The Maintenance Operation Protocol (MOP) is used for utility services such as uploading and downloading system software, remote testing and problem diagnosis. It was a proprietary protocol of Digital Equipment Corporation. MOP frames can be one of the following commands:[1]
| Command | Description |
|---|---|
| [dump service req] | Request for assistance with dump operation. |
| [mem dump request] | Request for next memory dump segment. |
| [memory dump data] | Contains memory dump data. |
| [dump completed] | Acknowledgment of dump completion. |
| [volunteer assist] | Offer of dump/load/loop assistance. |
| [request program] | Request for system or loader |
| [remote ID reqst] | Request for remote console identification. |
| [remote system ID] | Remote console identification information. |
| [counters request] | Request for communication information counters. |
| [counters reply] | Communication information counters. |
| [reserve console] | Remote console in reserved state. |
| [release console] | Release of remote console from reserved state. |
| [rem console poll] | Poll of remote console for status. |
| [rem console rply] | Response to remote console poll. |
| [loopback reply] | Response to loopback request with data. |