Re: [Gen-art] Genart telechat review of draft-ietf-ospf-ospfv3-segment-routing-extensions-19

"Acee Lindem (acee)" <> Mon, 03 December 2018 21:46 UTC

Return-Path: <>
Received: from localhost (localhost []) by (Postfix) with ESMTP id 1EE3112E036; Mon, 3 Dec 2018 13:46:41 -0800 (PST)
X-Virus-Scanned: amavisd-new at
X-Spam-Flag: NO
X-Spam-Score: -15.961
X-Spam-Status: No, score=-15.961 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DKIMWL_WL_HIGH=-1.46, 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: (amavisd-new); dkim=pass (1024-bit key)
Received: from ([]) by localhost ( []) (amavisd-new, port 10024) with ESMTP id 0tx71759TYHw; Mon, 3 Dec 2018 13:46:39 -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 9BEC012D4ED; Mon, 3 Dec 2018 13:46:38 -0800 (PST)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple;;; l=4632; q=dns/txt; s=iport; t=1543873598; x=1545083198; h=from:to:cc:subject:date:message-id:references: in-reply-to:content-id:content-transfer-encoding: mime-version; bh=GmCOV1R0OqouHUz7nctqLQMmVmd+Y8yAdWYrjykpwhs=; b=WQa2HjdfI+i+zercmnVojcILP7R6EIl0Sb2ikIAnVhe0pr96uIVf9bqM aJefmQowuyjwRaWM93IQlsxi91LQeBCqpwttq8hvTsH0BO23znhLaSbLn dOq6Pk+vzToLtxjaHVemZkZm209eQ+EJS72i43/+zeKgeW9H0W/91jtF+ g=;
X-IronPort-Anti-Spam-Filtered: true
X-IronPort-Anti-Spam-Result: =?us-ascii?q?A0ADAAAMowVc/5xdJa1jGQEBAQEBAQE?= =?us-ascii?q?BAQEBAQcBAQEBAQGBUQQBAQEBAQsBgVopZoECJwqDb4gYjXUll0iBegsBASe?= =?us-ascii?q?ERQIXgzAiNAkNAQMBAQIBAQJtHAyFPQYjEUUQAgEIFAYCJgICAjAVEAIEAQ0?= =?us-ascii?q?FgyEBggEPpiKBL4omBYELixEXgX+BEAEnDBOCTIMeAgIBF4RLMYImAolcjAK?= =?us-ascii?q?KDVUJAoZ+ijwYgVuFEYo6iQSBA4Niil0CERSBJx84gVVwFWUBgkGCJAMXEm0?= =?us-ascii?q?BCQSHUYU/QTEBikGBHwEB?=
X-IronPort-AV: E=Sophos;i="5.56,311,1539648000"; d="scan'208";a="490895696"
Received: from ([]) by with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 03 Dec 2018 21:46:37 +0000
Received: from ( []) by (8.15.2/8.15.2) with ESMTPS id wB3Lka0I015463 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=FAIL); Mon, 3 Dec 2018 21:46:37 GMT
Received: from ( by ( with Microsoft SMTP Server (TLS) id 15.0.1395.4; Mon, 3 Dec 2018 16:46:36 -0500
Received: from ([]) by ([]) with mapi id 15.00.1395.000; Mon, 3 Dec 2018 16:46:36 -0500
From: "Acee Lindem (acee)" <>
To: Pete Resnick <>, "" <>
CC: "" <>, "" <>, "" <>
Thread-Topic: Genart telechat review of draft-ietf-ospf-ospfv3-segment-routing-extensions-19
Thread-Index: AQHUiz0pMaH+VC1dX0GiD8BZ+Q47WaVtjNcA
Date: Mon, 3 Dec 2018 21:46:35 +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: <>
Subject: Re: [Gen-art] Genart telechat review of draft-ietf-ospf-ospfv3-segment-routing-extensions-19
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: "GEN-ART: General Area Review Team" <>
List-Unsubscribe: <>, <>
List-Archive: <>
List-Post: <>
List-Help: <>
List-Subscribe: <>, <>
X-List-Received-Date: Mon, 03 Dec 2018 21:46:41 -0000

Hi Pete, 

On 12/3/18, 2:19 PM, "Pete Resnick" <> wrote:

    Reviewer: Pete Resnick
    Review result: Ready with Issues
    I am the assigned Gen-ART reviewer for this draft. The General Area
    Review Team (Gen-ART) reviews all IETF documents being processed
    by the IESG for the IETF Chair. Please wait for direction from your
    document shepherd or AD before posting a new version of the draft.
    For more information, please see the FAQ at
    Document: draft-ietf-ospf-ospfv3-segment-routing-extensions-19
    Reviewer: Pete Resnick
    Review Date: 2018-12-03
    IETF LC End Date: 2018-11-16
    IESG Telechat date: 2018-12-06
    Summary: I think this document is ready, and I certainly don't want to stand in
    the way of it moving forward, but I do want to note the following issues I
    mentioned in my previous review. The document editor notes that similar sorts
    of things have been done in previous OSPF document without problems, but they
    still make me nervous. Thanks to the editor for quickly addressing all of the
    issues in my previous review.
    Major/minor issues:
    In 3.1:
          Length: Either 3 or 4 octets
          SID/Label: If length is set to 3, then the 20 rightmost bits
          represent a label.  If length is set to 4, then the value
          represents a 32-bit SID.
    This sort of mechanism worries me. The Length is not a length, but rather a
    flag. This means you can't have a general parsing implementation, as it would
    treat the field as a length and get the left-most 24 bits when the value is 3.
    Even if the implementation chooses the right-most 24 bits, it's only supposed
    to take the right-most 20 bits and mask off the extra 4 bits, which are not
    required to be zeroed. I understand that similar things have been done before
    without problems, but this seems like an implementation accident waiting to
    In 7.1 and 7.2:
    When the V-flag is set (making SID/Index/Label is a label), the value is in the
    low 20 bits of the first 3 bytes of the field (i.e., bits 4-23). As with the
    comment regarding 3.1, this seems like it has the potential for implementation
    problems. You could explicitly say to mask of bits 0-3 and 24-31 (since there
    is no requirement for producing implementations to clear those bits) and shift
    the value 8 bits to the right, but this just seems like a bad way to design
    this. That said, I again understand that similar things have been done before
    without problems.

While both you and I would have done it differently, the variable length SID encoding across the three LSR protocols (OSPFv2, OSPFv3, and IS-IS) has been implemented, deployed, and will not be changed during the IESG review (you'll note these SR protocol drafts have been in development for over 5 years). There is, however, an update to all three which clarifies the usage of the flags. See (for example):

Acee (Document Shepherd and LSR Co-chair) 

    Nits/editorial comments: