From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from korolev.univ-paris7.fr (korolev.univ-paris7.fr [IPv6:2001:660:3301:8000::1:2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.bufferbloat.net (Postfix) with ESMTPS id 053D83CB37 for ; Sat, 29 Oct 2022 05:15:31 -0400 (EDT) Received: from potemkin.univ-paris7.fr (potemkin.univ-paris7.fr [IPv6:2001:660:3301:8000::1:1]) by korolev.univ-paris7.fr (8.14.4/8.14.4/relay1/82085) with ESMTP id 29T9FTZ7011534 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO); Sat, 29 Oct 2022 11:15:29 +0200 Received: from mailhub.math.univ-paris-diderot.fr (mailhub.math.univ-paris-diderot.fr [81.194.30.253]) by potemkin.univ-paris7.fr (8.14.4/8.14.4/relay2/82085) with ESMTP id 29T9FTWT008917; Sat, 29 Oct 2022 11:15:29 +0200 Received: from mailhub.math.univ-paris-diderot.fr (localhost [127.0.0.1]) by mailhub.math.univ-paris-diderot.fr (Postfix) with ESMTP id 4ED45ED4B4; Sat, 29 Oct 2022 11:15:29 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=irif.fr; h= content-type:content-type:mime-version:user-agent:references :in-reply-to:subject:subject:from:from:message-id:date:date :received:received; s=dkim-irif; t=1667034927; x=1667898928; bh= FRvg4OXewdV7ibj/0bfqiiupgd6th5/3VkgSgxVSKjU=; b=pJbvlixt+FLz6axT SPinyxhSCvQvdXuLwEQMw0jLwEjXVWkJ/zv7KrbleWbqHWO5N71+gpu45DtRwl7/ BG4hgBq22ebulNQ9bCf0oVUxi5t4nWd35pQ0K72k1VDLBbUgygeXv5vLHFwQeAj2 qxOoLobvD3wZ1E4IZijhlZkAaCtb/DEZSCN0V02ICmNhHk45MF3nsxtRpTAGQKt4 Mmu8HNH9rwXhw3yA/el/UrwyzWogCs1f6cuYOWDgCeA7wcaLRByknoSUeMEWj95E uuZ0TWyAMPn7GpUuk1Sz8xuj8FMax4VrVL+Ld+9VWld67DFRd4jhRVRvgLXG2m8N bMxCkg== X-Virus-Scanned: amavisd-new at math.univ-paris-diderot.fr Received: from mailhub.math.univ-paris-diderot.fr ([127.0.0.1]) by mailhub.math.univ-paris-diderot.fr (mailhub.math.univ-paris-diderot.fr [127.0.0.1]) (amavisd-new, port 10023) with ESMTP id WLwg-ScH_pTN; Sat, 29 Oct 2022 11:15:27 +0200 (CEST) Received: from pirx.irif.fr (unknown [78.194.40.74]) (Authenticated sender: jch) by mailhub.math.univ-paris-diderot.fr (Postfix) with ESMTPSA id E346BED4AF; Sat, 29 Oct 2022 11:15:27 +0200 (CEST) Date: Sat, 29 Oct 2022 11:15:27 +0200 Message-ID: <87leozuh1s.wl-jch@irif.fr> From: Juliusz Chroboczek To: Dave Taht Cc: Herbert Wolverson , libreqos@lists.bufferbloat.net In-Reply-To: References: <87sfj7vczj.wl-jch@irif.fr> User-Agent: Wanderlust/2.15.9 (Almost Unreal) Emacs/28.1 Mule/6.0 MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") Content-Type: text/plain; charset=US-ASCII X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.2.7 (korolev.univ-paris7.fr [IPv6:2001:660:3301:8000::1:2]); Sat, 29 Oct 2022 11:15:29 +0200 (CEST) X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.2.7 (potemkin.univ-paris7.fr [194.254.61.141]); Sat, 29 Oct 2022 11:15:29 +0200 (CEST) X-Miltered: at korolev with ID 635CEF31.000 by Joe's j-chkmail (http : // j-chkmail dot ensmp dot fr)! X-Miltered: at potemkin with ID 635CEF31.001 by Joe's j-chkmail (http : // j-chkmail dot ensmp dot fr)! X-j-chkmail-Enveloppe: 635CEF31.000 from potemkin.univ-paris7.fr/potemkin.univ-paris7.fr/null/potemkin.univ-paris7.fr/ X-j-chkmail-Enveloppe: 635CEF31.001 from mailhub.math.univ-paris-diderot.fr/mailhub.math.univ-paris-diderot.fr/null/mailhub.math.univ-paris-diderot.fr/ X-j-chkmail-Score: MSGID : 635CEF31.000 on korolev.univ-paris7.fr : j-chkmail score : . : R=. U=. O=. B=0.000 -> S=0.000 X-j-chkmail-Score: MSGID : 635CEF31.001 on potemkin.univ-paris7.fr : j-chkmail score : . : R=. U=. O=. B=0.000 -> S=0.000 X-j-chkmail-Status: Ham X-j-chkmail-Status: Ham Subject: Re: [LibreQoS] routing protocols and daemons X-BeenThere: libreqos@lists.bufferbloat.net X-Mailman-Version: 2.1.20 Precedence: list List-Id: Many ISPs need the kinds of quality shaping cake can do List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 29 Oct 2022 09:15:32 -0000 > our toasts to the builders of Notre-Dame. ...which then burnt down :-/ > Dijkstra's algorithm remains a very natural approach to mapping a > graph I'm not sure what that means. Dijkstra's is a shortest path algorithm, it's not in the business of mapping. I guess the author meant that representing a graph as an adjacency list (the LSDB) is natural, which is certainly true, but in no way specific to OSPF. > I don't suppose you have ever had any ideas to how to improve things? Modern OSPF and IS-IS have pretty much reached a local optimum: all the low-hanging fruit has been picked, I doubt there's much that can still be done to improve them without a complete redesign. Well-implemented OSPF and IS-IS work beautifully in a well-administered network, any other protocol is going to converge slower and give less visibility into the network. On the other hand, OSPF is extremely fragile in the presence of bad implementation. If two routers have the same id, OSPF is going to create routing pathologies. If a router corrupts its LSDB (for example due to bad RAM), OSPF will create routing pathologies which will only go away once the faulty LSA expires (30 minutes worst case). If a router runs out of memory for its LSDB, it needs to stop participating in the protocol, lest it cause routing pathologies (IS-IS has the overload bit to deal with this case, which causes the router to become a stub router). Compare this with distance vector, where a corrupt routing table entry will only interfere with the traffic to that particular destination, and where it is perfectly correct to run with a partial routing table. OSPF also requires a skilled administrator. Splitting a network into areas without causing suboptimal routing takes significant skill, route filtering can only happen on area boundaries, and there are multiple different ways of redistributing routes into OSPF (external LSAs). In my opinion, you want to be running OSPF in parts of your network that are implemented with reliable gear and are managed by a competent administrator, but you'll prefer a modern distance-vector protocol (somebody mentioned Babel) where the hardware is cheap and the administator is busy with other things. Fortunately, due to the flexibility of route redistribution in distance-vector protocols, you can do both: a stable backbone using OSPF, and unadministered Babel bits at the edges. -- Juliusz