HCCL_RDMA_TC

Description

Sets the traffic class of the RDMA NIC.

The value of this environment variable ranges from [0, 255] and must be an integral multiple of 4. The default value is 132.

In the RoCE V2 protocol, this value corresponds to the type of service (ToS) field in the IP packet header. The ToS field consists of 8 bits. Specifically, bits [0, 1] are fixed at 0, and bits [2, 7] indicate the DSCP value (calculated by dividing the environment variable value by 4).

Example

# If this environment variable is set to 100 (25 × 4), the DSCP value is 25.
export HCCL_RDMA_TC=100

Constraints

If you call the HCCL C APIs to initialize a communicator with specific configurations and set the traffic class of the RDMA NIC using the hcclRdmaTrafficClass parameter in HcclCommConfig, the configuration at the communicator granularity takes precedence.

Applicability

Atlas 350 Accelerator Card

Atlas A3 training product / Atlas A3 inference product

Atlas A2 training product / Atlas A2 inference product (For Atlas A2 training product / Atlas A2 inference product , only the Atlas 800T A2 training server, Atlas 900 A2 PoD cluster basic unit, and Atlas 200T A2 Box16 heterogeneous subrack are supported.)

Atlas training product

Atlas inference product (For Atlas inference product , only Atlas 300I Duo Inference Card is supported.)