MAC Layer Address
Depends on the Physical layer technology:
MAC Address consists of a length, DLEN or SLEN and an ADR ( DADR, SADR )
MAC length of Zero
- Indicates broadcast
- If DNET is oxffff then it is a global broadcast
- If DNET is any other non-zero value, then it is a Remote Broadcast
See BACnet Broadcast
|Physical Layer||SLEN||Source of Address||Example|
|MSTP||1||(Usually switch on device)||27|
|LonTalk||6, 7||Neuron ID|
Other MAC Layer Address Lengths
The BACnet Implementation guide recommends that devices handle MAC addresses up to 18 octets long. (Section 2.9) BTL Implementation Guide. This has been deemed "no longer relevant" (see below).
Addresses are expected to be no more than 6 bytes. Addendum 135-2008q-2 which describes the VMAC layer approach, addresses are expected to be no more than 6 bytes. So there is no longer a need for implementations to expect longer addresses. The support for LON addresses of length 7 is so restrictive; only usable as a DLEN and never as an SLEN, that only routers and devices that themselves will utilize the form of LON addresses of length 7, are required to support that. i.e. Routers that potentially route messages to Lon networks should support a length of 7 still.
|APDU BBMD BVLC BVLL DADR DNET Encoding I-Am LSAP MAC NPCI NPDU NSAP NSDU SA SADR SNET|
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