Subject: 2 Extended Community introduced in draft-ietf-l3vpn-2547bis-mcast-bgp-05.txt

From: Subinoy Das <[email-masked]>
Date: Fri, 15 May 2009 12:20:02 +0530 (IST)

Hi,

In draft-ietf-l3vpn-2547bis-mcast-bgp-05.txt

in section 6. Source AS Extended Community

If for a given MVPN BGP is used for exchanging C-multicast routes, or
if segmented inter-AS tunnels are used, then when a PE that has sites
of that MVPN connected to it originates a (unicast) route to VPN-IP
addresses, the PE MUST include in the BGP Update message that carries
this route the Source AS extended community.

in section 7. VRF Route Import Extended Community

To support MVPN, in addition to the import/export Route Target(s)
extended communities used by the unicast routing, each VRF on a PE
MUST have an import Route Target extended community. We refer to
this Route Target as the "C-multicast Import RT", as this Route
Target controls imports of C-multicast routes into a particular VRF.

in section 11.1.3. Constructing the rest of the C-multicast route

From the selected UMH route the local PE extracts (a) the autonomous
system number of the upstream PE (as carried in the Source AS
extended community of the route), and (b) the C-multicast Import RT
of the VRF on the upstream PE (the value of this C-multicast Import
RT is the value of the VRF Route Import Extended Community carried by
the route). The Source AS field in the C-multicast route is set to
that autonomous system. The Route Target Extended Community of the Cmulticast
route is set to that C-multicast Import RT.

From these I understood that to support draft-ietf-l3vpn-2547bis-mcast-bgp-05.txt, 2 additional Extended Community Attributes "VRF Route Import Extended Community" and "Source AS Extended Community" are to be sent with VPN-IP update message.
MCAST-VPN update message does not carry these 2 Extended Communities.

Please let me know if my understandings are correct or not.

Regards,
Subinoy

      From Chandigarh to Chennai - find friends all over India. Go to http://in.promos.yahoo.com/groups/citygroups/

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From: Yakov Rekhter <[email-masked]>
Date: Fri, 15 May 2009 08:35:34 -0700

Subinoy,

> If for a given MVPN BGP is used for exchanging C-multicast routes,
> or if segmented inter-AS tunnels are used, then when a PE that has
> sites of that MVPN connected to it originates a (unicast) route to
> VPN-IP addresses, the PE MUST include in the BGP Update message
> that carries this route the Source AS extended community.
> 
> extended community of the route), and (b) the C-multicast Import
> RT of the VRF on the upstream PE (the value of this C-multicast
> Import RT is the value of the VRF Route Import Extended Community
> carried by the route). The Source AS field in the C-multicast route
> is set to that autonomous system. The Route Target Extended Community
> of the Cmulticast route is set to that C-multicast Import RT.
> 
> From these I understood that to support
> draft-ietf-l3vpn-2547bis-mcast-bgp-05.txt, 2 additional Extended
> Community Attributes "VRF Route Import Extended Community" and
> "Source AS Extended Community" are to be sent with VPN-IP update
> message.  

That is correct.

> MCAST-VPN update message does not carry these 2 Extended

That is correct too. But as stated in 11.1.3, the information carried
in these communities is used to construct C-multicast routes (as
described in the quote above).

Yakov.