IETF Logo Mail Archive

Re: [Lsr] Question about OSPF (transit area routing loop)

Sergey SHpenkov <sergey.v.shpenkov@gmail.com> Wed, 11 March 2020 20:34 UTC

Return-Path: <sergey.v.shpenkov@gmail.com>
X-Original-To: lsr@ietfa.amsl.com
Delivered-To: lsr@ietfa.amsl.com
Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id 5F0B03A0BBC for <lsr@ietfa.amsl.com>; Wed, 11 Mar 2020 13:34:06 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -2.096
X-Spam-Level:
X-Spam-Status: No, score=-2.096 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, FREEMAIL_FROM=0.001, HTML_IMAGE_RATIO_06=0.001, HTML_MESSAGE=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, URIBL_BLOCKED=0.001] autolearn=ham autolearn_force=no
Authentication-Results: ietfa.amsl.com (amavisd-new); dkim=pass (2048-bit key) header.d=gmail.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 Y2vWdDB4Sd8F for <lsr@ietfa.amsl.com>; Wed, 11 Mar 2020 13:34:04 -0700 (PDT)
Received: from mail-il1-x132.google.com (mail-il1-x132.google.com [IPv6:2607:f8b0:4864:20::132]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id 01A6A3A0A4F for <lsr@ietf.org>; Wed, 11 Mar 2020 13:34:03 -0700 (PDT)
Received: by mail-il1-x132.google.com with SMTP id c8so3388201ilm.1 for <lsr@ietf.org>; Wed, 11 Mar 2020 13:34:03 -0700 (PDT)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=M0DZ//7EDcUD5ML6i77dyECMajj4bboM+aYaTK7VZxU=; b=h/0gCDu7KCbJ9ZtkrJdeXYr1kT4yMZgwm5CekYN/gk+hEBKbXfckFc6jpSTlkmo2Ci 9qZP8m6TSdu8zKXqowgupuykWg4cxom3H/ZAnyfBgUjmjLfP56kXQXgIrA/8CitLCjck epyKsuKdyDzCHqNRL3J2Utzv64/tMBGeuLcdRXlODpNgOCeg2TpqH/oaZ5rlBTgXzVfg z1kjuFqpryWwndd/stGiMTAgHxpr6VYEjqMe8xY/VlG+nVnLPl+C+zU9XObjCEWi0VjI MLI1ZGJE8+YqHrovYk5cCvzQQEGIpCE+u6+emvVV0uVFinH5wBpdLtXXtielQx1T2qmv CAcg==
X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=M0DZ//7EDcUD5ML6i77dyECMajj4bboM+aYaTK7VZxU=; b=Za+NY93MUz1iWmmSUNWAml1zTHwbD0lyu42RxeIvYHwjVJbxwZxDG5UUkYZADN6Kxf ziGMffK+7CxI45s9fBbjpDwLGeD3hEsJjq1rtNdfDSobhtpRk/y4UzTuy7j9Lytul1YD 7eZHvX+8hzcgrRpZqTgmgHR7vujGCXcEnYk5xJY4sQVRMF9od+zQYdE8C4HGXcybszii C089wmM3PDPHygIzweOr9K81prNK0iBZEnrwo2ktyuXvmTxqRSdlJuAqjkOV1WgXOpqC BIZJn4SrWemBpXKT11IKjRsC8Qtxp7I0B/IKhr+t14knC8Im+THDVqgCcHZriEUcJISb t9Mw==
X-Gm-Message-State: ANhLgQ2Y8nxFKEqBIxZaIF98U4ic4Z1jkTG5nCPJK9NuUT3+RpLOkejX s1u1ARkLlpZUgxzrByersIhTtf7MxwsLBhmQGNQ0Z2SB
X-Google-Smtp-Source: ADFU+vtJ6j7z4AxNEcMC2aB5c12MH53923wbd02t9ZsOuB2bYilaTW7MQbIt1LLugIeGEGYQCtMk7Gt2+94hOL4WMy8=
X-Received: by 2002:a92:2c0b:: with SMTP id t11mr4511445ile.154.1583958842383; Wed, 11 Mar 2020 13:34:02 -0700 (PDT)
MIME-Version: 1.0
References: <CAD4HJpqOJC0DSeb_nrPOD3=bofRLgWzFhRrzXMnrtZRr0XNjsw@mail.gmail.com> <DDD60A40-5095-4973-B90D-556F4AC0B1F1@cisco.com> <CAD4HJppxJF9W6jXFRPiFy_RyZvAUiNCayBPqpy2jqrX7wGGcvw@mail.gmail.com> <011601d5f792$3e1c0fd0$ba542f70$@org.cn>
In-Reply-To: <011601d5f792$3e1c0fd0$ba542f70$@org.cn>
From: Sergey SHpenkov <sergey.v.shpenkov@gmail.com>
Date: Wed, 11 Mar 2020 23:31:24 +0300
Message-ID: <CAD4HJporCs1Qn4y=Aj0FM_SCHNWjaFek-5DZ4ux54pN+Sk1Vqw@mail.gmail.com>
To: Aijun Wang <wangaijun@tsinghua.org.cn>
Cc: lsr@ietf.org
Content-Type: multipart/mixed; boundary="00000000000024fd0a05a09a28d7"
Archived-At: <https://mailarchive.ietf.org/arch/msg/lsr/rPZK_euJTkK0TcRhnI-l1sehxRA>
Subject: Re: [Lsr] Question about OSPF (transit area routing loop)
X-BeenThere: lsr@ietf.org
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: Link State Routing Working Group <lsr.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/lsr>, <mailto:lsr-request@ietf.org?subject=unsubscribe>
List-Archive: <https://mailarchive.ietf.org/arch/browse/lsr/>
List-Post: <mailto:lsr@ietf.org>
List-Help: <mailto:lsr-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/lsr>, <mailto:lsr-request@ietf.org?subject=subscribe>
X-List-Received-Date: Wed, 11 Mar 2020 20:34:14 -0000

Hi Aijun,


ср, 11 мар. 2020 г. в 13:46, Aijun Wang <wangaijun@tsinghua.org.cn>:

> Hi, Sergey:
>
>
>
> If so, ABR-3 should also receive this SumLSA-4 for the ASBR(with cost
> 300), and then prefer the path via ABR-2 to reach ASBR(with cost 20).
>
> Then there will be no loop then?
>
>
no, because sumLSA-4 in step 16.3 will be less preferred for ABR_3 than
previously calculated using the Dijkstra algorithm (with cost 3)

>
>
> Or, how many SumLAS-4 will be advertised by ABR-1? If it selects and
> advertises only one (3 or 300), then the loop will not be emerged.
>
> Currently, it seems it advertises this SumLAS-4 with the cost 300 to RT_1
> and with the cost 3 to ABR-3?
>
>
>
only one with a cost of 300

>
>
> Best Regards.
>
>
>
> Aijun Wang
>
> China Telecom
>
>
>
> *发件人:* lsr-bounces@ietf.org [mailto:lsr-bounces@ietf.org] *代表 *Sergey
> SHpenkov
> *发送时间:* 2020年2月26日 15:20
> *收件人:* lsr@ietf.org
> *主题:* Re: [Lsr] Question about OSPF (transit area routing loop)
>
>
>
> Acee,
>
>
>
> Because ABR_1 creates SumLSA-4 for the ASBR not from the backbone
> area. The cost of SumLSA-4 for ASBR is 300.
>
>
>
> Thanks,
>
> Sergey
>
>
>
> вт, 25 февр. 2020 г. в 22:44, Acee Lindem (acee) <acee@cisco.com>:
>
> Hi Sergey,
>
> I don’t see why RT_1 wouldn’t go through ABR_1 to get to the ASBR.
>
> Thanks,
>
> Acee
>
>
>
> *From: *Lsr <lsr-bounces@ietf.org> on behalf of Sergey SHpenkov <
> sergey.v.shpenkov@gmail.com>
> *Date: *Tuesday, February 25, 2020 at 2:38 PM
> *To: *"lsr@ietf..org <lsr@ietf.org>" <lsr@ietf.org>
> *Subject: *[Lsr] Question about OSPF (transit area routing loop)
>
>
>
> Hi,
>
> In section 16.3 of the OSPF RFC 2328 standard, it is stated that all ABR
> routers
>
> connected to a transit area are required to check the sumLSA contained
> within
>
> this area in order to possibly improve the intra-area and inter-area
> backbone routes
>
> for themselves.
>
>
> See the picture:
>
> The RT_1 and ABR_3 routers will use different paths to the ASBR router:
>
> ABR_3 -> RT_1 -> ABR_1 -> ASBR = cost 3
> RT_1 -> ABR_3 -> ABR_2 -> ASBR = cost 21
>
> route loop between RT_1 and ABR_3
>
> Please explain this situation
>
> Thanks,
> Sergey
>
>
>
>

v2.23.0 | Report a Bug | By Email