Re: [mpls] working group last call for draft-ietf-mpls-extended-admin-group

"Andrew G. Malis" <agmalis@gmail.com> Tue, 04 February 2014 19:39 UTC

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From: "Andrew G. Malis" <agmalis@gmail.com>
Date: Tue, 04 Feb 2014 14:39:23 -0500
Message-ID: <CAA=duU3jTANV0myUvjtRnFJWspE=tz4LW24_mVkSoekKmrwKVw@mail.gmail.com>
To: Loa Andersson <loa@pi.nu>
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Cc: "mpls@ietf.org" <mpls@ietf.org>, "mpls-chairs@tools.ietf.org" <mpls-chairs@tools.ietf.org>, draft-ietf-mpls-extended-admin-group@tools.ietf.org
Subject: Re: [mpls] working group last call for draft-ietf-mpls-extended-admin-group
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I was asked by the WG chairs for a WG LC review of this draft. In
general, the draft is ready for publication, but I do have a few
comments.

[Editorial] Section 1: There are several unbracketed RFC references
that are in the actual list of references, and thus should be in
brackets in the text.

[Technical] Section 2.2: The numbering of the EAG's first word of bits
is discussed, but the numbering of the bits in subsequent words is not
described. It can be implied that the bit numbering will continue at
32 with the LSB of the second word of the EAG, but that is not
actually stated.

[Technical] Section 2.3.1: It is easy to predict that routers or
software loads that implement the EAG will be deployed in the same
network as those that only implement the AG. It can be expected that
routers that do not implement the EAG will simply ignore that
particular sub-TLG. Thus, those routers, upon receipt of both the AG
and EAG sub-TLVs, will ignore the EAG and use the AG. Thus, for
improved backwards compatibility, if the AG and EAG co-exist and the
AG is inconsistent with the first word of the EAG, it would seem that
the AG should take precedence. This is the opposite of what is stated
in the draft.

Of course, once all of the routers in a network support the EAG, the
AG will be unnecessary and only the EAG will be used.

[Technical] Section 2.3.2: I'm personally hard-pressed to find
usefulness in the flexibility in this section. For maximum
interoperability and simplicity of implementations, I would prefer
that the third paragraph be modified to say:

   To encourage maximum interoperability an
   implementation MUST treat desired but unadvertised EAG bits as if
   they are set to 0.  Consider the case where a node wants to only use
   links where the 127th bit of an EAG is set to 1.  If a link is only
   advertising 64 EAG bits, clearly the 127th EAG bit is not defined -
   that is, it is neither explicitly 0 nor 1.  The node which wants the
   127th EAG bit to be 1 MUST NOT use this link, as the assumption is
   than an unadvertised bit is set to 0.

and also completely remove the following paragraph.

[Technical] Section 3 contains a lot of unattributed hand-waving. I
would prefer that is simply say:

   Signaling EAG in RVSP is not addressed in this document. Addressing
this in the future is not precluded.

[Technical] Section 4: While the existing text is strictly true,
having available a virtually unlimited set of AGs does make it more
important for network administrations that want their traffic
engineering to operate correctly to be careful with their AG
allocation and usage, to avoid unintended side-effects of
unconstrained AG usage or router misconfiguration. What may have been
a relatively easy task with 32 AGs may be more difficult with 128, or
1000, or 1,000,000 attributes. Previously manual processes may need to
be automated to ensure correctness. Feel free to add text to this
effect to this section, or not, as you prefer.

Thanks,
Andy



On Tue, Feb 4, 2014 at 12:54 AM, Loa Andersson <loa@pi.nu> wrote:
> Working Group,
>
> This is to initiate a working group last call on
> draft-ietf-mpls-extended-admin-group-02.
>
> There are no IPR disclosures against this document. The author has
> stated that he is unaware of any IPRs that relate to this document.
>
> Please send your comments to the mpls wg mailing list (mpls@ietf.org)
>
> This working group last call ends Feb 18, 2014.
>
> /Loa
> for the MPLS wg chairs
> --
>
>
> Loa Andersson                        email: loa@mail01.huawei.com
> Senior MPLS Expert                          loa@pi.nu
> Huawei Technologies (consultant)     phone: +46 739 81 21 64
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