pimd: Why ssm.
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+WHY SSM
+
+Benefis of PIM SSM over PIM SM
+------------------------------
+
+- SSM consumes minimum link bandwidth
+- SSM simplifies multicast address management (specially important for
+ inter-domain multicast)
+- SSM does not suffer instabilities from traffic-driven SPT switchover
+- SSM does not use RP. Some RP issues:
+ - RP is possible point of failure
+ - RP demands redundancy management
+ - RP may require PIM dense mode support for RP election
+ - RP is possible performance bottleneck
+ - RP may demand lots of extra management
+
+PIM-SSM drawbacks
+-----------------
+
+- SSM requires IGMPv3 support on receivers
+- SSM may be memory intensive when managing (S,G) states for
+ many-to-many multicast distribution
+
+--EOF--