RE: BFD WG adoption for draft-haas-bfd-large-packets

"Les Ginsberg (ginsberg)" <> Tue, 23 October 2018 23:52 UTC

Return-Path: <>
Received: from localhost (localhost []) by (Postfix) with ESMTP id 7440D130DC6 for <>; Tue, 23 Oct 2018 16:52:54 -0700 (PDT)
X-Virus-Scanned: amavisd-new at
X-Spam-Flag: NO
X-Spam-Score: -14.969
X-Spam-Status: No, score=-14.969 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.47, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, HTML_MESSAGE=0.001, 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: (amavisd-new); dkim=pass (1024-bit key)
Received: from ([]) by localhost ( []) (amavisd-new, port 10024) with ESMTP id zKMkkWN1rlhE for <>; Tue, 23 Oct 2018 16:52:52 -0700 (PDT)
Received: from ( []) (using TLSv1.2 with cipher DHE-RSA-SEED-SHA (128/128 bits)) (No client certificate requested) by (Postfix) with ESMTPS id 1A1F9128CB7 for <>; Tue, 23 Oct 2018 16:52:52 -0700 (PDT)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple;;; l=11732; q=dns/txt; s=iport; t=1540338771; x=1541548371; h=from:to:subject:date:message-id:references:in-reply-to: mime-version; bh=vZKJTB249fCjnHlwO89hLauMfBu/iL6VWKWealu3BZQ=; b=Btpcu8VAESq3yxG2bVLGaLfaPaTQTaJ53DHAsPkNzw8Oij5nI8kIh9yp XQooFPFw8MForktU84QrOwzFTFoZVxBZFm5ZirXm/jw/3rbq60tHpSmfj 1nVXGgChr3jXuTSY32A+sM7+XRQ36N5IYne2GngMZ7eRfT+BO8xdunYhW k=;
X-IronPort-Anti-Spam-Filtered: true
X-IronPort-AV: E=Sophos;i="5.54,418,1534809600"; d="scan'208,217";a="467546463"
Received: from ([]) by with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 23 Oct 2018 23:52:50 +0000
Received: from ( []) by (8.15.2/8.15.2) with ESMTPS id w9NNqpCX032718 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=FAIL); Tue, 23 Oct 2018 23:52:51 GMT
Received: from ( by ( with Microsoft SMTP Server (TLS) id 15.0.1395.4; Tue, 23 Oct 2018 18:52:50 -0500
Received: from ([]) by ([]) with mapi id 15.00.1395.000; Tue, 23 Oct 2018 18:52:50 -0500
From: "Les Ginsberg (ginsberg)" <>
To: Albert Fu <>, "" <>
Subject: RE: BFD WG adoption for draft-haas-bfd-large-packets
Thread-Topic: BFD WG adoption for draft-haas-bfd-large-packets
Thread-Index: AQHUaudK2obCS5tWFUCJRL2ls+mZdKUtfuVw
Date: Tue, 23 Oct 2018 23:52:50 +0000
Message-ID: <>
References: <5BCF41E0027F048C00390652_0_50208@msllnjpmsgsv06>
In-Reply-To: <5BCF41E0027F048C00390652_0_50208@msllnjpmsgsv06>
Accept-Language: en-US
Content-Language: en-US
x-ms-exchange-transport-fromentityheader: Hosted
x-originating-ip: []
Content-Type: multipart/alternative; boundary="_000_b5569d2546694c4e87d00697790b3411XCHALN001ciscocom_"
MIME-Version: 1.0
Archived-At: <>
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: "RTG Area: Bidirectional Forwarding Detection DT" <>
List-Unsubscribe: <>, <>
List-Archive: <>
List-Post: <>
List-Help: <>
List-Subscribe: <>, <>
X-List-Received-Date: Tue, 23 Oct 2018 23:52:55 -0000

Albert -

From: Albert Fu (BLOOMBERG/ 120 PARK) <>
Sent: Tuesday, October 23, 2018 8:45 AM
To:; Les Ginsberg (ginsberg) <>
Subject: RE: BFD WG adoption for draft-haas-bfd-large-packets

Hi Les,

Given that it takes relative lengthy time to troubleshoot the MTU issue, and the associated impact on customer traffic, it is important to have a reliable and fast mechanism to detect the issue.

[Les:] This is  one of the points where we are not in full agreement. I agree you need an easy and reliable way to detect the problem when it occurs.
However, I disagree that you need to do this “fast” – when fast is defined as sub-second.

You have something that we know only occurs during some maintenance event – which is planned and only occurs “once/day,week”.
Checking for this even once/second is overly aggressive.
If it came for free, then no reason not to do so.
But as this discussion has shown, there are costs/risks.

For example, if you were using IS-IS and you detected this within the default adjacency hold time (30 seconds on p2p circuits) – would that be too slow for you? If so, please explain why this is too slow.

I think the primary issue here is ease of use and reliability. Whether detection time is one second or one minute seems relatively unimportant.

Do you disagree?