Updates to the Resource Reservation Protocol for Fast Reroute of Traffic Engineering GMPLS Label Switched Paths (LSPs)
draft-ietf-teas-gmpls-lsp-fastreroute-12

[Ballot discuss]
1) In Sec 4.5.1: "The downstream PLR can assign a bypass tunnel when
  processing the first Path message of the protected LSP, however, it
  can not update the forwarding plane until it receives the Resv
  message containing the downstream MP label."

Please explain how the downstream PLR can assign a bypass tunnel if the LSP
has a loose ERO - so the downstream PLR does not know the next-next-hop that
would be the MP for a node-protecting LSP.

2) Sec 4.5.1: "An upstream PLR (downstream MP) SHOULD check all BYPASS_ASSIGNMENT
  subobjects in the Path RRO in order to assign a reverse bypass
  tunnel.  The upstream PLR that detects a BYPASS_ASSIGNMENT subobject,
  selects a reverse bypass tunnel that terminates locally with the
  destination address and tunnel-ID from the subobject, and has a
  source address matching the Node-ID address."

This isn't very clear - particularly given that there will be many BYPASS_ASSIGNMENT subobjects
in the path RRO.  The case of BYPASS_ASSIGNMENT sub-objects being removed or changed is not
addressed at all.  In addition, I *assume* that the failure to treat the destination IP address in the
BYPASS_ASSIGNMENT as the source IP address for the upstream Bypass tunnel is an oversight?

I believe that what is meant  is:

"An upstream PLR (downstream MP) SHOULD check all BYPASS_ASSIGNMENT sub-objects
in the Path RRO to see if the destination IP address in the BYPASS_ASSIGNMENT matches
an address of the upstream PLR.  For each BYPASS_ASSIGNMENT sub-object that matches,
the upstream PLR looks for a local bypass tunnel that has a destination matching the
downstream PLR that inserted the BYPASS_ASSIGNMENT, as indicated by the Node-ID address,
and the same tunnel-ID as indicated in the BYPASS_ASSIGNMENT."

I recall that tunnel-ID is usually scoped by the address of the ingress LSR; this seems to assume
that the same tunnel-ID is provided to both the downstream PLR and upstream PLR??? 
Alternately, I am misunderstanding - and the information in the BYPASS_ASSIGNMENT is really
intended to be bypass tunnel to be used by the upstream PLR, which the downstream PLR
somehow(??details, hints in the document please) knows .

Then there needs to be text to handle the case where the previous PATH message contained a particular
BYPASS_ASSIGNMENT sub-object and that sub-object has been removed or changed.

3) Sec 4.5.3: "In both examples above, the upstream PLR SHOULD send a Notify message
  [RFC3473] with Error-code - FRR Bypass Assignment Error (value: TBA1)
  and Sub-code - Bypass Assignment Cannot Be Used (value: TBA2) to the
  downstream PLR to indicate that it cannot use the bypass tunnel
  assignment in the reverse direction.  Upon receiving this error, the downstream PLR
  MAY remove the bypass tunnel assignment and select an alternate bypass tunnel if one available."

This section is problematic because it creates the use of local policy when the ingress has a clear way
to signal what type of protection is desired and because it provides an error message to where it will
only cause pointless churn (the MP is the MP based on the type of protection desired - certainly for bypass)
rather than to the ingress where it could at least be acted upon.  The dynamics at time of failure also do
not seem to be well considered; asymmetry is unfortunate, but worse is lack of protection.

Consider the case in Example 1.  If R5 suffers a node failure, then there is no protection for the upstream
LSP from R6 if it prefers the link protection.  It simply doesn't matter what bypass tunnel R4 picks! Sending
a Notify message to R4 asking for a different tunnel is not productive.  If the ingress has requested node-protection, then there is simply nothing that can be done for this topology by R5.  It could be helpful to
send a Notify to the ingress or have a flag set in the RESV RRO to indicate the issue, but that's about it.

For the question about creating local policy, how are the SESSION_ATTRIBUTES used?  Obviously, they are available in
the PATH message that has the BYPASS_ASSIGNMENTs.  Why would the "Node Protection Desired" flag not be relevant here?

4) Sec 5: "  o  Upstream PLR reroutes traffic upon detecting the link failure or
      upon receiving RSVP Path message over the bidirectional bypass
      tunnel. 

  o  Upstream PLR also reroutes RSVP Resv signaling after receiving
      RSVP Path message over the bidirectional bypass tunnel. "

How does the upstream PLR detect that the message was received over the bypass
tunnel?  Is the assumption that the bypass LSP doesn't do penultimate hop popping?
Is the assumption that the PLR can tell because RSVP indicates the downstream PLR
as the previous hop in its signaling?  Please clarify and describe how this detection
is done - to ease interoperability.

5) In Sec 5.1.2:  "When upstream PLR R4 receives the protected LSP Path messages over
      the restored link, if not already done, it starts sending Resv
      messages and traffic flow of the protected LSP over the restored
      link and stops sending them over the bypass tunnel."

Is there a reason that "when the downstream PLR receives the protected LSP RESV messages
over the restored link, if not already done, it starts sending Path messages and traffic flow of the
protected LSP over the restored link and stops sending them over the bypass tunnel." doesn't also
make sense to put in this section?

If this is not a good idea, please explain clearly the issues that it causes.

I am assuming that "after the link is restored" implies that bidirectional communication has been
successfully tested - not merely that the physical layer is up but also that an IGP or BFD is successful
across it. (But this is standard for RSVP-TE FRR).

6) Sec 5.2.2: The behavior of R4 is not described.  When the link from R3-R4 fails, R4 will redirect traffic to R2.
As written at the start of Sec 5, R4 does not start sending its Resv across the bypass tunnel and R2 is thus not triggered to use its bypass tunnel.  Please clearly describe this and why.  It is this asymmetry in behavior for the downstream PLR
and upstream PLR that causes the downstream PLR's bypass tunnel to be prioritized.

7) Sec 5.2.2: The need for the PRR to look up the bypass tunnel and then reprogram the forwarding plane is quite concerning for having this operate at significant scale.  What could be done if one assumes that the selected bypass tunnel - from the BYPASS_PROTECTION handling - is used?  Is there a reason that decision has to be redone here? What is the issue that the solution is trying to work around?  I can certainly imagine scenarios with BFD sessions so that the PRR can be rapidly failed over as the result of the BFD session going down.  What scale of LSPs are you expecting this scenario to handle?

8) Sec 5.2.2: Given that the PRR will TEAR DOWN the LSP if it can't find a matching bypass tunnel, it would be quite useful for the ingress to have visibility as to the protection available.  In RFC 4090, Sec 4.4 defines both "local protection available" and "local protection in use" flags in the IPv4/IPv6 sub-objects.  Clearly, that isn't sufficient for the co-routed case because the ingress needs to know also that "local upstream protection available" and perhaps "local upstream protection in use". 

9) Sec 5.2.3: "  o  The upstream PLR R4 starts sending the traffic flow of the
      protected LSP over the restored link towards downstream PLR R3 and
      forwarding the Path messages towards PRR R5 and stops sending the
      traffic over the bypass tunnel.

  o  When upstream PLR R4 receives the protected LSP Path messages over
      the restored link, if not already done, it starts sending Resv
      messages and traffic flow over the restored link towards
      downstream PLR R3 and forwarding the Path messages towards PRR R5
      and stops sending them over the bypass tunnel."

In the referenced figures, R4 is NOT an upstream PLR; that is R5.  R4 could have forgotten all state associated with
the bi-directional LSP.  Please fix the text to actually describe the behavior.

10) Sec 5.3: "  Unidirectional link failures can result in the traffic flowing on
  asymmetric paths in the forward and reverse directions.  In addition,
  unidirectional link failures can cause RSVP soft-state timeout in the
  control-plane in some cases.  As an example, if the unidirectional
  link failure is in the upstream direction (from R4 to R3 in Figures 1
  and 2), the downstream PLR (node R3) can stop receiving the Resv
  messages of the protected LSP from the upstream PLR (node R4 in
  Figures 1 and 2) and this can cause RSVP soft-state timeout to occur
  on the downstream PLR (node R3)."

Is the assumption that there is no IGP or BFD running on the link? If not, then
the IGP or BFD session will go down on the link first, making it unavailable to
RSVP-TE and should trigger the fast-reroute.

Also - given this issue, why does the upstream MP not start using the bypass
tunnel when receiving Resv through a bypass tunnel? There is no explanation in the draft
and there should be - to prevent incorrect "optimizations".  Ideally, the draft would
specify something like MUST NOT or SHOULD NOT with explanation - if that is the case.

11) Sec 7.1: The description for the BYPASS_ASSIGNMENT completely fails to be clear
as to whether the contents are for the bypass tunnel used by the node inserting it into the
RRO or whether the contents are a direction for the node that receives it - based on the
Node ID that is included.

[Ballot comment]
a) Sec 5.2.2.1: The approach suggested here seems fairly intensive from a forwarding plane perspective.  It would be very helpful to indicate the range of expected/desired time for the fail-over.

b) Sec 5.2:  This section is about node failures - but while the bypass tunnels are node-protecting, the failures discussed are only link.  A brief example that describes the expected signaling for an actual node failure would be helpful.

[Ballot discuss]
What stops me from just providing a random IP address
that I don't control in BYPASS_ASSIGNMENT and thus
causing them to get spammed? I am assuming there are
mechanisms to prevent them, but it's not immediately
clear to me what those are, so they at minimum need
to spelled out in security considerations. This section
from RFC 4090 is not encouraging:

  This document does not introduce new security issues.  The security
  considerations pertaining to the original RSVP protocol [RSVP] remain
  relevant.

  Note that the facility backup method requires that a PLR and its
  selected merge point trust RSVP messages received from each other.

[Ballot comment]
You refer to Figure 2 on page 3 and it appears on page 12.
Probably either you should move it up or make a copy.

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

The IANA Services Operator has completed its review of draft-ietf-teas-gmpls-lsp-fastreroute-09.txt. 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 Sub-object type - 21 ROUTE_RECORD - Type 1 Route Record subregistry of the Class Names, Class Numbers, and Class Types registry on the Resource Reservation Protocol (RSVP) Parameters registry page located at:

https://www.iana.org/assignments/rsvp-parameters/

two new registrations are to be made as follows:

Value: [ TBD-at-registration ]
Description: BYPASS_ASSIGNMENT IPv4 subobject
Reference: [ RFC-to-be ]

Value: [ TBD-at-registration ]
Description: BYPASS_ASSIGNMENT IPv6 subobject
Reference: [ RFC-to-be ]

Second, in the Error Codes and Globally-Defined Error Value Sub-Codes registry also on the Resource Reservation Protocol (RSVP) Parameters registry page located at:

https://www.iana.org/assignments/rsvp-parameters/

a single new registration is to be made as follows:

Error Code: [ TBD-at-registration ]
Meaning: FRR Bypass Assignment Error
Reference: [ RFC-to-be ]

A new set of subcodes is to be established for the newly registered Error Code in this step. There will be three subcodes in the initial subcode registry as follows:

Value: [ TBD-at-registration ]
Description: Bypass Assignment Cannot Be Used
Reference: [ RFC-to-be ]

Value: [ TBD-at-registration ]
Description: Bypass Tunnel Not Found
Reference: [ RFC-to-be ]

Value: [ TBD-at-registration ]
Description: One-to-one Bypass Already In-use
Reference: [ RFC-to-be ]

The IANA Services Operator understands that these two actions are the only ones 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,

Sabrina Tanamal
IANA Services Specialist
PTI

The following Last Call announcement was sent out:

From: The IESG
To: IETF-Announce
CC: draft-ietf-teas-gmpls-lsp-fastreroute@ietf.org, teas-chairs@ietf.org, teas@ietf.org, db3546@att.com, vbeeram@juniper.net
Reply-To: ietf@ietf.org
Sender:
Subject: Last Call:  (Extensions to Resource Reservation Protocol For Fast Reroute of Traffic Engineering GMPLS LSPs) to Proposed Standard


The IESG has received a request from the Traffic Engineering Architecture and
Signaling WG (teas) to consider the following document: - 'Extensions to
Resource Reservation Protocol For Fast Reroute of
  Traffic Engineering GMPLS LSPs'
  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 2017-07-07. 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 defines Resource Reservation Protocol - Traffic
  Engineering (RSVP-TE) signaling extensions to support Fast Reroute
  (FRR) of Packet Switched Capable (PSC) Generalized Multi-Protocol
  Label Switching (GMPLS) Label Switched Paths (LSPs).  These signaling
  extensions allow the coordination of a bidirectional bypass tunnel
  assignment protecting a common facility in both forward and reverse
  directions of a co-routed bidirectional LSP.  In addition, these
  extensions enable the re-direction of bidirectional traffic onto
  bypass tunnels that ensure co-routedness of data paths in the forward
  and reverse directions after FRR and avoid RSVP soft-state timeout in
  control-plane.





The file can be obtained via
https://datatracker.ietf.org/doc/draft-ietf-teas-gmpls-lsp-fastreroute/

IESG discussion can be tracked via
https://datatracker.ietf.org/doc/draft-ietf-teas-gmpls-lsp-fastreroute/ballot/

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

  https://datatracker.ietf.org/ipr/2027/

> As required by RFC 4858, this is the current template for the Document
> Shepherd Write-Up.

> Changes are expected over time. This version is dated 24 February 2012.

> (1) What type of RFC is being requested (BCP, Proposed Standard,
> Internet Standard, Informational, Experimental, or Historic)? 

Standards Track.

> Why is this the proper type of RFC? 


Standards Track is apt because the document defines RSVP-TE related
formats and behaviors.


> Is this type of RFC indicated in the title page header?

Yes.

> (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

>  Relevant content can frequently be found in the abstract
>  and/or introduction of the document. If not, this may be
>  an indication that there are deficiencies in the abstract
>  or introduction.

This document defines Resource Reservation Protocol - Traffic
Engineering (RSVP-TE) signaling extensions to support Fast Reroute
(FRR) of Packet Switched Capable (PSC) Generalized Multi-Protocol
Label Switching (GMPLS) Label Switched Paths (LSPs).  These signaling
extensions allow the coordination of a bidirectional bypass tunnel
assignment protecting a common facility in both forward and reverse
directions of a co-routed bidirectional LSP.  In addition, these
extensions enable the re-direction of bidirectional traffic onto
bypass tunnels that ensure co-routedness of data paths in the forward
and reverse directions after FRR and avoid RSVP soft-state timeout in
control-plane.

> Working Group Summary
>
>  Was there anything in WG process that is worth noting? For
>  example, was there controversy about particular points or
>  were there decisions where the consensus was particularly
>  rough?

This document moved from the CCAMP WG to TEAS WG as part of the
routing WG changes. There was some serious debate regarding the
object-format/procedures defined for co-ordinating bidirectional
bypass tunnel assignment between the downstream and upstream PLRs.
All concerns raised in regard to this have been addressed by the
authors. The document went through three WG Last Calls before
being deemed “publication-request” ready as substantial comments
were raised during the first and second Last Calls.


> Document Quality

>  Are there existing implementations of the protocol? Have a
>  significant number of vendors indicated their plan to
>  implement the specification? Are there any reviewers that
>  merit special mention as having done a thorough review,
>  e.g., one that resulted in important changes or a
>  conclusion that the document had no substantive issues? If
>  there was a MIB Doctor, Media Type or other expert review,
>  what was its course (briefly)? In the case of a Media Type
>  review, on what date was the request posted?

The base (G)MPLS RSVP protocol has been implemented. The procedures
discussed in this document are compatible with earlier implementations.
While there have been no public statements on implementation, the
authors are from multiple vendors, and implementation is expected.

> Personnel
>
>  Who is the Document Shepherd?

Vishnu Pavan Beeram

> Who is the Responsible Area Director?

Deborah Brungard

> (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.

The Document Shepherd has reviewed the document as it has progressed
through the WG (first CCAMP, then TEAS). The Shepherd believes this
document is ready for publication.

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

No.

> (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?

No.

> If so, describe the review that took place.

N/A.


> (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.

No specific concerns.

> (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, see thread -
https://mailarchive.ietf.org/arch/msg/teas/G3Fu7-gdeuQnuL-mUfMwXRsqhY8


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

Yes, an IPR disclosure has been filed that references this document 
(see https://datatracker.ietf.org/ipr/2027/).There was no WG discussion
regarding the IPR disclosures.


> (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? 

Solid among those who are interested. "strong concurrence of a few
individuals, with others being silent" is a reasonable
characterization.

> (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.)

No extreme discontent seen.

> (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.

The document passes ID nits.

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

N/A.

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

Yes.

> (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?

No.

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

No.

> (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.

No.

> (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).

The IANA section was fully reviewed by the document shepherd. All protocol
extensions that the document makes are associated with the appropriate
reservations in IANA registries.


> (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.

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.

N/A.

IPR response 1 of 7: Manav Bhatia: https://mailarchive.ietf.org/arch/msg/teas/hOb6gIfNa_xYXe4zkyROzOUFWZY
IPR response 2 of 7: Rakesh Gandhi: https://mailarchive.ietf.org/arch/msg/teas/u9nJ6--BNuBH1OaHOypK-FqTh0o
IPR response 3 of 7: Zafar Ali: https://mailarchive.ietf.org/arch/msg/teas/apxcq_pxow-GEcJdiHxxZFHkcw0
IPR response 4 of 7: Tarek Saad: https://mailarchive.ietf.org/arch/msg/teas/OSwkeHfNCIZN57edZ4oNqZL1HVI
IPR response 5 of 7: Mike Taillon: https://mailarchive.ietf.org/arch/msg/teas/OFd25R1TqEoBhU_-hOwUMi6ArE8
IPR response 6 of 7: Lizhong Jin: https://mailarchive.ietf.org/arch/msg/teas/n8LMliDI37z3RONmhqF-RUguOro