Reference Guide

Interfaces | 609
Parameters
Defaults
C-Series: rx off tx off
E-Series: rx on tx on
S-Series: rx off tx off
S4810: rx on tx off
S4820T: rx on tx off
Command Modes
INTERFACE
Command
History
Usage
Information
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 a destination address equal to
this multicast address.
The pause:
•Starts when either the packet pointer or the buffer threshold is met (whichever is
met first). When the discard threshold is met, packets are dropped.
• Ends when both the packet pointer and the buffer threshold fall below 50% of the
threshold settings.
The discard threshold defines when the interface starts dropping the packet on the interface.
This may be necessary when a connected device does not honor the flow control frame sent
by the S-Series. The discard threshold should be larger than the buffer threshold so that the
buffer holds at least hold at least 3 packets.
rx on
Enter the keywords rx on to process the received flow control frames on this port.
This is the default value for the receive side.
rx off
Enter the keywords rx off to ignore the received flow control frames on this port.
tx on
Enter the keywords tx on to send control frames from this port to the connected
device when a higher rate of traffic is received. This is the default value on the
send side.
tx off
Enter the keywords tx off so that flow control frames are not sent from this port to
the connected device when a higher rate of traffic is received.
threshold
(C-Series and
S-Series only)
When tx on is configured, you can set the threshold values for:
Number of flow-control packet pointers: 1 to 2047 (default = 75)
Flow-control buffer threshold in KB: 1 to 2013 (default = 49KB)
Flow-control discard threshold in KB: 1 to 2013 (default= 75KB)
Version 8.3.19.0 Introduced on S4820T
Version 8.3.7.0 Introduced on S4810
Version 8.1.1.0 Introduced on E-Series ExaScale
Version 6.5.1.9 and 7.4.1.0 Introduced on E-Series
Version 7.8.1.0 Introduced on C-Series and S-Series with thresholds