Investigation into Alternative ITS Protocols for Center-to-Center Communications, 10-9274

Principal Investigator
Steven W. Dellenback, Ph.D., PMP
Associate Investigator
Mike Brown
Roger Strain

Inclusive Dates 11/01/01 - 09/30/02

Background - Eight years ago the Federal Highway Administration (FHWA), the U.S. Department of Transportation (USDOT), and the Joint Program Office (JPO) initiated a standards development effort. More than 100 different standards development efforts were initiated to provide a set of standards for the Intelligent Transportation Systems (ITS) industry. The standards are broadly termed the ITS National Standards and cover a wide range of application domains (e.g., sign control, information exchange) within the ITS industry. The standards development process differs from the traditional method of standards development in the software industry - that widely accepted, widely used applications become the standards (e.g., HTML). During the last ten years, the ITS industry has developed a number of systems that were not designed to interact. Each of these systems has been typically developed as an island and cannot communicate with any other system. A major component of the ITS National Standards is the development of protocols to allow standalone transportation centers to exchange data in a seamless and efficient fashion. The FHWA has mandated that all future ITS deployments be based on the ITS National Standards.

One of the most significant standardization efforts is the area of Center-to-Center (C2C) communications. As a committee member on the two committees developing the appropriate standards, SwRI has been active in understanding and defining the C2C technologies. Throughout the United States, five significant programs have been funded to interconnect ITS centers. One of these is in Texas, and SwRI has been funded $1.9 million to date to develop an infrastructure to allow centers to exchange data throughout the State of Texas.

The Texas project uses an ITS standard protocol known as DATEX/ASN (ISO standard) to support the information exchange. The Texas project is also unique in that it is the only C2C system that connects systems built on different software bases (i.e., heterogeneous software systems). Other significant deployments in the United States require each center to execute the same base software. The DATEX/ASN protocol has not received widespread acceptance and will more than likely become unused in the near future. The rapidly evolving XML (Extensible Markup Language) protocol is a candidate protocol to replace DATEX/ASN. Although some effort has been made in the ITS standards community to establish CORBA as a base protocol, many in the field believe XML will supplant DATEX/ASN and CORBA within the next five years.

This program was undertaken to determine if either CORBA or XML is appropriate to implement the real-time requirements of C2C applications. The program explored the use of these alternative protocols, and a prototype was developed that successfully demonstrated that CORBA and XML could be utilized as the transport protocol for C2C communications.

Approach - The original proposal defined five tasks to be performed. The following lists the project tasks and results of each task:

Task 1: Requirements Analysis

• Finalized the core requirements of what data needs to be exchanged.
• Investigated options to convert directly from ASN.1 to XML.
• Investigated the use of SSL/TLS security for use with C2C communications. The PIs concluded that SOAP should be used as SOAP uses http, which includes support for SSL/TLS.
• Identified SVG as a protocol to facilitate C2C data exchange.

Tasks 2, 3 and 4: CORBA Investigation, XML Investigation, Demonstration (task status combined for the purposes of status reporting because the efforts were intertwined)

• Developed a central communication and data server with the following features:
  • Collects ITS data from defined data providers in an XML format and distributes the data to clients using a data subscription/publication pattern.
  • Facilitates communication between C2C participants (TMC plugins, data clients, etc.) using three different communication architectures (Web Services/SOAP), (CORBA/IIOP), (XMLSocket/TCP/IP).
• Created a test program that simulates a XML capable TMC plugin with the following features:
  • Implements each of the three communication architectures
  • Simulates Asynchronous data updates for the following:
    • Network data
    • Incident data
    • Lane closure data
    • Traffic (speed/occupancy) conditions data
    • DMS status
    • LCS status
    • CCTV status
    • CCTV snapshots
  • Simulates the following synchronous requests/responses:
    • DMS info
    • DMS control
    • LCS info
    • LCS control
    • CCTV info
    • CCTV control
    • CCTV snapshot
    • All other status information (information for a current incident, lane closure, and so on.)

    The following illustration depicts the test environment created to support the exchange of information.

• Created a C#. NET data client of the Server as a Web Service running under Microsoft IIS.
• Developed a SVG (Scalable Vector Graphics) based map for display of information. The following illustration is a screen shot from the application developed.

Accomplishments - The project was recently completed, and promotional activities are continuing. The objectives for this project were:

• To determine if a software bridge can be designed and developed that would allow a DATEX- and CORBA-based ITS standard system to exchange information.
• To investigate the feasibility of utilizing XML to replace DATEX and CORBA or to use XML as a software bridge to facilitate exchange of information.
• To evaluate the performance aspects of each of the above solutions.

All these objectives were fulfilled on schedule and within budget. With respect to success criteria, at the time that the IR&D proposal was submitted, it was stated that the success of the project would be determined if SwRI could architect a solution that facilitated the exchange of information between environments that are built utilizing different protocols. The project very successfully demonstrated this exchange of information across multiple protocols. In fact, the effort was so successful that the Texas Department of Transportation (TxDOT) is funding SwRI under the Statewide Integrator program (10-05713) to implement an XML/SOAP solution in the next generation of the TxDOT Center-to-Center (C2C) program (task value is $1.2 million).

Additionally, SwRI and TxDOT will be considered the front-runner in developing the next generation of C2C low-level protocol standards. SwRI will be submitting the results of the XML/SOAP development efforts to the NTCIP Joint Committee for their consideration in funding a work item to develop a new ITS standard.

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