come from the CIsco Switch. With a crosscable (5e) between my
> > 2 computers (not servers) I get the same speed rate (around 50 and 60
> > MBytes/s)
> > I know TCP/IP has some overhead but 52% is really a lot.
> > - Could be a driver issue
> > - I haven't tried yet Jumbo Frame (I'm not even sure I have the option
> > in my Windows drivers)
> > - Netperf doesn't use disk, it is a RAM-RAM test, so no disk overhead.

>
> I know it's a RAM to RAM test, that's why I said that a 'real life case'
> probably would be even worse.
> TCP/IP doesn't have to be a problem, and you can account for that in
> your test. Not sure what you are testing precisely with netperf, but the
> parameters you are using can have enough impact on your measurements. I
> normally use iperf, I don't know netperf, but it might have the same
> options. You'll see different measurements for e.g. udp vs tcp, since
> udp is connectionless so no problems with window sizes. If you are using
> tcp, play around with the window size/buffer size, and see the
> difference.
> You might play with smaller/bigger sizes, you'll see a big difference.
>
> And I'm not entirely sure where PC hardware is nowadays. Can't tell you
> the max bandwidth of memory, PCI busses, etc. And you will see a big
> difference between using an el cheapo NIC and a topline NIC that does
> all kinds of offloading, because it will do stuff in hardware that your
> CPU doesn't have to worry about anymore.
>
> And to stress that again: don't expect to get anywhere near Gbit speed
> in real life usage with standard pc hardware. It's just not realistic.
>
> Mark



 
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6hopsaway
Guest
Posts: n/a
 
      11-16-2009
On Nov 14, 12:40*am, "Peter" <(E-Mail Removed)> wrote:
> Hi Personne,
>
> > I'm not expecting to get a real 1GB connection, but I'm surprise to
> > get only 50% of the theoretical number on a 1GB connection.
> > When I use a 100M connection (with cross cable or with a switch) I get
> > 88% of the 100MB bandwidth.

>
> If you have a 1Gbit interface and it negotiates a 1 Gbit link speed,
> then you really do have 1 Gbit CAPABILITY on that connection.
> HOWEVER... I work in Networking with lots of Cisco H/W and 100's of
> top end Servers (Dell, IBM, HP, Sun) using many different OS's and ALL
> machines have 1GB interfaces, and NONE of them are able to REGULARLY
> push more than around 800Mbit through that interface without issues.
> In fact most Servers rarely exceed around 700Mbit though a 1Gbit
> interface. This is a limitation with the design of the H/W and S/W
> being used in the Server, not with the Cisco H/W, as we really do see
> aggregate Link speeds of 9.98Mbit throughput on EACH 1Gbit interface
> of a MULTIPLE Gbit interfaces between Cisco Switches. The easiest way
> to see this is to create Channel groups that consist of Multiple Gbit
> interfaces.
>
> I hope this helps............pk.
>
> --
> Peter from Auckland.


For those of you looking to push the limits of your Ethernet
connections you will need to turn on a few tcp options in windows.
Check out RFC 1323 and Microsoft TcpOpts1323
It is recommended to turn these features on with any link generating
more than 16 mb/s operations. Cisco Routers enable this option by
default. Routers only need tuned outside of the default range when
using jumbo frames across them. Cisco gig links natively support up
to 9k frames where fast Ethernet typically does not. Side note...
Vista/ Windows 7 and 2008 Server all come with RFC1323 enabled. Linux
and Unix have had these options set natively for years. Have fun
pegging your links.
 
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Personne
Guest
Posts: n/a
 
      11-16-2009
Thanks for all your replies
 
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alexd
Guest
Posts: n/a
 
      11-18-2009
Meanwhile, at the comp.dcom.sys.cisco Job Justification Hearings, Tosh chose the
tried and tested strategy of:

> All the times I did the same test I saw one of the server's cpu hitting 100%
> usage, that was the limit.
> Providing that you have multiple cpus on both servers, maybe if you run
> iperf twice you can reach the adapter speed limit with the aggregate
> throughput.


Try 'iperf -c ... -P n', where 'n' is the number of threads to run. The man page
does say "The threading implementation is rather heinous", so who knows. A quick
loopback test [ie client and server] on this quad core shows -P 3 to give the
highest 'throughput' [19.2Gbps], which I suppose makes sense.

--
<http://ale.cx/> (AIM:troffasky) ((E-Mail Removed))
19:09:13 up 31 days, 23:04, 4 users, load average: 0.13, 0.18, 0.22
"Stupid is a condition. Ignorance is a choice" -- Wiley Miller

 
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