PIM-SM and PIM-SSM

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Jun 26th, 2007
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what is difference between both the technology?

Correct Answer by Harold Ritter about 9 years 11 months ago

PIM-SM refers to PIM Sparse Mode. It is one of the modes under Any Source Multicast (ASM), where multicast streams can be received from any multicast source.


PIM-SSM refers to PIM Source Specific Multicast, where the receiver can specify from which source it wants to receive a given multicast stream. Unlike with ASM, which most of the time requires the configuration of an RP, SSM doesn't have the concept of RP, which makes things quite a bit easier. The only drawback is the requirement for the support of IGMPv3 on the receiver, which is not widely deployed these days. IGMPv3 allows the receiver to specify the source along with the multicast stream.


Hope this helps,

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Correct Answer
Harold Ritter Tue, 06/26/2007 - 18:08
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PIM-SM refers to PIM Sparse Mode. It is one of the modes under Any Source Multicast (ASM), where multicast streams can be received from any multicast source.


PIM-SSM refers to PIM Source Specific Multicast, where the receiver can specify from which source it wants to receive a given multicast stream. Unlike with ASM, which most of the time requires the configuration of an RP, SSM doesn't have the concept of RP, which makes things quite a bit easier. The only drawback is the requirement for the support of IGMPv3 on the receiver, which is not widely deployed these days. IGMPv3 allows the receiver to specify the source along with the multicast stream.


Hope this helps,

dangal.43 Thu, 06/28/2007 - 10:07
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hi Hritter,


thanks for wonderful explanation. Will you please explain me the mechanism for finding out the IP address of the source of multicast traffic? How does it works? so IGMPv3 is used for the same function then what are the additional features are there which are useful in PIM-SSM?

Harold Ritter Thu, 06/28/2007 - 10:59
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Dan,


With PIM-SM, the receivers don't need to know the source for a given multicast group, hence the utilization of an Rendez-vous Point to allow receivers and source to "meet".


With PIM-SSM, the source address and multicast group are usually learnt via out of band communication such a web page for instance. Once the receiver learns the source for a given multicast stream, it can join by specifying both the multicast group and the source address in the IGMPv3 membership report message.


Hope this helps,

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