<div dir="ltr"><div>The rsync protocol might be appropriate.  See <a href="https://www.samba.org/~tridge/phd_thesis.pdf">https://www.samba.org/~tridge/phd_thesis.pdf</a> and <a href="https://rsync.samba.org/tech_report/node2.html">https://rsync.samba.org/tech_report/node2.html</a></div><div><br></div></div>