Brocade FastIron Ethernet Switch Administration Guide - Manual (Page 71)

XOFF Limit : 376(91%)
XON Limit : 312(75%)
Syntax: show symmetric-flow-control
PHY FIFO Rx and Tx depth configuration
PHY devices on Brocade devices contain transmit and receive synchronizing FIFOs to adjust for
frequency differences between clocks. The phy-fifo-depth command allows you to configure the depth
of the transmit and receive FIFOs. There are 4 settings (0-3) with 0 as the default. A higher setting
indicates a deeper FIFO.
The default setting works for most connections. However, if the clock differences are greater than the
default will handle, CRCs and errors will begin to appear on the ports. Raising the FIFO depth setting
will adjust for clock differences.
Brocade recommends that you disable the port before applying this command, and re-enable the port.
Applying the command while traffic is flowing through the port can cause CRC and other errors for any
packets that are actually passing through the PHY while the command is being applied.
Syntax: [no] phy-fifo-depth setting
• setting is a value between 0 and 3. (0 is the default.)
This command can be issued for a single port from the IF config mode or for multiple ports from the MIF
config mode.
NOTE
Higher settings give better tolerance for clock differences with the partner phy, but may marginally
increase latency as well.
Interpacket Gap (IPG) on a FastIron X Series switch
IPG is the time delay, in bit time, between frames transmitted by the device. You configure IPG at the
interface level. The command you use depends on the interface type on which IPG is being configured.
The default interpacket gap is 96 bits-time, which is 9.6 microseconds for 10 Mbps Ethernet, 960
nanoseconds for 100 Mbps Ethernet, 96 nanoseconds for 1 Gbps Ethernet, and 9.6 nanoseconds for 10
Gbps Ethernet.
IPG on a FastIron X series switch configuration notes
• The CLI syntax for IPG differs on FastIron X Series devices compared to FastIron Stackabledevices.
This section describes the configuration procedures for FastIron X Series devices. For FastIron
Stackabledevices, refer to
IPG on FastIron Stackable devices on page 72.
• IPG configuration commands are based on "port regions". All ports within the same port region
should have the same IPG configuration. If a port region contains two or more ports, changes to the
IPG configuration for one port are applied to all ports in the same port region. When you enter a
value for IPG, the CLI displays the ports to which the IPG configuration is applied.
PHY FIFO Rx and Tx depth configuration
FastIron Ethernet Switch Administration Guide 71
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