Operation Manual

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packet transmission with decreased error correction.
TTL: Time To Live: A value in an IP packet that indicates whether or not the packet has been propagating
through the network too long and should be discarded.
UBR: Unspecified Bit Rate: A transfer mode that is usually used in file transfers, email, etc. UBR can vary
depending on the data type.
USB: Universal Serial Bus: A standard interface between a computer and a peripheral (printer, external
drives, digital cameras, scanners, network interface devices, modems, etc.) that allows a transfer rate of
12Mbps.
UDP: User Datagram Protocol: A protocol that is used instead of TCP when reliable delivery is not required.
Unlike TCP, UDP does not require an acknowledgement (handshake) from the receiving end. UDP sends
packets in one-way transmissions.
VBR-nrt: Variable Bit Rate – non real time: With VBR-nrt, cell transfer is variable upon certain criteria.
VC: Virtual Circuit: A virtual circuit is a circuit in a network that appears to be a physically discrete path, but is
actually a managed collection of circuit resources that allocates specific circuits as needed to satisfy traffic
requirements.
VCI: Virtual Channel Identifier: A virtual channel identified by a unique numerical tag that is defined by a
16-bit field in the ATM cell header. The purpose of the virtual channel is to identify where the cell should
travel.
VC-Mux: Virtual Circuit based Multiplexing: In VC Based Multiplexing, the interconnect protocol of the carried
network is identified implicitly by the VC (Virtual Circuit) connecting the two ATM stations (each protocol must
be carried over a separate VC).
VPI: Virtual Path Identifier: Virtual path for cell routing indicated by an eight bit field in the ATM cell header.
WAN: Wide Area Network: A WAN covers a large geographical area. A WAN is consisted of LANs and the
Internet is consisted of WANs.