Discussion on E-Tree and H-VPLS

Sam,

Please see my comments in line. I also change the title to reflect the topic.

Regards
Yuanlong

-----Original Message-----
From: Sam Cao [mailto:yuqun.cao@...]
Sent: Monday, April 23, 2012 11:28 AM
To: Jiangyuanlong
Cc: l2vpn@...
Subject: RE: L2vpn Digest, Vol 95, Issue 58

Yuanlong,

I do apologize for my unclear description. I try to make it clear.

VPWS or Spoke PW, PE-rs will take the PW as Spoke PW. Or say, PE-rs really
does NOT care remote access is VPWS access (point-to-point, Fig. 3) or VPLS
spoke access (Fig. 4). PE-rs just know it is spoke PW and it is ENOUGH, and
does NOT care customer payload. is this correct?  At least it is correct in
RFC 4762.
[JY] why divide the remote access to VPWS access and VPLS access?

But, if remote is VPWS access (Fig. 3), PE-rs SHOULD configure AC-type for
remote VPWS access although it is still spoke PW in E-Tree. Please refer to
your answer to Josh's question. It seems reasonable. Ok, we think another
case in Fig. 4. In Fig. 4, PE-rs CAN NOT configure AC-type at all in this
case. In fact, on MTU-s it is VPLS and we should configure AC type on MTU-s.
[JY] Quite opposite, in case of Fig.4, IMHO, it is better to configure the E-Tree attribute on the PE-rs since the PE-r does not support any bridging functions. I think this case is provided in RFC4762 just to be compatible with some legacy routers.


Ok, problem came up for me. For spoke PW on PE-rs, in one case it should
configure AC type and work as agent; in another case, it can NOT configure
AC type and can not work as agent. In fact, PE-rs knows it is spoke PW, it
is enough; why spoke-PW has different configuration in same VPLS instance on
same PE? I am confused although I know why we should configure in that way.

I prefer not to configure AC type on PE-rs since we can take it as
"Switching PE" (NOT pefact here and it is not real "Switching Point") which
does NOT aware customer payload. Extension to VPWS? Seems not reasonable.
[JY] Not sure I got your points. PE-rs will terminate the PW and switch the Ethernet frames. IMO, whether configuring the E-Tree service on a PE-rs or a MTU-s is dependent on the topology of the service and how they are attached. H-VPLS can be seen as a transparent transport network, or as a service itself.

Thanks,

Sam

-----Original Message-----
From: Jiangyuanlong [mailto:jiangyuanlong@...]
Sent: Monday, April 23, 2012 9:59 AM
To: Sam Cao
Cc: l2vpn@...
Subject: RE: L2vpn Digest, Vol 95, Issue 58

Hi Sam,

If E-Tree service is provided in a scenario as Fig. 3 and Fig 4 in RFC 4762,
then a CE (leaf or root) is connected to the MTU-s or PE-r, thus the AC
should be terminated and the E-Tree service should be encapsulated by the
MTU-s or PE-r. I don't quite understand why you need to "take VPWS PW as one
AC", but even in that case, the attribute of the AC may be configured at the
PE-rs. So what is the problem for H-VPLS?

Thanks
Yuanlong

Date: Sun, 22 Apr 2012 22:03:52 +0800
From: "Sam Cao" <yuqun.cao@...>
To: "'Jiangyuanlong'" <jiangyuanlong@...>
Cc: l2vpn@...
Subject: RE: The status of the approaches to the E-Tree solution?
Message-ID: <962A848896EF4678B17D76C826A7EAEF@v2comsam>
Content-Type: text/plain; charset="us-ascii"

Yuanlong,

I just collect all issues we discussed before, and we still can not make
agreement. I gave my comments on 2 items below. I will think other items
over and give my comments tomorrow.

2) HVPLS: If we follow Fig 3 or Fig 4 in RFC 4762 to deploy HVPLS,
PE-rs works in different manner, PE-rs should figure out AC type in VPWS
case, but can NOT configure it at all in Spoke PW case;
[JY] In the first place, why PE-rs need to figure out the AC type for a
spoke? The VLAN should be processed in the MTU, not in the PE-rs.
[Sam] Yuanlong, I understand your idea. It does NOT make sense for me.
First, Fig. 3 and Fig 4 in RFC 4762 are different cases. For VPWS (Fig. 3),
we can take VPWS PW as one AC. You know, PE-rs is termination of VPWS, so it
will add VLAN-ID to identify Root/Leaf. BTW, you will map several VLAN IDs
into one Root-VLAN ID or Leaf-VLAN ID on PE-rs, so we need to configure
Root/Leaf on PE-rs (Refer to your reply to Josh's comments).

4)  Encapsulation mode: If deploy HVPLS with Spoke PW mode, PE-rs
should work in tagged mode, otherwise PE-rs or egress PE will stripe S-VLAN
ID;
[JY] Is anything not working with tagged PW mode?
[Sam] Tagged mode works.

Regards,
 
Yuqun (Sam) Cao
E-mail: Yuqun.cao@...