From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Ahern Subject: Re: [PATCH RFC net-next 0/7] net/ipv6: Add support for path selection using hash of 5-tuple Date: Wed, 14 Feb 2018 15:56:25 -0700 Message-ID: <9fa3779b-7dba-3819-02d0-2009101a81fb@gmail.com> References: <20180213000602.12150-1-dsahern@gmail.com> <20180213124205.GB17908@splinter> <8373febc-682f-5b8a-b9e7-9ef33f5f24ca@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Cc: Ido Schimmel , Linux Netdev List , Roopa Prabhu , Nikolay Aleksandrov , Ido Schimmel , Tom Herbert To: Or Gerlitz Return-path: Received: from mail-pl0-f44.google.com ([209.85.160.44]:35995 "EHLO mail-pl0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1031852AbeBNW41 (ORCPT ); Wed, 14 Feb 2018 17:56:27 -0500 Received: by mail-pl0-f44.google.com with SMTP id v3so9382435plg.3 for ; Wed, 14 Feb 2018 14:56:27 -0800 (PST) In-Reply-To: Content-Language: en-US Sender: netdev-owner@vger.kernel.org List-ID: On 2/14/18 3:45 PM, Or Gerlitz wrote: > On Tue, Feb 13, 2018 at 5:21 PM, David Ahern wrote: >> On 2/13/18 5:42 AM, Ido Schimmel wrote: >>> On Tue, Feb 13, 2018 at 01:03:14PM +0200, Or Gerlitz wrote: >>>> On Tue, Feb 13, 2018 at 2:05 AM, David Ahern wrote: >>>>> Hardware supports multipath selection using the standard L4 5-tuple >>>>> instead of just L3 and the flow label. In addition, some network >>>>> operators prefer IPv6 path selection to use the 5-tuple. >>>> >>>> The HW supports using flow label and AFAIK that is the preferred approach >>>> by the community (?) >>>> >>>>> To that end, add support to IPv6 for multipath hash policy >>>> >>>> so a question comes up if/what are the disadvantaged >>>> to support 5-tuple. E.g Tom was commenting that such DPI is problematic >>>> when multiple IPv6 header extensions are used. >> >> Pros and cons to both approaches (L3 only or L4). We (Cumulus Networks) >> use L4 5-tuple hash for both IPv4 and IPv6. When I asked around various >> experts all of them gave me a puzzled look as to why I was asking the >> question. Basically, the unanimous response was of course it is an L4 hash. > > how the various systems you are dealing with do with traffic that involves > ipv6 extension headers? what about environments with GRE? in ipv4 GRE > fabrics are just broken for ECMP, in ipv6 they can fly with flow label but > will crash again with L4 hash. > If you like your ecmp hash algorithm, you can keep your ecmp hash algorithm. This gives users a choice; it is not a requirement to move from L3 only to L4. Further, this makes IPv6 on par with IPv4 with a choice between L3 and L4 and allows users to decide what works best for them.