Re: [auth48] AUTH48: RFC-to-be 9262 <draft-ietf-bier-te-arch-13> for your review

[[e-mail]]

Authors,

While reviewing this document during AUTH48, please resolve (as necessary) 
the following questions, which are also in the XML file.

1) <!-- [rfced] First-page header:  We do not see multiple initials used
for the authors of this document in any published RFC or in the draft
references where the same authors are listed (e.g.,
draft-eckert-bier-te-frr).  Are the multiple initials intended as a
precedent for future RFCs?  If not, we suggest using single initials.

Original:
 T.T.E. Eckert, Ed.
 M.M. Menth
 G.C. Cauchie

Suggested (per published RFCs and current documents):
 T. Eckert, Ed.
 M. Menth
 G. Cauchie -->


2) <!-- [rfced] Please insert any keywords (beyond those that appear in the
title) for use on <https://www.rfc-editor.org/search>. -->


3) <!-- [rfced] We found a comment called "Removed for now by review
with Lou Berger" in the original XML file with the section title "BIER-TE and 
Traffic Engineering (BIER-TE)."  Please confirm that the removal of this section 
is correct.  (If you need to restore the section, we will do so via the 
pre-edited draft version.) -->


4) <!-- [rfced] Abstract and Section 1:  Because per other RFCs and
Internet searches "Interior Gateway Routing protocol" usually refers
to Cisco's IGRP, we looked up definitions of "IGP" and updated these
sentences accordingly, in an effort to avoid possible confusion for
some readers.  If these updates do not convey your intended meaning,
please provide clarifying text.

Original:
 Except for the optional routed adjacencies, BIER-TE does not require
 a BIER routing underlay, and can therefore operate without depending
 on an "Interior Gateway Routing protocol" (IGP).
...
 Except for
 the optional routed adjacencies, BIER-TE does not require a BIER
 routing underlay, and can therefore operate without depending on an
 "Interior Gateway Routing protocol" (IGP).

Currently:
 Except for the optional routed adjacencies,
 BIER-TE does not require a BIER routing underlay and can therefore
 operate without depending on a routing protocol such as the Interior
 Gateway Protocol (IGP).
...
 Except for
 the optional routed adjacencies, BIER-TE does not require a BIER
 routing underlay and can therefore operate without depending on a
 routing protocol such as the Interior Gateway Protocol (IGP). -->


5) <!-- [rfced] Section 2.1:  We defined "BFIR" as "Bit-Forwarding
Ingress Router" per RFC 8556 and per the definition of "BFER(s)".
Please let us know any objections.

Original:
 All BFRs
 can act as an ingress BFR (BFIR), BFR1, BFR3, BFR4 and BFR6 can also
 be BFERs.

Currently:
 All
 BFRs can act as a Bit-Forwarding Ingress Router (BFIR); BFR1, BFR3,
 BFR4, and BFR6 can also be BFERs. -->


6) <!-- [rfced] Section 2.1:  We found "This is showing the ability of
the shown BIER-TE Topology" difficult to follow.  We updated this
sentence as noted below.  Please let us know if this is incorrect.

Original:
 This is
 showing the ability of the shown BIER-TE Topology to make the traffic
 pass across any possible path and be replicated where desired.

Currently:
 This
 demonstrates the ability of the BIER-TE Topology, as shown in
 Figure 1, to make the traffic pass across any possible path and be
 replicated where desired. -->


7) <!-- [rfced] Section 2.1:  We had trouble with this sentence.
If the suggested text is not correct, please clarify "non-L2, but
routed/tunneled forwarding of BIER-TE packets".

Original:
 To emphasize non-L2, but routed/tunneled forwarding of
 BIER-TE packets, these adjacencies are called "forward_routed".

Suggested:
 To specify routed/tunneled forwarding of BIER-TE packets
 (i.e., not Layer 2), these adjacencies are called "forward_routed()"
 adjacencies. -->


8) <!-- [rfced] Section 2.1:  We had trouble following the "and"
relationships in these two sentences.  If the suggested text does not
preserve your intended meaning, please clarify.

Original:
 A
 packet from BFR1 to be received by BFR4, and from BFR4 to be received
 by BFR6 and from there to be received by BFR3 uses
 (p2,p3,p4,p6,p7,p9).  A packet from BFR1 to be received by BFR3, and
 from BFR3 to be received by BFR6 there to be received by BFR4 uses
 (p1,p3,p4,p5,p8,p9).

Suggested:
 A
 packet from BFR1 to be received by BFR4, then from BFR4 to be
 received by BFR6, and finally from BFR6 to be received by BFR3, uses
 (p2,p3,p4,p6,p7,p9).  A packet from BFR1 to be received by BFR3,
 then from BFR3 to be received by BFR6, and finally from BFR6 to be
 received by BFR4, uses (p1,p3,p4,p5,p8,p9). -->


9) <!-- [rfced] Section 2.3:  We had trouble following this sentence.
If the suggested text is not correct, please clarify "and therefore
also no unique BFR-id".

Original:
 2.  The BIER-TE layer forwarding plane does not require BFRs to
     have a unique BP and therefore also no unique BFR-id.

Suggested:
 2.  The BIER-TE layer forwarding plane does not require BFRs to
     have a unique BP; therefore, a unique BFR-id is not needed
     either. -->


10) <!-- [rfced] Section 3.1:  We had trouble following the use of "may
also be preferred to" in this sentence.  If the suggested text is not
correct, please clarify.

Original:
 When a BIER-TE controller is used, then the signaling for the
 Multicast Flow Overlay may also be preferred to operate through a
 central point of control.

Suggested:
 When a BIER-TE controller is used, it might also be preferable that
 Multicast Flow Overlay signaling be performed through a central
 point of control. -->


11) <!-- [rfced] Section 3.2:  We could not follow this sentence.  If the
suggested text is not correct, please clarify "but instead their
functions are summarized together in Section 4.2" (i.e., what do
"instead", "their", and "summarized together" refer to?).

Original:
 In the (non-TE) BIER architecture [RFC8279], the BIER control plane
 is not explicitly separated from the BIER forwarding plane, but
 instead their functions are summarized together in Section 4.2.

Suggested:
 In the (non-TE) BIER architecture [RFC8279], the BIER control plane
 is not explicitly separated from the BIER forwarding plane.  See
 Section 4.2 for a description of relevant functions. -->


12) <!-- [rfced] Section 3.2:  We changed "for a BIER-TE sub-domains" to
"for BIER-TE subdomains" in this sentence.  Please let us know if it
should be "for a BIER-TE subdomain" instead.

Original:
 1.  Determine the desired BIER-TE topology for a BIER-TE sub-
     domains: the native and/or overlay adjacencies that are
     assigned to BPs.

Currently:
 1.  Determine the desired BIER-TE topology for BIER-TE subdomains:
     the native and/or overlay adjacencies that are assigned to
     BPs. -->


13) <!-- [rfced] Section 3.2:  We do not see entropy/Entropy mentioned in
any of the cited sections.  Please confirm that these citations are
correct and will be clear to readers.

Original:
 2.  Determine the BitStrings and optionally Entropy.  This is
     discussed in Section 3.2.1.2, Section 3.5 and Section 5.3.4. -->


14) <!-- [rfced] Section 3.2:  To what does "the main responsibility"
refer?  If the suggested text is not correct, please clarify.

Original:
 Different aspects
 of this and the next point are discussed throughout
 Section 3.2.1 and in Section 4.3, but the main responsibility
 of these two points is with the Multicast Flow Overlay
 (Section 3.1), which is architecturally inherited from BIER.

Suggested:
 Different aspects
 of this point, as well as the next point, are discussed
 throughout Section 3.2.1 and in Section 4.3, but the main
 purpose of these two points relates to the Multicast Flow
 Overlay (Section 3.1), which is architecturally inherited from
 BIER. -->


15) <!-- [rfced] Regarding this note from you:

[RFC-Editor: the following text has three references to anchors 
topology-control, topology-control-1 and tree-control. Unfortunately, 
XMLv2 does not offer any tagging that reasonable references are generated
(i had this problem already in RFCs last year. Please make sure there 
are useful-to-read cross-references in the RFC in these three places 
after you convert to XMLv3.]

With v3, it appears to us that the "topology-control" and
"tree-control" tags, whose anchors are embedded in "top-level"
"<dd>" elements, are working properly in the .html and .pdf
outputs.  However, the "topology-control-1" link, whose anchor was
embedded in a nested "<li>" element, was translated in the text of
Section 3.2.1.1 by v3 (as it was in the submitted v2 copy) as
"(Section 3.2, Paragraph 3, Item 2.2.1)", which was inaccurate given
that the list is only two levels deep.

We applied 'format="none"' to the "topology-control-1" xref as
follows:  <xref target="topology-control-1" format="none">.  We also
included a pointer to Section 3.2, as noted below.  Please check the
updated links in the .html and .pdf outputs, and let us know any
concerns.

Original:
 The first item of BIER-TE topology control (Section 3.2, Paragraph 3,
 Item 2.2.1) includes network topology discovery and BIER-TE topology
 creation.

Currently (two links, the first more specific than the second):
 The first item listed for BIER-TE topology control (Section 3.2)
 includes network topology discovery and BIER-TE topology creation. -->


16) <!-- [rfced] Section 3.2.1.1:  We had trouble determining what is
listed in this sentence and how they relate to each other.  If the
suggested text is not correct, please clarify.

Original:
 In other networks, topology discovery may rely on protocols including
 extending a "Link-State-Protocol" based IGP into the BIER-TE
 controller itself, [RFC7752] (BGP-LS) or [RFC8345] (YANG topology) as
 well as BIER-TE specific methods, for example via
 [I-D.ietf-bier-te-yang].

Suggested:
 In other networks, topology discovery may rely on such protocols as
 those that include extending an IGP based on a link-state protocol
 into the BIER-TE controller itself, e.g., BGP-LS [RFC7752] or YANG
 topology [RFC8345], as well as methods specific to BIER-TE - for
 example, via [BIER-TE-YANG]. -->


17) <!-- [rfced] Section 3.2.1.1:  Should "BitPositions/adjacencies" be
"BPs/adjacencies", and should "SI:BitPositions" be "SIs:BPs"?
The only other instances of the form "BitPosition" that we see are
"GetFirstBitPosition" and "GetNextBitPosition" in the figures in
Section 4.4.

Original:
 When the BIER-TE topology is determined, the BIER-TE Controller then
 pushes the BitPositions/adjacencies to the BIFT of the BFRs.  On each
 BFR only those SI:BitPositions are populated that are adjacencies to
 other BFRs in the BIER-TE topology. -->


18) <!-- [rfced] Section 3.2.1.1:  For ease of the reader, we defined
"SDN" as "Software-Defined Network" per RFC 8279.  If this is
incorrect, please provide the correct definition.

Original:
 Vendor-specific CLI on the BFRs is also an option (as in many
 other SDN solutions lacking definition of standardized data models).

Currently:
 A vendor-specific CLI on the BFRs is also an option (as in
 many other Software-Defined Network (SDN) solutions lacking
 definitions of standardized data models). -->


19) <!-- [rfced] Section 3.2.1.2:  Does "such as shortest path trees, ..."
refer to the policy reasons or the different overlay flows?  If the
suggested text is not correct, please clarify.

Original:
 Likewise, the BitString from
 the same BFIR to the same set of BFER can be different for different
 overlay flows for policy reasons such as shortest path trees, Steiner
 trees (minimum cost trees), diverse path trees for redundancy and so
 on.

Suggested (assuming that the different overlay flows apply here):
 Likewise, for policy reasons, the BitString from
 the same BFIR to the same set of BFERs can be different for such
 different overlay flows as shortest path trees, Steiner trees
 (minimum-cost trees), diverse path trees for redundancy, and so on. -->


20) <!-- [rfced] Section 3.2.1.2:  We do not see the word "tree" used in
[I-D.ietf-bier-multicast-http-response].  Please confirm that this
citation is correct and will be clear to readers.

Original:
 See also [I-D.ietf-bier-multicast-http-response] for an application
 leveraging BIER-TE engineered trees. -->


21) <!-- [rfced] Section 3.2.1.4:  For ease of the reader, we expanded
"FRR" as "Fast Reroute".  Please let us know any objections.

Original:
 When link or nodes fail or recover in the topology, BIER-TE could
 quickly respond with FRR procedures such as [I-D.eckert-bier-te-frr],
 the details of which are out of scope for this document.

Currently:
 When links or nodes fail or recover in the topology, BIER-TE could
 quickly respond with Fast Reroute (FRR) procedures such as those
 described in [BIER-TE-PROTECTION], the details of which are out of
 scope for this document. -->


22) <!-- [rfced] Section 3.3:  Because the "or" in "and/or" would mean
that there would not be a combination, we updated this sentence as
follows.  If this update does not properly convey your intended
meaning, please provide clarifying text.

Original:
 This is driven by a combination of state established by
 the BIER-TE control plane and/or the multicast flow overlay as
 explained in Section 3.1.

Currently:
 This is driven by state established by the BIER-TE
 control plane, the multicast flow overlay as explained in
 Section 3.1, or a combination of both. -->


23) <!-- [rfced] Section 3.3:  For ease of the reader, we defined "DSCP"
as "Differentiated Services Code Point".  If this is incorrect,
please provide the correct definition.

Original:
 Processing of other BIER header fields such as DSCP
 is outside the scope of this document.

Currently:
 Processing of other BIER header fields, such as the
 Differentiated Services Code Point (DSCP) field, is outside the
 scope of this document. -->


24) <!-- [rfced] Section 3.4:  Does "This" mean "This process", "This
calculation", or something else?  Please clarify.

Original (the previous sentence is included for context):
 BIER relies on the routing underlay to calculate paths towards BFERs
 and derive next-hop BFR adjacencies for those paths.  This commonly
 relies on BIER specific extensions to the routing protocols of the
 routing underlay but may also be established by a controller. -->


25) <!-- [rfced] Section 3.4:  For ease of the reader, we expanded "BFD"
as "Bidirectional Forwarding Detection".  If this is incorrect,
please provide the correct definition.

Original:
 If the BFR intends to support FRR for BIER-TE, then the BIER-TE
 forwarding plane needs to receive fast adjacency up/down
 notifications: Link up/down or neighbor up/down, e.g. from BFD.

Currently:
 If the BFR intends to support FRR for BIER-TE, then the BIER-TE
 forwarding plane needs to receive fast adjacency up/down
 notifications: link up/down or neighbor up/down, e.g., from
 Bidirectional Forwarding Detection (BFD). -->


26) <!-- [rfced] Section 3.5:  Please confirm that "TE" stands for
"Traffic Engineering" and not "Tree Engineering" here.  We would
like to spell it out as appropriate, because the standalone term
"TE" is not used anywhere else in this document.

Original (the previous sentence is included for context):
 Traffic Engineering ([I-D.ietf-teas-rfc3272bis]) provides performance
 optimization of operational IP networks while utilizing network
 resources economically and reliably.  The key elements needed to
 effect TE are policy, path steering and resource management.

Suggested:
 The key elements needed to effect Traffic Engineering are
 policy, path steering, and resource management. -->


27) <!-- [rfced] Section 3.5:  Because Section 4.2.1 discusses
forward_connected() adjacencies and Section 4.2.2 discusses
forward_routed() adjacencies, we changed "4.2.1" to "4.2.2" here.
Please let us know any concerns (e.g., should the instances of
"forward_routed()" be "forward_connected()" here?).

Original:
 The resource usage of the BIER-TE traffic
 admitted by the BIER-TE controller can be solely tracked on the BIER-
 TE Controller based on local accounting as long as no
 forward_routed() adjacencies are used (see Section 4.2.1 for the
 definition of forward_routed() adjacencies).

Currently:
 The resource usage of the BIER-TE traffic
 admitted by the BIER-TE controller can be solely tracked on the BIER-
 TE Controller based on local accounting as long as no
 forward_routed() adjacencies are used (see Section 4.2.2 for the
 definition of forward_routed() adjacencies). -->


28) <!-- [rfced] Section 4.1:  This sentence reads oddly, as a BIFT is
already defined as being a table.  May we update as suggested?
If not, please clarify "it is a table as shown".

Original (the previous two sentences are included for context;
  "shown shown" has been corrected):
 The BIER-TE BIFT is the equivalent to the BIER BIFT for (non-TE)
 BIER.  It exists on every BFR running BIER-TE.  For every BIER sub-
 domain (SD) in use for BIER-TE, it is a table as shown shown in
 Figure 4.

Suggested:
 For every BIER subdomain (SD) in use
 for BIER-TE, the BIFT would be constructed per the example shown in
 Figure 4. -->


29) <!-- [rfced] Section 4.1:  Does "those adjacencies forwarding
entries" mean "those adjacencies that forward entries", "those
 adjacencies' forwarding entries", or something else?

Original:
 In BIER-TE, each BIFT-index and therefore SI:BP indicates one or more
 adjacencies between BFRs in the topology and is only populated with
 those adjacencies forwarding entries on the BFR that is the upstream
 for these adjacencies. -->


30) <!-- [rfced] We incorporated the "BIER-TE Bit Index Forwarding Table
(BIFT)" text that appeared at the bottom of Figure 4 into the
figure's title, as it appears to say the same thing as the original
figure title (but provides the expansion for "BIFT").  Please let us
know any objections.

Original:
...
      BIER-TE Bit Index Forwarding Table (BIFT)

 Figure 4: BIER-TE BIFT with different adjacencies

Currently:
...
 Figure 4: BIER-TE Bit Index Forwarding Table (BIFT) with
                  Different Adjacencies -->


31) <!-- [rfced] Section 4.1:  Please clarify the meaning of "the BIER-TE
Forwarding Procedures".  Are they found elsewhere in this document
or perhaps in another RFC?  Please specify the section number or RFC,
as applicable.

Original:
 The BIFT is then used to forward packets, according to the rules
 specified in the BIER-TE Forwarding Procedures. -->


32) <!-- [rfced] Section 4.1:  We do not see "controller" mentioned in
Section 5.1.6.  Please confirm that this citation is correct and will
be clear to readers.

Original:
 See Section 5.1.6 for an example of how a
 BIER-TE controller could assign BPs to (logical) adjacencies shared
 across multiple BFRs, Section 5.1.3 for an example of assigning the
 same BP to different adjacencies, and Section 5.1.9 for general
 guidelines regarding re-use of BPs across different adjacencies. -->


33) <!-- [rfced] Section 4.2.2:  We had trouble with the usage of
"either" and determining what "or by" refers to in this sentence.
If the suggested text is not correct, please clarify.

Original:
 This identification can either rely on the BIER/BIER-TE co-
 existence mechanisms described in Section 4.3, or by explicit support
 for a BIER-TE payload type in the tunneling encapsulation.

Suggested (assuming that this identification relies on either
  the mechanisms or explicit support):
 This identification can rely on either the BIER/BIER-TE co-
 existence mechanisms described in Section 4.3 or explicit support
 for a BIER-TE payload type in the tunneling encapsulation. -->


34) <!-- [rfced] Section 4.3:  We found the wording of this sentence
confusing, as it prompted us to search RFC 8279 for "maximum" and
"MTU" (only to find that it doesn't mention either term).  May we
rephrase as suggested?  If not, please provide clarifying text.

Original:
 Like [RFC8279], handling of "Maximum Transmission Unit" (MTU)
 limitations is outside the scope of this document and instead part of
 the BIER-TE packet encapsulation and/or flow overlay.  See for
 example [RFC8296], Section 3.

Suggested:
 The handling of Maximum Transmission Unit (MTU) limitations is
 outside the scope of this document and is not discussed in
 [RFC8279].  Instead, this process is part of the BIER-TE packet
 encapsulation and/or flow overlay; for example, see [RFC8296],
 Section 3. -->


35) <!-- [rfced] Section 4.3:  This paragraph is difficult to follow.
Does "which" mean that the fixed mapping never explicitly partitions
the BIFT-id space, or can the fixed mapping sometimes explicitly
partition the BIFT-id space, in which case "which" should be "that"?
Does "same or different SD" mean "same SD or a different SD",
"same SD or different SDs", or something else?

If the suggested text is not correct, please clarify.

Original:
 When a fixed mapping from BSL, SD and SI to BIFT-id is used which
 does not explicitly partition the BIFT-id space between BIER and
 BIER-TE, such as proposed for non-MPLS forwarding with [RFC8296]
 encapsulation in [I-D.ietf-bier-non-mpls-bift-encoding] revision 04,
 section 5, then it is necessary to allocate disjoint SDs to BIER and
 BIER-TE BIFTs so that both can be addressed by the BIFT-ids.  The
 encoding proposed in section 6. of the same document does not
 statically encode BSL or SD into the BIFT-id, but allows for a
 mapping, and hence could provide for the same freedom as when MPLS is
 being used (same or different SD for BIER/BIER-TE).

Suggested (assuming that the fixed mapping never explicitly
  partitions the BIFT-id space; also assuming "different SDs"):
 When a fixed mapping from BSL, SD, and SI to a BIFT-id is used,
 which does not explicitly partition the BIFT-id space between BIER
 and BIER-TE - for example, as proposed for non-MPLS forwarding with
 BIER encapsulation [RFC8296] in [NON-MPLS-BIER-ENCODING], Section 5
 - it is necessary to allocate disjoint SDs to BIER and BIER-TE BIFTs
 so that both can be addressed by the BIFT-ids.  The encoding
 proposed in Section 6 of [NON-MPLS-BIER-ENCODING] does not
 statically encode the BSL or SD into the BIFT-id, but the encoding
 permits a mapping and hence could provide the same freedom as when
 MPLS is being used (the same SD, or different SDs for BIER/BIER-TE). -->


36) <!-- [rfced] Section 4.4:  Because Figures 4 and 5 are referred to as
"pseudocode", we changed "<artwork>" in the XML file to <sourcecode>
with type="pseudocode".  Please let us know any concerns.  For
information regarding <sourcecode> types, please see
<https://www.rfc-editor.org/materials/sourcecode-types.txt>. -->


37) <!-- [rfced] Section 4.4:  We had trouble following this sentence.
If the suggested text is not correct, please clarify the meaning of
"to create duplicates".

Original:
 This protects against BIER replication on any
 possible further BFR to create duplicates ([2]).

Suggested:
 This prevents BIER's replication logic from creating duplicates on
 any possible further BFRs ([2]). -->


38) <!-- [rfced] Section 4.4:  This sentence does not parse.  If the
suggested text is not correct, please clarify.

Original:
 This Forwarding Pseudocode can support the required BIER-TE
 forwarding functions (see Section 4.5), forward_connected(),
 forward_routed() and local_decap(), but not the recommended functions
 DNC flag and multiple adjacencies per bit nor the optional function,
 ECMP() adjacencies.

Suggested:
 This Forwarding Pseudocode can support the required BIER-TE
 forwarding functions (see Section 4.5) - forward_connected(),
 forward_routed(), and local_decap() - but cannot support the
 recommended functions (DNC flag and multiple adjacencies per bit)
 or the optional function (i.e., ECMP() adjacencies). -->


39) <!-- [rfced] Section 4.4:  xml2rfc v3 now permits subscripting and
superscripting.  Would you like to use superscripting in "BSL^2*SI"?
If yes, should "2*SI" be superscripted, or only the "2"?

(For an example of superscripting in a recent RFC, see the
"Implementation Note" paragraph in Appendix A of RFC 9260
(https://www.rfc-editor.org/rfc/rfc9260.html).

Original:
 *  This pseudocode eliminates per-bit F-BM, therefore reducing the
    size of BIFT state by BSL^2*SI and eliminating the need for per-
    packet-copy BitString masking operations except for adjacencies
    with the DNC flag set: -->


40) <!-- [rfced] Section 4.5:  We changed "forwarded_routed" to
"forward_routed()", as this was the only instance of "forwarded"
in this document that was followed by an underscore.  Please let us
know if this is incorrect (i.e., should all instances of "forward_"
be "forwarded_"?).

Original:
 This is an
 optional requirement, because for ECMP deployments using BIER-TE one
 can also leverage ECMP of the routing underlay via forwarded_routed
 adjacencies and/or might prefer to have more explicit control of the
 path chosen via explicit BP/adjacencies for each ECMP path
 alternative.

Currently:
 This is an
 optional requirement, because for ECMP deployments using BIER-TE one
 can also leverage the routing underlay ECMP via forward_routed()
 adjacencies and/or might prefer to have more explicit control of the
 path chosen via explicit BPs/adjacencies for each ECMP path
 alternative. -->


41) <!-- [rfced] Section 5.1.1:  Does "P2P" stand for "peer-to-peer" or
"point-to-point" in this document?  We would like to define it for
ease of the reader.

Original:
 On a P2P link that connects two BFRs, the same bit position can be
 used on both BFRs for the adjacency to the neighboring BFR. -->


42) <!-- [rfced] Section 5.1.4:  Should the vertical line for p3 in
Figure 8 be aligned under a "+" sign, as are the other vertical
lines)?

Original (best viewed with a fixed-point font such as Courier;
  dashed lines are broken so that they will not be confused with a
  comment):
          BFR1
           |p1
    LAN1-+-+- -+- - -+
        p3|  p4|   p2|
        BFR3 BFR4  BFR7

 Figure 8: LAN Example

Perhaps:
          BFR1
           |p1
    LAN1-+-+- -+- - -+
       p3|   p4|   p2|
       BFR3  BFR4  BFR7

 Figure 8: LAN Example

Or possibly:
          BFR1
           |p1
    LAN1-+-+- - -+- - -+
         p3|   p4|   p2|
         BFR3  BFR4  BFR7

 Figure 8: LAN Example -->


43) <!-- [rfced] Section 5.1.4:  Please clarify the meaning of
"Adjacencies of such BFRs into their LAN".  Does it mean "Adding
adjacencies of such BFRs to these LANs" or something else?

Original:
 Adjacencies of such BFRs into their LAN still need a
 separate bit position. -->


44) <!-- [rfced] We have removed "(SA)" as SA is not used elsewhere in the 
text.  Please let us know any objections. 

Original:
   This type of optimized BP could be used for example when all traffic
   is "broadcast" traffic (very dense receiver set) such as live-TV or
   many-to-many telemetry including situation-awareness (SA).
-->


45) <!-- [rfced] Section 5.1.6:

a) As all other mentions of "ring" related to Figure 9 are singular,
we changed "the rings shown in Figure 9" to "the ring shown in
Figure 9".  Note:  If this update is incorrect, please review all
instances of the singular "ring" in this section, and let us know if
they should be changed to "rings" (e.g., "entering the ring", "any
BFR in the ring").

b) To what text does the colon after "to BFR1" refer - the next
paragraph or the next two paragraphs (in which case we should indent
the text in question)?  If neither, may we change the colon to a
period?

Original:
 For the rings shown in Figure 9, a single bit position will suffice
 to forward traffic entering the ring at BFRa or BFRb all the way up
 to BFR1:

Currently:
 For the ring shown in Figure 9, a single bit position will suffice to
 forward traffic entering the ring at BFRa or BFRb all the way up to
 BFR1: -->


46) <!-- [rfced] Section 5.1.7:  Regarding this question from you:
[RFC-Editor: A reviewer (Lars Eggert) noted that the infinite "to use" 
in the following sentence is not correct. The same was also noted for 
several other similar instances. The following URL seems to indicate 
though that this is a per-case decision, which seems undefined: https://writingcenter.gmu.edu/guides/choosing-between-infinitive-and-gerund-to-do-or-doing. What exactly should be done about this ?].

Thank you for asking this question.  We reviewed all such instances
in this document and updated the text where needed.  Please review,
and let us know any concerns regarding our updates. -->


47) <!-- [rfced] Section 5.1.9:  To which paragraph or paragraphs does
the colon in "useful path choices:" refer?  Should the paragraph or
paragraphs be indented?  If so, which paragraph(s)?  Alternatively,
may we change the colon to a period?

Original:
 Packets with both BP 0:5 and BP
 0:6 would now be able to reach both BFR2 and BFR3 and the still
 existing re-use of BP 0:7 between BFR2 and BFR3 is a case of (B)
 where reuse of BP is perfect because it does not limit the set of
 useful path choices: -->


48) <!-- [rfced] Section 5.1.9:  Does "5 areas" refer to areas 2...6, or
should it be "six areas"?  Also, please confirm that "through other
BPs for the Core to" should not be "through other BPs from the core
to".

Original:
 These two BPs could be reused across the 5
 areas.  Packets would be replicated through other BPs for the Core to
 the desired subset of areas, and once a packet copy reaches the ring
 of the area, the two ring BPs come into play. -->


49) <!-- [rfced] Section 5.1.10:  We had trouble following this sentence.
We updated it as follows.  If this is incorrect, please clarify
"subnet adjacent neighbor".

Original:
 Without any optimization, a BIER-TE Controller would attempt to map
 the network subnet topology 1:1 into the BIER-TE topology and every
 subnet adjacent neighbor requires a forward_connected() BP and every
 BFER requires a local_decap() BP.

Currently:
 Without any optimization, a BIER-TE Controller would attempt to map
 the network subnet topology 1:1 into the BIER-TE topology, every
 adjacent neighbor in the subnet would require a forward_connected()
 BP, and every BFER would require a local_decap() BP. -->


50) <!-- [rfced] Section 5.3.1:  We had trouble following "packets that
need to be sent ... require different BIER packets" in this sentence.
Is it correct to say that packets require packets?  If not, please
(1) let us know if the suggested text preserves your intended
meaning or (2) provide clarifying text.

Original:
 For (non-TE) BIER and BIER-TE forwarding, the most important result
 of using multiple SI and/or sub-domains is the same: Packets that
 need to be sent to BFERs in different SIs or sub-domains require
 different BIER packets: each one with a BitString for a different
 (SI,sub-domain) combination.

Suggested (guessing that the packets must be sent as distinct BIER
   packets):
 For (non-TE) BIER and BIER-TE forwarding, the most important result
 of using multiple SIs and/or subdomains is the same: packets that
 need to be sent to BFERs in different SIs or subdomains must be sent
 as distinct BIER packets, each one with a BitString for a different
 (SI,subdomain) combination. -->


51) <!-- [rfced] Section 5.3.1:  "BIER architecture shared by BIER-TE"
did not seem to be quite the correct wording here.  We updated this
sentence as follows.  If this update is incorrect, please provide
clarifying text.

Original:
 For BIER and BIER-TE forwarding themselves there is also no
 difference whether different SIs and/or sub-domains are chosen, but
 SI and sub-domain have different purposes in the BIER architecture
 shared by BIER-TE.

Currently:
 For BIER and BIER-TE forwarding, it doesn't matter whether or not
 different SIs and/or subdomains are chosen, but SIs and subdomains
 have different purposes in the BIER architecture in cases where it
 also applies to BIER-TE. -->


52) <!-- [rfced] Section 5.3.2:  We found this paragraph difficult to
follow.  We updated it as noted below.  Please review carefully.  If
anything is incorrect, please provide clarifying text.

Original:
 "Desired" topology because it depends on the physical topology, and
 on the desire of the operator to allow for explicit path steering
 across every single hop (which requires more bits), or reducing the
 number of required bits by exploiting optimizations such as unicast
 (forward_routed()), ECMP() or flood (DNC) over "uninteresting" sub-
 parts of the topology - e.g. parts where different trees do not need
 to take different paths due to path steering reasons.

Currently:
 "Desired" topology means that it depends on the physical topology and
 the operator's desire to

 *  permit explicit path steering across every single hop (which
    requires more bits), or

 *  reduce the number of required bits by exploiting optimizations
    such as unicast (forward_routed()), ECMP(), or flood (DNC) over
    "uninteresting" sub-parts of the topology, e.g., parts where, for
    path steering reasons, different trees do not need to take
    different paths. -->


53) <!-- [rfced] Section 5.3.4:  It appears to us that "it needs" refers
to the flow overlay applications, in which case it should be "they
need".  May we update as suggested?  If not, please clarify what "it"
refers to.

Original (the previous sentence is included for context.  "BIFR"
  has been corrected):
 The flow overlay on the BIFR can
 then independently of the controller calculate the SI:BitString for
 all desired BFERs by OR'ing their BitStrings.  This allows for flow
 overlay applications to operate independently of the controller
 whenever it needs to determine which subset of BFERs need to receive
 a particular packet.

Suggested:
 This allows flow
 overlay applications to operate independently of the controller
 whenever they need to determine which subset of BFERs needs to receive
 a particular packet. -->


54) <!-- [rfced] Section 5.3.5:  Does "their" in this sentence refer to
subdomains, BIER and BIER-TE, or something else?  If the suggested
text is not correct, please clarify.

Original (the previous sentence is included for context):
 A.  BIER and BIER-TE have different BFR-id in the same sub-domain.
 This allows higher replication efficiency for BIER because their BFR-
 id can be assigned sequentially, while the BitStrings for BIER-TE
 will have also the additional bits for the topology.

Suggested (assuming that "their" means "BIER and BIER-TE BFR-ids"):
 A.  BIER and BIER-TE have different BFR-ids in the same subdomain.
     This allows higher replication efficiency for BIER because the
     BIER and BIER-TE BFR-ids can be assigned sequentially, while the
     BitStrings for BIER-TE will also have the additional bits for
     the topology. -->


55) <!-- [rfced] Section 5.3.6.1:  These sentences did not parse well.
We updated as follows.  If these updates do not convey your intended
meaning, please provide clarifying text.

Original:
 Allocating SIs to areas with initially sufficiently many spare bits
 for growths can help to alleviate this issue.  Or renumber BFERs
 after network expansion.

Currently:
 Allocating SIs to areas that initially have sufficiently many spare
 bits for growth can help alleviate this issue.  Alternatively, BFERs
 can be renumbered after network expansion. -->


56) <!-- [rfced] Section 5.3.6.1:  We found the two "even"s in this
sentence confusing.  We updated as follows.  If this is incorrect,
please provide clarifying text.

Original:
 This example shows that intelligent BFR-id allocation within at least
 sub-domain 0 can even be helpful or even necessary in BIER.

Currently:
 This example shows that intelligent BFR-id allocation within at least
 subdomain 0 can be helpful or even necessary in BIER. -->


57) <!-- [rfced] Section 5.3.6.2:

a) To what does the colon in "area edge BFR:" refer - the next
paragraph, or the next two paragraphs?  We would like to indent the
text of the next paragraph or the next two paragraphs, as
appropriate.  Alternatively, could the colon be changed to a period?

b) We had trouble following the text in the second paragraph.  If the
suggested text is not correct, please clarify "the bits indicate bits
for topology and BFER" and "For BFER in the same area as in the BFIR".

Original:
 These bits are then set up with the
 right forward_routed() adjacencies on the BFIR and area edge BFR:

 On all BFIRs in an area j|j=1...6, bia in each BIFT:SI is populated
 with the same forward_routed(BFRja), and bib with
 forward_routed(BFRjb).  On all area edge BFR, bea in
 BIFT:SI=k|k=1...6 is populated with forward_routed(BFRka) and beb in
 BIFT:SI=k with forward_routed(BFRkb).

 For BIER-TE forwarding of a packet to a subset of BFERs across all
 areas, a BFIR would create at most 6 copies, with SI=1...SI=6, In
 each packet, the bits indicate bits for topology and BFER in that
 topology plus the four bits to indicate whether to pass this packet
 via the ingress area a or b border BFR and the egress area a or b
 border BFR, therefore allowing path steering for those two "unicast"
 legs: 1) BFIR to ingress area edge and 2) core to egress area edge.
 Replication only happens inside the egress areas.  For BFER in the
 same area as in the BFIR, these four bits are not used.

Suggested (second paragraph):
 For BIER-TE forwarding of a packet to a subset of BFERs across all
 areas, a BFIR would create at most six copies, with SI=1...SI=6.  In
 each packet, these bits in turn indicate bits for the topology and
 the BFERs in that topology, plus the four bits to indicate whether
 to pass this packet via the ingress area a or b border BFR and the
 egress area a or b border BFR, therefore allowing path steering for
 those two "unicast" legs: 1) BFIR to ingress area edge and 2) core
 to egress area edge.  Replication only happens inside the egress
 areas.  For BFERs that are in the same area as the BFIR, these four
 bits are not used. -->


58) <!-- [rfced] Section 6:  We had trouble following the meaning of
"results of the routing protocol".  Is "results of" necessary?
If the suggested text is not correct, please clarify.

Original:
 Attacking the protocols for the BIER routing
 underlay or (non-TE) BIER layer control plane, or impairment of any
 BFR in a domain may lead to successful attacks against the results of
 the routing protocol, enabling DoS attacks against paths or the
 addressing (BFR-id, BFR-prefixes) used by BIER.

Suggested:
 Attacking the protocols for the BIER routing
 underlay or (non-TE) BIER layer control plane, or the impairment of
 any BFRs in a domain, may lead to successful attacks that target the
 routing protocol, enabling DoS attacks against paths or the
 addressing (BFR-ids, BFR-prefixes) used by BIER. -->


59) <!-- [rfced] Section 6:  This sentence did not parse.  We updated it
as follows.  If this is incorrect, please clarify "same degree of
looping packets as possible".

Original:
 In
 result, BIER-TE has the same degree of looping packets as possible
 with unintentional or malicious loops in the routing underlay with
 BIER or even with unicast traffic.

Currently:
 As a result, looping packets can occur in BIER-TE to the same degree
 as is possible with unintentional or malicious loops in the routing
 underlay with BIER, or even with unicast traffic. -->


60) <!-- [rfced] We note that https://dl.acm.org/doi/10.5555/2692227.2692232 resolves, but <https://dx.doi.org/> was unable to find 10.5555/2692227.2692232 in the system.  We found this DOI: 10.3233/JHS-1994-3405, but it's unclear to use if you chose to avoid <https://content.iospress.com/articles/journal-of-high-speed-networks/jhs3-4-05> because it requires payment.  Please review and let us know if any updates are needed. 

Original:
   [RCSD94]   Zhang, H. and D. Domenico, "Rate-Controlled Service
              Disciplines",  Journal of High-Speed Networks, 1994, May
              1994, <https://dl.acm.org/doi/10.5555/2692227.2692232>.
-->


61) <!-- [rfced] Appendix A:  We made quite a few updates to this section
in an effort to clarify the text.  Please review all updates
carefully.  If anything is incorrect, please provide clarifying text.

For example, please clarify the following if our updates to the text
in question are incorrect:

* what "either" refers to in the second paragraph
* what "This can be called" refers to; we changed "This" to "These
  segments"
* what "SID" stands for; we defined it as "Segment Identifier" per
  RFC 8402
* what "would directly replicate to it" means; we changed it to "would
  directly replicate traffic on it" -->


62) <!-- [rfced] Please review the "Inclusive Language" portion of the
online Style Guide at
<https://www.rfc-editor.org/styleguide/part2/#inclusive_language>,
and let us know if any changes are needed.  Aside from "native", our script did not identify problematic terms. 
-->


63) <!-- [rfced] Please let us know if any changes are needed for the
following:

a) The following terms were used inconsistently in this document.
We chose to use the latter forms.  Please let us know any objections.

 BIFT index (1 instance) / BIFT-index (7 instances)

 ECMP adjacencies (2 instances) / ECMP() adjacencies (10 instances)

 FBM (1 instance) / F-BM

 forward_routed adjacency (or adjacencies) (3 instances) /
   forward_routed() adjacency (or adjacencies) (19 instances)

 Leaf BFER (1 instance in text) / leaf BFER (2 instances in text)

 Non-Leaf BFER (1 instance in text) /
   non-Leaf BFER (3 instances in text) /
   non-leaf BFER (5 instances in text)

 p2p / P2P (in running text)

 traffic engineering / Traffic Engineering (in running text)
   (We see that "Tree Engineering" is consistently
    initial-capitalized in this document, so we went with the
    initial-capitalized form for "Traffic Engineering" as well.)

b) The following terms appear to be used inconsistently in this
document.  Please let us know which form is preferred.

 accelerated hardware forwarding (text) /
   Accelerated/Hardware forwarding comparison (section title)
   (In other words, does the slash ("/") serve a specific purpose?)

 BIER-TE controller / BIER-TE Controller
   (For example, we see "... by the BIER-TE controller can be solely
    tracked on the BIER-TE Controller" in Section 3.5.)

   (We also see both "controller" and "Controller" where used more
    generally, e.g., "a controller", "a Controller".  For
    consistency, please advise regarding which form should be used.)

 BIER-TE Topology / BIER-TE topology (in running text)

 entropy / Entropy (for example, "entropy field", "Entropy fields",
   "and optionally Entropy", "the packet entropy")

 Flow overlay / flow overlay (in running text)
   (We see the lowercase form "routing underlay" used consistently
    in running text.)

 Forwarding Pseudocode / forwarding pseudocode (in running text)

 IP/IPv6 / IPv4/IPv6

 leaf-BFER (noun) / leaf BFER (noun)
  (We do not see any instances of  "non-leaf-BFER" where used as
   a noun.  We suggest removing the hyphen after "leaf", as it
   appears that the term appears to indicate whether or not a
   BFER is a "leaf".)

 Multicast Flow Overlay (3 instances in running text) /
   multicast flow overlay (6 instances in running text)

 SIs/BitStrings / SI:BitString / SI:BitStrings
   Should the slash ("/") be a colon (":"), and should
     "SI:BitStrings" be "SIs:BitStrings"?

   (We also see one instance of "SI:BitPositions".) -->


Thank you.

RFC Editor



On Jul 11, 2022, at 6:40 PM, [e-mail] wrote:

*****IMPORTANT*****

Updated 2022/07/11

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--------------------------------------
RFC9262 (draft-ietf-bier-te-arch-13)

Title            : Tree Engineering for Bit Index Explicit Replication (BIER-TE)
Author(s)        : T.T.E. Eckert, Ed., M.M. Menth, G.C. Cauchie
WG Chair(s)      : Tony Przygienda, Greg Shepherd

Area Director(s) : Alvaro Retana, John Scudder, Andrew Alston