Pseudowire (PW) Endpoint Fast Failure Protection
draft-ietf-pals-endpoint-fast-protection-05

Received changes through RFC Editor sync (created alias RFC 8104, changed title to 'Pseudowire (PW) Endpoint Fast Failure Protection', changed abstract to 'This document specifies a fast mechanism for protecting pseudowires (PWs) transported by IP/MPLS tunnels against egress endpoint failures, including egress attachment circuit (AC) failure, egress provider edge (PE) failure, multi-segment PW terminating PE failure, and multi-segment PW switching PE failure.  Operating on the basis of multihomed customer edge (CE), redundant PWs, upstream label assignment, and context-specific label switching, the mechanism enables local repair to be performed by the router upstream adjacent to a failure.  The router can restore a PW in the order of tens of milliseconds, by rerouting traffic around the failure to a protector through a pre-established bypass tunnel.  Therefore, the mechanism can be used to reduce traffic loss before global repair reacts to the failure and the network converges on the topology changes due to the failure.', changed pages to 43, changed standardization level to Proposed Standard, changed state to RFC, added RFC published event at 2017-03-15, changed IESG state to RFC Published)

[Ballot comment]
Editorial nits (From Sue Hares, part of her OPS-DIR review)

1.      Page 10  - style makes difficult reading of sentence  (very minor nit).

OLD /A PLR MUST Be able to detect a failure by using a rapid mechanism, such as physical layer failure detection, Bidirectional failure detection (BFD) [RFC5880], etc. /

NEW /A PLR MUST Be able to detect a failure by using a rapid mechanism, such as physical layer failure detection, Bidirectional failure detection (BFD) [RFC5880], and others/

2.      Page 32 – difficult to parse sentence

      Old/For Encoding type, 1 is defined for PWid FEC element format, and 2 is defined for the Generalized PWid FEC Element format [RFC4447]./

      New/ For type encoding type, the following two values are defined within this document:

-          Type 1 for PWid FEC element format (see section 6.4.1.), and

-          Type 2 for Generalized PWid FEC Element format [RFC4447

[Ballot comment]

- section 5: I'm not sure "revertive" is a useful term
here. Seems to me that it's a) admirably obscure, b) maybe
inaccurate, as we're not reverting to a previous state
here but rather changing paths, and maybe c) it's not
clear if we end up with a "fully functional" path after
"reverting." But maybe it's an accepted term of art in
routing - if so, some reference to where it's well
described might be nice.

- section 8, para 1: this assumes that "managed by network
operator" means "is secure." I think we have examples
where not all that happens within a network is under the
control of the owner of the network, so I question that
assumption. (I'm not now asking for a concrete change as
that'd be a major bit of work, but I am as willing as ever
to continue to call this out as it appears;-) If you could
remove text based on that assumption, that'd improve the
document I think.

[Ballot comment]
Minor:

1) The details in Figure 11 on p. 22 don't look quite right.    There is no forwarding state shown on PE4 to handle the incoming labels of 2000 (P3's outgoing label of bypass tunnel to PE4) or 3000 (P2's outgoing label of bypass tunnel to PE4).    Either there should be additional forwarding state on PE4 that says to pop 2000 (or 3000) and identify a context label space - or PE4 should have allocated the context label 999 to the bypass tunnels from P3 and PE2.

I see the same issue in Figures 12, 13, and 14.  Is there  a detail or explanation missing?

[Ballot comment]
A few smallish comments/questions:

1) This is no news but there are a lot of acronyms in this drafts which makes it partly hard to read. Some of them are never spelled out, such as PE, CE, RSVP... I would like to propose two changes to support the reader: 1) Spell out all acronyms in the abstract and 2) add a glossary. Further you could maybe also define some terminology at the beginning such as 'protector'.

2) This sentence/use of acronym is confusing:
"In Figure 1, the IP/MPLS network consists of PE and P routers."
NEW:
"In Figure 1, the IP/MPLS network consists of four PEs and two routers P1 and P2."

3) I don't fully understand this part in sec 4.1:
"Normally the router will attempt to
  forward PW packets in a load balance fashion over the ECMP set.  When
  the link fails, if the router reroutes only the portion of traffic
  originally traversing the link while letting the rest of traffic
  remain on the other ECMP branches, it will create a situation where
  the egress CE receives traffic from both the primary PE and the
  backup PE. "
If you have two ECMP branches, why don't you simply use the other one for all traffic? Isn't this the kind of protection your are discussing? Or are you assuming that this note somewhere on the PW does not apply this backup strategy?

4) Do you have references for mechanisms described in section 5?

One high level comment:
I was wondering while reading the whole time if this should be informational or standards track. Was there any discussion in the wg? Are there implementations?

[Ballot discuss]
Sections 6.4.1 and 6.4.2

The Ingress and Egress PE Addresses are encoded as 4 byte fields. How is this expected to work with IPv6 addresses for the PEs?

[Ballot comment]
1) This is no news but there are a lot of acronyms in this drafts which makes it partly hard to read. Some of them are never spelled out, such as PE, CE, RSVP... I would like to propose two changes to support the reader: Spell out all acronyms in the abstract and add a glossary.

2) This sentence/use of acronym is confusing:
"In Figure 1, the IP/MPLS network consists of PE and P routers."
NEW:
"In Figure 1, the IP/MPLS network consists of four PEs and two routers P1 and P2."

3) I don't fully understand this part in sec 4.1:
"Normally the router will attempt to
  forward PW packets in a load balance fashion over the ECMP set.  When
  the link fails, if the router reroutes only the portion of traffic
  originally traversing the link while letting the rest of traffic
  remain on the other ECMP branches, it will create a situation where
  the egress CE receives traffic from both the primary PE and the
  backup PE. "
If you have two ECMP branches, why don't you simply use the other one for all traffic? Isn't this the kind of protection your are discussing? Or are you assuming that this note somewher on the PW does not apply this backup strategy?

(Via drafts-lastcall@iana.org): IESG/Authors/WG Chairs:

The IANA Services Operator has completed its review of draft-ietf-pals-endpoint-fast-protection-04. If any part of this review is inaccurate, please let us know.

The IANA Services Operator understands that, upon approval of this document, there are two actions which we must complete.

First, in the TLV Type Name Space subregistry of the Label Distribution Protocol (LDP) Parameters registry located at:

https://www.iana.org/assignments/ldp-namespaces/

a new TLV is registered as follows:

Value: [ TBD-at-Registration ]
Description: Egress Protection Capability
Reference: [ RFC-to-be ]

Second, in the Forwarding Equivalence Class (FEC) Type Name Space also in the Label Distribution Protocol (LDP) Parameters registry located at:

https://www.iana.org/assignments/ldp-namespaces/

we'll update the reference to this document for the following existing registration:

Value  Hex  Name  Label Advertisement Discipline  Reference
-------------------------------------------------------------------
131  0x83  Protection FEC Element  DU  [draft-ietf-pwe3-endpoint-fast-protection][RFC7358]


The IANA Services Operator understands that these are the only actions required to be completed upon approval of this document.

Note:  The actions requested in this document will not be completed until the document has been approved for publication as an RFC. This message is only to confirm what actions will be performed.

Thank you,

Amanda Baber
Lead IANA Services Specialist
PTI

The following Last Call announcement was sent out:

From: The IESG
To: "IETF-Announce"
CC: draft-ietf-pals-endpoint-fast-protection@ietf.org, db3546@att.com, pals-chairs@ietf.org, "Stewart Bryant" , pals@ietf.org, stewart.bryant@gmail.com
Reply-To: ietf@ietf.org
Sender:
Subject: Last Call:  (PW Endpoint Fast Failure Protection) to Proposed Standard


The IESG has received a request from the Pseudowire And LDP-enabled
Services WG (pals) to consider the following document:
- 'PW Endpoint Fast Failure Protection'
  as Proposed Standard

The IESG plans to make a decision in the next few weeks, and solicits
final comments on this action. Please send substantive comments to the
ietf@ietf.org mailing lists by 2016-12-06. Exceptionally, comments may be
sent to iesg@ietf.org instead. In either case, please retain the
beginning of the Subject line to allow automated sorting.

Abstract


  This document specifies a fast mechanism for protecting pseudowires
  against egress endpoint failures, including egress attachment circuit
  failure, egress PE failure, multi-segment PW terminating PE failure,
  and multi-segment PW switching PE failure.  Operating on the basis of
  multi-homed CE, redundant PWs, upstream label assignment and context
  specific label switching, the mechanism enables local repair to be
  performed by the router upstream adjacent to a failure.  The router
  can restore a PW in the order of tens of milliseconds, by rerouting
  traffic around the failure to a protector through a pre-established
  bypass tunnel.  Therefore, the mechanism can be used to reduce
  traffic loss before global repair reacts to the failure and the
  network converges on the topology changes due to the failure.




The file can be obtained via
https://datatracker.ietf.org/doc/draft-ietf-pals-endpoint-fast-protection/

IESG discussion can be tracked via
https://datatracker.ietf.org/doc/draft-ietf-pals-endpoint-fast-protection/ballot/

The following IPR Declarations may be related to this I-D:

  https://datatracker.ietf.org/ipr/2825/
  https://datatracker.ietf.org/ipr/2243/
  https://datatracker.ietf.org/ipr/2805/
  https://datatracker.ietf.org/ipr/2262/

(1) What type of RFC is being requested (BCP, Proposed Standard,
Internet Standard, Informational, Experimental, or Historic)?  Why
is this the proper type of RFC?  Is this type of RFC indicated in the
title page header?

We request publication as Proposed Standard. This is corerctly
indicated in the title page header.


(2) The IESG approval announcement includes a Document Announcement
Write-Up. Please provide such a Document Announcement Write-Up. Recent
examples can be found in the "Action" announcements for approved
documents. The approval announcement contains the following sections:

Technical Summary

  This document specifies a fast mechanism for protecting pseudowires
  against egress endpoint failures, including egress attachment circuit
  failure, egress PE failure, multi-segment PW terminating PE failure,
  and multi-segment PW switching PE failure.  Operating on the basis of
  multi-homed CE, redundant PWs, upstream label assignment and context
  specific label switching, the mechanism enables local repair to be
  performed by the router upstream adjacent to a failure.  The router
  can restore a PW in the order of tens of milliseconds, by rerouting
  traffic around the failure to a protector through a pre-established
  bypass tunnel.  Therefore, the mechanism can be used to reduce
  traffic loss before global repair reacts to the failure and the
  network converges on the topology changes due to the failure.

Working Group Summary

  This has been reviewed by the WG and there is nothing contentious in
  it. There have been a number of attempts at designing a more general
  colution in the MPLS WG, but none have reached this level of
  maturity, and it is therefore appropriate to publish this pseudowire
  specific solution.
 
Document Quality

  This is a well written document. I do not anticipate any interworking
  issues between independent implementations.
 

Personnel

  Who is the Document Shepherd? Who is the Responsible Area
  Director?

  Stewart Bryant is the Document Shepherd.
  Deborah Brungard is the Responsible Area Director.

(3) Briefly describe the review of this document that was performed by
the Document Shepherd.  If this version of the document is not ready
for publication, please explain why the document is being forwarded to
the IESG.

This document has been reviewed by the Shepherd and is ready for
consideration by the responsible AD.

(4) Does the document Shepherd have any concerns about the depth or
breadth of the reviews that have been performed?

I beleive that the document has been adequately reviewed.

(5) Do portions of the document need review from a particular or from
broader perspective, e.g., security, operational complexity, AAA, DNS,
DHCP, XML, or internationalization? If so, describe the review that
took place.

The IETF standard review process should be adequate for this document.

(6) Describe any specific concerns or issues that the Document Shepherd
has with this document that the Responsible Area Director and/or the
IESG should be aware of? For example, perhaps he or she is uncomfortable
with certain parts of the document, or has concerns whether there really
is a need for it. In any event, if the WG has discussed those issues and
has indicated that it still wishes to advance the document, detail those
concerns here.

I have no concerns regarding the publication of this document.

(7) Has each author confirmed that any and all appropriate IPR
disclosures required for full conformance with the provisions of BCP 78
and BCP 79 have already been filed. If not, explain why.

Yes they have.

(8) Has an IPR disclosure been filed that references this document?
If so, summarize any WG discussion and conclusion regarding the IPR
disclosures.

There have been a number of IPR filings, but no one has expressed
any concerns. There have been many similar IPR disclosures against
other PALS (formerly PWE3) documents and these have never been
problematic.

(9) How solid is the WG consensus behind this document? Does it
represent the strong concurrence of a few individuals, with others
being silent, or does the WG as a whole understand and agree with it?

The WG as a body understands and supports this technology.


(10) Has anyone threatened an appeal or otherwise indicated extreme
discontent? If so, please summarise the areas of conflict in separate
email messages to the Responsible Area Director. (It should be in a
separate email because this questionnaire is publicly available.)

The shepherd is not aware of any threatened appeal, or significant
discontent with the document.


(11) Identify any ID nits the Document Shepherd has found in this
document. (See https://www.ietf.org/tools/idnits/ and the Internet-Drafts
Checklist). Boilerplate checks are not enough; this check needs to be
thorough.

There were no ID nits reported by the checker.

(12) Describe how the document meets any required formal review
criteria, such as the MIB Doctor, media type, and URI type reviews.

There are no formal reviews required for this document.

(13) Have all references within this document been identified as
either normative or informative?

Yes they have.

(14) Are there normative references to documents that are not ready for
advancement or are otherwise in an unclear state? If such normative
references exist, what is the plan for their completion?

There are no unpublished normative references.

(15) Are there downward normative references references (see RFC 3967)?
If so, list these downward references to support the Area Director in
the Last Call procedure.

There are no downrefs.

(16) Will publication of this document change the status of any
existing RFCs? Are those RFCs listed on the title page header, listed
in the abstract, and discussed in the introduction? If the RFCs are not
listed in the Abstract and Introduction, explain why, and point to the
part of the document where the relationship of this document to the
other RFCs is discussed. If this information is not in the document,
explain why the WG considers it unnecessary.

It will not change the status of any other document.


(17) Describe the Document Shepherd's review of the IANA considerations
section, especially with regard to its consistency with the body of the
document. Confirm that all protocol extensions that the document makes
are associated with the appropriate reservations in IANA registries.
Confirm that any referenced IANA registries have been clearly
identified. Confirm that newly created IANA registries include a
detailed specification of the initial contents for the registry, that
allocations procedures for future registrations are defined, and a
reasonable name for the new registry has been suggested (see RFC 5226).

IANA has already allocated a codepoint to this draft. This early
allocation has technically expired, but in this case confirming
the allocation is clearly in the best interests of the Internet.

(18) List any new IANA registries that require Expert Review for future
allocations. Provide any public guidance that the IESG would find
useful in selecting the IANA Experts for these new registries.

There are none.

(19) Describe reviews and automated checks performed by the Document
Shepherd to validate sections of the document written in a formal
language, such as XML code, BNF rules, MIB definitions, etc.

Not applicable.