Re: QoS & Flow-control

From: Darren Johnson (dazza_johnson@yahoo.co.uk)
Date: Tue Oct 09 2007 - 10:44:42 ART


Heh Thomas, check this out:

http://www.cisco.com/en/US/docs/switches/lan/catalyst3750/software/release/12.2_35_se/command/reference/cli1.html#wp2233510

I don't like just pasting URLs so here is my take. An
ethernet interface on a switch can respond to
flowcontrol frames it receives. For example. A PC CPU
is busy so it can send a pause flowcontrol frame to
the switch and the switch will stop transmitting to
it. This gives the PC CPU chance to recover and then
it can inform the switch to once again start
transmitting. The switch CANNOT send pause frames to
devices (Pcs/switches/etc). Its disabled by default
and I don't know anyone or any devices which use it!

Daz

--- thomas.rader@freesurf.ch wrote:

> Hello,
>
> When I switch on mls qos on my 3350's (default
> config) it askes me to ensure that flow control is
> not configured.
>
> Flow control sounds like RS232 stuff, anyone know
> what this is and why it needs to be switched off ?
>
> Switch(config)#mls qos
> QoS: ensure flow-control on all interfaces are OFF
> for proper operation.
> Switch(config)#
>
> thanks
> Thomas
>
>



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