The Address plus Port (A+P) within the

network layer In the seven-layer OSI model of computer networking, the network layer is layer 3. The network layer is responsible for packet forwarding including routing through intermediate routers. Functions The network layer provides the means of trans ...

communications protocol A communication protocol is a system of rules that allows two or more entities of a communications system to transmit information via any kind of variation of a physical quantity. The protocol defines the rules, syntax, semantics and synchro ...

for Internet networking is an experimental approach to the IPv4 address shortage. It is a technique for sharing single IPv4 addresses among several users without using stateful network address translation (NAT) in the carrier network. Normal routing only uses the IPv4 address to identify which host an IP packet is destined for. A+P uses the destination

TCP TCP may refer to: Science and technology * Transformer coupled plasma * Tool Center Point, see Robot end effector Computing * Transmission Control Protocol, a fundamental Internet standard * Telephony control protocol, a Bluetooth communication s ...

or UDP port in addition to the IP address to extend the range of available host addresses. Each host is assigned a unique range of ports which they set as the source port in outbound packets and which they use to receive inbound traffic. A+P is a stateless alternative to conventional stateful NAT, as the A+P gateway does not need to keep track of every TCP or UDP flow. However, it does require A+P aware software at the end-point, capable of limiting the range of port numbers used for originating connections to its allocated range, either in the end host, or, in the more common likely scenario, in the

customer premises equipment In telecommunications, a customer-premises equipment or customer-provided equipment (CPE) is any terminal and associated equipment located at a subscriber's premises and connected with a carrier's telecommunication circuit at the demarcation po ...

own local NAT44 implementation.

References

IPv4 Routing software {{Compu-network-stub

See also

References