Comments on draft-ietf-mmusic-sdp-directory-type-00.txt

[Colin Perkins <[e-mail]>]

Ross,

I have a couple of comments on the draft describing the "directory" SDP
media type.

 - When defining RTP payload formats, the combination of the m= and
   a=rtpmap lines in SDP to define a MIME type for the payload format. 
   This may imply that the use of m=directory is referencing a top level 
   MIME directory type, which is presumably not intended?

   I wonder if this link between top-level MIME types and SDP m= lines has
   other effects? For example, SDP defines "data" and "control" as possible
   values for the m= line, which may also not map well onto the MIME space.

 - I'm concerned with the handling of directories which timeout or which
   have exceeded their advertised lifetime. In particular, I am concerned
   by section 7 of the draft, which states that "parties that advertise
   within directories should also participate in advertising the directory
   itself".

   One reason for limiting the lifetime specified in the t= field of the
   directory announcement is that the announcer of that directory knows
   that the address allocated to the directory has a limited lifetime.
   Thus, allowing other participants to announce a directory is useful for
   robustness, but may cause problems if they extend the lifetime of a
   directory without renewing any "lease" on the address used for that
   directory.

   I suggest that text is added to state that sessions announced within a
   directory SHOULD NOT be announced outside the time period specified in
   the description of that directory, and SHOULD NOT be announced after a
   deletion message has been received for the directory. 

Colin