RFC 2149 (rfc2149) - Page 3 of 18

Multicast Server Architectures for MARS-based ATM multicasting

RFC 2149             Multicast Server Architectures             May 1997


3 MCS Architecture

   The MCS acts as a proxy server which multicasts data received from a
   source to the group members in the cluster.  All multicast sources
   transmitting to an MCS-based group send the data to the specified
   MCS. The MCS then forwards the data over a point to multipoint VC
   that it maintains to group members in the cluster.  Each multicast
   source thus maintains a single point-to-multipoint VC to the
   designated MCS for the group.  The designated MCS terminates one
   point-to-multipoint VC from each cluster member that is multicasting
   to the layer 3 group.  Each group member is the leaf of the point-
   to-multipoint VC originating from the MCS.

   A brief introduction to possible MCS architectures has been presented
   in [GA96].  The main contribution of that document concerning the MCS
   approach is the specification of the MARS interaction with the MCS.
   The next section lists control messages exchanged by the MARS and
   MCS.

3.1 Control Messages exchanged by the MCS and the MARS

   The following control messages are exchanged by the MARS and the MCS.

   operation code                Control Message

         1                       MARS_REQUEST
         2                       MARS_MULTI
         3                       MARS_MSERV
         6                       MARS_NAK
         7                       MARS_UNSERV
         8                       MARS_SJOIN
         9                       MARS_SLEAVE
        12                       MARS_REDIRECT_MAP

   MARSMSERV and MARS-UNSERV are identical in format to the MARSJOIN
   message.  MARSSJOIN and MARS-SLEAVE are also identical in format to
   MARSJOIN. As such, their formats and those of MARSREQUEST, MARS-
   MULTI, MARSNAK and MARSREDIRECT-MAP are described in [GA96].  Their
   usage is described in section 4.  All control messages are LLC/SNAP
   encapsulated as described in section 4.2 of [GA96].  (The "mar$"
   notation used in this document is borrowed from [GA96], and indicates
   a specific field in the control message.)  Data messages are
   reflected without any modification by the MCS.








Talpade & Ammar              Informational