User Manual

User’s Guide Glossary
PPPoE: PPPoE (Point-to-Point Protocol over
Ethernet) is a specification for connecting
multiple computer users on an Ethernet local
area network to a remote site through common
customer premises equipment, which is the
telephone company's term for a modem and
similar devices. PPPoE can be used to have
an office or building-full of users share a
common Digital Subscriber Line (DSL), cable
modem, or wireless connection to the Internet.
PPPoE combines the Point-to-Point Protocol
(PPP), commonly used in dialup connections,
with the Ethernet protocol, which supports
multiple users in a local area network. The
PPP protocol information is encapsulated
within an Ethernet frame.
PPPoE has the advantage that neither the
telephone company nor the Internet service
provider (ISP) needs to provide any special
support. Unlike dialup connections, DSL and
cable modem connections are "always on."
Since a number of different users are sharing
the same physical connection to the remote
service provider, a way is needed to keep
track of which user traffic should go to and
which user should be billed. PPPoE provides
for each user-remote site session to learn
each other's network addresses (during an
initial exchange called "discovery"). Once a
session is established between an individual
user and the remote site (for example, an
Internet service provider), the session can be
monitored for billing purposes.
PPTP: Point-to-Point Tunneling Protocol
(PPTP) is a protocol (set of communication
rules) that allows corporations to extend their
own corporate network through private
"tunnels" over the public Internet. Effectively, a
corporation uses a wide-area network as a
single large local area network. This kind of
interconnection is known as a virtual private
network (VPN).
port The abstraction used by Internet transport
protocols to distinguish among multiple
simultaneous connections to a single
destination host. A port is a transport layer
demultiplexing value. Each application has a
unique port number associated with it. It is
also used to refer to one of the physical
network connectors on the router.
protocol A formal description of message
formats and the rules two computers must
follow to exchange those messages. Protocols
can describe low-level details of machine-to-
machine interfaces (e.g., the order in which
bits and bytes are sent across a wire) or high-
level exchanges between allocation programs
(e.g., the way in which two programs transfer a
file across the Internet).
Q
QOS Quality of Service. Transmission system
qualities measure in terms of reliability and
availability.
R
RADIUS (Remote Authentication Dial-In User
Service)
is a client/server protocol and
software that enables remote access servers
to communicate with a central server to
authenticate dial-in users and authorize their
access to the requested system or service.
RADIUS allows a company to maintain user
profiles in a central database that all remote
servers can share. It provides better security,
allowing a company to set up a policy that can
be applied at a single administered network
point. Having a central service also means that
it's easier to track usage for billing and for
keeping network statistics.
route The path that network traffic takes from
the source to the destination. It may include
many gateways, routers, hosts and physical
networks.
route table A table listing information about
routes to other hosts or networks, such as the
remote network or host address, the interface
down which the route exists, the distance to
the remote address and the cost of sending
data over the route.
router A system responsible for making
decisions about which of several paths
network (or Internet) traffic will follow. To do
this it uses a routing protocol to gain
information about the network, and algorithms
to choose the best route based on several
criteria known as “routing metrics”.
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