User Manual

P380 Users guide
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necessary IP address translations. NAT is used for two main tasks – to provide a type of
firewall by hiding internal IP addresses and enable a company to use more internal IP
addresses. Since they're used internally only, there's no possibility of conflict with IP
addresses used by other companies and organizations.
Network A computer network is a data communications system which interconnects
computer systems at various different sites. A network may be composed of any
combination of LANs or WANs.
Network address The network portion of an IP address. For a class A network, the
network address is the first byte of the IP address. For a class B network, the network
address is the first two bytes of the IP address. For a class C network, the network
address is the first three bytes of the IP address. In each case, the remainder is the host
address. In the Internet, assigned network addresses are globally unique. See IP address.
Node An addressable device attached to a computer network. See host, router.
P
Packet The unit of data sent across a network. “Packet” is a generic term used to describe
units of data at all levels of the protocol stack, but it is most correctly used to describe
application data units. See datagram, frame.
Policy Organization-level rules governing acceptable use of computing resources,
security practices, and operational procedures.
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
Route The path that network traffic takes from the source to the destination. It may
include many gateways, routers, hosts and physical networks.