Re: SSM

[John Meylor <jmeylor@cisco.com>]

Ali Boudani wrote:
> 
> Hello,
> In the draft :
> 
>  A Framework for Source-Specific Multicast Deployment
>                  <draft-bhattach-ssm-framework-01.txt>
>  3. Limitations of Current Service Model
>    There exist several service model limitations associated with ASM:
>    A) Handling Well Known Sources via Shortest Path Forwarding
>        In cases where the address of the source is well known in advance
> 
>       of the receiver joining the group, and when the shortest
>       forwarding path is the preferred forwarding mode, then shared tree
> 
>       mechanisms and MSDP only represent unnecessary interim mechanisms,
> 
>       contributing to join latency and operational overhead.
> 
> So in which cases address of the source is well known in advance of the
> receiver joining the group??
> can u give me a simple example ??
> just I want to understand it well.

streaming content available via web.  The server may be known
and static for years.  application can access that information
(eg via file available via web) and initiate process to request
the information from that source,group directly and explicity.

previously with ASM, even if the source was well-known and could
be made available on web page, IGMPv2 had no mechanism to
convey that exclusive source interest to the PIM forwarding service
and the PIM service had no way to ensure delivery was limited
to the source(s) explicity requested.

 John