Re: [Lsr] Flooding Topology Computation Algorithm - draft-cc-lsr-flooding-reduction-08 Working Group Adoption Call

Gyan Mishra <> Sun, 24 May 2020 22:29 UTC

Return-Path: <>
Received: from localhost (localhost []) by (Postfix) with ESMTP id 3AC423A0B59 for <>; Sun, 24 May 2020 15:29:53 -0700 (PDT)
X-Virus-Scanned: amavisd-new at
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: (amavisd-new); dkim=pass (2048-bit key)
Received: from ([]) by localhost ( []) (amavisd-new, port 10024) with ESMTP id 4q4_Rdi2SDpV for <>; Sun, 24 May 2020 15:29:50 -0700 (PDT)
Received: from ( [IPv6:2607:f8b0:4864:20::d34]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by (Postfix) with ESMTPS id A01CF3A0B52 for <>; Sun, 24 May 2020 15:29:50 -0700 (PDT)
Received: by with SMTP id p20so3589793iop.11 for <>; Sun, 24 May 2020 15:29:50 -0700 (PDT)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=lGZ/mWWRuaHjMcfiR6rtSE95W/vCFMQuavbtdIGOo4c=; b=fQ6/N2cD9MJBRTVR1XJXXHYHWiRo0gXfEXFQK8GEd5WM3AO7vV1uebmxz1y6Tw830n GgEvaAwkze6GrRd6A5JJOQIOtrwkTN3CgAXUl8ObyENcnPY0cwhiQ6Vfy7jrMdzU+5w9 fnPO4AXTg3Ec9YsL+D8bkqhMlEBpoNoy/YJl+5tz3WeeZ9TB45nldRvk+t+UFvXW2JxE DmLN16UkT0gGOTyQ7OAy0oxIRBpomGgrZ3oHIc0bRLHM19vRBDNEDOx5aJ03+LnUd1KW HKrwHKlSz7b448GBnv5P+gX0Y0toetNLh4gnmS+QktIqNiXmUvYWz9KtTN4lqnUSJuxF aGJg==
X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=lGZ/mWWRuaHjMcfiR6rtSE95W/vCFMQuavbtdIGOo4c=; b=komYAMI38hGQrOkmcXaD8yYEEE2+ZUC7Y5qrpuOyeo5lRagpYGx93SuvRWYqrFnkHP m0hQlifRjbIR13ZbjbDIAEJe9BrUPxHrT10/PD6HjO3lcaolJ3xTITgC3YtLItbkT7eN 2sqt9BrnVsIVq5sM9wi22YjZZcM3Jrk11qkPgPxx3Diag8XzH1b9wbLvdznfRqy6Da6V uzykR9WlBBuwC+7wcj2xjP/qQaYsQ8qkls3BgWGnQ5hDbnce6a+WifP8Q0ZkvYj7OFbW Yj7E2klGZx27ghDQFNPfhfwdNtdjogPdgRXBcbWC5I3oPxYwX7LpPb5m2towJq6SdsXp R15g==
X-Gm-Message-State: AOAM5307biJcNioOMzc4rONlMnp37q1w1I36dmRd1h880kiSM5I6sAUw AAJ8ap+UUGOBYUHjqxASqB0b9FbWIRQsPM6dRTI=
X-Google-Smtp-Source: ABdhPJw7oooNOgDG2OSPHqA5N/2AB6kuW7HH5bx1bPK3cOapzqlV2DZaG0OW4QW6W2NQ40viQ9KihxoiWgix0kdPKWM=
X-Received: by 2002:a5d:914d:: with SMTP id y13mr964376ioq.48.1590359389835; Sun, 24 May 2020 15:29:49 -0700 (PDT)
MIME-Version: 1.0
References: <> <> <> <> <> <> <> <> <> <> <> <> <> <> <> <> <>
In-Reply-To: <>
From: Gyan Mishra <>
Date: Sun, 24 May 2020 18:29:39 -0400
Message-ID: <>
To: Sarah Chen <>,
Cc: "Acee Lindem (acee)" <>, Huaimo Chen <>, "" <>
Content-Type: multipart/alternative; boundary="0000000000007f182f05a66c66be"
Archived-At: <>
Subject: Re: [Lsr] Flooding Topology Computation Algorithm - draft-cc-lsr-flooding-reduction-08 Working Group Adoption Call
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: Link State Routing Working Group <>
List-Unsubscribe: <>, <>
List-Archive: <>
List-Post: <>
List-Help: <>
List-Subscribe: <>, <>
X-List-Received-Date: Sun, 24 May 2020 22:29:53 -0000

Hi Acee

Do you know if the dynamic flooding algorithm discussed during interim ietf
by Sarah and Toni is the same as the one implemented by Cisco on Nexus
platform or is Cisco’s Dynamic flooding a proprietary implementation?

Cisco’s flooding algorithm does seem almost identical to dynamic flooding.

Cisco Dynamic flooding - Nexus 9k

Dynamic Flooding - Arista - Sarah & Toni

Flood reduction- H Chen - WG adoption pending

I know we are trying to adopt an flooding algorithm
and from my reading up on all proposed algorithms, the dynamic flooding
seems to be geared towards Data Center  partial mesh high x ECMP leaf spine
architecture, where redundant flooding is problematic using either
centralized area leader or distributed flooding using same dynamic
algorithm,  versus the call for adoption flood reduction algorithm seems to
geared towards full mesh but from what I can tell would not be the
preferred for clos multi tier DC leaf spine topology with high x ECMP paths.

Why would we not want to adopt the best algorithm that is best for both
full mesh and non full mesh leaf spine topology algorithm that works for
all physical topologies and adopt that draft.

Unless a one size fits all won’t work I would like to understand why one
best solution draft we come up with for an FT algorithm for all possible
physical topologies cannot be picked for WG adoption.

Why would we want to adopt multiple flooding algorithms?


On Sat, May 23, 2020 at 4:43 PM Gyan Mishra <> wrote:

> On Fri, May 22, 2020 at 9:02 PM <> wrote:
>> Hi Gyan,
>> I think with clos spine leaf the mesh is much more intensive and
>> problematic with ECMP then a circular topology nodal mesh that results in
>> duplicate redundant flooding that slows down convergence.  With spine leaf
>> it’s like an X horizontal width axis and then depth is spine to leaf
>> links.  With spine leaf as you grow sideways and the spine expand the
>> redundant ECMP grows and redundant flooding grows exponentially and is much
>> worse then circular nodal mesh.
>> One very nice thing about dynamic flooding is that it computes a flooding
>> topology at the node level.  If the adjacency between A and B is on the
>> flooding topology, then any single link between them may be used for
>> flooding.  If you have 128 way parallel links, this is an immediate 128x
>> improvement in flooding overhead.  What’s more, A and B do not need to
>> agree on which link they are using and can use different links, resulting
>> in an asymmetric situation, without any loss of correctness or performance.
>    Gyan>. Agreed.  The dynamic flooding really helps with X way ECMP
> prevalent in high density data center clos multi tier leaf spine parial
> mesh topologies that scale massive bandwidth breadth wise horizontally for
> E-W flows.
>> Regards,
>> Tony
>> --
> <>
> *Gyan Mishra*
> *Network Solutions A**rchitect *
> *M 301 502-134713101 Columbia Pike *Silver Spring, MD
> --


*Gyan Mishra*

*Network Solutions A**rchitect *

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