RE: [EXT] Re: Last Call: <draft-ietf-6man-rfc2460bis-08.txt> (Internet Protocol, Version 6 (IPv6) Specification) to Internet Standard

Tal Mizrahi <> Tue, 14 February 2017 13:37 UTC

Return-Path: <>
Received: from localhost (localhost []) by (Postfix) with ESMTP id EBBD31295D9; Tue, 14 Feb 2017 05:37:16 -0800 (PST)
X-Virus-Scanned: amavisd-new at
X-Spam-Flag: NO
X-Spam-Score: -2.601
X-Spam-Status: No, score=-2.601 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, RCVD_IN_DNSWL_LOW=-0.7, SPF_PASS=-0.001] autolearn=ham autolearn_force=no
Received: from ([]) by localhost ( []) (amavisd-new, port 10024) with ESMTP id CdvaWRQjvAyL; Tue, 14 Feb 2017 05:37:15 -0800 (PST)
Received: from ( []) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by (Postfix) with ESMTPS id 4B55012948D; Tue, 14 Feb 2017 05:37:15 -0800 (PST)
Received: from pps.filterd ( []) by ( with SMTP id v1EDYuET022912; Tue, 14 Feb 2017 05:37:13 -0800
Received: from ([]) by with ESMTP id 28kgn853ru-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-SHA384 bits=256 verify=NOT); Tue, 14 Feb 2017 05:37:13 -0800
Received: from ( by ( with Microsoft SMTP Server (TLS) id 15.0.1210.3; Tue, 14 Feb 2017 15:37:10 +0200
Received: from ([fe80::5d63:81cd:31e2:fc36]) by ([fe80::5d63:81cd:31e2:fc36%20]) with mapi id 15.00.1210.000; Tue, 14 Feb 2017 15:37:10 +0200
From: Tal Mizrahi <>
To: Mark Smith <>
Subject: RE: [EXT] Re: Last Call: <draft-ietf-6man-rfc2460bis-08.txt> (Internet Protocol, Version 6 (IPv6) Specification) to Internet Standard
Thread-Topic: [EXT] Re: Last Call: <draft-ietf-6man-rfc2460bis-08.txt> (Internet Protocol, Version 6 (IPv6) Specification) to Internet Standard
Thread-Index: AdKF/X9u+WIK+SvpTdCAbZfIxgfsEgABO8eAADEQ/AA=
Date: Tue, 14 Feb 2017 13:37:10 +0000
Message-ID: <>
References: <> <>
In-Reply-To: <>
Accept-Language: en-US
Content-Language: en-US
x-ms-exchange-transport-fromentityheader: Hosted
x-originating-ip: []
Content-Type: text/plain; charset="utf-8"
Content-Transfer-Encoding: base64
MIME-Version: 1.0
X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:, , definitions=2017-02-14_08:, , signatures=0
X-Proofpoint-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1011 lowpriorityscore=0 impostorscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1612050000 definitions=main-1702140135
Archived-At: <>
Cc: "" <>, "" <>, IETF Discussion list <>, "" <>
X-Mailman-Version: 2.1.17
Precedence: list
List-Id: "IPv6 Maintenance Working Group \(6man\)" <>
List-Unsubscribe: <>, <>
List-Archive: <>
List-Post: <>
List-Help: <>
List-Subscribe: <>, <>
X-List-Received-Date: Tue, 14 Feb 2017 13:37:17 -0000

Hi Mark,

I certainly agree that hop-by-hop insertion/modification introduces potential security vulnerabilities.
Therefore, as I pointed out below, I would recommend to tackle this by defining something along the lines of “Hop-by-hop extensions can be inserted/removed/modified/processed by intermediate nodes *if* [……..] and the possible consequences are [……..]”

For example, hop-by-hop handling can be restricted only to a single administrative domain, or only to tunnels (as in the zero checksum case). 


>-----Original Message-----
>From: Mark Smith []
>Sent: Monday, February 13, 2017 6:07 PM
>To: Tal Mizrahi
>Cc:; IETF Discussion list; draft-ietf-6man-
>Subject: [EXT] Re: Last Call: <draft-ietf-6man-rfc2460bis-08.txt> (Internet
>Protocol, Version 6 (IPv6) Specification) to Internet Standard
>External Email
>On 14 February 2017 at 00:43, Tal Mizrahi <> wrote:
>> Hi,
>> Good discussion regarding the text about the hop-by-hop extension.
>> In my opinion there is a valid use case for intermediate nodes that
>> insert/remove/modify/process hop-by-hop extensions. Examples: IOAM, INT.
>> Since there is a use case, I believe we need explicit text about
>> intermediate handling of hop-by-hop extensions.
>Imagine you sent a letter through the postal system, and the postal system
>wanted to add information to that letter, that is then to be removed before the
>letter arrives at its final destination.
>The postal system have at least two choices as to how to add that information.
>They could:
>(a) unstick your envelope's seal, insert the information, reseal the envelope so
>well you can't tell and send it on its way, some how flagging to a destination
>device within the postal system that this specific envelop needs to be openned, a
>specific page removed, and then resealed.
>(b) take a new envelope with new internal postal system source and destination
>address information, insert your letter without touching it in addition to the new
>information, and then sending it on its way.
>Imagine that the information to be added by the postal system is printed on the
>same type of paper and is written in the same font as you've chosen to use to
>write your letter.
>Have a think about these two methods, what could fail with each of them, and
>what the consequences may be if any of those failures occur.
>Have a think of the benefits of each method, and whether they're worth it
>compared to the failure mode costs and consequences for the method.
>> This [somewhat] reminds me of the discussion a few years ago about the
>> IPv6/UDP zero checksum. The WG ended up defining that “Zero checksum
>> is permitted in IPv6/UDP *if* [……..] and the possible consequences are [……..]”.
>That is a far more trivial change to the packet - it is allowing a value in an existing
>field that was formerly prohibited, and nodes that did not understand that value
>would drop the packet because that is what they had been specified to do if they
>received this prohibited value. In other words, existing implementations '
>behaviour when this formerly unexpected value was encountered had already
>been specified and deployed.
>> I would argue that regarding hop-by-hop extension handling we also
>> need to define that “Hop-by-hop extensions can be
>> inserted/removed/modified/processed by intermediate nodes *if* [……..]
>> and the possible consequences are [……..]”.
>Some things that are possible to do in theory shouldn't be done in practice,
>because the consequences when their implementations fail can be severe and
>outweigh the benefits.
>In theory, inserted EHs will be removed 100% of the time. In practice they won't
>be, because implementations can have bugs and they can also fail in unexpected
>ways e.g., hardware faults.