HP ProCurve Switch 212M Management And Configuration Manual page 89

Auto-Negotiation Note: This feature complies with the IEEE 802.3u Auto
Negotiation standard, and is the default setting for the 10/100TX ports on the
switch. Using Auto, the port automatically selects the network speed (10 or
100 Mbps) and the data transfer operation (full- or half-duplex) for the
connection to another device, provided that the other device also complies
with the IEEE 802.3u Auto Negotiation protocol and is set to Auto. If the other
device does not comply with the 802.3u standard, or is not set to Auto, then
the port configuration on the switch must be manually set to match the port
configuration on the other device.
Flow Control Note:
IEEE 802.3 Flow Control is applied to ports that are configured to
operate in full-duplex mode only. When the switch detects congestion on
a port, it transmits a special "pause" (XOFF) packet out the port. The
receiving device must support 802.3x flow control in order to interpret
this packet. The receiving device will halt transmission of any packets
until the switch sends a "resume" (XON) packet.
Back pressure is applied to ports that are configured to operate in half-
duplex mode. When the switch detects congestion on the port, it issues a
JAM signal, simulating a collision that prevents other attached stations
from transmitting. It is recommended that if you use this flow control
method, it should be configured only on those ports that are connected
to a single end node, not on ports that are connected to a switch, hub,
bridge, or router.
Configuring the Switch
Port Settings
6-25