HP ProCurve Secure 7000dl Series Basic Management And Configuration Manual page 780

Appendix B: Glossary
UBR Unspecified Bit Rate. An ATM bandwidth-allocation service that does not
U-interface In an ISDN connection, the U-interface is the connection between the local
UDP User Datagram Protocol. A stateless protocol that is part of the IP protocol
UNI User to Network Interface. A term used in ATM and Frame Relay networks,
UTP Unshielded Twisted Pair. A common form of wiring in which two conductors
VBR Variable Bit Rate. A quality of service setting. VBR encoding varies the amount
VC Virtual Circuit. A circuit or path between points in a network that appears to
B-54
U
guarantee any throughput levels and uses only available bandwidth. UBR is
often used when transmitting data that can tolerate delays.
loop and NT1. For BRI ISDN, the U-interface is one twisted pair. For PRI ISDN,
the U-interface is two twisted pairs. There is only one U-interface on an ISDN
network.
suite. Using UDP, programs on network computers can send datagrams to one
another. UDP does not provide the reliability and ordering guarantees that
TCP does; datagrams may arrive out of order or go missing without notice.
However, UDP is faster and more efficient for many lightweight or time-
sensitive programs. For more information about UDP, see RFC 768 (at http://
www.ietf.org/rfc/rfc0768.txt).
UNI is the interface between the ATM or Frame Relay end user and a private
ATM/Frame Relay switch. It also can represent the interface between a private
ATM/Frame Relay switch and the public carrier ATM/Frame Relay network.
are wound around each other for the purposes of canceling out electromag-
netic interference, which can cause crosstalk. The number of twists per meter
make up part of the specification for a given type of cable. The greater the
number of twists, the more crosstalk is reduced. UTP is an unshielded form
of twisted pair wiring and is the primary wire type for telephone usage. UTP
is also common for computer networking, especially in patch cables or
temporary network connections.
V
of output data in each time segment based on the complexity of the input data
in that segment. The goal is to maintain constant quality instead of maintaining
a constant data rate. VBR is preferred for storage (as opposed to streaming)
because it makes better use of storage space. See also CBR.
be a discrete, physical path, but is not. The VC is actually a managed pool of
circuit resources from which specific circuits are allocated, as needed, to meet
traffic requirements.