ABB RBIP-01, User Manual

Page: 13 / 58

Overview
13
Overview
What this chapter contains
This chapter gives basic information on BACnet routing and describes the RBIP-01
BACnet/IP Router Module.
Introduction to BACnet routing
BACnet routers
BACnet routers are devices that interconnect BACnet networks to form a BACnet
internetwork. The BACnet routers use the messages of the BACnet network layer
protocol (layer 3) to maintain their routing tables and exchange their routing
information.
BACnet network numbers
BACnet network numbers are assigned to the BACnet router devices. Each single
router knows the BACnet network number of each of the data link layers and
interfaces supported by the router.
The network number is valid in the range from 1 to 65.535.
The BACnet network numbers must be unique within the entire BACnet network.
BACnet network layer messages
BACnet supports 10 network layer messages that the router devices exchange. The
two most important messages are "Who-Is-Router-To-Network" and "I-Am-Router-
To-Network". They are sent as broadcast to determine other router devices and to
distribute to the other router devices information about the router’s own routing
capabilities.
BACnet/IP vs. BACnet/Ethernet
BACnet/Ethernet (ISO 8802-2 type 1 on ISO 8802-3), the so-called layer 2 Ethernet
uses only ISO/OSI layer 1 and 2 for transport. Standard IT routers transport the
Internet Protocol up to layer 3, so BACnet/Ethernet would not be transported through
networks based on the Internet Protocol.
BACnet/IP uses the User Datagram Protocol (UDP) based on the Internet Protocol,
so BACnet/IP normally is transported through networks transporting IP messages.
The RBIP-01 BACnet/IP Router Module fully supports both BACnet/IP and BACnet/
Ethernet.