Which three statements are true about Source Specific Multicast?

Which three statements are true about Source Specific Multicast? (Choose three.)

A.
Is best suited for applications that are in the one-to-many category.

B.
SSM uses shortest path trees only.

C.
The use of SSM is recommended when there are many sources and it is desirable to keep the
amount of mroute state in the routers in the network to a

D.
There are no RPs to worry about

Explanation:
The Source Specific Multicast feature is an extension of IP multicast where datagram traffic is

forwarded to receivers from only those multicast sources to which the receivers have explicitly
joined. For multicast groups configured for SSM, only source-specific multicast distribution trees
(no shared trees) are created.
The current IP multicast infrastructure in the Internet and many enterprise intranets is based on
the PIM- SM protocol and Multicast Source Discovery Protocol (MSDP). These protocols have
proven to be reliable, extensive, and efficient. However, they are bound to the complexity and
functionality limitations of the Internet Standard Multicast (ISM) service model. For example, with
ISM, the network must maintain knowledge about which hosts in the network are actively sending
multicast traffic. With SSM, this information is provided by receivers through the source
address(es) relayed to the last hop routers by IGMP v3lite or URD. SSM is an incremental
response to the issues associated with ISM and is intended to coexist in the network with the
protocols developed for ISM. In general, SSM provides a more advantageous IP multicast service
for applications that utilize SSM.
ISM service is described in RFC 1112. This service consists of the delivery of IP datagrams from
any source to a group of receivers called the multicast host group. The datagram traffic for the
multicast host group consists of datagrams with an arbitrary IP unicast source address S and the
multicast group address G as the IP destination address. Systems will receive this traffic by
becoming members of the host group. Membership to a host group simply requires signalling the
host group through IGMP Version 1, 2, or 3. In SSM, delivery of datagrams is based on (S, G)
channels. Traffic for one (S, G) channel consists of datagrams with an IP unicast source address
S and the multicast group address G as the IP destination address. Systems will receive this traffic
by becoming members of the (S, G) channel. In both SSM and ISM, no signalling is required to
become a source. However, in SSM, receivers must subscribe or unsubscribe to (S, G) channels
to receive or not receive traffic from specific sources. In other words, receivers can receive traffic
only from (S, G) channels that they are subscribed to, whereas in ISM, receivers need not know
the IP addresses of sources from which they receive their traffic. The proposed standard approach
for channel subscription signalling utilizes IGMP INCLUDE mode membership reports, which are
only supported in Version 3 of IGMP.
SSM can coexist with the ISM service by applying the SSM delivery model to a configured subset
of the IP multicast group address range. The Internet Assigned Numbers Authority (IANA) has
reserved the address range 232.0.0.0 through 232.255.255.255 for SSM applications and
protocols. Cisco IOS software allows SSM configuration for an arbitrary subset of the IP multicast
address range 224.0.0.0 through 239.255.255.255.
When an SSM range is defined, existing IP multicast receiver applications will not receive any
traffic when they try to use addresses in the SSM range (unless the application is modified to use
explicit (S, G) channel subscription or is SSM enabled through URD).