IPUDP

IPUDP is a term used to describe the technique of carrying IP traffic inside UDP datagrams. In this approach, an ordinary IP packet is encapsulated within the payload of a UDP packet, and the receiving end decapsulates to recover the original IP packet. The outer UDP header provides traditional UDP transport, while the inner IP header and payload carry the actual data for routing by the destination network. IPUDP is not a single standardized protocol, but a concept employed by various tunneling or transport schemes to enable IP-level communication over networks that readily support UDP.

Technical considerations include encapsulation mechanics, MTU management, and fragmentation handling. Since UDP is a datagram protocol, the size of the inner IP packet must fit within the available space after accounting for the UDP and outer IP headers. If a single IP packet would exceed the path MTU, it may be fragmented at the IP layer or dropped, depending on the implementation. Consequently, IPUDP solutions often implement fragmentation avoidance, path MTU discovery, or fragmentation at the application layer to maintain reliability.

Security and reliability are not intrinsic to the IPUDP approach. UDP does not guarantee delivery, order, or protection against tampering. Therefore, IPUDP deployments typically rely on additional security and reliability measures such as encryption (for example, TLS/DTLS) and authentication, as well as higher-layer protocols to recover or reorder lost packets.

Usage and interoperability vary, since IPUDP is not a universally standardized protocol. It is most commonly encountered in tunneling and VPN-like scenarios where carrying IP traffic over UDP is advantageous for NAT traversal or firewall traversal, subject to the limitations and trade-offs described above.