[Lsr] IPv6 Flow Label QOS marking support for 5-tuple ECMP / LAG / MLAG hash

Gyan Mishra <hayabusagsm@gmail.com> Mon, 30 November 2020 20:22 UTC

Return-Path: <hayabusagsm@gmail.com>
X-Original-To: lsr@ietfa.amsl.com
Delivered-To: lsr@ietfa.amsl.com
Received: from localhost (localhost []) by ietfa.amsl.com (Postfix) with ESMTP id 950EF3A0EF3 for <lsr@ietfa.amsl.com>; Mon, 30 Nov 2020 12:22:00 -0800 (PST)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -2.087
X-Spam-Status: No, score=-2.087 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_MESSAGE=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_REMOTE_IMAGE=0.01, 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 ([]) by localhost (ietfa.amsl.com []) (amavisd-new, port 10024) with ESMTP id 4WsmqRcKtnuJ for <lsr@ietfa.amsl.com>; Mon, 30 Nov 2020 12:21:58 -0800 (PST)
Received: from mail-pf1-x42e.google.com (mail-pf1-x42e.google.com [IPv6:2607:f8b0:4864:20::42e]) (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 981683A0E1D for <lsr@ietf.org>; Mon, 30 Nov 2020 12:21:58 -0800 (PST)
Received: by mail-pf1-x42e.google.com with SMTP id b10so9754660pfo.4 for <lsr@ietf.org>; Mon, 30 Nov 2020 12:21:58 -0800 (PST)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:from:date:message-id:subject:to; bh=AZcF1wG3RBcX2L9FiALHc9aJf2Fp2JOLnnszSy8WRIg=; b=uOIgFbqoiYDMAAhlYqvWosUvrobEXplJlwxHjnkyJMUsHeJKOhfGNpHI3BxYh+P4Ba nJJvEWiM962L/sZxJlgVzteE6PbWAcXKWH6AO/53qegI2uUHIYpXJfFwfHDBwBetwFP9 k5ApaISYOBthxNiet79eVG9+WNR4l1dUtGMurIeUlB1hM/UIbFkwyFOKllX+ZmcHjnc9 xHQOn5DAYyjXqeR/QWOrGNyQtvSEy5609KRl9xndi7VHXFT0n5suk+bs2Lc8u+WQ0SJc HIc94+hGB3UYJMi5S8H+RDv2FUvBPcuBrx1EQ9aAKdljRpYJTdvnzH4Smgxre41V8M6X mukw==
X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:from:date:message-id:subject:to; bh=AZcF1wG3RBcX2L9FiALHc9aJf2Fp2JOLnnszSy8WRIg=; b=FXKeIABSaVMQyUB9YUt0mxWgnxM7JuRrahUMOI6jkP1mQg9cG3r8H6HDyGDiklEl/1 OOMCrx1sxflmmTX/PxDkh2VrLMiPhZ2+R3VsQxTZTcD1U9Vc5frhU7B4JKJNLlf3jwnt Hm75xOZpeM371wub3tnLt1Hm4t49d0e1HhW+P4LtXLYq8yRhzeLaD+DEsUMR1YVtLO/E bEXlTBDHUy2nCO/T3Rnq98Sub+qCfgi/rbasEiTLRCRMdSpw8FSd27Vh8z8WoxxGHotm C1eXNEBELUiitgSR9TaxYC50UgktFSDQQBdoVD3Pn4mStioZqqG9kv2xHJ6kKfhz4ysc fe5A==
X-Gm-Message-State: AOAM533J1wcnQzhgHoJmkMMf/383VSEQbZEgHIy4ppKfwLzb3DQFddw+ WUCVi8AomvjXdmbNot6dBHjO/kLnVEpgyLTqiBzHaBCoe9Q=
X-Google-Smtp-Source: ABdhPJzFOhBMduaQp4tSagBDszFSdgCGqoNwzFvoKwY9nv68IQPKmdYS+B97zgw52vr5/jrnQ+/kVw3lffnzyM0PNj4=
X-Received: by 2002:a65:4241:: with SMTP id d1mr18988563pgq.18.1606767717574; Mon, 30 Nov 2020 12:21:57 -0800 (PST)
MIME-Version: 1.0
From: Gyan Mishra <hayabusagsm@gmail.com>
Date: Mon, 30 Nov 2020 15:21:47 -0500
Message-ID: <CABNhwV3FGcEarfQH-SVuCCdgkNJnODwRrLSK3XhefQkt1Pws0A@mail.gmail.com>
To: lsr <lsr@ietf.org>
Content-Type: multipart/alternative; boundary="0000000000000af2e305b558c3a6"
Archived-At: <https://mailarchive.ietf.org/arch/msg/lsr/mdQjZKHUguPoj1KrXlwk1N_xcD8>
Subject: [Lsr] IPv6 Flow Label QOS marking support for 5-tuple ECMP / LAG / MLAG hash
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: Mon, 30 Nov 2020 20:22:01 -0000

Dear LSR WG experts,

Does anyone know if vendors have started or plan to start supporting IPv6
flow label 5-tuple dscp marking for ECMP hashing.

IPv6 flow label support for ECMP


IPv4 has traditionally always utilized recommended BCP of flow based load
balancing due to issues related to out of order and reordering of packets.
Although per packet load balancing is supported by most vendors it is not
recommended due to forwarding plane impact.

This IPv6 flow label feature of 5-tuple hash provides significant
advantages for operators much needed ECMP load balancing entropy as compare
to traditional “flow or session” based load balancing which is the case as
well with MPLS entropy label RFC 6790 load balancing contrasted below.

IPv6 flow label has significant  benefits for operators deploying  SRv6
which utilizes the IPv6 data plane to now have “native” built in ECMP
entropy as part of the protocol as compare to its predecessor IPv4.

This gives SRv6 another significant edge over MPLS predecessor.

Excerpt from RFC 6437:

      Forwarding nodes such as routers and load distributors MUST NOT
      depend only on Flow Label values being uniformly distributed.  In
      any usage such as a hash key for load distribution, the Flow Label
      bits MUST be combined at least with bits from other sources within
      the packet, so as to produce a constant hash value for each flow
      and a suitable distribution of hash values across flows.
      Typically, the other fields used will be some or all components of
      the usual 5-tuple.  In this way, load distribution will still
      occur even if the Flow Label values are poorly distributed.

   Although uniformly distributed flow label values are recommended
   below, and will always be helpful for load distribution, it is unsafe
   to assume their presence in the general case, and the use case needs
   to work even if the flow label value is zero.

   As a general practice, packet flows should not be reordered, and the
   use of the Flow Label field does not affect this.  In particular, a
   Flow label value of zero does not imply that reordering is

Below comparison of IPv6 flow label benefits over MPLS entropy label:

! MPLS Entropy label


As a comparison to MPLS entropy label, the mpls entropy label reduces
the control plane label binding and LFIB forwarding plane data
structure by not having a per ECMP path label allocation per FEC by
adding an additional entropy label to the label stack.

However MPLS entropy label is still uses the traditional flow or
session based load balancing algorithm which results in

uneven load balancing.

Kind Regards




*Gyan Mishra*

*Network Solutions A**rchitect *

*M 301 502-134713101 Columbia Pike *Silver Spring, MD