Bluetooth technology piece of Mesh understand the concept of address

Outline

As we all know, are inseparable from the concept of address many of the communication protocols, the famous IP address, the cornerstone of the MAC address, Bluetooth Mesh is no exception, this article will focus on explaining the concept of Mesh address, hoping to give the reader a clear understanding.

Classification address

Mesh in the Bluetooth specification, the addresses are divided into four categories:

1. Unicast address (Unicast Address) address uniquely identifies a network element nodes.
2. Multicast address (Group Address) is used to indicate the network group address, and group address can be shared by one or more nodes.
3. Similar virtual address (Virtual Address) role and group addresses, the address space is different in that it is 2 ^ 16.
4. Unassigned address (Unassigned address) indicates that the address can not be used.

Unicast Address

Unicast address is a unique identifier for the element Bluetooth Mesh network node (the Element), unicast address from 0x0001 to 0x7FFF start end, the address is assigned by the device are arranged in a Bluetooth device Mesh phase distribution network, unicast address can not be repeated among the nodes, the nodes must be incremented. For example: The network consists of three nodes, node A has an element, Node B has two elements, the address of the node C 2 elements, is 0x0001 node A, node B is the first element if it is 0x0002, the two elements must be 0x0003, node C empathy. Unicast address for unique identification element node network in the network, so the network packet source address (SRC) field must be set for the unicast address, the destination address (DST) does not require this.

Multicast address

Multicast address is generally used to subscribe to elements of the model (Subscribe) and release (Publish) address, multicast address 0xC000 from the beginning to the end 0xFEEE can be arbitrarily used and 0xFF00 to 0xFFFB reserved address can not be used. 0xFFFC to 0xFFFF for special use:

1. 0xFFFC all agents on behalf of that node (Proxy Node)
2. 0xFFFD on behalf of that all the friends node (Friend Node)
3. 0xFFFE on behalf of that all the forwarding node (Relay Node)
4. Refers to all nodes on behalf of 0xFFFF (All Nodes)

Mesh network Bluetooth communication model depends on the destination address (DST) field, if the destination address is a unicast address, then the message address is processed only unicast destination address for the element, if the destination address is a multicast address, then, the message may be the address of the subscription model process. Thus the introduction of communication model:

1. The client / server model
2. Publish / subscribe model

Virtual address

Virtual address general usage and multicast addresses similar to the virtual address is generated by Label UUID from start to finish 0x8000 0xBFFF, Label 16 bytes form, its address space is infinite, can make up for the space constraints of multicast addresses, but Label when UUID transport layer (upper transport layer) as parameters involved in the encryption operation to be
$EncAccessPayload, TransMIC = AES-CCM (AppKey, Application Nonce, AccessPayload, Label UUID)$

Unallocated address

Unassigned addresses 0x0000, an apparatus is in an DISTRIBUTION NETWORK publish or subscribe address is configured when the initial address. The network address can not be used to send data.