RFC 874 is not a protocol specification. It is a polemic — a sharp-tongued essay from MITRE's Mike Padlipsky arguing that CCITT's X.25 packet-switching standard was a technical dead end and that anyone considering it as an alternative to the ARPANET protocols was making a serious mistake. In 1982, this was a live question: the telecom world (PTTs, CCITT, and the emerging OSI camp) was pushing X.25 as the way to build public data networks, and the U.S. DoD was under real pressure to align.

Padlipsky's central charge is a layering violation. X.25, he argues, conflates the network access protocol (how a host talks to its local packet switch) with an end-to-end virtual circuit abstraction. In the ARPANET model — later canonized as TCP/IP — the host-to-IMP protocol (RFC 1822) was strictly a local matter, and end-to-end reliability lived in a separate transport layer (TCP). X.25 fused these, so a "virtual circuit" wasn't actually end-to-end; it was really a concatenation of local circuits stitched together by the network, with hop-by-hop acknowledgements masquerading as end-to-end delivery guarantees.

His specific complaints, still worth reading today:

• False end-to-end semantics. X.25 acknowledgements from the local switch don't mean the far host received anything. Applications that trust them will corrupt data.
• Connection-oriented in the wrong layer. Forcing every conversation through a network-layer virtual circuit denies applications the choice of datagram service, which is cheaper and simpler for many workloads (DNS, RPC, telemetry — everything we now build on UDP).
• Byte-count and window semantics leak across boundaries. Flow control at the network interface interferes with flow control the transport layer needs to do anyway.
• "Interface" confused with "protocol." X.25 was a specification for how a host plugs into a specific carrier's network — a local interface — but was marketed as an internetworking solution.

The essay is written in Padlipsky's trademark style: acerbic, footnoted, self-aware, and occasionally hilarious. He coined the phrase "the ARPANET reference model" as a jab at OSI's seven-layer edifice, and RFC 874 is part of a broader body of work (collected in his 1985 book The Elements of Networking Style) arguing that the internet's rough-consensus, running-code culture would beat the standards-committee approach. History proved him spectacularly right.

Why read it in 2026? Because the arguments are structural, not historical. Every time someone proposes a "smart" network that terminates connections on your behalf, provides "reliable" delivery at layer 3, or fuses application semantics into transport (looking at you, some middleboxes and some service meshes), Padlipsky's critique applies verbatim. The end-to-end principle — later formalized by Saltzer, Reed, and Clark — has one of its clearest early defenses right here. QUIC's design decision to run its own transport over UDP rather than trust the network is a direct descendant of this reasoning.

It's also just good writing. RFCs today are dry by policy; RFC 874 reminds you that the early internet community was a small group of engineers with strong opinions, and they weren't afraid to publish them under the RFC banner. The series was, quite literally, a request for comments — including comments like "this competing standard is broken and here's why."