No subject

   The control traffic should be limited to a small and known fraction
   of the session bandwidth: small so that the primary function of the
   transport protocol to carry data is not impaired; known so that the
   control traffic can be included in the bandwidth specification given
   to a resource reservation protocol, and so that each participant can
   independently calculate its share. It is suggested that the fraction
   of the session bandwidth allocated to RTCP be fixed at 5%. While the
   value of this and other constants in the interval calculation is not
   critical, all participants in the session must use the same values so
   the same interval will be calculated. Therefore, these constants
   should be fixed for a particular profile.

My interpretation of "all participants in the session must use the same
values" is that RTCP will scale "within a session". But why 5%? Why not 10?
or 15? or 1?
This question may not be as critical for RTCP as it is for control traffic
which needs extra processing by routers.

Cheers,
Michael