* Bypass flow control problems
@ 2010-12-22 17:51 Alkis Georgopoulos
2010-12-27 13:43 ` Pasi Kärkkäinen
0 siblings, 1 reply; 6+ messages in thread
From: Alkis Georgopoulos @ 2010-12-22 17:51 UTC (permalink / raw)
To: netdev
Hi,
I'm an IT teacher/LTSP developer. In LTSP, thin clients are netbooted
from a server and receive a lot of X and remote disk traffic from it.
Many installations have a gigabit NIC on the server, an unmanaged
gigabit switch, and 100 Mbps NICs on the clients.
With flow control on, the server is limited to sending 100 Mbps to all
the clients. So with 10 thin clients the server can concurrently send
only 10 Mbps to each one of them.
On NICs that support it, we turn flow control off and the server can
properly send 100 Mbps to each client, i.e. 1 Gbps to 10 clients.
* Is there any way to bypass that problem on NICs that do not support
turning off flow control, like e.g. realteks?
I.e. when a client sends a pause signal to the server, instead of the
server pausing, to continue sending data to another client?
Or even to limit the amound of data the server sends to each client,
so that the clients never have to send pause signals?
* I really don't understand why flow control is enabled by default on
NICs and switches. In which case does it help? As far as I
understand, all it does is ruin gigabit => 100 Mbps connections...
* As a side note, since rtl8169 is a very common chipset, is there a
way to disable flow control for that specific NIC?
This problem affects thousands of LTSP installations, we'd much
appreciate your knowledge and feedback on it.
Thank you,
Alkis Georgopoulos
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: Bypass flow control problems
2010-12-22 17:51 Bypass flow control problems Alkis Georgopoulos
@ 2010-12-27 13:43 ` Pasi Kärkkäinen
2010-12-29 5:05 ` Kirsher, Jeffrey T
2010-12-29 8:47 ` Alkis Georgopoulos
0 siblings, 2 replies; 6+ messages in thread
From: Pasi Kärkkäinen @ 2010-12-27 13:43 UTC (permalink / raw)
To: Alkis Georgopoulos; +Cc: netdev
On Wed, Dec 22, 2010 at 07:51:31PM +0200, Alkis Georgopoulos wrote:
> Hi,
>
> I'm an IT teacher/LTSP developer. In LTSP, thin clients are netbooted
> from a server and receive a lot of X and remote disk traffic from it.
>
> Many installations have a gigabit NIC on the server, an unmanaged
> gigabit switch, and 100 Mbps NICs on the clients.
>
> With flow control on, the server is limited to sending 100 Mbps to all
> the clients. So with 10 thin clients the server can concurrently send
> only 10 Mbps to each one of them.
>
> On NICs that support it, we turn flow control off and the server can
> properly send 100 Mbps to each client, i.e. 1 Gbps to 10 clients.
>
> * Is there any way to bypass that problem on NICs that do not support
> turning off flow control, like e.g. realteks?
> I.e. when a client sends a pause signal to the server, instead of the
> server pausing, to continue sending data to another client?
> Or even to limit the amound of data the server sends to each client,
> so that the clients never have to send pause signals?
>
You could set up QoS rules on the server to limit the network speed per client..
> * I really don't understand why flow control is enabled by default on
> NICs and switches. In which case does it help? As far as I
> understand, all it does is ruin gigabit => 100 Mbps connections...
>
> * As a side note, since rtl8169 is a very common chipset, is there a
> way to disable flow control for that specific NIC?
>
> This problem affects thousands of LTSP installations, we'd much
> appreciate your knowledge and feedback on it.
>
Did you try disabling flow control from the switch?
-- Pasi
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: Bypass flow control problems
2010-12-27 13:43 ` Pasi Kärkkäinen
@ 2010-12-29 5:05 ` Kirsher, Jeffrey T
2010-12-29 8:47 ` Pasi Kärkkäinen
2010-12-29 8:47 ` Alkis Georgopoulos
1 sibling, 1 reply; 6+ messages in thread
From: Kirsher, Jeffrey T @ 2010-12-29 5:05 UTC (permalink / raw)
To: Pasi Kärkkäinen; +Cc: Alkis Georgopoulos, netdev@vger.kernel.org
On Dec 27, 2010, at 8:43, Pasi Kärkkäinen <pasik@iki.fi> wrote:
> On Wed, Dec 22, 2010 at 07:51:31PM +0200, Alkis Georgopoulos wrote:
>> Hi,
>>
>> I'm an IT teacher/LTSP developer. In LTSP, thin clients are netbooted
>> from a server and receive a lot of X and remote disk traffic from it.
>>
>> Many installations have a gigabit NIC on the server, an unmanaged
>> gigabit switch, and 100 Mbps NICs on the clients.
>>
>> With flow control on, the server is limited to sending 100 Mbps to all
>> the clients. So with 10 thin clients the server can concurrently send
>> only 10 Mbps to each one of them.
>>
>> On NICs that support it, we turn flow control off and the server can
>> properly send 100 Mbps to each client, i.e. 1 Gbps to 10 clients.
>>
>> * Is there any way to bypass that problem on NICs that do not support
>> turning off flow control, like e.g. realteks?
>> I.e. when a client sends a pause signal to the server, instead of the
>> server pausing, to continue sending data to another client?
>> Or even to limit the amound of data the server sends to each client,
>> so that the clients never have to send pause signals?
>>
>
> You could set up QoS rules on the server to limit the network speed per client..
>
>> * I really don't understand why flow control is enabled by default on
>> NICs and switches. In which case does it help? As far as I
>> understand, all it does is ruin gigabit => 100 Mbps connections...
>>
>> * As a side note, since rtl8169 is a very common chipset, is there a
>> way to disable flow control for that specific NIC?
>>
>> This problem affects thousands of LTSP installations, we'd much
>> appreciate your knowledge and feedback on it.
>>
>
> Did you try disabling flow control from the switch?
He stated the switch was a un-managed switch, so he would be unable to disable flow control on the switch.
>
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: Bypass flow control problems
2010-12-29 5:05 ` Kirsher, Jeffrey T
@ 2010-12-29 8:47 ` Pasi Kärkkäinen
0 siblings, 0 replies; 6+ messages in thread
From: Pasi Kärkkäinen @ 2010-12-29 8:47 UTC (permalink / raw)
To: Kirsher, Jeffrey T; +Cc: Alkis Georgopoulos, netdev@vger.kernel.org
On Tue, Dec 28, 2010 at 09:05:42PM -0800, Kirsher, Jeffrey T wrote:
> On Dec 27, 2010, at 8:43, Pasi Kärkkäinen <pasik@iki.fi> wrote:
>
> > On Wed, Dec 22, 2010 at 07:51:31PM +0200, Alkis Georgopoulos wrote:
> >> Hi,
> >>
> >> I'm an IT teacher/LTSP developer. In LTSP, thin clients are netbooted
> >> from a server and receive a lot of X and remote disk traffic from it.
> >>
> >> Many installations have a gigabit NIC on the server, an unmanaged
> >> gigabit switch, and 100 Mbps NICs on the clients.
> >>
> >> With flow control on, the server is limited to sending 100 Mbps to all
> >> the clients. So with 10 thin clients the server can concurrently send
> >> only 10 Mbps to each one of them.
> >>
> >> On NICs that support it, we turn flow control off and the server can
> >> properly send 100 Mbps to each client, i.e. 1 Gbps to 10 clients.
> >>
> >> * Is there any way to bypass that problem on NICs that do not support
> >> turning off flow control, like e.g. realteks?
> >> I.e. when a client sends a pause signal to the server, instead of the
> >> server pausing, to continue sending data to another client?
> >> Or even to limit the amound of data the server sends to each client,
> >> so that the clients never have to send pause signals?
> >>
> >
> > You could set up QoS rules on the server to limit the network speed per client..
> >
> >> * I really don't understand why flow control is enabled by default on
> >> NICs and switches. In which case does it help? As far as I
> >> understand, all it does is ruin gigabit => 100 Mbps connections...
> >>
> >> * As a side note, since rtl8169 is a very common chipset, is there a
> >> way to disable flow control for that specific NIC?
> >>
> >> This problem affects thousands of LTSP installations, we'd much
> >> appreciate your knowledge and feedback on it.
> >>
> >
> > Did you try disabling flow control from the switch?
>
> He stated the switch was a un-managed switch, so he would be unable to disable flow control on the switch.
>
Oh, I missed that :) Never mind then.
-- Pasi
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: Bypass flow control problems
2010-12-27 13:43 ` Pasi Kärkkäinen
2010-12-29 5:05 ` Kirsher, Jeffrey T
@ 2010-12-29 8:47 ` Alkis Georgopoulos
2010-12-29 8:49 ` Pasi Kärkkäinen
1 sibling, 1 reply; 6+ messages in thread
From: Alkis Georgopoulos @ 2010-12-29 8:47 UTC (permalink / raw)
To: Pasi Kärkkäinen; +Cc: netdev
Στις 27-12-2010, ημέρα Δευ, και ώρα 15:43 +0200, ο/η Pasi Kärkkäinen
έγραψε:
> You could set up QoS rules on the server to limit the network speed per client..
That sounds promising. I'll try to limit the rate of packages that the
server sends to each client to 90 Mbps and see if that works around the
flow control problem. Any tips for a good method to do that?
Thank you.
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: Bypass flow control problems
2010-12-29 8:47 ` Alkis Georgopoulos
@ 2010-12-29 8:49 ` Pasi Kärkkäinen
0 siblings, 0 replies; 6+ messages in thread
From: Pasi Kärkkäinen @ 2010-12-29 8:49 UTC (permalink / raw)
To: Alkis Georgopoulos; +Cc: netdev
On Wed, Dec 29, 2010 at 10:47:15AM +0200, Alkis Georgopoulos wrote:
> ???????? 27-12-2010, ?????????? ??????, ?????? ?????? 15:43 +0200, ??/?? Pasi Kärkkäinen
> ????????????:
> > You could set up QoS rules on the server to limit the network speed per client..
>
> That sounds promising. I'll try to limit the rate of packages that the
> server sends to each client to 90 Mbps and see if that works around the
> flow control problem. Any tips for a good method to do that?
>
I guess you need to read the Linux Advanced Routing and Traffic Control howto..
it has examples how to use the Linux QoS stuff.
There are also some scripts out there that make it easier to set it up.
-- Pasi
^ permalink raw reply [flat|nested] 6+ messages in thread
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2010-12-22 17:51 Bypass flow control problems Alkis Georgopoulos
2010-12-27 13:43 ` Pasi Kärkkäinen
2010-12-29 5:05 ` Kirsher, Jeffrey T
2010-12-29 8:47 ` Pasi Kärkkäinen
2010-12-29 8:47 ` Alkis Georgopoulos
2010-12-29 8:49 ` Pasi Kärkkäinen
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