Reference Guide

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Table 20-3 lists the range for each transmission media.
Ethernet Pause Frames
Ethernet Pause Frames is supported on platforms s z
Threshold Settings are supported only on platforms: s z
Ethernet Pause Frames allow for a temporary stop in data transmission. A situation may arise where a
sending device may transmit data faster than a destination device can accept it. The destination sends a
PAUSE frame back to the source, stopping the sender’s transmission for a period of time.
The globally assigned 48-bit Multicast address 01-80-C2-00-00-01 is used to send and receive pause
frames. To allow full duplex flow control, stations implementing the pause operation instruct the MAC to
enable reception of frames with destination address equal to this multicast address.
The PAUSE frame is defined by IEEE 802.3x and uses MAC Control frames to carry the PAUSE
commands. Ethernet Pause Frames are supported on full duplex only. The only configuration applicable to
half duplex ports is
rx off tx off.
Note that if a port is over-subscribed, Ethernet Pause Frame flow control does not ensure no
loss behavior.
Threshold Settings
Threshold Settings are supported only on platforms: s z
When the transmission pause is set (tx on), 2 thresholds can be set to define the controls more closely.
pause-threshold: Buffer threshold limit for generating PAUSE frames.(default = 59KB)
resume-offset: Offset value for generating PAUSE frames to resume traffic.(default = 9KB)
When a port receives traffic at a higher rate than it can process, the frames are stored in the port buffer. As
a result, buffer usage increases.
When the buffer usage reaches the value specified in the “pause-threshold” argument, the port sends
PAUSE frame to the connected link partner to stop sending traffic. Eventually this reduces the buffer
usage.
Table 20-3. MTU Range
Transmission Media MTU Range (in bytes)
Ethernet 594-12000 = link MTU
576-9234 = IP MTU