Subject: Re: Eric Rosen's comments on Hybrid VPLS

From: "Cheng-Yin Lee" <[email-masked]>
Date: Wed, 02 Apr 2003 11:46:16 -0500

Eric,
> It  seems to me  that what  you call  CLEs are  really CEs,  as the  term is
> generally used in PPVPN. 
CLEs exist and are deployed in operational networks and when used are
not the same box as Customer Equipment (CE), as defined in the PPVPN
framework document.

> So the solution you are proposing is: 
> 
> a. Interconnect  the CEs of  a particular  customer with  a topology  of p2p
>    links provided by a VPWS service
> 
> b. The CEs function as  bridges, extending the customer's spanning tree over
>    that p2p topology. 
> 
> My comment  is that this  solution does not  appear to require any  new work
> from the PPVPN WG.  From the PPVPN perspective, it is simply VPWS.  
It is not simply VPWS. A provider may offer a VPLS service when the
provider manages the CLEs.
A provider may use p2p PW to build a VPLS service for customers, as
discussed in IETF-56 PPVPN WG meeting. In this case, the CE sees a VPLS
service. 

A customer may also choose to subscribe to a VPWS instead, in this case
the CE sees a VPWS and the CE is responsible to do any bridging or
routing it is configured and designed for, and it is not necessary for
the provider to manage or provide any CLEs.

> The fact
> that the CEs are bridges rather than hosts or routers doesn't matter. 
Yes.
 
> I believe this same comment has been  made a number of times, by a number of
> different people.
Norm Finn commented it is a VPWS and I clarified this along the same
lines and during the discussion in IETF-56 PPVPN. May I know which part
of the above clarification is still not clear?

> It may  well be the case  that bridging over  VPWS is a good  solution.  But
> there's nothing for the PPVPN WG to specify. 
As I understand the PPVPN WG charter is about making use of existing
technologies (other WG shall specify any necessary mechanisms/extensions
to a protocol), it's goal does not appear to be about specifying any new
mechanisms or protocols specifically.
Quoting the PPVPN WG charter:
"The effort will produce a small number of approaches that are based
on collections of individual technologies that already exist (see
below for specifics). The goal is to foster interoperability among
implementations of a specific approach. Standardization of specific
approaches will be gauged on (I)SP support.  Note that it is not a
goal of this WG to develop new protocols or extend existing
ones. Rather, the purpose is to document and identify gaps and
shortcomings in individual approaches with regards to the
requirements. In the case that specific work items are identified,
such work will be done in an appropriate WG.  Taking on specific
protocol work items in this WG will require rechartering"

Hybrid VPLS is an example of a "vertical" solution, specifying how
existing protocols and any extensions required may be used to offer
Hybrid VPLS, so different vendors equipment may interoperate to provide
the service.

regards
Cheng-Yin

---

From: Eric Rosen <[email-masked]>
Date: Wed, 02 Apr 2003 12:46:54 -0500

Eric> It seems to me that what you call CLEs are really CEs, as the term is 
Eric> generally used in PPVPN. 

Well, your  answer to this is  "no they aren't".  That's  not a particularly
helpful response.

Cheng-Yin> Norm Finn commented  it is a VPWS and I  clarified this along the
Cheng-Yin> same lines and during the discussion in IETF-56 PPVPN. May I know
Cheng-Yin> which part of the above clarification is still not clear? 

I don't believe any clarification was ever made; the same claims were merely
repeated. 

Eric> It may  well be the case that  bridging over VPWS is  a good solution.
Eric> But there's nothing for the PPVPN WG to specify. 

Cheng-Yin> As  I understand  the PPVPN  WG charter  is about  making  use of
Cheng-Yin> existing  technologies  (other  WG  shall specify  any  necessary
Cheng-Yin> mechanisms/extensions to  a protocol), it's goal  does not appear
Cheng-Yin> to  be   about  specifying   any  new  mechanisms   or  protocols
Cheng-Yin> specifically.  

If  a  particular solution  does  not  require the  PPVPN  WG  to issue  any
specifications, then there  is no need to  take up the time of  the PPVPN WG
discussing it.  I don't think this is a particularly subtle point.

---

From: "Cheng-Yin Lee" <[email-masked]>
Date: Wed, 02 Apr 2003 14:06:01 -0500

Eric,

> I don't believe any clarification was ever made; the same claims were merely
Ok, I see the problem now, you've deleted/or ignored the clarification
;-). I have repasted it below.

"It is not simply VPWS. A provider may offer a VPLS service when the
provider manages the CLEs.
A provider may use p2p PW to build a VPLS service for customers, as
discussed in IETF-56 PPVPN WG meeting. In this case, the CE sees a VPLS
service. "

Perhaps you can say what is not clear in the above.
If the CE sees a VPLS service, why is this not a VPLS service?

thanks
Cheng-Yin

---

From: "Vach Kompella" <[email-masked]>
Date: Wed, 2 Apr 2003 11:21:11 -0800

Cheng-Yin,

Just because the CE sees it as a VPLS, it doesn't become a VPLS (from the
provider's point of view).  It still looks like a VPWS which the customer turns
into a VPLS by putting bridges with split horizon, etc.

The basic point is that the customer needs a VPWS service from the provider, so
from a ppvpn perspective, what you presented is that a customer can turn a ppvpn
VPWS into a customer-based VPLS.

That's a customer deployment/use scenario.

-Vach

> -----Original Message-----
> From: Cheng-Yin Lee [mailto:[email-masked]]
> Sent: Wednesday, April 02, 2003 11:06 AM
> To: [email-masked]
> Cc: [email-masked]
> Subject: Re: Eric Rosen's comments on Hybrid VPLS
>
>
> Eric,
>
> Eric Rosen wrote:

---

From: "Cheng-Yin Lee" <[email-masked]>
Date: Wed, 02 Apr 2003 14:27:46 -0500

Vach, 

> into a VPLS by putting bridges with split horizon, etc.
The point is the provider manages the CLEs and provide a VPLS.
The "UNI" is at CE to provider device/CLE and the CE sees a VPLS service
from the provider.

> VPWS into a customer-based VPLS.
This is the VPWS case, not the VPLS service described above.

regards,
cheng-yin

---

From: "Cheng-Yin Lee" <[email-masked]>
Date: Wed, 02 Apr 2003 14:33:24 -0500

Eric Rosen wrote:
> 
> Cheng-Yin> Perhaps you  can say what is not  clear in the above.   If the CE
> Cheng-Yin> sees a VPLS service, why is this not a VPLS service?
> 
> And round and round we go ...
> 
> The CE doesn't see a VPLS service,  it sees a VPWS service.  
No, I'm afraid you've misunderstood this point, Eric. 
I just sent a clarification to Vach about this.

> The CE provides
> an emulated lan service to other nodes at its site.  You keep obscuring this
> by calling the CE "CLEs" and calling other routers at the sites "CEs".
Perhaps people may want to read the draft first, just a suggestion ...
Also, CEs are not CLEs and CEs are not necessarily routers.

thanks,
Cheng-Yin

---

From: Eric Rosen <[email-masked]>
Date: Wed, 02 Apr 2003 14:25:43 -0500

The CE doesn't see a VPLS service,  it sees a VPWS service.  The CE provides
an emulated lan service to other nodes at its site.  You keep obscuring this
by calling the CE "CLEs" and calling other routers at the sites "CEs".