Code change:
The basic design philosophy of DTLS is to construct "TLS over datagram transport".  Datagram transport does not require nor provide reliable or in-order delivery of data.  The DTLS protocol preserves <del> this property for application data.  Applications such as media </del> <ins> this property for application data.  Applications, such as media </ins> streaming, Internet telephony, and online gaming use datagram transport for communication due to the delay-sensitive nature of transported data.  The behavior of such applications is unchanged when the DTLS protocol is used to secure communication, since the DTLS protocol does not compensate for lost or reordered data traffic. <ins> Note that while low-latency streaming and gaming use DTLS to protect data (e.g. for protection of a WebRTC data channel), telephony utilizes DTLS for key establishment, and Secure Real-time Transport Protocol (SRTP) for protection of data RFC5763. </ins> TLS cannot be used directly in datagram environments for the following five reasons:

Related discussion:
text: This document has been reviewed as part of the transport area review team's ongoing effort to review key IETF documents. These comments were written primarily for the transport area directors, but are copied to the document's authors and WG to allow them to address any issues raised and also to the IETF discussion list for information. When done at the time of IETF Last Call, the authors should consider this review as part of the last-call comments they receive. Please always CC EMAIL if you reply to or forward this review. TSV-ART Review of draft-ietf-tls-dtls13-41 Reviewer: Bernard Aboba Summary: The timeout and retransmission scheme looks workable for common cases, but could use some refinement to make it more robust. Technical Comments Handling Invalid Records Unlike TLS, DTLS is resilient in the face of invalid records (e.g., invalid formatting, length, MAC, etc.). In general, invalid records SHOULD be silently discarded, thus preserving the association; however, an error MAY be logged for diagnostic purposes. [BA] How does silent discard of invalid records interact with retransmission timers? Implementations which choose to generate an alert instead, MUST generate error alerts to avoid attacks where the attacker repeatedly probes the implementation to see how it responds to various types of error. Note that if DTLS is run over UDP, then any implementation which does this will be extremely susceptible to denial-of-service (DoS) attacks because UDP forgery is so easy. Thus, this practice is NOT RECOMMENDED for such transports, both to increase the reliability of DTLS service and to avoid the risk of spoofing attacks sending traffic to unrelated third parties. [BA] "this practice" refers to "generate an alert instead", correct? Timer Values Though timer values are the choice of the implementation, mishandling of the timer can lead to serious congestion problems, for example if [BA] Saying "timer values are the choice of the implementation" seems odd, because it is followed by normative language. I would delete this and start the sentence with "Mishandling...". many instances of a DTLS time out early and retransmit too quickly on a congested link.