Re: [Ntp] Comments on draft-langer-ntp-nts-for-ptp

Miroslav Lichvar <> Mon, 08 March 2021 10:37 UTC

Return-Path: <>
Received: from localhost (localhost []) by (Postfix) with ESMTP id 445913A003F for <>; Mon, 8 Mar 2021 02:37:01 -0800 (PST)
X-Virus-Scanned: amavisd-new at
X-Spam-Flag: NO
X-Spam-Score: -2.368
X-Spam-Status: No, score=-2.368 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.248, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_MSPIKE_H3=-0.01, RCVD_IN_MSPIKE_WL=-0.01, SPF_HELO_NONE=0.001, SPF_PASS=-0.001] 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 XuwdhRt--c2L for <>; Mon, 8 Mar 2021 02:36:59 -0800 (PST)
Received: from ( []) (using TLSv1.2 with cipher ECDHE-RSA-AES256-SHA384 (256/256 bits)) (No client certificate requested) by (Postfix) with ESMTPS id B07E43A003D for <>; Mon, 8 Mar 2021 02:36:59 -0800 (PST)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;; s=mimecast20190719; t=1615199818; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=ZKX/QD/hltRvvb2Xl+ZcDvxa3XiQruhkzQslxxW9YNs=; b=HdhLOwjceAC8sRfU3wt0i9sJZIesv3wgqLHFGayr5/JQUsfLWE8ZWFHk3LhqvbCsdAgY13 IYqQfVPOfcYHhXa4d6ferdShNDnY3SnhX9STvRKI0FpvyDzjEKi1ey5iGul2BKyILNHUTw imN7qgZdvsoGNkvC5EPnXEjcT0IzXB4=
Received: from ( []) (Using TLS) by with ESMTP id us-mta-151-7DL72O3tO_SQgxjY-D-sig-1; Mon, 08 Mar 2021 05:36:56 -0500
X-MC-Unique: 7DL72O3tO_SQgxjY-D-sig-1
Received: from ( []) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by (Postfix) with ESMTPS id B11451005D4A; Mon, 8 Mar 2021 10:36:55 +0000 (UTC)
Received: from localhost ( []) by (Postfix) with ESMTPS id 0B86D5D9D0; Mon, 8 Mar 2021 10:36:54 +0000 (UTC)
Date: Mon, 08 Mar 2021 11:36:53 +0100
From: Miroslav Lichvar <>
To: Watson Ladd <>
Cc: NTP WG <>
Message-ID: <YEX+RYP1vXLgt5f8@localhost>
References: <>
MIME-Version: 1.0
In-Reply-To: <>
X-Scanned-By: MIMEDefang 2.79 on
Authentication-Results:; auth=pass smtp.auth=CUSA124A263
X-Mimecast-Spam-Score: 0
Content-Type: text/plain; charset="us-ascii"
Content-Disposition: inline
Archived-At: <>
Subject: Re: [Ntp] Comments on draft-langer-ntp-nts-for-ptp
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: <>
List-Unsubscribe: <>, <>
List-Archive: <>
List-Post: <>
List-Help: <>
List-Subscribe: <>, <>
X-List-Received-Date: Mon, 08 Mar 2021 10:37:01 -0000

On Fri, Mar 05, 2021 at 11:55:22AM -0800, Watson Ladd wrote:
> I think this is an important draft that covers a real usecase, but
> should try to break the flow of NTS a bit less. I hope these comments
> are useful.

There might be a more general question that needs to be answered
first. What exactly it means for "NTS" to be applied to a time
synchronization protocol? IIRC we originally had a general NTS
draft and a separate NTS-for-NTP draft.

PTP, like the NTP broadcast mode, cannot be secured to the same extent
as the NTP client-server mode. We had some attempts and they failed.

If I understand it correctly, this draft is not trying to apply the
NTS-NTP principles to PTP. That's not possible. It just reuses the
NTS-KE protocol for its own security protocol. I think that's
perfectly fine as long as there is no confusion about the NTS part.

Miroslav Lichvar