Re: [Teas] Benjamin Kaduk's No Objection on draft-ietf-teas-assoc-corouted-bidir-frr-06: (with COMMENT)

"Rakesh Gandhi (rgandhi)" <rgandhi@cisco.com> Fri, 26 October 2018 17:29 UTC

Return-Path: <rgandhi@cisco.com>
X-Original-To: teas@ietfa.amsl.com
Delivered-To: teas@ietfa.amsl.com
Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id 93FA5127133; Fri, 26 Oct 2018 10:29:38 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -14.971
X-Spam-Level:
X-Spam-Status: No, score=-14.971 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.47, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, RCVD_IN_DNSWL_HI=-5, SPF_PASS=-0.001, USER_IN_DEF_DKIM_WL=-7.5] autolearn=ham autolearn_force=no
Authentication-Results: ietfa.amsl.com (amavisd-new); dkim=pass (1024-bit key) header.d=cisco.com
Received: from mail.ietf.org ([4.31.198.44]) by localhost (ietfa.amsl.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id Ya9b45qEudMR; Fri, 26 Oct 2018 10:29:36 -0700 (PDT)
Received: from alln-iport-5.cisco.com (alln-iport-5.cisco.com [173.37.142.92]) (using TLSv1.2 with cipher DHE-RSA-SEED-SHA (128/128 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id 19EF512870E; Fri, 26 Oct 2018 10:29:36 -0700 (PDT)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=cisco.com; i=@cisco.com; l=7710; q=dns/txt; s=iport; t=1540574976; x=1541784576; h=from:to:cc:subject:date:message-id:references: in-reply-to:content-id:content-transfer-encoding: mime-version; bh=RGt/U/Imx706vTNX1xonrtcTXEevxZc09p5ZVURwDPk=; b=cgMROT6f7Gbc2RF0jIqU3jmH8uRTyCzn/2kI5zQ8V7ZnZylPwazt8/4p dCxf+df8pqXBnYtDMGM8HRCuFcKesHuEf5VYpnxzMJ+6252Wcuid1Iw/G jWwyQlvjdeH8L7TjG4CkOwvhAc6tJ0Cw5lWMqPHxYQuFVR3RG+cBFtGFa k=;
X-IronPort-Anti-Spam-Filtered: true
X-IronPort-Anti-Spam-Result: =?us-ascii?q?A0AEAADwTdNb/4oNJK1jDgwBAQEBAQI?= =?us-ascii?q?BAQEBBwIBAQEBgVEFAQEBAQsBgVUvZn8oCoNriBiMGJkqFIFmCgEBASWERwI?= =?us-ascii?q?XgwEhNA0NAQMBAQIBAQJtHAyFOwYjEUUQAgEIGgImAgICMBUQAgQBDQWDIQG?= =?us-ascii?q?CAQ+mGYEuhD5AhRsFgQuIFYJIF4FBP4EQAScfgkyDGwIBAgGBKgESAR8HECE?= =?us-ascii?q?CgkoxgiYCiHiWBwkChmeDH4Z3EgaBUoR3iXyMbYl+AhEUgSYdOEEjWBEIcBV?= =?us-ascii?q?lAYJBgk+ISoUEOm8BiwWBH4EfAQE?=
X-IronPort-AV: E=Sophos;i="5.54,428,1534809600"; d="scan'208";a="191533879"
Received: from alln-core-5.cisco.com ([173.36.13.138]) by alln-iport-5.cisco.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 26 Oct 2018 17:29:35 +0000
Received: from XCH-RCD-016.cisco.com (xch-rcd-016.cisco.com [173.37.102.26]) by alln-core-5.cisco.com (8.15.2/8.15.2) with ESMTPS id w9QHTZgf002655 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=FAIL); Fri, 26 Oct 2018 17:29:35 GMT
Received: from xch-aln-018.cisco.com (173.36.7.28) by XCH-RCD-016.cisco.com (173.37.102.26) with Microsoft SMTP Server (TLS) id 15.0.1395.4; Fri, 26 Oct 2018 12:29:34 -0500
Received: from xch-aln-018.cisco.com ([173.36.7.28]) by XCH-ALN-018.cisco.com ([173.36.7.28]) with mapi id 15.00.1395.000; Fri, 26 Oct 2018 12:29:34 -0500
From: "Rakesh Gandhi (rgandhi)" <rgandhi@cisco.com>
To: Benjamin Kaduk <kaduk@mit.edu>, The IESG <iesg@ietf.org>
CC: "draft-ietf-teas-assoc-corouted-bidir-frr@ietf.org" <draft-ietf-teas-assoc-corouted-bidir-frr@ietf.org>, Vishnu Beeram <vishnupavan@gmail.com>, "teas-chairs@ietf.org" <teas-chairs@ietf.org>, "teas@ietf.org" <teas@ietf.org>
Thread-Topic: Benjamin Kaduk's No Objection on draft-ietf-teas-assoc-corouted-bidir-frr-06: (with COMMENT)
Thread-Index: AQHUbBCOnvGXh4ldeEuQo/D//L4THqUx24cA
Date: Fri, 26 Oct 2018 17:29:34 +0000
Message-ID: <EFBB1444-EA94-4C2A-ADCE-B7C695F2B194@cisco.com>
References: <154043714468.6859.14289090911132674656.idtracker@ietfa.amsl.com>
In-Reply-To: <154043714468.6859.14289090911132674656.idtracker@ietfa.amsl.com>
Accept-Language: en-US
Content-Language: en-US
X-MS-Has-Attach:
X-MS-TNEF-Correlator:
user-agent: Microsoft-MacOutlook/f.1d.0.161209
x-ms-exchange-messagesentrepresentingtype: 1
x-ms-exchange-transport-fromentityheader: Hosted
x-originating-ip: [10.82.249.236]
Content-Type: text/plain; charset="utf-8"
Content-ID: <95B1A80207B20848AA3E57FC9DFAEC16@emea.cisco.com>
Content-Transfer-Encoding: base64
MIME-Version: 1.0
X-Outbound-SMTP-Client: 173.37.102.26, xch-rcd-016.cisco.com
X-Outbound-Node: alln-core-5.cisco.com
Archived-At: <https://mailarchive.ietf.org/arch/msg/teas/C4vRw6Izdh_i78jOXdcVAilWapo>
Subject: Re: [Teas] Benjamin Kaduk's No Objection on draft-ietf-teas-assoc-corouted-bidir-frr-06: (with COMMENT)
X-BeenThere: teas@ietf.org
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: Traffic Engineering Architecture and Signaling working group discussion list <teas.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/teas>, <mailto:teas-request@ietf.org?subject=unsubscribe>
List-Archive: <https://mailarchive.ietf.org/arch/browse/teas/>
List-Post: <mailto:teas@ietf.org>
List-Help: <mailto:teas-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/teas>, <mailto:teas-request@ietf.org?subject=subscribe>
X-List-Received-Date: Fri, 26 Oct 2018 17:29:39 -0000

Hi Benjamin,

Thank you for the detailed review. Please see inline replies with <RG>…

On 2018-10-24, 11:12 PM, "Benjamin Kaduk" <kaduk@mit.edu>; wrote:

    Benjamin Kaduk has entered the following ballot position for
    draft-ietf-teas-assoc-corouted-bidir-frr-06: No Objection
    
    When responding, please keep the subject line intact and reply to all
    email addresses included in the To and CC lines. (Feel free to cut this
    introductory paragraph, however.)
    
    
    Please refer to https://www.ietf.org/iesg/statement/discuss-criteria.html
    for more information about IESG DISCUSS and COMMENT positions.
    
    
    The document, along with other ballot positions, can be found here:
    https://datatracker.ietf.org/doc/draft-ietf-teas-assoc-corouted-bidir-frr/
    
    
    
    ----------------------------------------------------------------------
    COMMENT:
    ----------------------------------------------------------------------
    
    How does the unidirectional link failure logic and the revertive logic
    interact?  That is, in the unidirectional failure case a node should be
    detecting that there is a failure case and rerouting reverse traffic onto
    the protection path to match the forward path.  But a node in the process
    of reverting back on to the primary path (before its counterpart in the
    other direction) would seem to observe the same packet/path behavior as in
    the case of a unidirectional link failure.  Do we need to rely on the
    flooding of link status information to differentiate between these cases?

<RG> The basic idea is as following: After FRR, RSVP messages are sent with modified “IPV4 tunnel sender address" in the SENDER_TEMPLATE Object of the protected LSP, this is how the receiving node knows if FRR has been triggered and it can use it to trigger co-route. After revertive back when the failure is repaired, the RSVP Path message SENDER_TEMPLATE is restored as before [RFC4090, Section 6.5.2], which can be then used by the receiving node to trigger revertive behavior.

<RG> Yes, flooding link status / topology database can be used for Global revertive behavior.


    Are the state-keeping and resource consumption burdens large for the
    midpoint nodes that now must correlate whether they see traffic on
    original/protection paths for associated flows?  (E.g., Section 4.1.3's
    "when it receives the un-modified RSVP path messages and traffic".)
    It seems like it should just be a linear scaling factor at worst, with no
    real path to an attack, but perhaps there are security considerations
    relating to router capacity.
   

    Section 2
    
       In packet transport networks, there are requirements where the
       reverse LSP of a bidirectional LSP needs to follow the same path as
       its forward LSP [RFC6373].  [...]
    
    Does this need a qualifier (e.g., "some packet transport networks" or
    "there are sometimes requirements")?

<RG> Updated to “some packet transport networks”.
    
    
    Section 3.2
    
       tunnel S (on path B-F-G-D) to reach downstream MP node D whereas the
       upstream PLR node C reroute the protected reverse LSP2 traffic over
       the bypass tunnel N (on path C-I-H-A) to reach the upstream MP node
       A.  [...]
    
    nit: "reroutes"

<RG> Fixed.
    
    Section 4.1.1
    
       As shown in Figure 2, when using a node protection bypass tunnel with
       protected co-routed LSPs, asymmetry of paths can occur in the forward
       and reverse directions after a link failure [RFC8271].  In order to
       restore co-routing, the downstream MP node D (acting as an upstream
       PLR) SHOULD trigger the procedure to restore co-routing and reroute
       the protected reverse LSP2 RSVP Path messages and traffic over the
       bypass tunnel S (on path D-G-F-B) to the upstream MP node B upon
    
    Why is this only a SHOULD?

<RG> It is MUST to restore co-route. Updated.

    
    Section 4.2
    
                                                            An endpoint node
       MAY set the Extended Association ID to the value shown in Appendix A.
    
    The contents of Appendix A do not include a distinguished single value, but
    rather a data structure, so I think that a phrase other than "to the
    value" should be used.

<RG> Updated using suggestion from Adam Roach as: "... set the Extended Association ID to a value formatted according to the
structure shown in Appendix A."
    
       o  For double-sided provisioned bidirectional LSPs [RFC7551], both
          endpoints need to ensure that the bidirectional LSP has a unique
          Extended ASSOCIATION Object for each forward and reverse LSP pair
          by selecting appropriate unique Extended Association IDs signaled
          by them.
    
    How does this signalling/selection process get the two endpoints to agree
    on the same value?

<RG> Added text: A controller can be used to provision unique Extended Association ID on both endpoints.  The procedure for selecting unique Extended Association ID is outside the scope of this document.  
    
    Appendix A
    
    (Again, "to the value" is not appropriate to describe the general format.
    Perhaps, "to a value using the format".)
    
<RG> Updated as above.

    Please also explicitly describe the semantics of the "Reserved" field(s)
    (i.e., set to zero on transmission and ignored on receipt).
    
<RG> Added.

Thanks,
Rakesh