Re: [trill] Suresh Krishnan's Discuss on draft-ietf-trill-irb-13: (with DISCUSS and COMMENT)

Donald Eastlake <> Thu, 30 June 2016 18:13 UTC

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From: Donald Eastlake <>
Date: Thu, 30 Jun 2016 14:13:02 -0400
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To: Suresh Krishnan <>
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Subject: Re: [trill] Suresh Krishnan's Discuss on draft-ietf-trill-irb-13: (with DISCUSS and COMMENT)
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Hi Suresh,

Thanks for your comments. See below.

On Wed, Jun 29, 2016 at 7:08 PM, Suresh Krishnan
<> wrote:
> Suresh Krishnan has entered the following ballot position for
> draft-ietf-trill-irb-13: Discuss
> ...
> ----------------------------------------------------------------------
> ----------------------------------------------------------------------
> * Section 6 has a few errors that need to get fixed before this document
> goes forward. e.g. It is not clear what a "" subnet means
> especially since the only host shown to be on the subnet cannot
> obviously fall inside the subnet range. The /32 needs to be replaced with
> something shorter depending on what the authors/WG intended (say a /24).

Yes. That should have been "/24".

> * RB2 seems to be advertising ES2s IPv4 address instead
> of the prefix of the subnet while RB1 seems to be advertising the the
> IPv4 prefix of the ES1 subnet. One of these is wrong. Not sure which one
> is intended.

It should be the prefix in both cases.

> * What is the rationale for using a /112 IPv6 prefix for numbering an
> IPv6 link with hosts? Things like SLAAC (RFC4862) will not work in such
> links. Is there a reason the authors want to use a longer than /64?
> Please read RFC7421 for advantages of using a /64 instead and to find out
> what things break if you do not use a /64.

The Distributed Layer 3 gateway specified in this draft is expect to
primarily be used in data centers where I would expect everything to
be strictly configured by an orchestration system. Thus stateless
autoconfiguration seems less likely and I suspect it just wasn't
through of. However, I don't see a problem with changing this to "/64"
and the mechanism specified could be used in other contexts outside
data centers.

> ----------------------------------------------------------------------
> ----------------------------------------------------------------------
> Section 5: What does "Layer 2 routing" mean in this context?

Previously standardized TRILL routing, which is based on destination
MAC address as mapped into a TRILL nickname. The wording can be

> Sections 7.3 & 7.4: What is the point of including these sub-TLVs if no
> prefix is being advertised? (The Total Length=0 case specified in the
> document)

Sometimes a zero length has some special meaning. The draft just says
that it has the obvious meaning although it is not a particularly
useful value.

 Donald E. Eastlake 3rd   +1-508-333-2270 (cell)
 155 Beaver Street, Milford, MA 01757 USA