Re: [Idr] RFC 4684 pedantry - routes with no Route Target

[Jakob Heitz <[e-mail]>]

I am for 1. No RT, no RT-C filtering.
Moreover, for ANY address family (including RT-C) if an UPDATE includes an RT, then RT-C filter it. No special exceptions if an RT-C UPDATE contains the same RT in the NLRI and the attribute field.

--
Jakob Heitz.


> On May 21, 2014, at 5:48 AM, "Jeffrey Haas" <[e-mail]> wrote:
> 
> IDR,
> 
> RFC 4684 (Constrained Route Target Distribution) is obviously a useful tool.
> At work, we've run into an interesting case and I thought I'd share some of
> the internal debate on it.
> 
> In RFC 6037 ("draft-rosen" multicast VPNs), the MDT SAFI has the following
> documentation in section 4.4:
> 
> :   When a PE distributes this NLRI via BGP, it may include a Route
> :   Target (RT) Extended Communities attribute.  This RT must be an
> :   "Import RT" [RFC4364] of each VRF in the MD.  The ordinary BGP
> :   distribution procedures used by [RFC4364] will then ensure that each
> :   PE learns the MDT-SAFI "address" of each of the other PEs in the MD,
> :   and that the learned MDT-SAFI addresses get associated with the right
> :   VRFs.
> 
> RFC 4684's procedure says in section 6:
> :   A VPN NLRI route should be advertised to a peer that participates in
> :   the exchange of Route Target membership information if that peer has
> :   advertised either the default Route Target membership NLRI or a Route
> :   Target membership NLRI containing any of the targets contained in the
> :   extended communities attribute of the VPN route in question.
> 
> Quite frankly, we have a bug in that MDT's are not getting propagated when
> RT-C is in use because we're treating it as a "VPN NLRI".  Simple fix, but
> one that leaves me wondering if the issue is more general - and perhaps
> worthy of an errata for RFC 4684.
> 
> For the MDT case, one can make the argument that since it may be distributed
> without RTs, it's only a "VPN NLRI" if it contains RTs.
> 
> The broader question I'd put to the working group is whether any NLRI not
> having RTs isn't really a "VPN NLRI" for purposes of RT-C filtering.  This
> really leaves two simple schools of thought:
> 1. No RT, no RT-C filtering.
> 2. MDT SAFI is an odd-ball case, just deal with that.  (And perhaps warn in
> future BGP documents that may use RT-C about how to deal with no RTs when
> they're optional.)
> 
> -- Jeff
> 
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