Panasonic 1200N - Manual (Page 243)

Glossary U
Centillion 1200N ATM Switch User Manual B-81
NTP 297-8103-903
TSI
Telecommunications Standards Institute: The primary telecommunications
standards organization
TTC
Telecommunications Technology Council: A Japanese standards committee.
TTCN
Tree and Tabular Combined Notation: The internationally standardized test script
notation for specifying abstract test suites. TTCN provides a notation which is
independent of test methods, layers and protocol.
TTL
Transitor transitor logic
U
UBR
Unspecified Bit Rate: An ATM service category which does not specify traffic
related service guarantees. Specifically, UBR does not include the notion of a per-
connection negotiated bandwidth. No numerical commitments are made with
respect to the cell loss ratio experienced by a UBR connection, or as to the cell
transfer delay experienced by cells on the connection.
UCFAD
Universal Cell Frame Assembly/Disassembly
UDP
User Datagram Protocol: This protocol is part of the TCP/IP protocol suite and
provides a means for applications to access the connectionless features of IP. UDP
operates at layer 4 of the OSI reference model and provides for the exchange of
data grams without acknowledgements or guaranteed delivery.
UL
Underwriting Laboratory: A privately owned company that charges manufacturers
a stiff tee to make sure their products meet the safety standards which UL itself
develops. A UL label on a product has a very specific message. It says the product
conforms to the safety standards UL has developed, nothing more. It does not
affirm that the product will work.