The MPLS WG Archive

[Ajay Simha <asimha@cisco.com>]

On Thu, 27 Sep 2001, Eric Gray wrote:

> Jay,
>
>     The phrase/term 'VPN-IPv4 Address Family' is certainly misleading, if it
> is not also an outright misnomer.  There is nothing at all special about it
> and
> there is no (IANA) assigned family identifier associated with it.  It is, in
> fact,
> special only to BGP.  Indeed, it should have been identified as an address
> 'format', rather than an address 'family'.
>
>     As you know, the distinction between this address format and that of IPv4
> is that it includes an 8 byte route distinguisher (RD) and a 4 byte IPv4
> prefix.
> Other VPN proposals uses a (proposed standard) VPN identifier (consisting
> of a 3 byte OUI and a 4 byte index - or 7 bytes total), instead of a route
> distinguisher.  See RFC 2685 for more about VPN Identifiers.  Note that it
> would be a trivial matter to embed a VPN ID in an RD.

Eric,

If in fact we want to use VPN ID (rfc 2685) to uniquely identify a vpn, RD and
VPN ID may not be interchangeable in all situations.  For example, for the
same VPN in a hub-and-spoke scenario, we may need to have 2 different RDs for
at the hub site (since we need to keep the routes on seperate VRFs) and thus
precluding use of vpnid in place of rd.

Thoughts?

-ajay
> > -- > Eric Gray
>
> You wrote:
>
> > LDP does not have a provision to carry information like VPN-IPv4 Address
> > Family and can't be a substitute for BGP in implementing VPN. But the core
> > routers in the provider domain, can facilitate PE to PE communication even
> > without BGP being enabled.
> >
> > Jay
> >
> > At 04:09 AM 9/27/01 -0700, Ramyanshu Datta wrote:
> > >hi,
> > >
> > >    the present  rfc on MPLS based VPNs uses BGP for
> > >route  distribution. Can we  use LDP in place of BGP
> > >for the same purpose.  and has  there been any work
> > >done in this direction. if yes then please tell me the
> > >links where i can find information about it
> > >
> > >Thanks in advance
> > >Ramyanshu
> > >
> > >__________________________________________________
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>

-- 
Ajay Simha
MPLS Deployment Engineer
IOS Technology Division
(919) 392-3141

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