From: asadovnikov (asadovnikov@comcast.net)
Date: Sun Feb 08 2004 - 14:54:00 GMT-3
The sparse-dense mode is not recommended because any given group can be put
in sparse or in dense. Actually there are 3 types of groups in pim
sparse-dense:
- service groups which always stay in dense and used for learning and
distribution of auto RP information
- user groups operating in sparse mode
- user groups operating in dense mode
The service groups do not have issue with joins/pruns per say but there are
considerations where an RP or a mapping agent need to be put on the network
to provide information redistribution and connectivity. There was a thread
here couple days ago which went into details on this.
For the user groups operating in sparse mode sparse-dense is not any
different then dense.
For the user groups operating in dense mode, pim nbma will not be able to
provide any assistance, hence they will operate just like dense over nbma.
This is I believe is primary reason for the message.
As long as all user groups do operate in sparse mode and RP / mapping agent
were placed in appropriate places, sparse-dense will work just fine on top
of pim nbma, but for user groups operating in dense mode it will not work
any better then dense mode.
Best regards,
Alexei
-----Original Message-----
From: Hossam [mailto:sam6626@yahoo.com]
Sent: Saturday, February 07, 2004 5:18 AM
To: asadovnikov
Cc: ccielab@groupstudy.com
Subject: RE: NBMA- Mode with Dense and sparse-dense PIM!
Well thanks Asadovnikov,
I think i was not so clear in my first post.
Let me reword it. The real case is that we can configure routers with the
NBMA-MODE along with any of the PIM modes. We can have NBMA-MODE with
PIM-DM, PIM-SM, and PIM-sparse-dense mode.
BUT when i configure the NBMA-Mode with either PIM-DM or with
PIM-Sparse-Dense the routers gets back to me with a noticifation "NMBA-Mode
is NOT RECOMMENDED for PIM_DM or PIM-Spare-Dense".
I can understand this notification for PIM-DM. PIM-DM does't have join/prune
message. Which is a MUST for NBMA-Mode. I am ok with this case.
On the other hand i can't understand (on theortical bases) why it is NOT
recomended to use NBMA-Mode on PIM-Spase-Dense mode. I did test that in my
lab.
In my case everything worked fine with NMBA-Mode on a PIM-Sparse-Dense mode.
I did't face any other problems in my LAB while testing with the MRM tool.
So i started to wonder why do routers send this notificaton. And in which
cases it is NOT recommended to use NBMA-Mode with PIM-Sparse-Dense mode.
Does anyone have insight into this ??
Thanks a lot
SAM
From: "asadovnikov" <asadovnikov@comcast.net>
To: "'Hossam'" <sam6626@yahoo.com>, ccielab@groupstudy.com
Subject: RE: NBMA- Mode with Dense and sparse-dense PIM!
Date: Fri, 6 Feb 2004 23:19:07 -0500
Although there is nothing in PIM NBMA to make dense implementation
technically impossible, it currently not implemented (there are certain
scalability concerns I understand to get it implemented, and on top of
that
dense mode is not really popular in production networks). So it would
be
possible to do dense implementation of pim nbma, but currently sparse
is all
which is there.
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Hossam
Sent: Friday, February 06, 2004 2:30 PM
To: ccielab@groupstudy.com
Subject: NBMA- Mode with Dense and sparse-dense PIM!
As stated in the Doc CD and Cisco web site, i understand the NBMA-mode
over
NBMA networks as a better solution to save unneeded traffic to routers
that
share an NBMA network.
The techique uses the PIM-SM join packets to learn abt the NMBA
neighbours
IPs.
In summary the nmba-mode 2 functions are:
1- To identify all routers on the NMBa interface with their IPs. So
when any
routers sends a PIM join packet to the HUB, the HUB will only send the
multicast traffic to this intersted router only.
Without the NMBA mood the HUB will copy the multicast packets to all
nmba
neighbours(wheather they r intrested or not) who has a the broadcast
keyword.
2- To solve the problem that arrises from the fact that the PRUNE -
Override
technique is not efficent over the NMBA.
Knowing these facts i can understand why it is useless to use NMBA mode
with
PIM -Dense mode ( PIM-Dense uses flood and prune and and it has no
join/prune messages).
My question is Why is it NOT recommended to use the NBMA mode with PIM
-
Sparse - Dense mode.
I hope someone can help....
Thanks
SAM
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