Subject: [MMUSIC] Review (by Albrecht) of draft-ietf-mmusic-udptl-dtls-02

From: "Schwarz, Albrecht (Albrecht)" <[email-masked]>
Date: Wed, 18 Dec 2013 15:29:20 +0000

Dear All,
did a review of the -02 draft version.
The content is technically pretty complete in my opinion.

Like to propose three comments concerning the addition of complementary information, see below.

Regards,
Albrecht

to 3.1<http://tools.ietf.org/html/draft-ietf-mmusic-udptl-dtls-02#section-3.1>.  Secure Channel Establishment
      Paragraph:

   In addition to the usual contents of an SDP media description ("m="

   line) specified for UDPTL over the UDP, each SDP media description

   for UDPTL over DTLS over the UDP will also contain several SDP

   attributes, as specified in [RFC4145<http://tools.ietf.org/html/rfc4145>] and [RFC4572<http://tools.ietf.org/html/rfc4572>].

proposed to be detailed by:

   In addition to the usual contents of an SDP media description ("m="

   line) specified for UDPTL over the UDP, each SDP media description

   for UDPTL over DTLS over the UDP will also contain several SDP

   attributes, which were introduced in the context of TCP and TLS (but reused here for DTLS-over-UDP), as specified in [RFC4145<http://tools.ietf.org/html/rfc4145>] (TCP) and [RFC4572<http://tools.ietf.org/html/rfc4572>] (TLS).

List item:

   o  The endpoint MUST use the SDP setup attribute [RFC4145<http://tools.ietf.org/html/rfc4145>].  The

      offerer SHOULD assign the SDP setup attribute with a setup:actpass

      value, and MAY assign the SDP setup attribute with a setup:active

      value or setup:passive value.  The offerer MUST NOT assign the SDP

      setup attribute with a setup:holdconn value.  If the offerer ...

proposed to add further background information:

   o  The endpoint MUST use the SDP setup attribute [RFC4145<http://tools.ietf.org/html/rfc4145>].  The

      offerer SHOULD assign the SDP setup attribute with a setup:actpass

      value, and MAY assign the SDP setup attribute with a setup:active

      value or setup:passive value (NOTE: these rules allow to decouple the establishment direction of the DTLS session from the establishment direction of the SIP session (which may be demanded due to security considerations, NAT traversal aspects, etc.)).
The offerer MUST NOT assign the SDP

      setup attribute with a setup:holdconn value.  If the offerer ....

to 3.2<http://tools.ietf.org/html/draft-ietf-mmusic-udptl-dtls-02#section-3.2>.  Secure Channel Usage

      Paragraph:

   DTLS is used as specified in [RFC6347<http://tools.ietf.org/html/rfc6347>].  Once the DTLS handshake is

   completed, the UDPTL packets SHALL be transported in DTLS record

   layer "application_data" packets.

proposed to be detailed by:

   DTLS is used as specified in [RFC6347<http://tools.ietf.org/html/rfc6347>].  Once the DTLS handshake is

   successfully completed, the UDPTL packets SHALL be transported in DTLS record

   layer "application_data" packets.
NOTE: such a proceeding ensures that the application (i.e., T.38) does not start to transmit facsimile data already during an ongoing underlying DTLS session establishment. This aspect might be important for end-to-end scenarios with gateway equipment and a possible "UDPTL/DTLS/UDP-to-UDPTL/UDP" interworking function).

__________________________________________________
Dr. Albrecht Schwarz
Alcatel-Lucent
[email-masked]<mailto:[email-masked]>