Appendix D: Glossary
Megabit Modem 400F, 500L, 600F, and 700F User Manual 121
UDP User Datagram Protocol is a transport protocol used to map inbound traffic (from a
remote IP address) to an internal (LAN) IP address. Uses a protocol port number for
the destination at the remote location.
upstream traffic Communications from a user to a service provider.
VCI Virtual Channel Identifier is a 16-bit field addressing identifier in the header of an ATM
cell used to route cell traffic. It identifies a particular VC link for a given VP.
VCMUX Virtual Channel Multiplexer-based encapsulation used for networks with large
numbers of virtual channels making it practical to carry a single protocol per virtual
channel.
VC A Virtual Channel is a logical connection in the ATM network over which ATM cells are
transmitted.
VPI Virtual Path Identifier is an 8-bit field addressing identifier in the header of an ATM
cell that is used to route cell traffic. It identifies a particular VP link.
VP A Virtual Path is a group of VCs carried between two points. The VP provides a means
of bundling traffic traveling in the same direction. VPs are defined by a unique VPI
value.
WAN Wide Area Network is a network consisting of nodes located across a large
geographical area. Also, the connection between a service provider and Megabit 700F
Modem.