Reference Guide

Interfaces | 393
When the buffer usage drops by the value specified in the “resume-threshold”, the port again sends a
PAUSE frame with 0 as wait-time. This results in resume of the paused traffic flow.”
Enable Pause Frames
Ethernet Pause Frames flow control must be enabled on all ports on a chassis or a line card. If not, the
system may exhibit unpredictable behavior.
On the S-Series systems, the flow-control sender and receiver must be on the same port-pipe. Flow control
is not supported across different port-pipes on the S-Series system
.
Configure MTU Size on an Interface
If a packet includes a Layer 2 header, the difference in bytes between the link MTU and IP MTU must be
enough to include the Layer 2 header. For example, for VLAN packets, if the IP MTU is 1400, the Link
MTU must be no less than 1422:
1400-byte IP MTU + 22-byte VLAN Tag = 1422-byte link MTU
Note: On the S-Series (non-S4810) platforms, Ethernet Pause Frames TX should be enabled only after
consulting with the Dell Networking Technical Assistance Center.
Command Syntax Command Mode Purpose
flowcontrol rx [off | on] tx [off | on]
{pause-threshold <1-12480>} {resume-offset
<1-12480>}
INTERFACE Control how the system responds to and
generates 802.3x pause frames on 1 and 10Gig
line cards.
Defaults:
S6000: rx off tx off
S-Series: rx off tx off
S4810: rx off
Parameters:
rx on: Enter the keywords rx on to process the received flow control frames
on this port.
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.
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 ( S-Series): When tx on is configured, you can set the
threshold values for:
pause-threshold : Buffer threshold limit for generating PAUSE
frames.(default = 59KB)
resume-offset: Offset value for generating PAUSE frames to resume
traffic.(default = 9KB)