Agilent Technologies J3972A - Manual (Page 178)

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Topology
The organization of network devices in a network. FDDI uses a ring topology,
Ethernet uses a bus Topology, and Token-Ring uses a ring topology.
Trailer
The last few octets or nibbles of a frame that fall outside the column and row view
of the frame structure.
Transmission Convergence Sublayer (TC)
This sublayer of the physical layer maps ATM cells to and from the physical
transmission medium with three key processes: cell delineation, cell
synchronization, and cell rate decoupling.
Unassigned Cell
A cell used to fill unused bandwidth. Unassigned cells are similar to Idle or Fill
cells. See also Idle Cell or Fill Cell.
User Network Interface (UNI)
The physical and electrical demarcation point between the user and the public
network service provider.
UTP (Unshielded Twisted Pair)
A cable that is twisted in pairs. Pair twisting reduces crosstalk by canceling the
magnetic fields generated in each of the twisted wires.
Virtual Channel (VC)
A communications path between two nodes identified by label rather than a fixed
physical path.
Virtual Channel Identifier (VCI)
A Virtual Channel Identifier is a 16-bit field in the ATM header. The VPI and VCI
are used together to determine the destination address of the ATM cell.
Virtual Path (VP)
A collection of virtual channels grouped together for routing purposes sharing a
common VPI.