Technical data

54 FastIron Ethernet Switch Administration Guide
53-1002637-02
Basic port parameter configuration
2
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 Stackable
devices. This section describes the configuration procedures for FastIron X Series devices. For
FastIron Stackable devices, refer to “IPG on FastIron Stackable devices” on page 55.
• 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.
Example
Brocade(config-if-e1000-7/1)# ipg-gmii 120
IPG 120(112) has been successfully configured for ports 7/1 to 7/12
• When you enter a value for IPG, the device applies the closest valid IPG value for the port mode
to the interface. For example, if you specify 120 for a 1 Gbps Ethernet port in 1 Gbps mode, the
device assigns 112 as the closest valid IPG value to program into hardware.