# Scale-Out via Host-NIC¶

Multi-node scale-out for Gaudi accelerator devices via host NIC interfaces is enabled. This functionality is provided by HCCL library. Data transfer between nodes is supported with Scale-Out via Host-NIC over OFI mode.

## Scale-Out via Host-NIC over OFI¶

HCCL interacts with libFabric to utilize any underlying HW and networking mode.

### Configuration Knobs¶

HCCL exports several environment variables that control the behavior of scale-out communication over libFabric. The table below lists the environment variables needed.

Environment Variable

Description

HCCL_OVER_OFI

Enables scale-out communications over OFI libFabric. Possible values are 0 (disable) or 1 (enable).Default value is 0.

HCCL_SOCKET_IFNAME

Identifies the network interface(s) that should be used for scale-out comms.

HCL_COMM_ID

Identifies the root process (rank 0) of the global communicator group. Typically set to <IPaddress:port> the IP address of the network interface used by the root. This must be set for all HCCL processes when there is no alternate network to broadcast this.

### Usage¶

1. To check the HCCL OFI Wrapper built, run your test while setting the environment variable HCCL_OVER_OFI=1.