Use the flowcontrol interface configuration command to set the receive or send flow-control value for an interface. When flow control send is on for a device and it detects any congestion at its end, it notifies the link partner or the remote device of the congestion by sending a pause frame. When flow control receive is on for the remote device and it receives a pause frame, it stops sending any data packets. This prevents any loss of data packets during the congestion period.
Use the receive off and send off keywords to disable flow control.
flowcontrol {receive | send} {desired | off | on}
For the further details follow the URL :
http://www.cisco.com/en/US/docs/switches/lan/catalyst3550/software/release/12.1_19_ea1/command/reference/cli1.html#wp1861670
