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How to understand the data linker layer and physical layer in the Mesh network?

lgs

Hi There,

I have a question now. If I want to alter the frame format in the data linker, how do I do? 

I try to find the source code of the data linker layer in the Mesh SDK, I cannot find it. I just find the bearer layer. 

Could you help me answer the question?

Best regards,

Gaosheng Liu

Parents
  • +1

    Hi,

    Few (if any) network specifications follow the OSI model completely, and Bluetooth mesh is no exception. What corresponds to the data link layer from the OSI model would be a combination of the bearer layer, some of the underlying BLE specification, and maybe even some of the network layer.

    The bearer layer consists of two options for bearer: BLE advertisements (ADV bearer) and BLE connections (GATT bearer). The format used follows the Bluetooth specification for those options. Changing this may be difficult, in particular the GATT bearer which uses the precompiled BLE stack (that we call "SoftDevice") which cannot be altered.

    Further, changing any part of the Bluetooth mesh stack will void the qualification.

    What is the purpose of changing anything in the bearer layer? Maybe there are other ways to achieve the same goal.

    Regards,
    Terje

  • 0 in reply to tesc

    Hi Terje,

    I am looking back for a further question.

    1. I am still confused about the "bearer" layer.  I am still not sure of its functions. For example,  is it if including some parts of the network layer, and some parts of the linker layer.

    2. When a packet transmits to the bearer, is it a "datagram" like in the network layer? 

    3. Does the network layer have routing functions?

    4. Does the transport layer have control functions?

    With best regards,

    Gaosheng

Reply
  • 0 in reply to tesc

    Hi Terje,

    I am looking back for a further question.

    1. I am still confused about the "bearer" layer.  I am still not sure of its functions. For example,  is it if including some parts of the network layer, and some parts of the linker layer.

    2. When a packet transmits to the bearer, is it a "datagram" like in the network layer? 

    3. Does the network layer have routing functions?

    4. Does the transport layer have control functions?

    With best regards,

    Gaosheng

Children
  • 0 in reply to lgs

    Hi,

    1. The bearer layer is the bottom layer of the Bluetooth mesh stack, below the Network layer. Basically it is the very thin layer that you need, for Network PDUs to be transported over either BLE advertisemens (using specific advertising types for the advertising data) or in a BLE connection (using a specific GATT service). See the Mesh profile specification v1.0.1 section 3.3 Bearers for the details of the bearer layer.

    2. The bearer gets a Network PDU from the network layer. The Network PDU is described in the Mesh profile specification v1.0.1 section 3.4.4 Network PDU.

    3. Bluetooth mesh is a managed flooding network. Packets propagate through the network through relay nodes, who resend the message up to the TTL number of jumps. There is no routing, as in a routed network.

    4. I am not familiar with "control functions", can you elaborate a bit on what you mean?

    Regards,
    Terje

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