RFC 760: DoD Standard Internet Protocol

Overview
RFC 760, titled "DoD Standard Internet Protocol" and authored by Jon Postel in 1980, presents an early, formalized specification of the packet format and basic behaviors needed to interconnect diverse packet-switched networks. It codifies a datagram-based, best-effort delivery model in which each packet carries enough information for independent forwarding and eventual delivery to a destination host, regardless of the underlying networks' differences.
The specification concentrates on a simple, general-purpose protocol layer that treats the network as a transparent substrate for end-to-end communication. Its design emphasizes minimal assumptions about underlying networks, interoperability through gateways, and mechanisms to cope with heterogeneous link characteristics.

Historical context
This document stems from practical experience with ARPANET and early internetworking experiments, where differing network technologies and imperfect gateway implementations revealed the need for a unified packet format and forwarding semantics. The "DoD Standard" label reflects endorsement within Department of Defense networking circles and a push toward a single interoperable protocol for military and research networks.
RFC 760 sits chronologically between the ARPANET protocols and later, more polished definitions of the Internet Protocol; it captures the lessons learned from early deployments and drove standardization that ultimately fed into the TCP/IP suite adopted widely in the early 1980s.

Protocol structure and design principles
At the core of RFC 760 is a compact datagram header that supplies addressing, basic control flags, and the information needed for fragmentation and reassembly. The header is designed to be parsed quickly by gateways and hosts, enabling routers to make forwarding decisions without relying on per-connection state. Error detection for the header is included to catch on-the-wire corruption affecting routing-critical fields.
The protocol intentionally follows a "best-effort" philosophy: there is no guarantee of delivery, ordering, or duplicate suppression at the network layer. Reliability and flow control are left to higher-layer protocols, permitting the network layer to remain simple and scalable.

Fragmentation, reassembly, and heterogeneity
RFC 760 introduces mechanisms to accommodate networks with differing maximum packet sizes. Datagrams may be fragmented by gateways to traverse links with smaller transmission units and are reassembled at the destination host. Identification and offset fields in the header allow fragments to be associated correctly and placed in the original byte stream.
These mechanisms were essential for connecting networks that had widely varying link-level properties. The specification accepts a performance cost in reassembly complexity to preserve end-to-end transparency and interoperability across diverse media.

Addressing, routing, and gateways
The addressing scheme in RFC 760 provides global identifiers for source and destination hosts, enabling routing across multiple networks. Gateways perform forwarding based on destination addresses and the datagram header, while routing protocols external to the specification supply the topology and next-hop information gateways use.
The protocol assumes a cooperative gateway environment where simple forwarding rules and a small set of control semantics are sufficient to interconnect administrative domains without embedding complex routing functions in every packet.

Impact and legacy
RFC 760 helped crystallize core ideas that defined the Internet Protocol family: a minimalist, connectionless network layer that prioritizes interoperability and simplicity, paired with richer end-to-end mechanisms at higher layers. Its design choices, datagram independence, fragmentation to handle MTU diversity, explicit addressing, and best-effort delivery, proved durable and influenced subsequent, more detailed standards.
By providing a practical, implementable specification for inter-networking, RFC 760 contributed to the emergence of a common protocol that could scale beyond ARPANET, laying groundwork for the later formalizations and the global growth of packet-switched internets.