SSM stands for source-specific multicast; this method is used to deliver the packet of multicast in which just packets are transmitted to the recipient those are initiating from a particular source address applied by a recipient. Demands are reduced by SSM on the system and security factor is improved too due to limited source.
Source-specific is considered as a better as compare to ASM (any-source multicast). In the model of ASM service a recipient shows concern in traffic of multicast address. The network of multicast is necessary to
- Determine all the sources of multicast transmitting to that channel or address, and
- Forward data or information from every source to all recipients who are interested.
The performance is specifically go well with applications of groupware where
- All participants want to know about other participants in the existed group, and
- The participant list is not disclosed earlier.
The load of source discovery on the system can be considerable when the sources have the large number. There is need to support by SSM in last-hop operating system of sender and receiver. The supporting role of SSM is not necessary in other devices or components of network, comprising routers and even the broadcasting host.
Operations of SSM
- A launched network, wherein PIM-SM is base of IP multicast service, by which SSM services can be supported. SSM can be installed also separately in a system with no protocols fully range which is necessary for PIM-SM of interdomain (such as, BSR, Auto-RP, or MSDP) if just SSM service is required.
- When SSM is installed in a system already built up for PIM-S, then just the routers of last hop need to be upgraded or improved to the IOS Release 12.1(3) T or image of later releases that is supported by SSM. Those routers which are not attached directly to the recipients can precede IOS Release 12.0 or the later releases. Usually, the router having non last hop must be able to lead PIM-SM within the range of SSM, and may require further access hold configuration to control the signaling of MSDP, registering, or staked the tree operations of PIM-SM from taking place in the SSM range.
- The operation mode of SSM in the Cisco IOS Release 12.1(3) T and later releases can be enabled by designing the range of SSM by using command of IP PIM-SM. The following effects can be seen by this configuration:
- In the SSM range, subscriptions of (S, G) channel are received by IGMP v3lite or URD for groups and every process from them have to be configured on the basis of per-interface. Outside groups from the SSM range are not considered for the subscriptions of IGMP v3lite or URD (S, G) channel.
- Both of IGMP v3lite or URD are basically depends on the utilizing present application or function of group connection with IGMP and expanding it by their own procedure or method of (S, G) channel subscription.
- PIM operations modify to PIM-SM in the SSM range of channels and addresses, a form resultant from PIM-SM. In this method, merely PIM (S, G) link/reduce the messages are originated by the transmitter or router and no any (*, G) RPT or (S, G) rendezvous point tree (RPT) messages are produced. RPT operations are declined or ignored that are containing incoming information or messages and incoming or newly PIM Register messages are instantly replied by Register-Stop messages. PIM-SSM is rearward well-matched to the PIM-SM, if not a router is a last hop transmitter. Hence, those routers which are not considered as last hop router can lead PIM-SM for the groups of SSM.
- In the SSM range, no any MSDP Source-Active (SA) information would be able to admitted, produced or even forwarded.