Glossary
Layer 2
The data link layer in the OSI Model. For Ethernet, this applies to the Ethernet
frame that contains the Ethernet destination address, Ethernet source address and
802.1Q/1p fields. See also Layer 3.
Layer 3
The physical layer in the OSI Model. For TCP/IP, this applies to the IP packet that
contains the IP destination address, IP source address and ToS byte. See also Layer 2.
Multicast
Single packet copied by the network and sent to a specific subset of network
addresses.
Packet
A block of data with a "header" attached that can indicate what the packet con-
tains and the destination where it is headed. Think of a packet as a data envelope,
with the header acting as an address.
QoS
Quality of service. A set of intelligent features that enables the network to classify,
mark, and prioritize traffic, reducing congestion and bringing order to the flow of
data and services.
Router
A device that moves data between different network segments and can look into
a packet header to determine the best path for the packet to travel. Routers can
connect network segments that use different protocols. They also allow all users
in a network to share a single connection to the Internet or WAN.
Server
A computer or even a software program that provides clients with services —such
as file storage (file server), programs (application server), printer sharing (print
server), fax (fax server) or modem sharing (modem server). See also Client.
Switch
A device that improves network performance by segmenting the network. When a
switch port receives data packets, it forwards those packets only to the appropriate
port for the intended recipient. This capability further reduces competition for
bandwidth between the clients, servers, or workgroups connected to each switch
port. See also Hub.
WAN
Wide-area network. Typically refers to a network that connects devices over greater
distances, such as geographical regions. A WAN often connect two or more LANs
together. See also LAN (Local Area Network).
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