Subject: [PWE3] A litmus test for the NSP Capabilities TLV in draft-vkompella-pwe3-ethernet-pw-bis-01.txt

From: Alexander Vainshtein <[email-masked]>
Date: Tue, 29 Jul 2008 18:56:03 +0300

Hi all,

IMHO there is a simple enough litmus test regarding usefulness (or lack thereof) of the NSP Capabilities TLV in the above-mentioned draft:

If there is a valid use case when mismatch between expected and actual capabilities of the NSPs prevents normal operation of the PW, such a TLV is required.

Otherwise it looks as if we could do without...

My 2c.
    Sasha
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From: "BALUS Florin" <[email-masked]>
Date: Thu, 31 Jul 2008 16:52:53 -0500

Sasha,

The main purpose of draft-vkompella-pwe3-ethernet-pw-bis was to clearly
differentiate between the NSP and the PW termination functions so that
it is easier to accommodate new specifications from other SDOs (e.g.
IEEE) without having to rewrite every time the IETF documents. 

The NSP capabilities TLV was introduced to address some specific
requirements we heard from Service Providers. For example, see slide  8
of the package we presented during L2VPN for PBB-VPLS extensions
(draft-balus-l2vpn-vpls-802.1ah-03) at
http://www3.ietf.org/proceedings/08jul/slides/l2vpn-5.ppt .  Address
separation between the I-VPLS and B-VPLS domains can provide a way to
minimize the occurrences of PW miss-connectivity but if a Service
Providers wants to avoid it altogether then the NSP capability TLV can
be used together with an implementation knob.

It is important to note that there are some use cases where in fact
connectivity between an I-VPLS, a B-VPLS and regular VPLS instances
might be required: i.e. in some migration scenarios there might be a
need to connect B-VPLS or I-VPLS instances to regular VPLS ones just
because existing PEs do not support the PBB-VPLS. Another example might
be future Carrier of Carrier services where a B-VPLS might connect to
the I-VPLS.  That is why an implementation knob should be used where a
Service Provider can control whether to use or not the NSP capability on
a per remote PE. 

I hope this answers your question.
Florin

From: [email-masked] [mailto:[email-masked]] On Behalf Of
Alexander Vainshtein
Sent: Tuesday, July 29, 2008 8:56 AM
To: [email-masked]
Subject: [PWE3] A litmus test for the NSP Capabilities TLV in
draft-vkompella-pwe3-ethernet-pw-bis-01.txt

Hi all,

IMHO there is a simple enough litmus test regarding usefulness (or lack
thereof) of the NSP Capabilities TLV in the above-mentioned draft:

If there is a valid use case when mismatch between expected and actual
capabilities of the NSPs prevents normal operation of the PW, such a TLV
is required.

My 2c.

    Sasha

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From: "BALUS Florin" <[email-masked]>
Date: Thu, 31 Jul 2008 17:07:28 -0500

I would like to add here that we welcome feedback also from L2VPN WG
about the possible applicability of the NSP capability TLV. 

For the example described below this is a new functionality IEEE did not
consider for the IEEE 802.1ah (PBB) specification. 

Florin

From: [email-masked] [mailto:[email-masked]] On Behalf Of
BALUS Florin
Sent: Thursday, July 31, 2008 2:53 PM
To: Alexander Vainshtein; [email-masked]
Subject: Re: [PWE3] A litmus test for the NSP Capabilities TLV
indraft-vkompella-pwe3-ethernet-pw-bis-01.txt

Sasha,

 

Hi all,

My 2c.

    Sasha