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 Router (computing), routers. Functions The network layer provides t ...

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 variation of a physical quantity. The protocol defines the rules, syntax, semantics (computer science), sem ...

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 Network address translation (NAT) is a method of mapping an IP address space into another by modifying network address information in the IP header of packets while they are in transit across a traffic Router (computing), routing device. The te ...

in the carrier network. Normal routing uses the IPv4 address only to identify which host an Internet Protocol packet is destined for. A+P uses the destination

Transmission Control Protocol The Transmission Control Protocol (TCP) is one of the main communications protocol, protocols of the Internet protocol suite. It originated in the initial network implementation in which it complemented the Internet Protocol (IP). Therefore, th ...

User Datagram Protocol In computer networking, the User Datagram Protocol (UDP) is one of the core communication protocols of the Internet protocol suite used to send messages (transported as datagrams in Network packet, packets) to other hosts on an Internet Protoco ...

port in addition to the Internet Protocol 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 network address translation as the A+P gateway does not need to keep track of every Transmission Control Protocol or User Datagram Protocol 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