Re: [Int-area] I-D Action: draft-ietf-intarea-tunnels-05.txt

Joe Touch <touch@isi.edu> Tue, 16 May 2017 23:21 UTC

Return-Path: <touch@isi.edu>
X-Original-To: int-area@ietfa.amsl.com
Delivered-To: int-area@ietfa.amsl.com
Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id 69942129B18 for <int-area@ietfa.amsl.com>; Tue, 16 May 2017 16:21:17 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -5.002
X-Spam-Level:
X-Spam-Status: No, score=-5.002 tagged_above=-999 required=5 tests=[BAYES_40=-0.001, RCVD_IN_DNSWL_HI=-5, RP_MATCHES_RCVD=-0.001] autolearn=ham autolearn_force=no
Received: from mail.ietf.org ([4.31.198.44]) by localhost (ietfa.amsl.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id tCYjxYqW8m6h for <int-area@ietfa.amsl.com>; Tue, 16 May 2017 16:21:16 -0700 (PDT)
Received: from vapor.isi.edu (vapor.isi.edu [128.9.64.64]) (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 81C8B12751F for <int-area@ietf.org>; Tue, 16 May 2017 16:17:18 -0700 (PDT)
Received: from [128.9.160.211] (mul.isi.edu [128.9.160.211]) (authenticated bits=0) by vapor.isi.edu (8.13.8/8.13.8) with ESMTP id v4GNGhL3026890 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES128-SHA bits=128 verify=NOT); Tue, 16 May 2017 16:16:43 -0700 (PDT)
To: "Templin, Fred L" <Fred.L.Templin@boeing.com>
Cc: "int-area@ietf.org" <int-area@ietf.org>
References: <149062888196.30638.8369941985115982808@ietfa.amsl.com> <f5ab0422-fd49-9082-147b-8312e974de7e@isi.edu> <4d2a86f4948c4dc49ab3b0729743d028@XCH15-06-08.nw.nos.boeing.com>
From: Joe Touch <touch@isi.edu>
Message-ID: <6573ad04-a1a6-3f2c-8470-c2babaf36110@isi.edu>
Date: Tue, 16 May 2017 16:16:43 -0700
User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.1.0
MIME-Version: 1.0
In-Reply-To: <4d2a86f4948c4dc49ab3b0729743d028@XCH15-06-08.nw.nos.boeing.com>
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 7bit
Content-Language: en-US
X-ISI-4-43-8-MailScanner: Found to be clean
X-MailScanner-From: touch@isi.edu
Archived-At: <https://mailarchive.ietf.org/arch/msg/int-area/B48xHxdkTuWfZFvNizAaRVqp5UU>
Subject: Re: [Int-area] I-D Action: draft-ietf-intarea-tunnels-05.txt
X-BeenThere: int-area@ietf.org
X-Mailman-Version: 2.1.22
Precedence: list
List-Id: IETF Internet Area Mailing List <int-area.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/int-area>, <mailto:int-area-request@ietf.org?subject=unsubscribe>
List-Archive: <https://mailarchive.ietf.org/arch/browse/int-area/>
List-Post: <mailto:int-area@ietf.org>
List-Help: <mailto:int-area-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/int-area>, <mailto:int-area-request@ietf.org?subject=subscribe>
X-List-Received-Date: Tue, 16 May 2017 23:21:17 -0000

Fred,

Regarding the following point:


On 3/28/2017 9:36 AM, Templin, Fred L wrote:
> 19) Section 4.3.3, third paragraph, I thought it was said earlier
>     that all ingress/egress pairs must support the same MTU. I
>     thought we agreed earlier on that that multi-MTU subnets
>     don't work. So, I think it should say that all ingress pairs
>     MUST support a uniform MTU.
The cited section allows for ingress/egress pairs that don't support the
same MTU, but then says that the MTU used for that set is the minimum of
those MTUs.

There's no way (short of configuration management) to ensure that
ingress/egress pairs MUST support the same MTU, but no real value to
requiring that - AFAICT, we just use the min across that set (which is
what that section says to do).

So yes, we do not *use* different MTUs per-destination, but we don't
need to require it AFAICT.

Joe