UNBREAKABLE-LINK® Adapter and Switch Technology

NVIDIA adapter, switch, and interconnect products support a unique UNBREAKABLE-LINK® technology that ensures the network links stay connected (operational) even in a bad connectivity environment.

MLNX-OS offers PHY profile configuration for InfiniBand interfaces. PHY profile includes Link Level Retransmission (LLR) configuration. A PHY profile is bound to any InfiniBand interface.

Link Level Retransmission (LLR) is used on signal integrity marginal systems to decrease and/or eliminate the impact of physical errors on the system’s performance.

LLR transmitter breaks the transmitted Layer 2 data stream into Cells and adds a CRC checksum to each cell.

LLR receiver checks the Cell CRC, in case there is no CRC errors, it forwards the cell and acknowledges the peer.

If a cell is dropped by the receiver the transmitter retransmits the cell.

The following LLR modes are applicable per port per speed:

• disable—no LLR

• enable—the port becomes passive, only if it got a request to use LLR it activates, otherwise it remains disabled

• enable-request—the port becomes active, it keeps sending LLR requests to the peer

Both ports on the link perform LLR discovery and negotiation. In order the LLR to be in active state on the link, the following should apply:

• One port must be configured with LLR “enable-request” on the specified speed.

• The other port (peer) may be configured with LLR “enable-request” or “enable” on the same specified speed

  Note

  If both the local port and remote port configured with LLR “enabled” the LLR negotiation will not be activated—the ports will remain in LLR in-active state.

LLR status is a port parameter that states the current state of the LLR.

• Active—LLR is operationally running

• In-Active—LLR is not running

show interfaces ib llr

switch (config) # show interfaces ib llr
-----------------------------
Interface      LLR status 
-----------------------------
IB1/1          Inactive
IB1/2          Inactive
IB1/3          Inactive
IB1/4          Inactive
IB1/5          Inactive
IB1/6          Inactive
IB1/7          Inactive
IB1/8          Inactive
IB1/9          Inactive
IB1/10         Inactive
IB1/11         Inactive
IB1/12         Inactive
IB1/13         Inactive
...