Subject: Re: draft-so-pwe3-ethernet

From: "W. Mark Townsley" <[email-masked]>
Date: Thu, 18 Jul 2002 16:46:06 +0900

My thought is that a pseudowire should be able to be instantiated between any
two nodes, regardless of whether they are owned or managed by a customer or
provider (as this is not always so easy to define for some applications). 

Perhaps the framework needs to be adjusted to allow this. 

- Mark

Cheng-Yin Lee wrote:
> 
> Tricci et al,
> Would it be possible to specify Ethernet over L2TP/GRE (in
> draft-so-pwe3-ethernet.txt ) for device to device, instead of
> specifically for PE to PE only?
> 
> I understand the PWE framework document describes pwe for PE-PE only,
> but the PWE3 charter does not preclude device to device pwe.
> 
> thanks
> cheng-yin
> 
> _______________________________________________
> pwe3 mailing list
> [email-masked]
> https://www1.ietf.org/mailman/listinfo/pwe3

---

From: Stewart Bryant <[email-masked]>
Date: Thu, 18 Jul 2002 12:19:33 +0100

> specifically for PE to PE only?

Do you mean from CE to CE?
In the L2TP case this will (does) just work.

> but the PWE3 charter does not preclude device to device pwe.

The charter starts "Service providers (SP) are seeking to offer multiple 
services across a common packet switched network (PSN)...", and the Edge
to Edge title implies SPs.

For the packet services, and some cell running CE-CE will work just fine, 
although in the case of MPLS you have to carry the MPLS over GRE. 
However the bit payloads need to be deployed with care, and
may not work unless the SP provides suitable traffic engineering.

Stewart

---

From: "Cheng-Yin Lee" <[email-masked]>
Date: 18 Jul 2002 21:51:46 -0400

Mark,
Thanks for sharing your thoughts.

> provider (as this is not always so easy to define for some applications).

I agree with this, applications may use the specification between any two nodes
(PE/MTU/CE/?) if needed in the longer term ...

regards
cheng-yin

---

From: "Cheng-Yin Lee" <[email-masked]>
Date: 18 Jul 2002 21:51:55 -0400

Stewart,

> In the L2TP case this will (does) just work.

Understood, but the current draft description is in terms of PE to PE.

> may not work unless the SP provides suitable traffic engineering.

... at this point, I have only requested device to device pwe description for
Ethernet.

thanks
cheng-yin

---

From: "W. Mark Townsley" <[email-masked]>
Date: Fri, 19 Jul 2002 11:07:09 +0900

> Understood, but the current draft description is in terms of PE to PE.

The L2TP portion of this is going to be rewritten into a separate document.
There will be nothing to prohibit use of eth over l2tp with any of the
device-oriented reference models identified in
draft-ietf-l2tpext-l2tp-base-03.txt.

> ... at this point, I have only requested device to device pwe description for

I prefer "Device to Device" for pwe3 in general, with ppvpn or other WGs
focusing more on PE, CE, and such designations. L2TPEXT will certainly support a
"device to device" description.

---

From: Stewart Bryant <[email-masked]>
Date: Mon, 22 Jul 2002 10:08:41 +0100

Re the exchange below:

What are the views of the WG, should we change the PWE3 protocol
layering/framework/architecture document to be provider/customer
neutral?

Stewart

---

From: Eric Rosen <[email-masked]>
Date: Mon, 22 Jul 2002 11:14:10 -0400

Stewart> What are  the views of the  WG, should we change  the PWE3 protocol
Stewart> layering/framework/architecture  document  to be  provider/customer
Stewart> neutral?

I'd just as soon leave it as it is. 

It's true that the PE/CE dichotomy  comes from the VPN work, and is oriented
towards a  customer/SP interface.  However,  in any environment,  there does
need  to be  a  clear functional  distinction  between the  provider of  the
pseudowire service and  the user of the pseudowire service,  and I think the
existing terminology does capture that as well as anything. 

We  might try  to  make it  clear  that "PE"  and  "CE" describe  functional
entities which admit of different deployment models.  For example: 

- We want  to accommodate PW  "splicing", in which  a PE switches one  PW to
  directly another, with no CE between  them.  We could model this as the PE
  device being two logical PEs separated by a logical CE.

- We want  to accommodate PW-to-routing, where the device at  one end of the
  PW serves as both PE and CE. 

We could  try to abstract the terminology  a bit by replacing  "PE" with "PW
provider", or  something like  that, and replacing  "CE" with "PW  user", or
something like that, but I don't think that would create any less confusion.
Generally switching  terminology in  midstream just creates  more confusion,
unless the new terminology has a very significant advantage.

---

From: "Mitsuru Higashiyama" <[email-masked]>
Date: Tue, 23 Jul 2002 08:55:25 +0900

Stewart,

I like changing layering/framework/architecture document.
Basically, it does not limit PE/CE except
section 3 "Architecture of Pseudo Wires".

I think adding CE to CE model will complete document.

Thanks,
Mitsuru Higashiyama