Shepherd's Review: G3 Editorial Class: Issues 11-20

[suehares]

Editorial Issues 11-20

G3-11 - Editorial - Section 2.5 BGP CAR Route Resolution

There are 3 parts to this editorial issues (11-a, 11-b, 11-c).
In each case, it is important to clearly specify what "N" is,
and what (N,C2) is.

Is "N" the BGP peer or is "N" the next hop or a prefix?
If "N" is next hop, then a possible text is:

11-a: Clarify what "N" is - Peer or Next Hop.
Old Text:/
Local policy SHOULD provide additional control:

• A BGP color-aware route (E2, C1) from N may be resolved over a
  color-aware route (N, C2): i.e. the local policy maps the
  resolution of C1 over a different color C2.
  /

New text: If "N" is next hop /
Local policy SHOULD provide additional control:
* A BGP color-aware route (E2, C1) from a BGP Peer with next hop N may be resolved over a
color-aware route Next Hop N, Color C2 (N, C2). This means the local policy maps the
resolution of C1 over a different color C2.
/
#11-b: Here, it appears you are specifying a route to (N, C1)
Old text:/
- Another example is, if no (N, C1) path is available, and the
user has allowed resolution to fallback via C2.
/
Problem-2: Section 8 gives a case for setting next-hop self. Is this getting mixed up?

current text in section 8/
A BGP transport CAR speaker that supports packet forwarding lookup based on
IPv6 prefix route (such as a BR) will set itself as next hop while
advertising the route to peers. It will also install the IPv6 route into
forwarding with the received next hop and/or encapsulation.
/

#11-c - Section 2.5 Technical/Editorial - Route Resolution,

Old Text:/

• The resolution of (N, C1) may be egress driven. In an SRv6
  domain, node N selects and advertises an SRv6 SID from a locator
  for intent C1, with a BGP CAR route. In such a case, the ingress
  node resolves the SRv6 SID over a route for the intent aware
  locator of N or its summary provided by SRv6 Flex Algo or BGP CAR
  Type-2 route itself (e.g., Appendix C.2).
  /
  Problem:
  Here's the scenario:
  segments for SRv6 SID-1
  ingress (node N2) ---------------------- egress (Node N)

The SID is just like a link between N1 and N2. 

                                   Node N (advertises) 
					<-----  	 Route V/v with (E,C)  
								 with tunnel identified by SID-1
							BGP announces 	 
	Ingress receives 
    route. 

Resolves Next Hop N over link SRPM with SRV6 SID-1 

It is unclear wht the text says. Do I understand the scenario?
If so, the text needs to be improved.

G3-12 - section 2.5, resolution mapping

Old Text:
/

• Resolution may be mapped to traditional mechanisms that are
  unaware of color or that provide best effort, such as RSVP-TE,
  IGP/LDP, BGP LU/IP (e.g., Appendix A.3.2).
  /

New Text:
/

• Based on local policy for resolution may map the route to
  traditional mechanisms that are unaware of color or that
  provide best effort, such as RSVP-TE, IGP/LDP,
  or BGP LU/IP (e.g., Appendix A.3.2).
  /
  Problem: The mapping is done via policy.

G3-13 - Section 2.5, Editorial

Old text/
Route resolution via a different color C2 can be automated by
attaching BGP Color Extended-Community C2 to CAR route (E2, C1),
leveraging Automated steering as described in Section 8.4 of Segment
Routing Policy Architecture [RFC9256] for BGP CAR routes. This
mechanism is illustrated in section B.2. This mechanism SHOULD be
supported./

New text: /
Route resolution via a different color C2 can be automated by
attaching BGP Color Extended-Community C2 (Color-EC C2) to CAR route (E2, C1),
leveraging automated steering as described in Section 8.4 of Segment
Routing Policy Architecture [RFC9256] for BGP CAR routes.
The [RFC9256] mechanism uses the Extended Community defined in [RFC9012].

This mechanism is illustrated in section B.2. This mechanism SHOULD be
supported.
/

Problem:
a) use Color-EC to help reader grasp which extended communmity,
b) Clearly differentiate between procedures and editorial by breaking the
paragraph into two parts.

G3-14 - Editorial, Section 2.5

Old Text:/
CAR Type-2 route is allowed to be without color for best effort. In
this case, resolution is based on BGP next hop N, or when present, a
best-effort SRv6 SID advertised by node N. /

Problem: The resolution is to a next hop of Node N,
through the pathway of segments defined by SRv6 SID.

Suggested New Text:/
CAR Type-2 route is allowed to be without color for best effort. In
this case, resolution is based on BGP next hop N either directly or
through the SR path defined a best-effort SRv6 SID. /

G3-15 - Editorial, Section 2.6, paragraph 4, last sentence.

Old Text:/
If BGP CAR routes traverse across a discontinuity in the transport
path for a given intent, a penalty is added in accumulated IGP metric
(value set by user policy). For instance, when color C1 path is not
available, and route resolves via color C2 path (e.g., Appendix A.3). /

New Text:/
If BGP CAR routes traverse across a discontinuity in the transport
path for a given intent, a penalty is added in accumulated IGP metric
(value set by user policy). For instance, when color C1 path is not
available, and route resolves via color C2 path (see Appendix A.3 for an example).
/

Problem: e.g. is unclear in the English text when you already used "For instance,"
English grammar.

G3-16 - Editorial, section 2.8, paragraph 1

Old Text:/
Let us assume a BGP CAR route (E2, C2) is signaled from B to A; two
border routers of respectively domain 2 and domain 1. Let us assume
that these two domains do not share the same color-to-intent mapping.
Low-delay in domain 2 is color C2, while it is C1 in domain 1 (C1 <>
C2). /

New Text:/
Let us assume a BGP CAR route (E2, C2) is signaled from B to A, the two
border routers of respectively color domain 2 and color domain 1. Let us assume
that these two color domains do not share the same color-to-intent mapping.
Low-delay in domain 2 is color C2, while it is C1 in domain 1 (C1 <>
C2). /

Why-1: English Grammar. A semi-colon is used when the two clauses provide
parallel information. You do not have parallel information, but
an augmentation in the text "two border routers of respectively domain 2 and domain 1."

Why-2: "two color domains" - The purpose is that you are crossing a color domian.
Make this clear by adding the adjective.

G3-17 - Editorial, section 2.8 - "described" is better than illustrated.

Old text:/
The solution works as illustrated below: /

New text:/
The solution works as described below:/
/

G3-18 - Editorial, section 2.8 - clarify sending/receiving actions

Old text:/
The following procedures apply at a color domain boundary for BGP CAR
routes, performed by route policy at the sending and/or receiving
peer:

• Control which routes are advertised to or accepted from a peer in
  a different color domain.

• Attach LCM-EC if not present, or if present update the value to
  re-map the color as needed. This may be done by the advertising
  speaker or the receiving speaker as determined by the operator
  peering agreement.
  /
  New text:/
  The following procedures apply at a color domain boundary for BGP CAR
  routes, performed by route policy at the sending and receiving
  peer:

• Use local policy to control which routes are advertised to or accepted from
  a peer in a different color domain.

• Attach LCM-EC if not present in the UPDATE message. If an LCM-EC is
  present in the UPDATE message the value to re-map the color as needed.

  -This function may be done by the advertising BGP speaker or the receiving
  BGP speaker as determined by the operator peering agreement, and
  indicated by local policy on the BGP peers.
  /

Reason: Clarity in "how to control" (via local policy) and clarity in what is
being modified in the procedure.

G3-19 - Editorial, Section 2.9.1

Old Text:/

• Type-Specific Key Fields: Depend on the NLRI type and of length
  indicated by the Key Length.

• Type-Specific Non-Key Fields: optional and variable depending on
  the NLRI type. The NLRI definition allows for encoding of
  specific non-key information associated with the route (i.e. the
  key) as part of the NLRI for efficient packing of BGP updates.
  /

New Text:/

• Type-Specific Key Fields: This exact definition of these fields
  depends on the NLRI type and of length indicated by the Key Length.

• Type-Specific Non-Key Fields: These fields are optional and variable
  depending on the NLRI type. The NLRI definition allows for encoding of
  specific non-key information associated with the route as part of
  the NLRI for efficient packing of BGP updates.
  /

Reason: For Clarity, the English sentence needs a specified subject
rather than an implied subject (in the verb).

G3-20 - Editorial, Section 2.9.1, Clearly indicate procedures versus benefits:

Old text:/
It also helps make error handling more resilient and minimally
disruptive as described in Section 2.11.

A route (NLRI) can carry more than one non-key TLV (of different
types). This provides significant benefits such as signaling
multiple encapsulations simultaneously for the same route, each with
a different value (label/SID etc). This enables simpler, efficient
migrations with low overhead :

• avoids need for duplicate routes to signal different
  encapsulations

• avoids need for separate control planes for distribution

• preserves update packing (e.g. Appendix D)

The non-key portion of the NLRI MUST be omitted while carrying it
within the MP_UNREACH_NLRI when withdrawing the route advertisement.
/

New text:/
A route (NLRI) can carry more than one non-key TLV (of different
types). See Section 2.11 for the error handling of multiple
non-key TLVs.

The non-key portion of the NLRI MUST be omitted while carrying it
within the MP_UNREACH_NLRI when withdrawing the route advertisement.

Benefits:
The TLV formats in key and non-key fields helps make error handling
more resilient and minimally disruptive as described in Section 2.11.

The ability of a route (NLRI) to carry more than one non-key TLV (of different
types) provides significant benefits such as signaling
multiple encapsulations simultaneously for the same route, each with
a different value (label/SID etc). This enables simpler, efficient
migrations with low overhead :

• avoids need for duplicate routes to signal different
  encapsulations

• avoids need for separate control planes for distribution

• preserves update packing (e.g. Appendix D)
  /

Why: Clearly delineate between procedures versus benefits.

[suehares]

G3-11: (Section 2.5) - Review of -07 text changes

-07-status: Issue 11-a resolved Issue 11-b + 11-c are technical and need to be discussed.
-08-status: Issues 11-b and 11-c are closed. 11-a reopened for a punctuation nit.

11-a: Punctuation nit.
-08 text:/
A BGP color-aware route (E2, C1) with next hop N may be resolved
over a color-aware route (N, C2): i.e. the local policy maps the
resolution of C1 over a different color C2./
New text:/
A BGP color-aware route (E2, C1) with next hop N may be resolved
over a color-aware route (N, C2): i.e., the local policy
maps the resolution of C1 over a different color C2./

NIT is that "i.e." must be "i.e.".

11-b:
-07-text:/
- Another example is, if no (N, C1) path is available, and the
user has allowed resolution to fallback via C2/
New text:/
- Another example is: if no (N, C1) path is available and the
user has allowed resolution to fall back to a C2 path. /

Question: Do you mean the C2 path? How does this match with

11-c
The text is really improved, but this sentence still needs aid:
07-text: / In such a case, the
ingress node resolves the received SRv6 SID over an IPv6 route for
the intent-aware locator of the egress node for C1 or a summary
route, provided by SRv6 Flex Algo or BGP CAR Type-2 route itself
(e.g., Appendix C.2)./

07-new-text (proposed):/ In such a case, the
ingress node resolves the received SRv6 SID over an IPv6 route for
the intent-aware locator of the egress node for C1 or a summary
route that includes the locator. This summary route may be provided
by SRv6 Flex Algo or BGP CAR Type-2 route itself (e.g., Appendix C.2)./

[suehares]

G3-12: (Section 2.5) - Review of text in section 2.5

Content: Section 2.5, resolution mapping
-07-status: Not resolved,
-08-status: closed

Why: The policy on the local router is to doing the mapping.
-07 text:/

• Resolution may be mapped to traditional mechanisms that are
  unaware of color or that provide best effort, such as RSVP-TE,
  IGP/LDP, BGP LU/IP (e.g., Appendix A.3.2) for brownfield
  scenarios./

Suggested New text:/
Based on local policy for resolution may map the route to
traditional mechanisms that are unaware of color or that
provide best effort, such as RSVP-TE, IGP/LDP,
or BGP LU/IP (e.g., Appendix A.3.2)./

-08 New text:/

• Local policy may map the CAR route to traditional mechanisms that
  are unaware of color or that provide best effort, such as RSVP-TE,
  IGP/LDP, BGP LU/IP (e.g., Appendix A.3.2) for brownfield
  scenarios.

[suehares]

G3-13: Section 2.5 - Review of -07 changes

status: Resolved, closed

[suehares]

G3-14, Section 2.5 - Review of -07 text

status: resolved, closed.

[suehares]

G3-15 (Section 2.6, paragraph 4) - review of -07 text

-07-status: not resolved,
-07 next steps: Discuss with editors.
-08-status: closed

-07-text:/For instance, when color C1 path is not
available, and route resolves via color C2 path (e.g., Appendix A.3)./
New text:/For instance, when color C1 path is not
available, and route resolves via color C2 path
(See Appendix A.3 for an example)./
-08 text:/ For instance, when color C1 path is not
available, and route resolves via color C2 path (See Appendix A.3 for
an example)./

Why: e.g. is unclear in the English text when you already used "for instance".

[suehares]

G3-16: (Section 2.8, paragraph 1) - Review of -07 and -08 text

-07-Status: Not resolved.
-08-Status: Resolved

[suehares]

G3-17 (Section 2.8, paragraph 3) - Review of -07 and -08 text

-07-Status: Not resolved. Did the editors miss this comment?
-08-Status: Resolved

[suehares]

G3-18 (section 2.8, paragraph 3) in -07.txt and -08.txt

-07-status: not resolved. (Discussed with editors)
-08-status: resolved.

Why: Bullet item below lacks clarity and correct sentence grammar (subject, verb, direct-object).
Change:
-07 text:/

• Control which routes are advertised to or accepted from a peer in
  a different color domain.
• Attach LCM-EC if not present, or if present update the value to
  re-map the color as needed. This may be done by the advertising
  speaker or the receiving speaker as determined by the operator
  peering agreement.
  /
  New text:/
• Use local policy to control which routes are advertised to or accepted from
  a BGP peer in a different color domain.
• Attach LCM-EC if not present. If LCM-EC is present, then update the value to
  re-map the color as needed. These operations may be done by the advertizing
  BGP speaker or the receiving BGP speaker as determined by the operator
  peering agreement./

[suehares]

G3-19 - (Section 2.9.1, Editorial) - Review of -07 Text and -08 text

-07-Status: Not resolved. Text did not change from -06 text. Did the editors miss this comment? (Discussed with editors)
-08-status: Closed

Why: Clarity of definition
-07 text:/

• Type-Specific Key Fields: Depend on the NLRI type and of length
  indicated by the Key Length.

• Type-Specific Non-Key Fields: optional and variable depending on
  the NLRI type. The NLRI definition allows for encoding of
  specific non-key information associated with the route (i.e. the
  key) as part of the NLRI for efficient packing of BGP updates.
  /
  New text:/

• Type-Specific Key Fields: The exact definition of these fields
  depend on the NLRI type and length indicated by the Key Length.

• Type-Specific Non-Key Fields: These fields are optional and variable
  depending on the NLRI type. The NLRI definition allows for encoding of
  specific non-key information associated with the route as part of the
  NLRI for efficient packing of BGP updates./

[suehares]

G3-20: (Section 2.9.1, clearly indicate procedures versus benefits) - Review of -07 text and -08 text

-07-status: -06 text unchanged. Not resolved.
-08-status: Resolved, and closed

[suehares]

Resolved: G3-13, G3-14,
Partially Resolved: G3-11 (G11a)
Unresolved: G3-11 (11b + G11c), G3-12, G3-15, G3-16, G3-17, G3-18, G3-19, G3-20

[suehares]

-08 Text resolution of G3-11 to G3-20

Resolved: G3-11 (G3-11b + 11C), G3-12, G3-13, G3-14, G3-15, G3-16, G3-17, G3-18, G3-19, G3-20
Nit remaining: G3-11a NIT

Next steps: Discuss NIT (4/24), transfer to "NITs" issue, and close issue G3:11-20.

[suehares]

G3-11a: NIT (Section 2.5) - Review of -08 text changes

-09 text: Resolved, Closed
-08 text: Punctuation NIT.

11-a: Punctuation nit.
-08 text:/
A BGP color-aware route (E2, C1) with next hop N may be resolved
over a color-aware route (N, C2): i.e. the local policy maps the
resolution of C1 over a different color C2./
New text:/
A BGP color-aware route (E2, C1) with next hop N may be resolved
over a color-aware route (N, C2): i.e., the local policy
maps the resolution of C1 over a different color C2./

[suehares]

Resolved: G3-11 (11a, 11b, 11c), G3-12, G3-13, G3-14, G3-15, G3-16, G3-17, G3-18, G3-19, G3-20