User Manual

Network architecture
BACnet architecture (MLN & ALN)
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Key
B Bridge, e.g., IP router, LonWorks router
R Repeater, e.g., LonWorks physical repeater
RT Router, e.g., PXG3
½
RT Half router, e.g., PX..-T
Internetwork
In BACnet, the BACnet internetwork is defined as the largest BACnet unit. It consists of one or more
BACnet networks. Only one active connection can exist between any two BACnet devices in a BACnet
internetwork.
All bus subscribers from the ALN and MLN, including BACnet third-party devices, are part of the BACnet
internetwork. The devices in the FLN are part of the Desigo system but not part of the BACnet
internetwork, because they do not communicate via BACnet.
Network
Desigo devices use LonTalk (BACnet/LonTalk), IP (BACnet/IP) or MS/TP (BACnet MS/TP) as their
transport protocol. If different transport protocols are used, different physical networks are created, which
must be connected to the PXG3 router. BACnet routers connect networks on the BACnet network layer and
transmit messages via the network number.
If the transport protocol changes, the BACnet network also changes, e.g., BACnet devices that use LonTalk
as their transport protocol are always located in a different network than devices that use IP as their
transport protocol. This also applies to PTP connections.
Desigo devices use LonTalk (BACnet/LonTalk) or IP (BACnet/IP) as their transport protocol and MS/TP
(BACnet MS/TP) to integrate third-party devices. If different transport protocols are used, different BACnet