Re: [mpls] applicability of draft-wijnands-mpls-mldp-in-band-signaling-02

[Yakov Rekhter <yakov at juniper.net>]

Eric,

> Eric> Supporting PIM-SM in ASM mode does require that there be a way to
> Eric> discover the active sources, but joining a shared tree is not the only
> Eric> way to do that.
> 
> Yakov> PIM-SM is specified in rfc4601. Support for the ASM service model
> Yakov> with PIM-SM, as defined in rfc4601, *does require a shared tree* to
> Yakov> discover the active sources.
> 
> Please see RFC 4611, which explains how to support the ASM service model
> with PIM-SM and MSDP. In this BCP, active sources are not always discovered
> via the shared tree, yet PIM-SM is still used.

To support the ASM service model over an MPLS network the combination
of PIM-SM (rfc4601) and rfc4611 is insufficient, as the deployment
scenarios described in rfc4611 do not cover MPLS network.
  
> You may also wish to look at draft-rekhter-pim-sm-over-mldp-00.txt, which
> specifies another way of using PIM-SM in ASM mode without using a shared
> tree to discover the active sources.

Thanks for repeating what I said in my previous e-mail:

   Eric> The notion of discovering the active sources without using 
   Eric> a shared tree isn't exactly new; see, e.g., section 14 of 
   Eric> draft-ietf-l3vpn-2547bis-mcast-bgp.

   Yakov> That is correct. Please see draft-rekhter-pim-sm-over-mldp-00.txt 
   Yakov> for more details.

> Yakov>     supporting the ASM service model over an MPLS network is outside
> Yakov>     the scope of this document.
> 
> I don't really see what's wrong with what I proposed:
> 
>       "When PIM-SM is used in ASM mode, the usual means of discovering
>       active sources is to join a sparse mode shared tree.  However, this
>       document does not provide any method of transporting a sparse mode
>       shared tree across an MPLS network.  To apply the technique of this
>       document to PIM-SM in ASM mode, there must be some other means of
>       discovering the active sources.  One possible means is the use of
>       MSDP, but specification of such means is outside the scope of this
>       document".

What's wrong with what you proposed is that it still refuses to
explicitly spell out that supporting the ASM service model over an
MPLS network is outside the scope of this document. In other words,
what is missing in what you proposed is the following sentence:

   Supporting the ASM service model over an MPLS network
   is outside the scope of this document.

> We'd be happy to add that another possible means of dicovering the active
> sources is specified in draft-rekhter-pim-sm-over-mldp-00.txt.

That would be fine. 

Yakov.