Re: Data and Defaukt MDT

Prakash,

Hopefully you're nit running for the R&S track this is purely an SP topic.

If you have a MPLS VPN service provider one of the requests that you may
receive from your customers is that they want to have multicast packet
transmission across the SP network. For example one of your customers has 10
sites and they're all connected back to your network as the SP. They have
only one RP and one Mcast Source installed in one of their buildings, say
site 5. So the rest of the sites should be able to receive multicast traffic
from this site and they have to be communicating with their RP installed in
that building.

When you configure the SP network you need to make sure that your (involved)
PEs are able to exchange (hang on a sec) the customer's multicast traffic.
In the IOS we have a few simple commands to configure multicast enabled PEs.
One of them is the command that you use to define your default MDT
(multicast distribution tree) (mandatory) and the other one is utilized to
define the data MDT group. But let's jump back to your question; what are
these things and how they differ?

In a provider network the default MDT is used in a VPN to map all the
multicast groups in use in that particular VPN (a student may say to
"represent" them...but this is not very technical). At the beginning you
start by using this group across the core and use it for all low bw and
control traffic.(hopefully you know the GRE stuff used here).

The IOS also supports the dynamic creation of MDTs for high-bandwidth
transmission.

But what does this mean? What if in their VPN my customer has a high bw
source like live video broadcasting (technically multicasting) ? any special
treatment in the SP core required? or it doesn't really matter?

In my case, I'd like to make sure that this takes the another path (tree) if
needed (may be optimum).

You can use the MDT data command to define a threshold at which we switch
over to our data MDT group. When the generated multicast traffic exceeds the
threshold, the sending PE (which is the closest to the source in customer
premises - very important in terms of design) creates the data MDT using UDP
messages notifies all other default MDT peers in the core. This is not
MP-BGP.

Here are some important facts about Data MDT:

- Control and low bandwidth stuff generally use the default MDT.

- Data MDT information again is not carried by MP-BGP. Please note that when
a PE creates the default MDT group it uses MP-BGP to have its peers updated.

- In contrast to default MDTs which are created between all mcast PE routers
your data MDTs are only generated between those PE routers engaged in high
BW traffic (bursts).

- Cisco IOS checks the threshold every 10 seconds.

- Cisco IOS uses Data MDTs only for (S,G) stuff and (*,G) entries can not
trigger the creation of data MDTs.

Here is my recommendation:

- Create a simple SP using only 3-4 routers and implement this but turn in
debugging and see various stages that your routers go through. You can find
some nice debug options.

- Take a look at Chapter 7 of MPLS VPN Architecture vol2 by Ivan.

- Fine tune your knowledge by taking a look at cisco PSA articles on this.
Like this :

http://www.cisco.com/en/US/tech/tk436/tk428/technologies_configuration_example09186a0080242aa8.shtml

HTH

Kambiz Agahian

CCIE Instructor/Consultant
M.Eng Telecom, CCIE# 25341, CCSI# 33326, MCSE, MCSA

On Thu, Aug 12, 2010 at 12:21 AM, Prakash Kalsaria <
kalsaria.prakash_at_gmail.com> wrote:

> Data and Default MDT which to use and when when
> i tried to find difference but could not get much success
> can any one Provide me more info
>
> regards;
> Prakash Kalsaria
> http://prakashkalsaria.wordpress.com
>
>
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Received on Thu Aug 12 2010 - 01:26:07 ART