Appendix C. Glossary
197
receives a packet decrements this field by one. When the TTL
reaches zero, the packet is discarded.
twisted pair The ordinary copper telephone wiring long used by telephone
companies. It contains one or more wire pairs twisted together to
reduce inductance and noise. Each telephone line uses one pair.
In homes, it is most often installed with two pairs. For Ethernet
LANs, a higher grade called Category 3 (CAT 3) is used for
10BASE-T networks, and an even higher grade called Category
5 (CAT 5) is used for 100BASE-T networks. See also 10BASE-T,
100BASE-T, Ethernet.
upstream The direction of data transmission from the user to the Internet.
USB Universal Serial Bus
A serial interface that lets you connect devices such as printers,
scanners, etc. to your computer by simply plugging them in. The
Hurricane 9200/S is equipped with a USB interface (H9200 only)
for connecting to a stand-alone PC.
VC Virtual Circuit
A connection from your ADSL router to your ISP.
VCI Virtual Circuit Identifier
Together with the Virtual Path Identifier (VPI), the VCI uniquely
identifies a VC. Your ISP will tell you the VCI for each VC they
provide. See also VC.
VPI Virtual Path Identifier
Together with the Virtual Circuit Identifier (VCI), the VPI uniquely
identifies a VC. Your ISP will tell you the VPI for each VC they
provide. See also VC.
WAN Wide Area Network
Any network spread over a large geographical area, such as a
country or continent. With respect to the Hurricane 9200/S, WAN
refers to the Internet.
