Choosing A High Speed Flow Control Mode; Symmetric Mode - Nortel business policy switch 2000 User Manual

214 Chapter 3 Using the console interface
Table 30 High Speed Flow Control Configuration Screen Fields (continued)
Field
Flow Control
Preferred Phy
Active Phy

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 Business Policy 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.
When a pause frame is received (by either the Gigabit MDA port or its link
partner), the port suspends transmission of frames for a number of slot times
specified in the control frame or until a pause-release control frame is received.
Both devices on the link must support this mode when it is selected.
208700-C
Description
Allows you to control traffic and avoid congestion on the Gigabit MDA port. Two
modes are available (see
about the two modes). The Flow Control field cannot be configured unless you
set the Autonegotiation field value to Disabled.
Default Value Disabled
Range Disabled, Symmetric, Asymmetric
Note:
The following two fields only appear when a single MAC
MDA (450-1LR-MDA or 450-1SR MDA) with a separate redundant Phy
port is installed.
Allows you to choose a preferred Phy port; the other Phy port reverts to backup.
Default Value Right
Range Right, Left
Indicates the operational Phy port.
Default Value: None
Range: None, Right, Left
"Choosing a high speed flow control mode" for details