I found the following current language of section 4.1 confusing. It seems like the last sentence of the paragraph is unfinished.
If the caller intends to use DTLS-SRTP, the SIP INVITE MUST also contain an attribute line that contains the DTLS fingerprint attribute. Because VVP proves the prevents man-in-the-middle attacks and allows the When combined with VVP, DTLS-SRTP a=callee-passport:X attribute line to the SDP [RFC8866] body of the callee's
I found the following current language of section 4.1 confusing. It seems like the last sentence of the paragraph is unfinished.