RFC 521 · UNKNOWN · 1973
SUN · 14 JUN 2026
Restricted use of IMP DDT
Overview
RFC 521, “Restricted use of IMP DDT”, is an Unknown document published in May 1973 by A.M. McKenzie. The canonical text is published by the RFC Editor.
What “Unknown” means
The standards-track status of this early RFC was never formally classified.
Read this RFC
The canonical text of RFC 521 is hosted at rfc-editor.org. Available in TXT,HTML.
Other RFCs from 1973
- RFC 520 Memo to FTP group: Proposal for File Access Protocol
- RFC 522 Traffic Statistics
- RFC 519 Resource Evaluation
- RFC 523 SURVEY is in operation again
- RFC 518 ARPANET accounts
- RFC 524 Proposed Mail Protocol
- RFC 525 MIT-MATHLAB meets UCSB-OLS -an example of resource sharing
- RFC 516 Lost message detection