The MPLS WG Archive

["Miguel Angel Chana" <machana@cisco.com>]

> -----Original Message-----
> From: owner-mpls@UU.NET [mailto:owner-mpls@UU.NET]On Behalf Of Arun
> Kumar Dheena
> Sent: Friday, February 22, 2002 1:08 PM
> To: mpls@UU.NET
> Subject: LDP - VPN
> 
> 
> Hi,
>       The RFC 2547bis uses BGP to distribute the VPN routes. 
> But, we can
> modify LDP itself to carry the information carried in BGP like the VPN
> routes, route targets and VPN labels etc (by defining, new 
> TLVs and new LDP
> messages).
> 

LDP distributes LABELS bindings to FECs, those being IPv4, VPNv4, 
MAC addresses, VC's or whatever else. Imagine a situation where 
PEs are separated by LSR routers that do not have any notion of 
the FEC for which you are binding the label. Since they don't
understand the FEC, they can not give you a label binding. This
is why LDP directed sessions are used for anything else than
IPv4 (for example, Martini). Either that or you have to do all
the LSR in the path "aware" of the FEC. The idea of MP-BGP is 
pretty much the same, you are using BGP sessions between all the
peers to exchange VPNv4 information.  


> The motivation for this is, firstly, the LDP-VPNs can provide the same
> scalability as in mentioned RFC2547, as the intermediate 
> LSR's (P routers)
> need not maintain the VPN-Lables and routes. (This can be achieved by
> maintaining LDP sessions between the PE LSR's). Secondly, we 
> can avoid using
> BGP for MPLS-VPNs.

Sure you can, but in this case remember you will have to maintain
a LDP session for each of the PEs (full mesh) I'd like to see you
maintaining a couple hundreds PEs with full meshing requirements, 
without all the handy mechanisms BGP has (for example, Route Reflectors)
Or maybe we can add the notion of Route Reflectors to LDP...

> 
> Will this apparach be an alternate for BGP/MPLS VPN?
> Or am I missing something  fundamental?
> I want to know whether any work has been done in this direction.
> 

Ask the folks at PPVPN


> Thanks in advance.
> regards
> arun
> 
> Wipro-CDC
> 
> 
> 
> 
> 
>