The LM (Link Manager) is the part of a Bluetooth device responsible for connecting to and disconnecting from other devices, and for the control of the connection. An LMP (Link Manager Protocol) message is a packet, or PDU (Packet Data Unit), sent between the LMs of a master and slave Bluetooth device; these messages are not propagated to the device's host, but they may trigger an HCI event to be sent to the device's host.
An LMP message is normally transmitted on the ACL link using a DM1 type packet, with the L_CH (Logical Channel) bits of the payload header set to 112. Alternatively, an LMP message may be sent on a SCO link using a DV type packet. The payload body (i.e. the packet data) contains:
- Op-code and transaction ID (1 byte):
- Transaction ID (least significant 1 bit):
- 0 for a transaction initiated by the master
1 for a transaction initiated by the slave
- Op-code (most significant 7 bits): see below.
- Message parameters: the number of parameters and their length is message specific.
| Op-code | Bluetooth version |
Mandatory or Optional |
LMP PDU | Length (bytes) |
Packet type |
Possible direction |
Parameters | Position in payload |
||
| 1 | V1.1 | V1.2 | EDR | M | LMP_name_req | 2 | DM1/DV | m↔s | name offset | 2 |
| 2 | V1.1 | V1.2 | EDR | M | LMP_name_res | 17 | DM1 | m↔s | name offset | 2 |
| name length | 3 | |||||||||
| name fragment | 4-17 | |||||||||
| 3 | V1.1 | V1.2 | EDR | M | LMP_accepted | 2 | DM1/DV | m↔s | op code | 2 |
| 4 | V1.1 | V1.2 | EDR | M | LMP_not_accepted | 3 | DM1/DV | m↔s | op code | 2 |
| error code | 3 | |||||||||
| 5 | V1.1 | V1.2 | EDR | M | LMP_clkoffset_req | 1 | DM1/DV | m→s | - | |
| 6 | V1.1 | V1.2 | EDR | M | LMP_clkoffset_res | 3 | DM1/DV | m←s | clock offset | 2-3 |
| 7 | V1.1 | V1.2 | EDR | M | LMP_detach | 2 | DM1/DV | m↔s | error code | 2 |
| 8 | V1.1 | V1.2 | EDR | M | LMP_in_rand | 17 | DM1 | m↔s | random number | 2-17 |
| 9 | V1.1 | V1.2 | EDR | M | LMP_comb_key | 17 | DM1 | m↔s | random number | 2-17 |
| 10 | V1.1 | V1.2 | EDR | M | LMP_unit_key | 17 | DM1 | m↔s | key | 2-17 |
| 11 | V1.1 | V1.2 | EDR | M | LMP_au_rand | 17 | DM1 | m↔s | random number | 2-17 |
| 12 | V1.1 | V1.2 | EDR | M | LMP_sres | 5 | DM1/DV | m↔s | authentication response | 2-5 |
| 13 | V1.1 | V1.2 | EDR | O | LMP_temp_rand | 17 | DM1 | m→s | random number | 2-17 |
| 14 | V1.1 | V1.2 | EDR | O | LMP_temp_key | 17 | DM1 | m→s | key | 2-17 |
| 15 | V1.1 | V1.2 | EDR | O (M) | LMP_encryption_mode_req | 2 | DM1/DV | m↔s | encryption mode | 2 |
| 16 | V1.1 | V1.2 | EDR | O (M) | LMP_encryption_key_size_req | 2 | DM1/DV | m↔s | key size | 2 |
| 17 | V1.1 | V1.2 | EDR | O (M) | LMP_start_encryption_req | 17 | DM1 | m→s | random number | 2-17 |
| 18 | V1.1 | V1.2 | EDR | O (M) | LMP_stop_encryption_req | 1 | DM1/DV | m→s | - | |
| 19 | V1.1 | V1.2 | EDR | O (M) | LMP_switch_req | 5 | DM1/DV | m↔s | switch instant | 2-5 |
| 20 | V1.1 | V1.2 | EDR | O | LMP_hold | 7 | DM1/DV | m↔s | hold time | 2-3 |
| hold instant | 4-7 | |||||||||
| 21 | V1.1 | V1.2 | EDR | O | LMP_hold_req | 7 | DM1/DV | m↔s | hold time | 2-3 |
| hold instant | 4-7 | |||||||||
| 23 | V1.1 | V1.2 | EDR | O | LMP_sniff_req | 10 | DM1 | m↔s | timing control flags | 2 |
| Dsniff | 3-4 | |||||||||
| Tsniff | 5-6 | |||||||||
| sniff attempt | 7-8 | |||||||||
| sniff timeout | 9-10 | |||||||||
| 24 | V1.1 | V1.2 | EDR | O | LMP_unsniff_req | 1 | DM1/DV | m↔s | - | |
| 25 | V1.1 | V1.2 | EDR | O | LMP_park_req | 17 | DM1 | m↔s | timing control flags | 2 |
| DB | 3-4 | |||||||||
| TB | 5-6 | |||||||||
| NB | 7 | |||||||||
| ΔB | 8 | |||||||||
| PM_ADDR | 9 | |||||||||
| AR_ADDR | 10 | |||||||||
| NBsleep | 11 | |||||||||
| DBsleep | 12 | |||||||||
| Daccess | 13 | |||||||||
| Taccess | 14 | |||||||||
| Nacc-slots | 15 | |||||||||
| Npoll | 16 | |||||||||
| Maccess | 17:0-3 | |||||||||
| access scheme | 17:4-7 | |||||||||
| 27 | V1.1 | V1.2 | EDR | O | LMP_set_broadcast_scan_window | 4 or 6 | DM1 | m→s | timing control flags | 2 |
| DB | 3-4 | |||||||||
| broadcast scan window | 5-6 | |||||||||
| 28 | V1.1 | V1.2 | EDR | O | LMP_modify_beacon | 11 or 13 | DM1 | m→s | timing control flags | 2 |
| DB | 3-4 | |||||||||
| TB | 5-6 | |||||||||
| NB | 7 | |||||||||
| ΔB | 8 | |||||||||
| Daccess | 9 | |||||||||
| Taccess | 10 | |||||||||
| Nacc-slots | 11 | |||||||||
| Npoll | 12 | |||||||||
| Maccess | 13:0-3 | |||||||||
| access scheme | 13:4-7 | |||||||||
| 29 | V1.1 | V1.2 | EDR | O | LMP_unpark_BD_ADDR_req | variable | DM1 | m→s | timing control flags | 2 |
| DB | 3-4 | |||||||||
| LT_ADDR 1st unpark | 5:0-2 | |||||||||
| LT_ADDR 2nd unpark | 5:4-6 | |||||||||
| BD_ADDR 1st unpark | 6-11 | |||||||||
| BD_ADDR 2nd unpark | 12-17 | |||||||||
| 30 | V1.1 | V1.2 | EDR | O | LMP_unpark_PM_ADDR_req | variable | DM1 | m→s | timing control flags | 2 |
| DB | 3-4 | |||||||||
| LT_ADDR 1st unpark | 5:0-3 | |||||||||
| LT_ADDR 2nd unpark | 5:4-7 | |||||||||
| PM_ADDR 1st unpark | 6 | |||||||||
| PM_ADDR 2nd unpark | 7 | |||||||||
| LT_ADDR 3rd unpark | 8:0-3 | |||||||||
| LT_ADDR 4th unpark | 8:4-7 | |||||||||
| PM_ADDR 3rd unpark | 9 | |||||||||
| PM_ADDR 4th unpark | 10 | |||||||||
| LT_ADDR 5th unpark | 11:0-3 | |||||||||
| LT_ADDR 6th unpark | 11:4-7 | |||||||||
| PM_ADDR 6th unpark | 12 | |||||||||
| PM_ADDR 6th unpark | 13 | |||||||||
| LT_ADDR 7th unpark | 14:0-3 | |||||||||
| PM_ADDR 7th unpark | 15 | |||||||||
| 31 | V1.1 | V1.2 | EDR | O | LMP_incr_power_req | 2 | DM1/DV | m↔s | for future use | 2 |
| 32 | V1.1 | V1.2 | EDR | O | LMP_decr_power_req | 2 | DM1/DV | m↔s | for future use | 2 |
| 33 | V1.1 | V1.2 | EDR | O | LMP_max_power | 1 | DM1/DV | m↔s | - | |
| 34 | V1.1 | V1.2 | EDR | O | LMP_min_power | 1 | DM1/DV | m↔s | - | |
| 35 | V1.1 | V1.2 | EDR | O | LMP_auto_rate | 1 | DM1/DV | m↔s | - | |
| 36 | V1.1 | V1.2 | EDR | O | LMP_preferred_rate | 2 | DM1/DV | m↔s | data rate | 2 |
| 37 | V1.1 | V1.2 | EDR | M | LMP_version_req | 6 | DM1/DV | m↔s | VersNr | 2 |
| CompId | 3-4 | |||||||||
| SubVersNr | 5-6 | |||||||||
| 38 | V1.1 | V1.2 | EDR | M | LMP_version_res | 6 | DM1/DV | m↔s | VersNr | 2 |
| CompId | 3-4 | |||||||||
| SubVersNr | 5-6 | |||||||||
| 39 | V1.1 | V1.2 | EDR | M | LMP_features_req | 9 | DM1/DV | m↔s | features | 2-9 |
| 40 | V1.1 | V1.2 | EDR | M | LMP_features_res | 9 | DM1/DV | m↔s | features | 2-9 |
| 41 | V1.1 | V1.2 | EDR | M | LMP_quality_of_service | 4 | DM1/DV | m→s | poll interval | 2-3 |
| NBC | 4 | |||||||||
| 42 | V1.1 | V1.2 | EDR | M | LMP_quality_of_service_req | 4 | DM1/DV | m↔s | poll interval | 2-3 |
| NBC | 4 | |||||||||
| 43 | V1.1 | V1.2 | EDR | O | LMP_SCO_link_req | 7 | DM1/DV | m↔s | SCO handle | 2 |
| timing control flags | 3 | |||||||||
| DSCO | 4 | |||||||||
| TSCO | 5 | |||||||||
| SCO packet | 6 | |||||||||
| air mode | 7 | |||||||||
| 44 | V1.1 | V1.2 | EDR | O | LMP_remove_SCO_link_req | 3 | DM1/DV | m↔s | SCO handle | 2 |
| error code | 3 | |||||||||
| 45 | V1.1 | V1.2 | EDR | M | LMP_max_slot | 2 | DM1/DV | m↔s | max slots | 2 |
| 46 | V1.1 | V1.2 | EDR | M | LMP_max_slot_req | 2 | DM1/DV | m↔s | max slots | 2 |
| 47 | V1.1 | V1.2 | EDR | O | LMP_timing_accuracy_req | 1 | DM1/DV | m↔s | - | |
| 48 | V1.1 | V1.2 | EDR | O (M) | LMP_timing_accuracy_res | 3 | DM1/DV | m↔s | drift | 2 |
| jitter | 3 | |||||||||
| 49 | V1.1 | V1.2 | EDR | M | LMP_setup_complete | 1 | DM1 | m↔s | - | |
| 50 | V1.1 | V1.2 | EDR | O | LMP_use_semi_permanent_key | 1 | DM1/DV | m→s | - | |
| 51 | V1.1 | V1.2 | EDR | M | LMP_host_connection_req | 1 | DM1/DV | m↔s | - | |
| 52 | V1.1 | V1.2 | EDR | O (M) | LMP_slot_offset | 9 | DM1/DV | m↔s | slot offset | 2-3 |
| BD_ADDR | 4-9 | |||||||||
| 53 | V1.1 | V1.2 | EDR | O | LMP_page_mode_req | 3 | DM1/DV | m↔s | paging scheme | 2 |
| paging scheme settings | 3 | |||||||||
| 54 | V1.1 | V1.2 | EDR | O | LMP_page_scan_mode_req | 3 | DM1/DV | m↔s | paging scheme | 2 |
| paging scheme settings | 3 | |||||||||
| 55 | V1.1 | V1.2 | EDR | M | LMP_supervision_timeout | 3 | DM1/DV | m→s | supervision timeout | 2-3 |
| 56 | V1.1 | V1.2 | EDR | O | LMP_test_activate | 1 | DM1/DV | m→s | - | |
| 57 | V1.1 | V1.2 | EDR | O | LMP_test_control | 10 | DM1 | m→s | test scenario | 2 |
| hopping mode | 3 | |||||||||
| TX frequency | 4 | |||||||||
| RX frequency | 5 | |||||||||
| power control mode | 6 | |||||||||
| poll period | 7 | |||||||||
| packet type | 8 | |||||||||
| length of test data | 9-10 | |||||||||
| 58 | — | V1.2 | EDR | O | LMP_encryption_key_size_mask_req | 1 | DM1 | m→s | - | |
| 59 | — | V1.2 | EDR | O | LMP_encryption_key_size_mask_res | 3 | DM1 | m←s | key size mask | 2-3 |
| 60 | — | V1.2 | EDR | O (M) | LMP_set_AFH | 16 | DM1 | m→s | AFH_instant | 2-5 |
| AFH_mode | 6 | |||||||||
| AFH_channel_map | 7-16 | |||||||||
| 127,1 | — | V1.2 | EDR | O | LMP_accepted_ext | 4 | DM1 | m↔s | escape op code | 3 |
| extended op code | 4 | |||||||||
| 127,2 | — | V1.2 | EDR | O | LMP_not_accepted_ext | 5 | DM1 | m↔s | escape op code | 3 |
| extended op code | 4 | |||||||||
| error code | 5 | |||||||||
| 127,3 | — | V1.2 | EDR | O | LMP_features_req_ext | 12 | DM1 | m↔s | features page | 3 |
| max supported page | 4 | |||||||||
| extended features | 5-12 | |||||||||
| 127,4 | — | V1.2 | EDR | O | LMP_features_res_ext | 12 | DM1 | m↔s | features page | 3 |
| max supported page | 4 | |||||||||
| extended features | 5-12 | |||||||||
| 127,11 | — | — | EDR | O | LMP_packet_type_table_req | 3 | DM1 | m↔s | packet type table | 3 |
| 127,12 | — | V1.2 | EDR | O | LMP_eSCO_link_req | 16 | DM1 | m↔s | eSCO handle | 3 |
| eSCO LT_ADDR | 4 | |||||||||
| timing control flags | 5 | |||||||||
| DeSCO | 6 | |||||||||
| TeSCO | 7 | |||||||||
| WeSCO | 8 | |||||||||
| SCO packet type M→S | 9 | |||||||||
| SCO packet type S→M | 10 | |||||||||
| packet length M→S | 11-12 | |||||||||
| packet length S→M | 13-14 | |||||||||
| air mode | 15 | |||||||||
| negotiation state | 16 | |||||||||
| 127,13 | — | V1.2 | EDR | O | LMP_remove_eSCO_link_req | 4 | DM1 | m↔s | eSCO handle | 3 |
| error code | 4 | |||||||||
| 127,16 | — | V1.2 | EDR | O | LMP_channel_classification_req | 7 | DM1 | m→s | AFH_reporting_mode | 3 |
| AFH_min_interval | 4-5 | |||||||||
| AFH_max_interval | 6-7 | |||||||||
| 127,17 | — | V1.2 | EDR | O | LMP_channel_classification | 12 | DM1 | m←s | AFH_channel_classification | 3-12 |