An independent European test lab has uncovered systems interoperability issues that carriers could face if they're planning to launch broadcast TV and video services over their DSL networks.

The European Advanced Networking Test Center AG (EANTC) performed a multivendor test late last year for the European Telecommunications Standards Institute (ETSI) and identified a number of problems.

The unveiling of the test results comes as a number of European operators are launching, or planning to launch, such services (see French Say Oui to DSL TV, Euro Telcos Flirt With TV , and TV Over DSL Over Italy ). Just this week France Telecom SA (NYSE: FTE) extended its service beyond its Lyon pilot and into the biggest French market, Paris.

Despite the fact that various commercial services are already up and running, it's still very early days for this emerging sector, and EANTC found some basic configuration and interoperability problems during its testing process, though most functionality test goals were reached.

The German test company set up a trial network incorporating DSL modems from Arescom Inc. (No. 6 in Light Reading's 50 Worst Company Names); a DSLAM and an Ethernet switch from LM Ericsson (Nasdaq: ERICY); a DSLAM from Net to Net Technologies Inc.; and a load generator and protocol emulator from Spirent Communications.

EANTC checked service quality from a video headend to a modem across Ethernet and ATM backbones; channel provisioning using various video headends and set top boxes; and service management, including the interoperability of program guides and channel controls. Although all devices eventually passed the tests, EANTC encountered configuration issues -- in tagging packets for prioritization in one instance, and in ATM traffic management in another.

The team also performed transport tests to check the scaleability and functionality of the network elements. Here, the key issue was the interopeability of one of Arescom's DSL modems regarding the Internet Group Management Protocol (IGMP), which is used for multicasting and controls the switching of channels at the DSLAM. Arescom is to resolve the software issue for future releases.

EANTC also tested the "zapping time" -- the time it takes to change a video stream or TV channel -- of the DSLAMs under full subscriber load. The test team describes this as "one of the most critical DSLAM and DSL modem multicast performance tests," as it is a major customer satisfaction issue, and found the results "very promising," with zap times of between 13 milliseconds and 230 milliseconds.

Overall, the results show that, while it's possible to set up a multivendor network and deliver adequate TV service over DSL, the sector is still some ways from delivering full multivendor interoperability. This, believes EANTC, will be an issue for service providers that already have a massive installed base of DSL equipment, yet want to deploy best-of-breed solutions and be able to source critical components from multiple sources.

EANTC believes the key problem areas for interoperability are the set-top boxes and the specific middleware required for video on demand and broadcasting services. Getting the new systems to work with extant provisioning, network management, and billing systems is also set to be a key challenge.

— Ray Le Maistre, International Editor, Boardwatch