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Re: [PWE3] Mandatory Control Word

"Delregno, Christopher N (Nick DelRegno)" <nick.delregno@verizon.com> Wed, 27 October 2010 16:20 UTC

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Thread-topic: [PWE3] Mandatory Control Word
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From: "Delregno, Christopher N (Nick DelRegno)" <nick.delregno@verizon.com>
To: stbryant@cisco.com, pwe3 <pwe3@ietf.org>
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Subject: Re: [PWE3] Mandatory Control Word
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So, maybe it is not clear in the draft.  Let me see if I can clarify.

The aim of the draft is making the Control Word mandatory.  If there is
consensus with this approach I would ultimately see an RFC needed to
update the existing encapsulations to make CW mandatory.  For legacy
equipment which may never support such, they can adhere to the original
RFCs.  For these, preferably, they would also adhere to our VCCV
Mandatory Features draft to ensure interoperability of the control
channel in the absence of the Control Word mandate.

The second paragraph below is an aside.  At some point in time (note no
time frame given or even suggested, e.g. "if ever"), when all
encapsulations support the mandatory nature of the Control Word, the
need to negotiate such is obviated.  It can certainly be retained if
desired for the support of legacy or posterity, and therefore RFC4447
would never superceded.

Thanks,
Nick


-----Original Message-----
From: pwe3-bounces@ietf.org [mailto:pwe3-bounces@ietf.org] On Behalf Of
Stewart Bryant
Sent: Tuesday, October 26, 2010 12:24 PM
To: pwe3
Subject: [PWE3] Mandatory Control Word

From

draft-delregno-pwe3-mandatory-control-word/

=======
2.  Mandatory Control Word

    The Control Word SHALL be mandatory for all PWE3 encapsulations.
The
    use of the sequence number remains OPTIONAL.

    As a result of the Control Word being Mandatory, all implementations
    of the PWE3 encapsulations SHALL follow Section 6.1 of [RFC4447]
    wherein the "PWs MUST have c=1".  This requirement SHALL remain
until
    such time, if ever, RFC4447 is superceded and the support for
Control
    Word negotiation is removed as a result of this mandate.

======

Given the reality of network deployments I do not see how we can talk
about removing the requirement to negotiate the CW in any realistic time
frame.

It's fine to require the CW for all new PW types, and it's probably OK
to RECOMMEND operation with the CW, but it's unrealistic to remove the
option given the extent of the deployed systems.

- Stewart



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