Animated Optical Glossary
Search a term

EXFO Glossary

X (browse from .......... to)
X.25 Data Protocol...............xDSL
X.25 Data ProtocolxDSL
from X.25 Data Protocol... to xDSL

X.25 Data Protocol

A packet-switching standard developed in the mid-1970s for transmission of data over twisted-pair copper wire.


Generic name for digital-subscriber-line technology. The x is a variable that, in context, is replaced according to the appropriate variety of DSL (such as SDSL, IDSL, and ADSL). 

The branch of testing that applies to the deployment of comprehensive DSL (ADSL, VDSL, etc.) and IP triple-play services. These deployments are rendered complex by the need to set-up user names, passwords, DSLAM port settings, subscribed video channels (IPTV), Internet service provider settings, e-mail settings and VoIP settings. Given all these factors, it is likely that service-impairing errors will affect a percentage of subscribers. This requires multilayer testing on copper and optical fiber, bandwidth rate validation (upstream/downsream), quality of service validation and customer equipment/wiring verification.