NTAF makes interoperability progress

Engineers prove concept of standardized interface to automate test equipment.

By Martin Rowe, Senior Technical Editor -- Test & Measurement World, 11/29/2010 11:09:53 AM

Numerous manufacturers produce telecommunication network elements and test equipment. While these products help us communicate, they may not communicate well with each other, especially when multiple manufacturers are involved. To eliminate that problem, network equipment makers, test equipment hardware and software makers, and service providers formed NTAF, (Network Test Automation Forum), on March 16, 2010. The first technical meeting was on April 22 in Montreal. The article "Forum to define network test interface" explains the NTAF concept.

NTAF's goal is to create a common programming interface for network elements and test equipment. Once completed, the programming layer should let service providers ease automation of test equipment or networking elements much in the way that GPIB and VXI test instruments use VISA. (The NTAF held its first plugfest in October; see below.)

NTAF president Keith Kidd of Verizon explained that at one time, you could connect a test instrument from Ixia, Spirent, Exfo, or others to network equipment, run a test, and call it automated. "Those days are gone," Kidd said. "You can no longer rely on the output of one test device for the success or failure of a test."

The impetus for test automation came when networks became too complex for single devices to validate them. Kidd explained that Verizon used to be able to utilize a single test device to verify a network element with test instrumentation from Ixia, Spirent, or Agilent. That's impossible now because of the complexity of traffic carried over networks today. Thus, NTAF's goal is to get all of those network elements, testers, and test software talking to one another in an integrated and automated test. Test engineers also need remote access to networks and test tools.

Networks may include broadband switches and routers, DSLAMs, video conferencing systems, firewalls, and scheduling products. Tests include throughput of a single element or an entire network based on varying traffic patterns generated by software products from companies such as Shunra and Breaking-Point Systems. For example, a test on a 100-Gbit link must not cause degradation of voice or video over IP. Labs at carriers such as NTAF members Verizon and British Telecom need test equipment for measuring throughput and for measuring voice or video quality. Testing requires at least two types of network elements, which may go beyond the expertise of any one test-equipment company. Test labs may also have test equipment from more than one company that can do the same test. They want to easily switch among those testers without the need for changing test-automation software.

"Good programmers can write code that will talk to more than one tester or network element, but the development of that code can take months even with the industry-standard Tcl scripting language," Kidd explained. "Ixia and Spirent both support Tcl, but they have different implementations." That forces programmers to become familiar with those differences. In addition, third-party tools such as iTest from Fanfare make testing easier through GUI implementations. Such software takes the programming out of developing automated tests, but those who develop the test still have to know the syntax for each product that the software supports.

Kidd explained that network-equipment and test-equipment providers don't share their programming interfaces until they release their products. As a result, test developers at test-software companies are always playing catch up. NTAF should close that development gap with a common interface, making network equipment "plug-and-play" for testing.

"Standardization occurs at the point when people can no longer accept the pain of living without it," said Kidd. "They become willing to put in the time required to develop standards." NTAF's technical-committee members hold conference calls every other week to continue development of the standard. "Everyone has lots of homework," said Kidd.

When you connect equipment to a network, the other network elements need to know what you've connected and what it can do. Network scheduler software needs to know what each network element does, who might use it, and when. That's the kind of information that is going into the NTAF schema.

Over the last several months, engineers have begun developing the programming interface, which is based on XMPP (Extensible Messaging and Presence Protocol). XMPP lets you develop standardized tags by leveraging XML. In April, engineers proposed a schema in XMPP to provide a common set of tags for network-equipment functions. Because XMPP, like XML, is extensible, new devices can not only use standard tags, but NTAF members can add tags to the schema, which will then be available to others. Member companies can develop tags for their products prior to the adoption of the standard.

XMPP will work regardless of the programming language or operating system that each product uses. Members won't have to migrate their equipment to a single platform. To begin testing the concept, software engineers developed models in the languages that their equipment uses, such as C, C#, Java, and Tcl. The models are designed to work with the NTAF schema "Engineers are spending nights, weekends, and holidays working on the schema and their own equipment models for using it," said Kidd.

First plugfest

NTAF held its first plugfest on October 18–20, 2010, at Fanfare's offices in Mt. View, CA, with equipment there talking to equipment at Verizon Labs in Texas. Engineers at the member companies have developed models of their equipment. People were also observing the tests at locations in the US, Canada, UK, and Germany. The plugfest was the first opportunity for NTAF members to test their software models. By connecting network equipment through the cloud, engineers will be able to run tests without the need for a central facility.

This plugfest consisted of four prototypes developed by NTAF members—Ixia, Spirent, Fanfare and Verizon—and were written in C#, C++, Tcl, and Java. By the end of the plugfest, the four models—and the equipment behind them—were communicating with each other. Software engineers could find the bugs and fix them during the event. The plugfest proved that the models could work. Kidd noted that engineers in San Jose were able to connect to the phone dialer prototype in Texas and get it to make a call. In a second demonstration, two suppliers were able to discover one another's prototypes, test capabilities, and set up for a hypothetical test session.

Engineers are now working on documentation, including best practices. Kidd estimates that NTAF 1.0 draft will be available to members by spring of 2011.