Users Guide

Broadcom NetXtreme-E-UG304-2CS
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NetXtreme-E User Guide User Guide for Dell Platforms
2. As the Egress Queue of the switch reaches the congestion marking threshold as defined by the user, the switch starts
marking the ECN bits to CE(11b) to notify to the notification point that congestion has been detected for that port.
3. Once the CE bit is detected, the notification point transmits Congestion Notification Packet (CNP) packet(s) to the
reaction points(s) to signify congestion.
4. Upon the reception of the CNP(s), the reaction point reduces its transmit rate based on a certain algorithm so that the
congestion can be mitigated.
5. The reaction point continues to react to rate limit requests until Congestion Notification Packet (CNP) packets are no
longer received.
6. At times when CNPs are not received by the transmitter, the transmitter attempt to gradually increase its transmission
rate.
NOTE: Both reduction in rate and increase in rate are be accomplished per QP
Figure 40: Congestion Control Flow
14.2.5.3 NIC Configuration
In order to configure the NIC to be lossless for RoCE, the correct traffic class is required to be used as the default traffic
class is currently set to lossy. There are two available methods to configure the traffic classes and other QoS settings:
 LLDP Agent
 BnxtQoS
14.2.5.4 LLDP Agent
The LLDP agent is used to set QoS mappings (user priority, Linux TC, or NIC CoS queue) and configure Enhanced
Transmission Selection (ETS) to configure bandwidth allocation if required. It is required to install the LLDP agent in order
to properly configure QoS, which is necessary for maximum performance.
14.2.5.4.1 Debian/Ubuntu
To install the LLDP agent using Debian/Ubuntu, use the following commands:
sudo apt install libconfig9 libnl-3-200
wget http://ftp.us.debian.org/debian/pool/main/l/lldpad/lldpad_0.9.46-3.1_amd64.deb
sudo dpkg -i lldpad_0.9.46-3.1_amd64.deb
sudo systemctl enable lldpad
sudo systemctl start lldpad
TOR
Receiver
(2) Senders
Congestion
25G
25G
25G
Notification
Point
Reaction
Points
CNP CE(11b)
ECT1(01b)
ECT1(01b)