Nortel Networks 450 manual Choosing a High Speed Flow Control Mode, Symmetric Mode

Using the BayStack 450 10/100/1000 Series Switch

Table 3-13. High Speed Flow Control Configuration Screen Fields (continued)

Field	Description
Autonegotiation	When enabled, the port only advertises support for 1000 Mb/s operation, in
	full-duplex mode.
	Default Value	Enabled
	Range	Enabled, Disabled
Flow Control	Allows you to control traffic and avoid congestion on the gigabit MDA port. Two
	modes are available (see “Choosing a High Speed Flow Control Mode” on
	page 3-36 for details about the two modes). Autonegotiation must be disabled
	for this port when using this feature.
	Default Value	Disabled
	Range	Disabled, Symmetric, Asymmetric
	Note: The following two fields only appear when a (single MAC) MDA with a
	separate redundant Phy port is installed.
Preferred Phy
	Allows you to choose the preferred Phy port; the other Phy port reverts to
	backup.
	Default Value	Right
	Range	Right, Left
Active Phy	Indicates the operational Phy port.

Choosing a High Speed Flow Control Mode

The High Speed Flow Control feature allows you to control traffic and avoid congestion on the gigabit full-duplex link. If the receive port buffer becomes full, the BayStack 450 switch issues a flow-control signal to the device at the other end of the link to suspend transmission. When the receive buffer is no longer full, the switch issues a signal to resume the transmission.

You can choose Symmetric or Asymmetric flow control mode:

Symmetric Mode

This mode allows both the gigabit MDA port and its link partner to send flow control pause frames to each other.

3-36 302401-D Rev 00