Subject: [pim] (*,*,RP) state

From: "Maren Peasley" <[email-masked]>
Date: Mon, 28 Jan 2008 13:08:45 -0700

Hello,
 
I apologize if this has already been asked before, but what is the
purpose of (*,*,RP) state?  It is mentioned in RFC 4601 with some
details given in section 4.1.
 
Thank you in advance,
 
________________________________

Maren Peasley, CISSP, CCNP
Technical Support Engineer
High-End Security Products
Symantec Technical Support
Symantec Corporation
www.symantec.com <http://www.symantec.com/>  

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From: Christopher Thomas Brown <[email-masked]>
Date: Wed, 30 Jan 2008 20:01:03 -0800

> details given in section 4.1.

To allow sources in a PIM-SM domain to be reachable in a PIM-DM or
DVMRP domain. A border router gets all the sources forwarded to
it so that it can then flood it into the other protocol(s).

Chris

---

From: "Maren Peasley" <[email-masked]>
Date: Thu, 31 Jan 2008 12:27:01 -0700

Hello Chris,

Thank you for replying.  It makes sense that in order for PIM-DM or
DVMRP to receive information from PIM-SM, that a PMBR would need to
reach into PIM-SM and pull everything (with subsequent prunes reducing
traffic flow to the needed level).  This seems like projecting push-mode
concepts into the pull-mode domain.  I haven't looked at PIM-DM or DVMRP
in any detail, so please pardon my ignorance, but is there an equivalent
concept in these to project a pull-mode concept into them?  Maybe
something like the idea of a (*,G) Join: every PIM-DM/DVMRP router
registering with the PMBR(s) when it has any IGMP requests for a
particular group?  The PMBR could then (*,G) Prune from the PIM-SM
domain(s) if there was a source within the PIM-DM/DVMRP domain.

Thank you again,

www.symantec.com 

-----Original Message-----
From: Christopher Thomas Brown [mailto:[email-masked]] 
Sent: Wednesday, January 30, 2008 8:01 PM
To: Maren Peasley
Cc: [email-masked]
Subject: Re: [pim] (*,*,RP) state

> details given in section 4.1.

To allow sources in a PIM-SM domain to be reachable in a PIM-DM or DVMRP
domain. A border router gets all the sources forwarded to it so that it
can then flood it into the other protocol(s).

Chris

---

From: Christopher Thomas Brown <[email-masked]>
Date: Thu, 31 Jan 2008 16:12:57 -0800

> domain(s) if there was a source within the PIM-DM/DVMRP domain.

No need for any support in the other protocols.

The PMBR register encapsulates sources from the DM or DVMRP domain to the
RP(G). Similarly, it prunes once it has received a register stop (presuming
no other PIM-SM state would keep it unpruned like an (S,G) join)).

Chris
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From: "Nicholas, Jonathan - ACD " <[email-masked]>
Date: Thu, 31 Jan 2008 14:42:38 -0500

PIM-DM doesn't have any such mechanism.  It really isn't needed, since
by default all multicast get pushed to everyone, any such PMBR would get
the messages without doing anything.  If the PMBR doesn't want the
messages, then they can issue a (*,G) Prune.

Jonathan Nicholas

> From: Maren Peasley [mailto:[email-masked]]
> Sent: Thursday, January 31, 2008 2:27 PM
> To: Christopher Thomas Brown
> Cc: [email-masked]
> Subject: RE: [pim] (*,*,RP) state
>
> Hello Chris,
>
> Thank you for replying.  It makes sense that in order for
> PIM-DM or DVMRP to receive information from PIM-SM, that a
> PMBR would need to reach into PIM-SM and pull everything
> (with subsequent prunes reducing traffic flow to the needed
> level).  This seems like projecting push-mode concepts into
> the pull-mode domain.  I haven't looked at PIM-DM or DVMRP in
> any detail, so please pardon my ignorance, but is there an
> equivalent concept in these to project a pull-mode concept
> into them?  Maybe something like the idea of a (*,G) Join:
> every PIM-DM/DVMRP router registering with the PMBR(s) when
> it has any IGMP requests for a particular group?  The PMBR
> could then (*,G) Prune from the PIM-SM
> To allow sources in a PIM-SM domain to be reachable in a
> PIM-DM or DVMRP domain. A border router gets all the sources
> forwarded to it so that it can then flood it into the other
> protocol(s).
>
> Chris
>

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From: "Maren Peasley" <[email-masked]>
Date: Thu, 31 Jan 2008 14:02:22 -0700

Hello Jonathan, 

If I understand correctly, PIM-SM (per RFC 4601) has the ability to
support a push-equivalent that PIM-DM and DVMRP use, but PIM-DM and
DVMRP do not have a pull-equivalent that PIM-SM uses.  This tells me
that it is better to (*,*,RP) pull from n PMBRs to m RPs within PIM-SM
than it is to pull from k PIM-DM-speakers to n PMBRs.  At known levels
of state overhead in PIM-DM/DVMRP and PIM-SM, it seems like we could
determine the density of RPs in a PIM-SM domain within which it makes
sense to operate in a pull-manner and at what level it makes sense to
operate in a push-manner.

I am uncertain as to how solid the last statement is.  I would very much
appreciate any thoughts, feedback, etc.

Thank you,

-----Original Message-----
From: Nicholas, Jonathan - ACD [mailto:[email-masked]] 
Sent: Thursday, January 31, 2008 11:43 AM
To: Maren Peasley
Cc: [email-masked]
Subject: RE: [pim] (*,*,RP) state

Jonathan Nicholas

> traffic flow to the needed level).  This seems like projecting 
> push-mode concepts into the pull-mode domain.  I haven't looked at 
> PIM-DM or DVMRP in any detail, so please pardon my ignorance, but is 
> there an equivalent concept in these to project a pull-mode concept 
> every PIM-DM/DVMRP router registering with the PMBR(s) when it has any

> IGMP requests for a particular group?  The PMBR could then (*,G) Prune

> from the PIM-SM
> DVMRP domain. A border router gets all the sources forwarded to it so 
> that it can then flood it into the other protocol(s).
>
> Chris
>

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ITT Corporation. The recipient should check this e-mail and any
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From: John Zwiebel <[email-masked]>
Date: Thu, 31 Jan 2008 17:41:26 -0800

> appreciate any thoughts, feedback, etc.

2cents (meaning my opinion)

You generally don't want to try to do interdomain multicast routing with
a flood and prune protocol.

You'd have to have a very good reason do do so.

WRT:
>  At known levels
After 15 years of working on PIM -- I'm not going to tell you you can't
do this.  But you might want to consider that many of us are advocating
simplifying multicast to just SSM and Bidir.

And then you have to determine how you plan on getting the folks who
have the deployed multicast (using ASM, MSDP and MBGP) to configure
their networks to support your proposal, and what equipment you are
going to have them run it on.

But I'm assuming you want to connect to the internet.  Perhaps not.

And I'm not claiming to know what might happen in the future.  Maybe
you have a really great idea?
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