Rick Nelson

Who are you and what do you do?
November 27, 2006

The LXI LAN/Web Working Group worked on an improved discovery and identification protocol during the recent PlugFest in Boston. The working group is co-chaired by Nick Barendt (VXI Technology) and John Ryland (Keithley).

The LXI specification requires that all LXI devices implement a protocol called “discovery” that allows LXI conformant devices to be located on the Ethernet network. GPIB systems can simply interrogate each of the 15 possible device addresses to learn what devices are attached, but this strategy is not suitable for Ethernet with its much larger address space. Therefore LXI devices implement a discovery protocol, based on VXI-11, standards that provides equivalent functionality over Ethernet.

The existing discovery protocol has limitations that have motivated the LXI Consortium to seek improvements. For example, using the existing protocol, only a limited amount of information can be learned about each device, such as model number, serial number, and firmware version. Consortium members have agreed that it is highly desirable to have a richer protocol that better serves the anticipated needs of tomorrow’s test systems.

The working group examined several alternative commercially available protocols, including Universal Plug and Play and Rendezvous (Bonjour). Unfortunately, the group concluded that none of the alternatives meets all the needs of LXI, nor have they achieved the widespread adoption in the market required to make them readily available and easy to use. For these reasons, the working group elected to stay with the existing protocol for the immediate future and to focus on addressing the key need to obtain more in-depth information about LXI devices during the discovery process.

Toward the end, the working group has defined a simple mechanism that uses the built-in web server capability included in all LXI devices to provide detailed information about the device upon request. This information is in the form of an XML document that includes a great deal of useful and detailed information about the device. During the working session, the members reviewed and discussed a proposed schema for the XML document. This work will continue during in the group’s regular meetings, and the results will be incorporated in a future version of the LXI specification.

The working group has also been discussing its approach with the ATML (Automated Test Markup Language) working group, which is undertaking a related, but much larger effort to define XML schemas that describe all aspects of the test system in great detail. By virtue of luck or good planning, the ATML working group was meeting on the same days and in the same hotel as the LXI Consortium. This allowed for some good and useful cross-pollination of ideas between the two groups, but that is a topic for another day.--Paul Franklin, Keithley Instruments, LXI Technical Committee Chair

Posted by Rick Nelson on November 27, 2006 | Comments (0)