The MPLS WG Archive

["Metz, Eduard" <Eduard.Metz@KPNQwest.com>]

I think both L2VPN drafts support a mode in which the L2VPN carries MPLS as
the L2 protocol across the network. So in that way what you suggest is
supported already. 

When doing so, the PE becomes transparent to the MPLS payload however. This
means specific functionality in relation to the termination the L2 circuit
now moves towards the CE, and cannot be expected to be fullfilled on the PE
anymore.

cheers,
	Eduard


> -----Original Message-----
> From: Bernard Zelmans [mailto:bzelmans@calynet.com]
> Sent: 28 June 2001 18:32
> To: 'Sasha Vainshtein'; mpls@UU.NET
> Cc: Alik Shimelmits; Gonen Zilber; Israel Sasson
> Subject: RE: L2 MPLS based VPN
> 
> 
> let me describe what I'm thinking of and let me know if it's stupid.
> basically the idea is to distribute the initiation of the LSP 
> for the VC (as
> per Martini definition), closer to the customer. so I could 
> have a simple L2
> device that would be MPLS enable so that it learns from the 
> PE (through LDP)
> the FEC information. Then you would map all ethernet traffic 
> coming on one
> port or one VLAN id onto that LSP. On the PE you would 
> receive this labelled
> packet and would tunnel it to the peer egress point. so 
> basically you don't
> change the protocol (Martini or Kompella) but you extend to 
> another hop the
> initialisation of the LSP (corresponding to the VC or inner 
> label once in
> the tunnel from the PE)and advertise the FEC through LDP from 
> the PE to this
> MPLS enable device.
> the point is that I could implement PE function on my box but 
> which one to
> go to (Martini or Kompella)? it looks to me that Kompella has more
> advantages. but it also looks like that there will be 2 different
> implementations out there.
> Thanks in advance for your input,
> 
> b
> 
> -----Original Message-----
> From: Sasha Vainshtein [mailto:Sasha@AXERRA.com]
> Sent: Wednesday, June 27, 2001 10:34 AM
> To: Bernard Zelmans; mpls@UU.NET
> Cc: Alik Shimelmits; Gonen Zilber; Israel Sasson
> Subject: RE: L2 MPLS based VPN
> 
> 
> Bernard,
> Inner labels in both Martiti-Transport and Kompella L2 VPN drafts 
> are distributed directly between peer edge devices, and have meaning
> only between these devices. Both Martini and Kompella drafts 
> allow using
> targeted LDP sessions for this purpose, and Kompella also allows using
> MP-BGP for this purpose.
> For the aggregation device to allocate the outer label, it 
> has to be able
> to infer somehow the FEC of the incoming packet.
> I see the following options for the packet transmitted by the 
> access device
> to the aggregation one:
> 1. It is a label packet with the outer label in the stack 
> being the inner
> label
> of the virtual connection. This label cannot be valid in the 
> aggregation
> device
> (as it did not participate in its distribution) so it either drops the
> packet or, even
> worse, misuses it.
> 2. It is an IP packet (say, with MPLS-in-IP protocol type and 
> the inner label following the IP header). In this case the 
> access device:
> * Has to operate as an IP router
> * Has to know IP address of its remote peer device
> * The aggregation device may push the "outer" label on top of 
> IP header
> or just to forward the unlabeled
> *The remote access device must recognize the incoming IP packet as 
> one carying MPLS-in-IP, strip its IP header and then process 
> the incoming
> label.
> I.e., the 2nd option will work, but it imposes restrictions on access
> devices. E.g.,
> you cannot connect Ethernet switches (which are not IP 
> routers) in this way.
> PE devices in both Martini and Kompella are assumed to be 
> LERs (as defined
> in RFC 3031)
> with additional capabilities allowing support of encapsulation of L2
> packets; this approach
> does not impose any restrictions on the access (presumably, 
> CPE) devices.
> With best regards,
>                                    Sasha Vainshtein
> email:     sasha@axerra.com <mailto:sasha@axerra.com> 
> tel:       +972-3-7659993 (office)
>            +972-8-9254948 (res.)
>            +972-58-674833 (cell.)
>  
> 
> 
> > -----Original Message-----
> > From: Bernard Zelmans [mailto:bzelmans@calynet.com]
> > Sent: Wednesday, June 27, 2001 4:49 AM
> > To: mpls@UU.NET
> > Subject: L2 MPLS based VPN
> > 
> > 
> > Hi all,
> > 
> > looking at both Martini and Kompella draft on L2 based VPN, 
> > the LSP with the
> > inner+outer label is started from the same node (PE). Is 
> > there a particular
> > reason for that? why don't we allow an access device to 
> > initiate the inner
> > label LSP and have an aggregation device start the tunnel?
> > Thanks in advance,
> > 
> > b
> > 
>