Coupler function (KNXnet/IP Routing)
- Wolfgang Granzer
The NETx KNX IP Secure Router secure operates as a line or backbone coupler. In both cases, the LAN (IP) is used as a backbone. The following table shows the application possibilities of the KNX IP Router compared to the classic topology:
| Classical Topology (without IP) | IP coupling of areas (IP area coupl.) | IP coupling of lines (IP line coupler) | |
|---|---|---|---|
| Area (Backbone) | TP | IP | IP |
| Coupling | KNX line coupler (max. 15 Pcs.) | KNX IP router (max. 15 Pcs.) | Directly via LAN switch |
| Main line | TP | TP | IP |
| Coupling | KNX line coupler (max. 15x15 Pcs.) | KNX Line coupler (max. 15x15 Pcs.) | KNX IP router (max. 225 Pcs..) |
| Line | TP | TP | TP |
Figure 1: KNX IP router as line coupler
The individual address assigned to the NETx KNX IP Secure Router determines whether the device operates as a line or area coupler. If the individual address is in the form of x.y.0 (x, y: 1..15), the router operates as a line coupler. If it is in the form of x.0.0 (x: 1..15), the router acts as a backbone coupler.
Figure 2: KNX IP router as area coupler
If the NETx KNX IP Secure Router is used as a area coupler (x.0.0), there must not be a KNX IP router in the topology beneath it. For example, if a KNX IP router has the individual address 1.0.0, there must be no KNX IP router with the address 1.1.0.
If the NETx KNX IP Secure Router is used as a line coupler (x.y.0), there must not be a KNX IP router in the topology above it. For example, if a KNX IP router has the individual address 1.1.0, there must be no KNX IP router with the address 1.0.0.
Figure 3: KNX IP router as as area and line coupler
The KNX IP Router has a filter table and thus contributes to reducing the bus load. The filter table (8kB) supports the extended group address range (main groups 0..31) and is automatically generated by the ETS.
Because of the speed difference between the Ethernet (10/100 MBit/s) and KNX TP (9.6 kBit/s), a far greater number of telegrams can be transmitted on IP. If several consecutive telegrams are transmitted for the same line, they must be buffered in the router to avoid telegram loss. The NETx KNX IP Secure Router has a memory for 150 telegrams (from IP to KNX).