Re: [Lsr] WG Adoption Call for "IGP Flexible Algorithms (Flex-Algorithm) In IP Networks" - draft-bonica-lsr-ip-flexalgo-01

"Dongjie (Jimmy)" <jie.dong@huawei.com> Wed, 09 December 2020 12:52 UTC

Return-Path: <jie.dong@huawei.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 6FC073A1261 for <lsr@ietfa.amsl.com>; Wed, 9 Dec 2020 04:52:10 -0800 (PST)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -1.9
X-Spam-Level:
X-Spam-Status: No, score=-1.9 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, URIBL_BLOCKED=0.001] autolearn=ham autolearn_force=no
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 qyn5o3A4o6Yn for <lsr@ietfa.amsl.com>; Wed, 9 Dec 2020 04:52:08 -0800 (PST)
Received: from frasgout.his.huawei.com (frasgout.his.huawei.com [185.176.79.56]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id 9F10A3A126C for <lsr@ietf.org>; Wed, 9 Dec 2020 04:52:08 -0800 (PST)
Received: from fraeml738-chm.china.huawei.com (unknown [172.18.147.207]) by frasgout.his.huawei.com (SkyGuard) with ESMTP id 4CrcMX0nDtz67FX4 for <lsr@ietf.org>; Wed, 9 Dec 2020 20:50:00 +0800 (CST)
Received: from dggeme751-chm.china.huawei.com (10.3.19.97) by fraeml738-chm.china.huawei.com (10.206.15.219) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256) id 15.1.2106.2; Wed, 9 Dec 2020 13:52:05 +0100
Received: from dggeme754-chm.china.huawei.com (10.3.19.100) by dggeme751-chm.china.huawei.com (10.3.19.97) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.1913.5; Wed, 9 Dec 2020 20:52:04 +0800
Received: from dggeme754-chm.china.huawei.com ([10.6.80.77]) by dggeme754-chm.china.huawei.com ([10.6.80.77]) with mapi id 15.01.1913.007; Wed, 9 Dec 2020 20:52:03 +0800
From: "Dongjie (Jimmy)" <jie.dong@huawei.com>
To: Peter Psenak <ppsenak@cisco.com>, "Acee Lindem (acee)" <acee=40cisco.com@dmarc.ietf.org>, lsr <lsr@ietf.org>
Thread-Topic: [Lsr] WG Adoption Call for "IGP Flexible Algorithms (Flex-Algorithm) In IP Networks" - draft-bonica-lsr-ip-flexalgo-01
Thread-Index: AQHWyCa69SgvuXvqQUSruOMjcUOnRanukOqg//+JYYCAAJ+NMA==
Date: Wed, 9 Dec 2020 12:52:03 +0000
Message-ID: <c779c9da19264b718effd3d0442c8616@huawei.com>
References: <777B2AC4-CACF-4AB0-BFC7-B0CFFA881EEB@cisco.com> <169b063524dc4420b37016d2428fc85c@huawei.com> <29d3d16a-237d-e657-e84c-c74a1e5a841f@cisco.com>
In-Reply-To: <29d3d16a-237d-e657-e84c-c74a1e5a841f@cisco.com>
Accept-Language: en-US, zh-CN
Content-Language: zh-CN
X-MS-Has-Attach:
X-MS-TNEF-Correlator:
x-originating-ip: [10.45.188.116]
Content-Type: text/plain; charset="utf-8"
Content-Transfer-Encoding: base64
MIME-Version: 1.0
X-CFilter-Loop: Reflected
Archived-At: <https://mailarchive.ietf.org/arch/msg/lsr/ARpLGv73fl2g7VG9b7M4LQ1ktpk>
Subject: Re: [Lsr] WG Adoption Call for "IGP Flexible Algorithms (Flex-Algorithm) In IP Networks" - draft-bonica-lsr-ip-flexalgo-01
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, 09 Dec 2020 12:52:10 -0000

Hi Peter,

> -----Original Message-----
> From: Peter Psenak [mailto:ppsenak@cisco.com]
> Sent: Wednesday, December 9, 2020 6:45 PM
> To: Dongjie (Jimmy) <jie.dong@huawei.com>om>; Acee Lindem (acee)
> <acee=40cisco.com@dmarc.ietf.org>rg>; lsr <lsr@ietf.org>
> Subject: Re: [Lsr] WG Adoption Call for "IGP Flexible Algorithms
> (Flex-Algorithm) In IP Networks" - draft-bonica-lsr-ip-flexalgo-01
> 
> Jimmy,
> 
> On 09/12/2020 11:10, Dongjie (Jimmy) wrote:
> > Hi authors,
> >
> > Here is one comment following the previous discussion on the mail list
> > and the IETF meeting.
> >
> > The IP Algorithm TLV is defined to advertise the IP Flex-Algorithm
> > participation information, there is no separate TLV for IPv4 or IPv6
> > Flex-Algo participation.
> 
> the draft clearly says:
> 
>     "The IP Flex-Algorithm participation advertised in ISIS IP Algorithm
>     Sub-TLV is topology independent."

This does not answer my question. 

Section 7 gives the rules of IP Flex-Algo Path calculation: 

" IP Flex-Algorithm application only considers participating nodes during the Flex-Algorithm calculation.  When computing paths for a given Flex-Algorithm, all nodes that do not advertise participation for IP Flex-Algorithm, as described in Section 5, MUST be pruned from the topology. "

From IP Algorithm TLV, one cannot tell whether a node participates in Flex-Algo 128 for IPv4, IPv6 or both. This would cause the problem described below: 

When one node uses IP Flex-Algo participation to compute a path for an IPv6 address advertised with Flex-Algo 128, it will not prune the nodes which participate in Flex-Algo 128 for IPv4 only from the topology. Thus IPv6 packets following that path may get dropped on nodes which participates in Flex-Algo 128 for IPv4 only.

> 
> > If some nodes participate in IPv4 Flex-Algo 128, and some of these
> > nodes participate in IPv6 Flex-Algo 128, how to ensure that the path
> > computed for IPv6 Flex-Algo will not use the nodes which only
> > participate in IPv4 Flex-Algo 128?
> 
> there is no such thing as "IPv4 Flex-Algo 128" or "IPv6 Flex-Algo 128".
> There is only algo 128.

Agree that Flex-Algo 128 is application or data plane agnostic, and as we discussed the same Flex-Algo can be used with both IPv4 and IPv6 (maybe also for SR-MPLS, SRv6). These terms are used as shorthand of "Flex-Algo 128 used with IPv4 or IPv6"

> You are mixing data plane support with algo participation.

I understand Flex-Algo definition is application agnostic, and Flex-Algo participation is application specific, it is just not clear to me whether IPv4 and IPv6 can be treated as one application.

> If you want an algo to only include nodes that supports specific data plane,
> you would need to define a specific algo for it.

This IMO contradicts with the base concept: Flex-Algo definition is application (or data plane) agnostic. 

Best regards,
Jie

> 
> thanks,
> Peter
> 
> 
> >
> > Best regards,
> >
> > Jie
> >
> > *From:*Lsr [mailto:lsr-bounces@ietf.org] *On Behalf Of *Acee Lindem
> > (acee)
> > *Sent:* Wednesday, December 2, 2020 5:13 AM
> > *To:* lsr <lsr@ietf.org>
> > *Subject:* [Lsr] WG Adoption Call for "IGP Flexible Algorithms
> > (Flex-Algorithm) In IP Networks" - draft-bonica-lsr-ip-flexalgo-01
> >
> > This IP Flex Algorithm draft generated quite a bit of discussion on
> > use cases and deployment prior to IETF 109 and there was generally
> > support for WG adoption. This begins a two week WG adoption call.
> > Please indicate your support or objection to WG adoption on this list
> > prior to
> > 12:00 AM UTC on December 16^th , 2020. Also, review comments are
> > certainly welcome.
> >
> > Thanks,
> >
> > Acee
> >