Re: [Bier] Warren Kumari's No Objection on draft-ietf-bier-architecture-07: (with COMMENT)

Tony Przygienda <> Thu, 06 July 2017 21:08 UTC

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From: Tony Przygienda <>
Date: Thu, 6 Jul 2017 14:07:25 -0700
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To: Warren Kumari <>
Cc: The IESG <>,, Greg Shepherd <>, "" <>,
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Subject: Re: [Bier] Warren Kumari's No Objection on draft-ietf-bier-architecture-07: (with COMMENT)
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> Nits and notes:
> 1: " A router that supports BIER is known as a "Bit-Forwarding Router"
> (BFR)."
> -- this makes me sad; the BFR acronym was already in use, and had
> interesting
> history behind it (Big er... Fast Router) -

Some of the authors are known as mild punsters so for the old hands it may
look like some of the acronym choices have not been innocuous ;-)

> 2: "MVPN signaling also has several components that depend on the
>    type of "tunneling technology" used to carry multicast data though
>    the network." -- though the network what?! I suspect you meant
> "through" :-)
> 3: Section 6.1.  Overview
> "If a BFR receives a BIER-encapsulated packet whose sub-domain, SI and
> BitString identify that BFR itself, ..." -- identifies.


> O: "When BIER on a BFER is to pass a packet to the multicast flow overlay,
> it
> of course decapsulates..." P: "When BIER on a BFER is to pass a packet to
> the
> multicast flow overlay, it, of course decapsulates" C: Missing a comma. I
> suspect: "When BIER on a BFER is to pass a packet to the multicast flow
> overlay, it decapsulates..." would be even better.
> Section 6.9.  When Some Nodes do not Support BIER
> "In this section, we assume that the routing underlay is an SPF-based IGP
> that
> computes a shortest path tree from each node to all other nodes in the
> domain."
> C: I *think* that this should actually be "the shortest path", but I'm not
> sure; everything talks about e.g Dijkstra's algorithm finding the shortest
> path, but what if there are multiple equal cost paths? But, this is a
> singular
> tree, but may not be unique, so any SP tree will... erk... Good this this
> is a
> nit and I can move on :-)

in fact, it is a DAG with SPF properties and BIER is free to use the DAG to
ECMP. The ECMP section should make that pretty obvious.

> Section 6.10.3.  Transitioning from One BitStringLength to Another
> Typo:  Dispostion ->  Disposition