User Manual

Psion Teklogix 9160 Wireless Gateway User Manual E-19

Appendix E: Glossary

NIC

A Network Interface Card is an adaptor or expansion board inserted into a computer

to provide a physical connection to a network. Most NICs are designed for a

particular type of network, protocol, and media, for example, Ethernet or wireless.

NTP

The Network Time Protocol assures accurate synchronization of the system clocks

in a network of computers. NTP servers transmit Coordinated Universal Time

(UTC, also known as Greenwich Mean Time) to their client systems. An NTP client

sends periodic time requests to servers, using the returned time stamp to adjust its

clock.

OSI

The Open Systems Interconnection (OSI) reference model is a framework for

network design. The OSI model consists of seven layers:

• Layer 1, the Physical layer, identifies the physical medium used for com-

munication between nodes. In the case of wireless networks, the physical

medium is air, and radio frequency (RF) waves are a components of the

physical layer.

• Layer 2, the Data-Link layer, defines how data for transmission will be

structured and formatted, along with low-level protocols for communica-

tion and addressing. For example, protocols such as

CSMA/CA and components like MAC addresses, and Frames are all

defined and dealt with as a part of the Data-Link layer.

• Layer 3, the Network layer, defines the how to determine the best path for

information traversing the network. Packets and logical IP Addresses

operate on the network layer.

• Layer 4, the Transport layer, defines connection oriented protocols such as

TCP and UDP.