SMC Networks WUSB32 - annexe 2 Manual page 194

Terminology
TFTP (Trivial File Transfer Protocol)
A protocol for file transfers, TFTP is easier to use than
File Transfer Protocol (FTP) but not as capable or secure.
TTL (Time To Live)
A field in an IP packet that limits the life span of that packet.
Originally meant as a time duration, the TTL is usually
represented instead as a maximum hop count; each router
that 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.
VC (Virtual Circuit)
A connection from your ADSL routers 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.
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