Re: Deborah Brungard's Discuss on draft-ietf-rtgwg-backoff-algo-07: (with DISCUSS)

"Acee Lindem (acee)" <> Sun, 25 February 2018 01:52 UTC

Return-Path: <>
Received: from localhost (localhost []) by (Postfix) with ESMTP id CCA49124BFA; Sat, 24 Feb 2018 17:52:50 -0800 (PST)
X-Virus-Scanned: amavisd-new at
X-Spam-Flag: NO
X-Spam-Score: -14.531
X-Spam-Status: No, score=-14.531 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, RCVD_IN_DNSWL_HI=-5, RCVD_IN_MSPIKE_H4=-0.01, RCVD_IN_MSPIKE_WL=-0.01, SPF_PASS=-0.001, T_RP_MATCHES_RCVD=-0.01, USER_IN_DEF_DKIM_WL=-7.5] autolearn=ham autolearn_force=no
Authentication-Results: (amavisd-new); dkim=pass (1024-bit key)
Received: from ([]) by localhost ( []) (amavisd-new, port 10024) with ESMTP id 2H7Q2gI9Tlw8; Sat, 24 Feb 2018 17:52:48 -0800 (PST)
Received: from ( []) (using TLSv1.2 with cipher DHE-RSA-SEED-SHA (128/128 bits)) (No client certificate requested) by (Postfix) with ESMTPS id 8A0941205D3; Sat, 24 Feb 2018 17:52:48 -0800 (PST)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple;;; l=7448; q=dns/txt; s=iport; t=1519523568; x=1520733168; h=from:to:cc:subject:date:message-id:references: in-reply-to:content-id:content-transfer-encoding: mime-version; bh=K7X/0RiB6or2CAygRmI+ShqxBAIfYX3IpEasuJUCV5I=; b=YAfohB/F4RjzZVImBFASqdk2lNV/sWUilzu4RwqVW6p/XV4CW9nn5tRO byxJ2OEl1qzaAQ57GMeNoNYkORgllAzub6bVGaawqd7bDlPXFOW9sbvyj gGT+vkbmVWGm5FnHq2UnrQFZwwzzRxjoFNVWpDhagc3nnSyJVEaLh5Ucz k=;
X-IronPort-Anti-Spam-Filtered: true
X-IronPort-AV: E=Sophos;i="5.47,391,1515456000"; d="scan'208";a="361320306"
Received: from ([]) by with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 25 Feb 2018 01:52:47 +0000
Received: from ( []) by (8.14.5/8.14.5) with ESMTP id w1P1qkM8008584 (version=TLSv1/SSLv3 cipher=AES256-SHA bits=256 verify=FAIL); Sun, 25 Feb 2018 01:52:47 GMT
Received: from ( by ( with Microsoft SMTP Server (TLS) id 15.0.1320.4; Sat, 24 Feb 2018 20:52:46 -0500
Received: from ([]) by ([]) with mapi id 15.00.1320.000; Sat, 24 Feb 2018 20:52:45 -0500
From: "Acee Lindem (acee)" <>
CC: "" <>, Uma Chunduri <>, "" <>, "" <>
Subject: Re: Deborah Brungard's Discuss on draft-ietf-rtgwg-backoff-algo-07: (with DISCUSS)
Thread-Topic: Deborah Brungard's Discuss on draft-ietf-rtgwg-backoff-algo-07: (with DISCUSS)
Thread-Index: AQHTqp72NqhoQQMJl0Ocdr+OlgE/IqOvmZcAgATL9wD///vcgA==
Date: Sun, 25 Feb 2018 01:52:45 +0000
Message-ID: <>
References: <> <> <>
In-Reply-To: <>
Accept-Language: en-US
Content-Language: en-US
x-ms-exchange-messagesentrepresentingtype: 1
x-ms-exchange-transport-fromentityheader: Hosted
x-originating-ip: []
Content-Type: text/plain; charset="utf-8"
Content-ID: <>
Content-Transfer-Encoding: base64
MIME-Version: 1.0
Archived-At: <>
X-Mailman-Version: 2.1.22
Precedence: list
List-Id: Routing Area Working Group <>
List-Unsubscribe: <>, <>
List-Archive: <>
List-Post: <>
List-Help: <>
List-Subscribe: <>, <>
X-List-Received-Date: Sun, 25 Feb 2018 01:52:51 -0000

Hi Deborah, 

On 2/24/18, 4:07 PM, "BRUNGARD, DEBORAH A" <> wrote:

    Hi Acee,
    Sorry for not responding earlier, I had an unexpected disruption to my schedule these last days.
    I was concerned as the document itself says "Optionally, implementations may also offer alternative algorithms." So it is not clear if it is the algorithm or the parameters which are intended PS.

This is the reality that IGP implementations that have been using their proprietary SPF backoff algorithms for decades are not going to move to the standard mechanisms as their default overnight. 
    And especially concerning is section 7 on partial deployment. It states the algorithm is only effective if it is deployed on all routers, and partial deployment will increase the frequency and duration of micro-loops. It does go on to say operators have progressively replaced an implementation of a given algorithm by a different one.
    If this is to be PS, then you need to provide guidance on how an operator is to do the upgrade to this new algorithm on a network. I understand there are prototype implementations, but I'm concerned on field grade deployments in existing networks.

The IETF can't just mandate that vendors implement the new standard SPF backoff algorithm, make it the default SPF Backoff, or that operators deploy it. I believe we have provided ample guidance by indicating that the full benefit is only obtained when the same algorithm is deployed over the IGP domain (or at least an area). The standardization of the SPF Backoff algorithm is the start of the journey, not the destination. 

    -----Original Message-----
    From: Acee Lindem (acee) [] 
    Sent: Wednesday, February 21, 2018 7:53 PM
    To: BRUNGARD, DEBORAH A <>om>; The IESG <>
    Cc:; Uma Chunduri <>om>;;
    Subject: Re: Deborah Brungard's Discuss on draft-ietf-rtgwg-backoff-algo-07: (with DISCUSS)
    Hi Deborah, 
    Given that the goal of RFC 6976 was much more ambitious and the mechanisms are much more complex, I don't think this draft should be put in the same category. 
    What we have done is precisely specify a standard algorithm for IGP SPF back-off. When deployed, this standard algorithm will greatly improve (but not eliminate) micro-loops in IGP routing domains currently utilizing disparate SPF back-off algorithms. The problem statement draft best articulates the impact of differing SPF back-off algorithms: . Finally, there have been several prototype implementations validating the algorithm specification's completeness and clarity. 
        Deborah Brungard has entered the following ballot position for
        draft-ietf-rtgwg-backoff-algo-07: Discuss
        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 
        for more information about IESG DISCUSS and COMMENT positions.
        The document, along with other ballot positions, can be found here:
        While I agree with Alvaro's concerns, my concern is the appropriateness of this document as PS.
        This document should have a similar status as RFC6976 (Informational) which also provided a
        mechanism that prevented transient loops saying "the mechanisms described in this
        document are purely illustrative of the general approach and do not constitute a protocol
        specification". Especially as this document compares itself to RFC6976, saying RFC6976 is a
        "full solution".
        With a change of status to Informational, this document would be better
        scoped as providing guidance vs. a specification.