Re: [Teas] RtgDir review: draft-ietf-teas-p2mp-loose-path-reopt-07.txt

"Rakesh Gandhi (rgandhi)" <> Fri, 09 December 2016 02:16 UTC

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From: "Rakesh Gandhi (rgandhi)" <>
To: "Joel M. Halpern" <>, "" <>
Thread-Topic: RtgDir review: draft-ietf-teas-p2mp-loose-path-reopt-07.txt
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Subject: Re: [Teas] RtgDir review: draft-ietf-teas-p2mp-loose-path-reopt-07.txt
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Hi Joel,

Thank you for the prompt review.


On 2016-12-08, 9:02 PM, "Joel M. Halpern" <> wrote:

>Those changes address my concerns.  The RFC Production Center Editors 
>may choose to discuss the abstract further (it is still a bit longer 
>than they usually like), but they may not.  I can live with it as you 
>Thank you,
>On 12/8/16 8:57 PM, Rakesh Gandhi (rgandhi) wrote:
>> Hi Joel,
>> Thank you for the detailed review of the document. Please see inline <RG> for replies..
>> On 2016-11-23, 4:10 PM, "Joel M. Halpern" <> wrote:
>>> Hello,
>>> I have been selected as the Routing Directorate reviewer for this draft.
>>> The Routing Directorate seeks to review all routing or routing-related
>>> drafts as they pass through IETF last call and IESG review, and
>>> sometimes on special request. The purpose of the review is to provide
>>> assistance to the Routing ADs. For more information about the Routing
>>> Directorate, please see
>>> ​
>>> Although these comments are primarily for the use of the Routing ADs, it
>>> would be helpful if you could consider them along with any other IETF
>>> Last Call comments that you receive, and strive to resolve them through
>>> discussion or by updating the draft.
>>> Document: draft-ietf-teas-p2mp-loose-path-reopt-07.txt
>>> Reviewer: Joel M. Halpern
>>> Review Date: 23-November-2016
>>> IETF LC End Date: N/A
>>> Intended Status: Standards Track
>>> Summary: I have some moderate concerns about this document that I think
>>> should be resolved before publication is approved.
>>> Comments:
>>> Major:
>>>     The use of SHOULD and MAY in section 4.1 seems to lead to a device
>>> which ostensibly supports this document, but does the wrong things.
>>>     First, with regard to the SHOULDs, in the absence of any indication
>>> as to why it would not do this, it appears that the SHOULD is really
>>> "MUST if the device supports this document" which is what MUST in a
>>> document actually means.
>>>     Section 4.2 first bullet says that a mid-point LSR "SHOULD" check
>>> for a preferable P2MP-TE LSP Tree.  But if it doesn't, it is not
>>> supporting this document.  As written, it could decide to ignore the
>>> message, even though it claims to support this RFC.
>>>     Looking at the handling when a preferable P2MP-TE LSP tree is
>>> found, according to the document, the LSR MAY send the PathErr response.
>>>  My assumption is that if it does not send the PathErr, it MUST
>>> propagate the request.  If it does not do either one, the protocol does
>>> not function.  It seems likely that if this is really intended to be
>>> optional (MAY), the document would be improved my giving implementors
>>> some hint as to when it is desirable or undesirable to send the message.
>>>     Then in the third bullet, it is only a SHOULD to pass on the
>>> request.  Thus, a device which supports this mechanism, but chooses not
>>> to pass on the request, is compliant to this document while preventing
>>> other devices from properly supporting the mechanism.
>> <RG> Ok, how about following text in Section 4.1?
>> -----------
>> A mid-point LSR that expands loose next-hop(s) for one or more S2L
>>    sub-LSP path(s) does the following upon receiving a Path message with
>>    the "P2MP-TE Tree Re-evaluation Request" flag set:
>>    o  The mid-point LSR MUST check for a preferable P2MP-TE LSP tree by
>>       re-evaluating all S2L sub-LSP(s) that are expanded paths of the
>>       loose next-hops of the P2MP-TE LSP.
>>    o  If a preferable P2MP-TE LSP tree is found, the mid-point LSR MUST
>>       send an RSVP PathErr with the Notify error code 25 defined in
>>       [RFC3209] and sub-code "Preferable P2MP-TE Tree Exists (value
>>       TBA2)" defined in this document to the ingress node.  The mid-
>>       point LSR, in turn, SHOULD NOT propagate the "P2MP-TE Tree Re-
>>       evaluation Request" flag in the subsequent RSVP Path messages sent
>>       downstream for the re-evaluated P2MP-TE LSP.
>>    o  If no preferable tree for P2MP-TE LSP can be found, the mid-point
>>       LSR that expands loose next-hop(s) for one or more S2L sub-LSP
>>       path(s) MUST propagate the request downstream by setting the
>>       "P2MP-TE Tree Re-evaluation Request" flag in the LSP_ATTRIBUTES
>>       Object of the RSVP Path message.
>>    The sending of an RSVP PathErr with the Notify error code and
>>    "Preferable P2MP-TE Tree Exists" sub-code to the ingress node
>>    notifies the ingress node of the existence of a preferable P2MP-TE
>>    LSP tree and upon receiving this PathErr, the ingress node MUST
>>    trigger re-optimization of the LSP using the MBB method with a
>> different LSP-ID.
>> ---------------
>>> Minor:
>>>     The abstract is much too long.  Much of the content of the abstract
>>> belongs in the introduction.  Even teh second paragraph has too much
>>> detail for an abstract.
>>> Editorial:
>>>     In the last paragraph of the introduction, it says that this
>>> document "proposes" solutions.  Given we are now in the position of
>>> evaluating publication as a Proposed Standard, I would say that this
>>> document "defines" solutions.
>> <RG> Ok, how about following Abstract?
>> ----------
>> Re-optimization of a Point-to-Multipoint (P2MP) Traffic Engineered
>>    (TE) Label Switched Path (LSP) may be triggered based on the need to
>>    re-optimize an individual source-to-leaf (S2L) sub-LSP or a set of
>>    S2L sub-LSPs, both using Sub-Group-Based Re-optimization method, or
>>    the entire P2MP-TE LSP tree using the Make-Before-Break (MBB) method.
>>     This document discusses the application of the existing mechanisms
>>    for path re-optimization of loosely routed Point-to-Point (P2P) TE
>>    LSPs to the P2MP-TE LSPs, identifies issues in doing so and defines
>>    procedures to address them.  When re-optimizing a large number of S2L
>>    sub-LSPs in a tree using the Sub-Group-Based Re-optimization method,
>>    the S2L sub-LSP descriptor list may need to be semantically
>>    fragmented.  This document defines the notion of a fragment
>>    identifier to help recipient nodes unambiguously reconstruct the
>>    fragmented S2L sub-LSP descriptor list.
>> ----------
>> Thanks,
>> Rakesh (for authors and contributors)