The CN/IP device is a more complex connector because is connects two different protocols and may also connect the protocols at different layers. On the IP side, a CN/IP (LON/IP) router operates at the application layer and so is appropriately called an IP Gateway. On the 709.1 side the CN/IP router device operates at the network layer and is appropriately called a 709.1 router. So depending on the user’s perspective a CN/IP device could be called a gateway or router or a router/gateway. The typical approach is to name the device from the standpoint of it behavior on the CN side, that is a CN/IP router. A block diagram of two CN router / IP gateways connected via IP Ethernet is show below.
Fig. 1.3: CN to IP Router/Gateway Architecture
A CN/IP router forwards 709.1 packets to or from an IP channel (using an Ethernet or WiFi transceiver) and a CN channel (using twisted pair FT-10 or other transceiver). The CN/IP router has a presence on, or physical connection to, both channels. The router takes 709.1 messages from the component network, wraps them in an 852 packet and sends them over the IP network. The device also receives 852 packets on its IP interface, unwraps them and puts the 709.1 messages on the CN channel. The virtual 852 channel looks like a CN channel to CN nodes. The IP element is transparent. This enables a “flat” (single protocol for endpoints) network and is more easily managed and scaled than using CN to IP interfaces that do not hide the IP element from the CN nodes. The important thing to the systems integrator is not so much what the CN/IP device is called but how transparent it makes the IP network appear to the CN nodes. Typically a CN/IP router also also employs a web server for configuration purposes. The block diagram is shown below.
Fig. 1.4: GRouter 3 Architecture