Subject: hello option for nbr mode

From: Tom Pusateri <[email-masked]>
Date: Mon, 16 Nov 1998 11:56:15 -0500

Has anyone already defined a v2 hello option for nbr mode
(sparse, dense, sparse-dense)? This is mostly useful
for problem determination but I didn't want to re-invent
the wheel.

Thanks,
Tom

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From: Bill Fenner <[email-masked]>
Date: Mon, 16 Nov 1998 17:22:45 PST

sparse-dense is a PIMv1 artifact, right?

  Bill

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From: Tom Pusateri <[email-masked]>
Date: Mon, 16 Nov 1998 22:33:41 -0500

>sparse-dense is a PIMv1 artifact, right?

Yes and no.

Its not in the spec (it wasn't in the v1 spec either) but
transitioning from v1 to v2 is going to result in some
interesting version smearing...

That said, I'm happy to leave it out. ;-)

Thanks,
Tom

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From: Shahzad Ali <[email-masked]>
Date: Mon, 16 Nov 1998 22:37:21 -0500 (EST)

Hi,

> sparse-dense is a PIMv1 artifact, right?

Dont think so, although it seems to be a cisco artifact for sure.  This
was present in cisco's V1 implementation and has carried on from there.
What it means is that groups are classified as "Dense" or "Sparse", the
former being groups with no RP-mapping available.  Thus running pim in
SDM (sparse-dense-mode) would mean that on any interface either DM or SM
can run depending on whether a group has a valid mapping to an RP
available.  So any events, such as IGMP joins or Data packet arrivals are
treated according to SM or DM specification based on the "sparseness" and
the "denseness" of the group respectively.

> (sparse, dense, sparse-dense)?

I dont think anybody has.  Anyway, if Dense [Sparse] is running on an
interface it is clear that all nbrs on that interface are running Dense
[Sparse] mode, unless there is a mis-configuration, which might be the
reason you want the option in the first place. As for Sparse-dense mode, I
dont know if that is any help, because no matter what the nbr is running,
an SDM interface has capability to handle both kinds of PIM (SM & DM).

or are there other reasons for putting the option in?

-Shahzad

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From: Tom Pusateri <[email-masked]>
Date: Mon, 16 Nov 1998 22:47:50 -0500

In message <[email-masked]> yo
u write:
>
>[unless there is a mis-configuration, which might be the
>reason you want the option in the first place.

bingo.

>or are there other reasons for putting the option in?

Nope, thats it.

Thanks,
Tom

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From: Shahzad Ali <[email-masked]>
Date: Mon, 16 Nov 1998 22:54:47 -0500 (EST)

> That said, I'm happy to leave it out. ;-)

I thought this was independent of v1 or v2 spec. This looks more like
a combination of SM and DM to me.  Again, I might be mis-interpretting the
whole Sparse-dense-mode.  IMHO it is a useful feature to have (that is, if
it is what I perceive it to be ).

-Shahzad

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From: Shahzad Ali <[email-masked]>
Date: Mon, 16 Nov 1998 23:00:43 -0500 (EST)

Hi,

> >reason you want the option in the first place.

That makes sense too, but only is SM or DM.  however, if you are running
in Sparse-Dense-mode, it doesnot have much use. And as i already pointed
out, that to me seems like a desirable feature.
One problem with SDM is that the "Sparseness" ["Denseness"] of groups is
not explicit and therefore there are more chances of groups that were
meant to be Dense, ending with RP mappings for them (thus becoming
Sparse implicitly).  

-Shahzad

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From: Dino Farinacci <[email-masked]>
Date: Mon, 16 Nov 1998 20:09:18 -0800 (PST)

>> it is what I perceive it to be ).

    Shahzad, you are not misinterpreting cisco's interpretation of sparse-
    dense-mode.

    BTW, sparse-dense-mode was invented so Auto-RP messages (for PIMv1) can
    be sent in dense-mode but the data groups would use sparse-mode. Otherwise,
    there is a catch-22.

Dino