User Manual

Rev 4.70

Mellanox Technologies

8.13.7.1 Enabling Lossless TCP Using The Registry Key DelayDropTimeout:

Registry Key location:

For instructions on how to find interface index in registry <nn>, Please refer to C.2 “Finding the

Index Value of the Network Interface,” on page 175

8.13.7.2 Entering/Exiting Lossless Mode Using Set OID OID_MLX_DROPLESS_MODE:

In order to enter poll mode, registry value of DelayDropTimeout should be non-zero and

OID_MLX_DROPLESS_MODE Set OID should be called with Information Buffer containing

• OID_MLX_DROPLESS_MODE value: 0xFFA0C932

• OID Information Buffer Size: 1 byte

• OID Information Buffer Contents: 0 - exit poll mode; 1 - enter poll mode

8.13.8 Monitoring Lossless TCP State

In order to allow state transition monitoring, events are written to event log with mlx4_bus as the

source. The associated events are listed in Table 9.

HKLM\SYSTEM\CurrentControlSet\Control\Class\Class\{4d36e972-

e325-11ce-bfc1-08002be10318}\<nn>\DelayDropTimeout

Key Name Key Type Values Description

DelayDropTime-

out

REG_SZ

• 0= disabled

(default)

•1-

65535=enabled

Choosing values between 1-65534 enables the

feature, but the chosen value limits the amount

of time a packet may wait for a free descriptor.

The value is in units of 100 microseconds with

inaccuracy of up to 2 units. The chosen time

ranges between 100 microseconds and ~6.5 sec-

onds. For example, DelayDropTimeout=3000

limits the wait time to 300 miliseconds (+/- 200

microseconds)

Choosing the value of 65535 enables the feature

but the amount of time a packet may wait for a

free descriptor is infinite.

Note: Changing the value of the DelayDrop-

Timeout registry key requires restart of the net-

work interface

Table 9 - Lossless TCP Associated Events

Event ID Event Description

0x0057 <Device Name> Dropless mode entered on port <X>. Packets will not be dropped.

0x0058 <Device Name> Dropless mode exited on port <X>. Drop mode entered; packets

may now be dropped.

0x0059 <Device Name> Delay drop timeout occurred on port <X>. Drop mode entered;

packets may now be dropped.