Hello,

I have reviewed this document as part of the security directorate's ongoing effort to review all IETF documents being processed by the IESG. These comments were written primarily for the benefit of the security area directors. Document editors and WG chairs should treat these comments just like any other last call comments.

The document is clear and understandable, and the Security Considerations section is very good.

I liked section 9.1 which highlights privacy concerns specific to calendars, although I believe that all of these concerns also apply to email. Yes, pretty much any event in my calendar says what I'm going to be doing at a certain time, and very often where I'm going to be; contacts include phone numbers and addresses, but things like that are discussed over email all the time.

Section 9.3 of calendar-specific DoS was educational for me.

NITS:
 - in section 9.3.2 s/pused/pushed/