Perle Systems presents the – according to Perle – first and only Terminal Server on the market able to provide HTTP Tunneling. Perle Iolan products ought to securely connect and transport serial data between remote serial peers over the internet without the need to change firewall settings.
Connecting to remote serial communication based devices – for example the serial console port on a piece of equipment or an industrial PLC – is a simple matter when using a closed, dedicated network. By using a serial to Ethernet terminal server such as a Perle Iolan serial data to and from the port are packetized onto Ethernet packets and transported to a remote IP application or a peer Iolan where it is converted back to serial for connection to the remote serial device peer. The IP address of all the elements involved are known and the client server relationship is clear.
When attempting to do this across the internet however, it is not as simple. In corporate environments, connections to the internet are safeguarded by firewalls, routers and proxy servers. The individual device IP addresses appear as a dynamic translated network address (NAT) to entities on the internet and are not directly addressable.
Firewalls are also very particular on the type of IP sessions that are allowed to and from the internet. HTTP (port 80) is firewall-safe and is universally allowed to pass through. Other protocols such as SSH (port 22) or Telnet (port 23) are normally blocked. To allow these, the firewall configuration must be changed which compromises the existing corporate security policy.
According to Perle it’s Iolan’s with HTTP Tunneling technology solve this problem: A remote HTTP Tunneling Iolan client behind a firewall establishes an HTTP session with an Iolan server counterpart on the internet located in an enterprise DMZ (De-Militarized Zone) or Service Provider location. By utilizing standard HTTP GET and SET commands, these peers now have the ability to exchange packets. Serial data from an attached device can now be converted by the Iolan and sent across the internet to its HTTP tunnel peer. The Iolan peer will then exchange the packet back to serial. The result is a firewall-safe, seamless serial connection through the internet. (Source: Perle Systems/GST)