The IGUANA Gateway

The architecture of the gateway - depicted in figure 37 - basically consists of three separate layers, namely an ``Internet layer'' for providing Internet access to the gateway, a ``services and data processing layer'' that handles routing and implements several services, and a ``fieldbus layer'' which provides connectivity to underlying fieldbus systems. The IGUANA gateway implements four types of modules that fit into one of these layers. These modules communicate with each other with certain protocols and communication paths⁸⁵.

Figure 37: Basic Architecture of the IGUANA Gateway

The modules are currently implemented as daemons on a UNIX⁸⁶ operating system and communicate via stream-oriented TCP/IP protocols. This kind of communication enables these modules to be placed on different hardware devices. This way an Internet front-end could be situated on a device outside of the IGUANA gateway. However, the current implementation consists of one hardware device that incorporates all modules.

The IGUANA gateway implements the following four module types:

1. Extended Service Daemon (ESD):

This is the main module of the gateway and implements routing between fieldbus and Internet modules. Moreover, it implements the gateway services, such as event processing and data logging.

2. Internet Front-Ends:

These modules implement various Internet protocols. Currently there are implementations for the following protocols:

• Simple Network Management Protocol (SNMP)
• Lightweight Directory Access Protocol (LDAP)
• Structured Query Language (SQL)
• World Wide Web protocols (WWW)
• Extended Service Daemon Protocol (ESD protocol)

More information about the implementation of these protocols can be found in [PRA01] and [SAUT02].

A SOAP Web Service on the IGUANA gateway would be implemented as an additional Internet front-end.

3. Internet Notification Originator (INO):

These modules can be used to send asynchronous notifications by means of Internet protocols. Currently available protocols are SMTP and SNMP.

4. FAN Connections:

These modules provide connectivity to underlying fieldbus systems. Currently there are only implementations for LonWorks and two proprietary protocols.