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Port
Data is exchanged between two applications in a Network via a port.
Port Forwarding
The Internet gateway (e.g. your router) forwards data packets from the Internet that are
directed to a certain Port to the port concerned. This allows servers in the LAN to offer
services on the Internet without you needing a public IP address.
Port number
Indicates a specific application of Network subscribers. Depending on the setting in
the LAN, the port number is permanently assigned or else it is newly assigned with each
access.
The combination of IP address/Port number uniquely identifies the recipient or sender
of a data packet within a network.
PPPoE
Point-to-Point Protocol over Ethernet
Protocol for connecting network subscribers within an Ethernet network to the Inter-
net via a modem.
PPTP
Point-to-Point Tunnelling Protocol
Protocol for setting up a virtual private network (Virtual Private Network VPN) via the
Internet. This allows the Point-to-Point protocol to tunnel through the IP network.
Private IP Address
See Public IP address.
Protocol
Describes the agreements for communicating within a Network. It contains rules for
opening, administering and closing a connection, about data formats, time frames and
possible error handling.
Proxy/Proxy server
Computer program that controls the exchange of data between Client and Server in
computer networks. If the phone sends a query to the VoIP server, the proxy acts as a
server towards the phone and as a client towards the server. A proxy is addressed via IP
address/Domain name and Port.
Public IP address
The public IP address is the address for a network component on the Internet. It is
assigned by the Internet service provider. Devices that act as a link from a local network
to the Internet (gateway or router) have a public and a local IP address.
See also: IP address, NAT
Q
Quality of Service (QoS)
Describes the Quality of Service in communication networks. Differentiations are made
between various Quality of Service classes.
QoS influences the flow of data packets on the Internet e.g. by prioritising data packets,
bandwidth reservation and packet optimisation.
In VoIP networks, QoS influences the voice quality. If the whole infrastructure (router,
network server etc.) has QoS, the voice quality is better, i.e. fewer delays, less echoing,
less crackling.
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