Why did Fujitsu choose to move to an automated test bed for its NGN products?
It's a thankless task delivering broadband - like good plumbing, people only notice it when it goes wrong. The trouble with 99.9% reliable delivery is that people only remember the point one percent non-delivery - and it drives them mad.
Fujitsu Telecommunications' (FTEL) GeoStream Access Gateway Copper MultiService Access Node (CMSAN) does a lot better than that. It delivers comprehensive NGN services across prime-line POTS, Voice over IP, high speed broadband, ISDN Primary and Basic Rate, and IPTV with far higher 'five nines' reliability, and a performance equivalent to legacy PSTN services.
But FTEL, as part of the worldwide Fujitsu Group, cannot rest on its laurels. If any unanticipated interference condition, or new equipment at the customer premises, should result in a drop in service reliability or performance, then Fujitsu's reputation could be at stake. To defend FTEL's name as a leading supplier of next generation telecommunications technology and services, their team must keep testing, testing testing...
To enable that, they needed a dedicated automatic DSL test bed. This would allow lengthy test cycles to run unattended, so that more tests could be run with less risk of human error. So they chose the services of a leading communications testing company - Spirent Communications - to provide a solution.
Spirent Communications, based in Sunnyvale, California, is a global provider of integrated performance analysis and service assurance systems that enable the development and deployment of next-generation networking technology such as Internet telephony, broadband services, 3G wireless, global navigation satellite systems, and network security equipment. The company's solutions are used by more than 1,700 customers in 30 countries, including manufacturers, service providers, enterprises and governments.
FTEL's CMSAN system
CMSAN is designed to serve thousands of xDSL and ISDN customers and is able to concentrate all the traffic into a single backhaul network. As the only multi-service platform field-proven to deliver all required NGN applications, it is a key part of BT's 21CN programme.
CSMAN consists of two main elements: a switch hub and racks of line cards. The Switch Hub performs cell/packet traffic cross-connection, concentration and policing, as well as shaping to/from the line cards up to the backhaul interfaces, while each line card can provide 64 xDSL channels as well as ATM termination, a PPP intermediate agent and a range of traffic management features. All card options are interchangeable and can be hot-swapped, and the tests must address each of these options as well as pre-testing the performance of updated CPE and CO chipsets before they are launched. Variables to be addressed in the tests include:
- Different customer premises equipment - to ensure the service is compatible with a range of equipment at the customer end, and to keep ahead of new products coming to market.
- The different noise and interference conditions that can arise on the DSL line and must be allowed for - notably the defined test standards TR-67 (for ADSL) and TR-100 (for ADSL 2 and ADSL2+).
The Spirent Test Bed
Flexibility was a key factor in the design of the test bed - being able not only run standard test conditions but also to define new test scripts embracing a wide range of variables and conditions. Fully automated testing was another factor - so that lengthy tests could be run in background mode or unattended, and the results be consolidated into user-friendly reports.
Spirent created a test bed that connects any selected line card via a switch matrix to either a .4mm andor a .5mm wire DSL line simulator, defining variable loop lengths to within 50 metres. Specified noise profiles can then be generated and injected into the line while the switch matrix also links to any of 16 different DSL modems currently being evaluated.
The test script is programmed via a simple graphical interface and allows the user to specify the channel, the modem, line type and noise conditions, and a series of standard power up and data forwarding tests - that are then run automatically. Finally, the test results are consolidated into a user-defined spreadsheet report.
The FTEL team used to spend a lot of time running lengthy manual tests that now can run automatically and unattended out of hours or in background mode while they get on with other tasks.
The test bed is kept busy as it is used in different ways and at different stages - including regression testing existing configurations as well as for development tests. In addition it is used to provide a rapid response to issues raised by customers - replicating their usage environment to see if the issue can be repeated and analyzed under test conditions. Tests are automatically out of hours, so the team can return from a weekend with a wealth of data already generated.
According to Paul Norris, Hardware Platforms Engineer at FTEL, "The advantage now is that we can get through a lot more testing quickly and identify potential problems much sooner. The test bed is working very well".