# 11.6.3. End-to-end data reliability for MPI messages

Current Open MPI releases have no support for end-to-end data reliability, at least not more than currently provided by the underlying network.

Previous releases included a data reliability PML component (`dr`) that assumed that the underlying network is unreliable. It could drop / restart connections, retransmit corrupted or lost data, etc. The end effect was that data sent through MPI API functions would be guaranteed to be reliable.

For example, if you’re using TCP as a message transport, chances of data corruption are fairly low. However, other interconnects do not guarantee that data will be uncorrupted when traveling across the network. Additionally, there are non-zero possibilities that data can be corrupted while traversing PCI buses, etc. (some corruption errors at this level can be caught/fixed, others cannot). Such errors are not uncommon at high altitudes (!).

Note that such added reliability does incur a performance cost — latency and bandwidth suffer when Open MPI performs the consistency checks that are necessary to provide such guarantees.

Most clusters/networks do not need data reliability. But some do (e.g., those operating at high altitudes). The `dr` PML was intended for these rare environments where reliability was an issue; and users were willing to tolerate slightly slower applications in order to guarantee that their job does not crash (or worse, produce wrong answers).

Note

The `dr` component has been removed from current releases of Open MPI, but is still available in older releases.