U - W
- UPSR (unidirectional path-switched ring).
A method of providing redundancy for fiber-optic lines on a SONET ring. The SONET ring consists of two fiber-optic lines, each carrying the same traffic, but transmitting it in opposite directions around the ring. If one line fails, the backup line is already carrying the same traffic.
- VCI (virtual channel identifier).
The VCI is a 16-bit field in the header of an ATM cell. Its value defines the logical path to the next destination of the ATM cell. ATM switches use the value of the VPI/VCI fields to identify the next ATM node.
- VCSEL (vertical cavity surface emitting laser).
Lasers with a vertical cavity that emit light from their surface, in contrast to regular edge emitters.
- VPI (virtual path identifier). ...
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