Re: [Lsr] [spring] FlexAlgo and Global Adj-SIDs
Peter Psenak <ppsenak@cisco.com> Tue, 05 March 2019 15:28 UTC
Return-Path: <ppsenak@cisco.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 472AD1275F3; Tue, 5 Mar 2019 07:28:35 -0800 (PST)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -14.501
X-Spam-Level:
X-Spam-Status: No, score=-14.501 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, RCVD_IN_DNSWL_HI=-5, SPF_PASS=-0.001, URIBL_BLOCKED=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 vQTUIafI4h8i; Tue, 5 Mar 2019 07:28:32 -0800 (PST)
Received: from aer-iport-2.cisco.com (aer-iport-2.cisco.com [173.38.203.52]) (using TLSv1.2 with cipher DHE-RSA-SEED-SHA (128/128 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id A15661200D8; Tue, 5 Mar 2019 07:28:31 -0800 (PST)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=cisco.com; i=@cisco.com; l=5593; q=dns/txt; s=iport; t=1551799713; x=1553009313; h=from:subject:to:references:cc:message-id:date: mime-version:in-reply-to:content-transfer-encoding; bh=Bno35MmmWZJkN5/NeKZqlyvb3QqVZnTN/LMvldu9mmE=; b=jU6RfXINMP2SaUASKo7I1OyP/ux++NNUyDcUOIa51n9XVPaIJfXd3hsF NnDCGrBq3b1ZdsbBH1WmOHFGIsgn+Xu1Cx5dI8BGYjtvT36YC63CJdKMi vQcPsrB39Lw50nbSP1wBYjB1HidaahpQftfhqDbO6dtYQzcGx9N6hKl5K w=;
X-IronPort-Anti-Spam-Filtered: true
X-IronPort-Anti-Spam-Result: A0AFAAA2lX5c/xbLJq1kGQEBAQEBAQEBAQEBAQcBAQEBAQGBUgMBAQEBAQsBgndxEieNAYx4mCEUgWcNGAuEA0YChE01CA0BAQMBAQMBAwJtHAyFSgEBAQMBAQE2NgsOAgsRBAEBAS4WESgIBg0GAgEBgx4BgW0ID6tUhDMChXMFBYEqAYs+gUA/gRAogmuDHgEBA4EmBQESAUUGhTUCiXgchx6SVQmHQ4EaihEGGYF0hWSDIogtkEGMcYFJAzNlcTMaCBsVO4JsghYXiF+FQD4DMI5Xgj4BAQ
X-IronPort-AV: E=Sophos;i="5.58,444,1544486400"; d="scan'208";a="10556778"
Received: from aer-iport-nat.cisco.com (HELO aer-core-2.cisco.com) ([173.38.203.22]) by aer-iport-2.cisco.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 05 Mar 2019 15:28:29 +0000
Received: from [10.147.24.27] ([10.147.24.27]) by aer-core-2.cisco.com (8.15.2/8.15.2) with ESMTP id x25FSSJF012151; Tue, 5 Mar 2019 15:28:28 GMT
From: Peter Psenak <ppsenak@cisco.com>
To: Alexander Vainshtein <Alexander.Vainshtein@ecitele.com>
References: <AM6PR03MB38302990EFFB7482B5C7F55F9D750@AM6PR03MB3830.eurprd03.prod.outlook.com> <20493a62-cf70-a182-900d-e55dd68f5149@cisco.com> <AM0PR03MB38286EFCFC0357EDB1D782679D770@AM0PR03MB3828.eurprd03.prod.outlook.com>
Cc: "lsr@ietf.org" <lsr@ietf.org>, "spring@ietf.org" <spring@ietf.org>, "draft-ietf-isis-segment-routing-extensions.all@ietf.org" <draft-ietf-isis-segment-routing-extensions.all@ietf.org>
Message-ID: <fc1b73eb-d57f-22f5-26c4-ecea60d2c2e3@cisco.com>
Date: Tue, 05 Mar 2019 16:28:28 +0100
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.14; rv:45.0) Gecko/20100101 Thunderbird/45.8.0
MIME-Version: 1.0
In-Reply-To: <AM0PR03MB38286EFCFC0357EDB1D782679D770@AM0PR03MB3828.eurprd03.prod.outlook.com>
Content-Type: text/plain; charset="windows-1252"; format="flowed"
Content-Transfer-Encoding: 7bit
X-Outbound-SMTP-Client: 10.147.24.27, [10.147.24.27]
X-Outbound-Node: aer-core-2.cisco.com
Archived-At: <https://mailarchive.ietf.org/arch/msg/lsr/WeQNL8nslpuEejCxp3FvJKY9tqY>
Subject: Re: [Lsr] [spring] FlexAlgo and Global Adj-SIDs
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: Tue, 05 Mar 2019 15:28:36 -0000
Hi Sasha, On 02/03/2019 18:57 , Alexander Vainshtein wrote: > Peter, > Lots of thanks for a prompt and hivhly informative response. > > It seems that per-FlexAlgo Adj-SIDs can be useful even if they are local. > The relevant use case could be a protected local Adj-SID that is used in > a SR-TE LSP that has been set up with some constraints in mind. These > constraints would be preserved when the protected adjacency in question > is UP, but could be violated when it fails and the shortest path to the > node at the remote end of adjacency is used. yes, this is a possible use case. This would require a new Algo specific Adj-SID sub-TLV to be defined. This could be done. thanks, Peter > > Local protected Adj-SIDs for sure have bern implemented, so this looks > like a more relevant use case than global adjacencies to me. > > What do you think? > > Regards, and lots of thanks in advance, > > Thumb typed by Sasha Vainshtein > > ------------------------------------------------------------------------ > *From:* Peter Psenak <ppsenak@cisco.com> > *Sent:* Thursday, February 28, 2019 9:56:49 PM > *To:* Alexander Vainshtein; > draft-ietf-isis-segment-routing-extensions@ietf.org > *Cc:* lsr@ietf.org; spring@ietf.org > *Subject:* Re: [spring] FlexAlgo and Global Adj-SIDs > > Hi Alexander, > > On 28/02/2019 19:19 , Alexander Vainshtein wrote: >> Dear colleagues, >> >> I have a question regarding global Adj-SIDs in >> draft-ietf-isis-segment-routing-extensions. >> >> >> >> Section 3.4 of RFC 8402 <https://tools.ietf.org/html/rfc8402> defines >> definition and handling of global Adj-SIDs. >> >> The relevant text is given below: >> >> >> >> <quote> >> >> Similarly, when using a global Adj-SID, a packet injected anywhere >> >> within the SR domain with a segment list {SNL}, where SNL is a global >> >> Adj-SID attached by node N to its adjacency over link L, will be >> >> forwarded along the shortest path to Nand then be switched by N, >> >> without any IP shortest-path consideration, towards link L. >> >> ... >> >> The use of global Adj-SID allows to reduce the size of the segment list >> >> When expressing a path at the cost of additional state (i.e., the global >> >> Adj-SID will be inserted by all routers within the area in their >> >> forwarding table). >> >> <end quote> >> >> >> >> The definition of the Adjacency Segment Identifier Sub-TLV in Section >> 2.2.1 of the draft matches the behavior defined in RFC 8402, i.e., it >> allows advertisement of global Adj-SIDs. >> >> These advertisements can be associated with a specific IGP adjacency >> and, in multi-topology scenarios, a specific topology. But it is not >> associated with any specific algorithm since the default algorithm for >> reaching the advertising node is implicitly assumed in full alignment >> with RFC 8402. >> >> >> >> My question is about the situation in which multiple algorithms are >> supported by the routers in the SR domain, so that each node advertises >> a dedicated Node SID for each of these algorithm. >> >> In this scenario, the operator can set up a SR-TE LSP that meets >> specific constraints (incorporated in one of these algorithms, see IGP >> Flexible Algorithm >> <https://tools.ietf.org/html/draft-ietf-lsr-flex-algo-01> draft) by >> using Node SIDs that have been advertised with the corresponding >> algorithm and local Adj-SIDs. However, global Adj-SIDs cannot be used >> (e.g., for reducing the label stack depth) in this situation. >> >> I wonder if the possibility to advertise global Adj-SID (that can be >> considered as replacing a combination of the Node SID of the advertising >> node and one of its local Adj-SIDs) as associated with a specific >> algorithm has ever been considered? > > to be honest, it has been not. > > The usage of the global Adj-SID has not been widely considered due to > the additional forwarding entries it requires on rest of the routers in > the area. Not sure if there are implementations of the global ADj-SID > out there. > > If you believe this is important, we can certainly addressed that in a > small draft. > > thanks, > Peter > > > > >> >> >> >> Regards, and lots of thanks in advance, >> >> Sasha >> >> >> >> Office: +972-39266302 >> >> Cell: +972-549266302 >> >> Email: Alexander.Vainshtein@ecitele.com >> >> >> >> >> ___________________________________________________________________________ >> >> This e-mail message is intended for the recipient only and contains >> information which is >> CONFIDENTIAL and which may be proprietary to ECI Telecom. If you have >> received this >> transmission in error, please inform us by e-mail, phone or fax, and >> then delete the original >> and all copies thereof. >> ___________________________________________________________________________ >> >> >> _______________________________________________ >> spring mailing list >> spring@ietf.org >> https://www.ietf.org/mailman/listinfo/spring >> > > > ___________________________________________________________________________ > > This e-mail message is intended for the recipient only and contains > information which is > CONFIDENTIAL and which may be proprietary to ECI Telecom. If you have > received this > transmission in error, please inform us by e-mail, phone or fax, and > then delete the original > and all copies thereof. > ___________________________________________________________________________
- [Lsr] FlexAlgo and Global Adj-SIDs Alexander Vainshtein
- Re: [Lsr] [spring] FlexAlgo and Global Adj-SIDs Peter Psenak
- Re: [Lsr] [spring] FlexAlgo and Global Adj-SIDs Alexander Vainshtein
- Re: [Lsr] [spring] FlexAlgo and Global Adj-SIDs Peter Psenak
- Re: [Lsr] [spring] FlexAlgo and Global Adj-SIDs Alexander Vainshtein
- Re: [Lsr] [spring] FlexAlgo and Global Adj-SIDs Peter Psenak
- Re: [Lsr] [spring] FlexAlgo and Global Adj-SIDs Les Ginsberg (ginsberg)
- Re: [Lsr] [spring] FlexAlgo and Global Adj-SIDs Alexander Vainshtein
- Re: [Lsr] [spring] FlexAlgo and Global Adj-SIDs Les Ginsberg (ginsberg)
- Re: [Lsr] [spring] FlexAlgo and Global Adj-SIDs Alexander Vainshtein