Help¶

Maximum number of segments supported for outgoing messages. This value should typically be fine-tuned based on what models the local node supports, i.e. what’s the largest message payload that the node needs to be able to send. This value affects memory and call stack consumption, which is why the default is lower than the maximum that the specification would allow (32 segments).

The maximum outgoing SDU size is 12 times this number (out of which 4 or 8 bytes is used for the Transport Layer MIC). For example, 5 segments means the maximum SDU size is 60 bytes, which leaves 56 bytes for application layer data using a 4-byte MIC and 52 bytes using an 8-byte MIC.

Be sure to specify a sufficient number of advertising buffers when setting this option to a higher value. There must be at least three more advertising buffers (BT_MESH_ADV_BUF_COUNT) as there are outgoing segments.

Direct dependencies¶

BT_MESH && BT_HCI_HOST && BT_HCI && BT

(Includes any dependencies from if’s and menus.)

Defaults¶

3 if BT_MESH && BT_HCI_HOST && BT_HCI && BT

Kconfig definition¶

At subsys/bluetooth/host/mesh/Kconfig:219

Included via Kconfig:10 → Kconfig.zephyr:35 → subsys/Kconfig:8 → subsys/bluetooth/Kconfig:155 → subsys/bluetooth/host/Kconfig:125

Menu path: (top menu) → Bluetooth → Bluetooth Mesh support

config BT_MESH_TX_SEG_MAX
    int
    prompt "Maximum number of segments in outgoing messages" if BT_MESH && BT_HCI_HOST && BT_HCI && BT
    range 2 32 if BT_MESH && BT_HCI_HOST && BT_HCI && BT
    default 3 if BT_MESH && BT_HCI_HOST && BT_HCI && BT
    depends on BT_MESH && BT_HCI_HOST && BT_HCI && BT
    help
      Maximum number of segments supported for outgoing messages.
      This value should typically be fine-tuned based on what
      models the local node supports, i.e. what's the largest
      message payload that the node needs to be able to send.
      This value affects memory and call stack consumption, which
      is why the default is lower than the maximum that the
      specification would allow (32 segments).

      The maximum outgoing SDU size is 12 times this number (out of
      which 4 or 8 bytes is used for the Transport Layer MIC). For
      example, 5 segments means the maximum SDU size is 60 bytes,
      which leaves 56 bytes for application layer data using a
      4-byte MIC and 52 bytes using an 8-byte MIC.

      Be sure to specify a sufficient number of advertising buffers
      when setting this option to a higher value. There must be at
      least three more advertising buffers (BT_MESH_ADV_BUF_COUNT)
      as there are outgoing segments.

(Definitions include propagated dependencies, including from if’s and menus.)