RPKI Repository Delta Protocol (RRDP) Delta File Retention Policy

This document updates RFC 8182 (The RPKI Repository Delta Protocol) by specifying an optimized delta file retention policy based on client access patterns. The proposed mechanism allows RRDP servers to maintain only the delta files required by active clients, reducing storage requirements while maintaining compatibility with existing clients. By tracking which serial numbers are being requested by active clients, the repository can determine the minimum serial number needed by any client and safely prune delta files that update from earlier serial numbers. The proposed mechanism provides several benefits, including reduced storage requirements, smaller notification files, and more efficient use of bandwidth and processing resources. It also maintains backward compatibility with existing RRDP clients, requiring no changes to client implementations.