Bacnet Ip; Bacnet Ip Broadcast Management Device (Bbmd) - ABB Cylon FBXi Series User Manual

BACNET IP

BACnet/IP uses the User Datagram Protocol (UDP) to send data packets. ASHRAE adopted BACnet/IP
in annex j of the 135- 1995
BACnet/IP communicates using four methods.
•
BACnet/IP to BACnet/IP (same subnet): Assuming that two devices know each other's IP addresses
and the UDP ports they are using, i.e., their respective B/IP addresses, there is nothing that restricts
them from communicating directly.
•
BACnet/IP to BACnet/IP (different subnet): The location of the two devices is already known by the
host and the message is routed to the device using switches and routers.
•
Broadcast (same subnet): This is a standard Who is/ I am message sent across a local subnet for the
BBMD to discover what the address are for the BACnet devices on the subnet.
•
Broadcast (different subnet): This is a standard Who is/ I am message sent across a local subnet for
the BBMD to discover what the address are for the BACnet devices on other subnets.

BACNET IP BROADCAST MANAGEMENT DEVICE (BBMD)

Some BACnet services use "broadcasts" (e.g. "
"blocked". Thus, BACnet
network of 2 or more
A BBMD located on an
constructs a "peer to peer"
received by other BBMDs on other
Since the BBMD messages are directed messages, individual messages must be sent to each BBMD. Each
BBMD device maintains a
BBMDs within the network. BBMDs must know the
It is possible to communicate to a device on a subnet that does not have a
Workstation example above. This type of device is called a
subnet from devices attempting to communicate with it.
Usually, in BACnet/IP,
The foreign device (e.g. BOWS) registers with each BBMD, after which it can communicate with all other
devices on the network. The
devices.
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standard.
Who-Is
broadcasts are limited to the
IP subnets, a device with BBMD
IP subnet monitors the origin of a broadcast message on that subnet and, in turn,
message
in order to pass through an
IP subnets and transmitted as a broadcast on their attached subnets.
Broadcast Distribution Table (BDT)
a foreign device is on a different subnet.
BBMD then maintain a
BACnet® Networking
FBXi Series |
"). On a LAN with standard routers, these broadcasts are
IP Subnet of the BACnet
can be used.
IP router. This "peer to peer" message is
, the content of which is usually the same for all
IP address of all other BBMDs in the network.
BBMD
foreign device since it resides on a different IP
Foreign Device Table (FDT)
device. With a BACnet/IP
as in the BACnet
which keeps track of foreign
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