Legacy Serial Leased Line Modem to IP Migration

Leased lines have been the most common way for devices to communicate over a wide geographical area for decades. Typically, an analogue modem connected to each end of the line would interface with the RS-232 or RS-485 ports on an RTU, PLC or SCADA. Since then, time and technology have progressed and telecoms suppliers around the world are withdrawing support for leased lines. The replacement technology is IP based broadband over fixed-line, or more commonly, over 4G (LTE) and presumably, it will be 5G in the future.    

Westermo provides a range of solutions for seamlessly connecting legacy serial devices to the replacement broadband technology.

• No code, configuration, or hardware changes will be required for the remote device

• Communications over broadband is much more cost effective than leased line

• Communication between sites is protected by encrypted VPN (IEC 62443 Data Conduit)

• Futureproof the remote location, when it is time to upgrade the site to full IP connectivity

Broadband routers from Westermo are equipped with serial ports. The serial interface works the same way as a serial port on a router which means that the end device will not be aware that the media has been exchanged for broadband. The only difference is the method of data transport. When a datagram is received from the connected device it is inserted into an IP packet and transmitted to a preconfigured IP address. An IP device receiving a serial datagram strips off the IP wrapper and passes it to the serial interface.

Typically, the routers at either end of the conversation are linked by a VPN (Virtual Private Network). A VPN, in essence, can be seen as a pseudo leased line. The advantage is that the data is encrypted between the two routers regardless of whether the VPN passes over the public Internet or a private network.