User Manual

Rev 2.3-1.0.1

Mellanox Technologies

Additional Tools

tc tool compiled with the

sch_mqprio module is required to support kernel v2.6.32 or higher.

This is a part of

iproute2 package v2.6.32-19 or higher. Otherwise, an alternative custom sysfs

interface is available.

•

mlnx_qos tool (package: ofed-scripts) requires python >= 2.5

•

tc_wrap.py (package: ofed-scripts) requires python >= 2.5

3.1.3 Quantized Congestion Notification (QCN)

Congestion control is used to reduce packet drops in lossy environments and mitigate congestion

spreading and resulting victim flows in lossless environments.

The Quantized Congestion Notification (QCN) IEEE standard (802.1Qau) provides congestion

control for long-lived flows in limited bandwidth-delay product Ethernet networks. It is part of

the IEEE Data Center Bridging (DCB) protocol suite, which also includes ETS, PFC, and

DCBX. QCN in conducted at L2, and is tar

geted for hardware implementations. QCN applies to

all Ethernet packets and all transports, and both the host and switch behavior is detailed in the

standard.

QCN user interface allows the user to configure QCN activity. QCN configuration and retrieval

of information is done by the

mlnx_qcn tool. The command interface provides the user with a set

of changeable attributes, and with information regarding QCN's counters and statistics. All

parameters and statistics are defined per port and priority. QCN command interface is available if

and only the hardware supports it.

3.1.3.1 QCN Tool - mlnx_qcn

mlnx_qcn is a tool used to configure QCN attributes of the local host. It communicates directly

with the driver thus does not require setting up a DCBX daemon on the system.

The mlnx_qcn enables the user to:

• Inspect the current QCN configurations for a certain port sorted by priority

• Inspect the current QCN statistics and counters for a certain port sorted by priority

• Set values of chosen QCN parameters

Usage:

mlnx_qcn -i <interface> [options]

Options:

UP 2

UP 3

UP 4

UP 5

UP 6

UP 7

--version Show program's version number and exit

-h, --help Show this help message and exit