Re: [mpls] Eric Rescorla's Discuss on draft-ietf-mpls-tp-shared-ring-protection-05: (with DISCUSS and COMMENT)

Huub van Helvoort <> Thu, 25 May 2017 09:36 UTC

Return-Path: <>
Received: from localhost (localhost []) by (Postfix) with ESMTP id 18E271201FA; Thu, 25 May 2017 02:36:13 -0700 (PDT)
X-Virus-Scanned: amavisd-new at
X-Spam-Flag: NO
X-Spam-Score: -2
X-Spam-Status: No, score=-2 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, FREEMAIL_FROM=0.001, SPF_PASS=-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 ms8NhTkWAv1l; Thu, 25 May 2017 02:36:11 -0700 (PDT)
Received: from ( [IPv6:2a00:1450:400c:c09::242]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by (Postfix) with ESMTPS id AE5AC12EA6A; Thu, 25 May 2017 02:36:10 -0700 (PDT)
Received: by with SMTP id g15so32011397wmc.2; Thu, 25 May 2017 02:36:10 -0700 (PDT)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;; s=20161025; h=reply-to:subject:references:to:cc:from:message-id :disposition-notification-to:date:user-agent:mime-version :in-reply-to:content-transfer-encoding; bh=OAkvKCokLPEXiIKbSrqlOl2i7559zD/IV9KIZPKy9nw=; b=Mbs14JncRnenQggnDyNSU2aGi83Gg0rc9KG0QS7S03UsR+thH4nkk1DAduJUvADsCc IfvuUwo4GfaLx1lDRvhLB1vHvH3qkRFcoW64rIDwksk/FVBCO8m1lKsbY/QqkhuXd1Ng 0v9mCk2Tg+U/Gv/3iFxcnFII7e/QvX+ksB+lT+3BEYKPBCTNnpQ5JbzbsGQve3iM94MT trZEl4dhFeiLtKhudn0WkbgNi34zXq4bG5102K93BLIdkDElkTjnHTKGSSeiGbKUoQ+u t9rL8nRoV3ILF4c5lqT1lRIZAWkk9e7wcQBdDmGsdhj6thUqBtRRZw9m+0G+9q8+74iA MikA==
X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed;; s=20161025; h=x-gm-message-state:reply-to:subject:references:to:cc:from :message-id:disposition-notification-to:date:user-agent:mime-version :in-reply-to:content-transfer-encoding; bh=OAkvKCokLPEXiIKbSrqlOl2i7559zD/IV9KIZPKy9nw=; b=pm07igrI5YdpyqIEwZhYUAP/xg/ABo35Yr39g8OFgVTfDxkrf7OcP1GGOpksWs34K9 kWgo0PO7oVgMzedpI2HtxHM8dvdwNqg+DJBAPQfyo9Gn8Td8ZPyKNBIa3pnTXMFuJpbW 5NPUIUCr3wplTfkBh6j7ksjTG3+06bKoDbmq8a4gM+VC8PrlXIeYBIyFW0cYNAzsbFKs s7l3O0RTfXstXn432QoM41FIO7y2TkwmeAh91U/jM9111aH6a+Reza62OmciqbRd7j9Q y/VxGDPZciecYGXl5JlD5YnkQ7HfFNehUDwWQYNXxsNeOh6y8lIIvDSsZgToTVUyoIO4 th8w==
X-Gm-Message-State: AODbwcB1vdU+OajwHMdHjf5SvPr4z/T9g/5qa4ghkLLHI++gl45/iSb2 rqpz/H0izteRyQ==
X-Received: by with SMTP id l39mr29330893edc.105.1495704969197; Thu, 25 May 2017 02:36:09 -0700 (PDT)
Received: from McAsterix.local ([]) by with ESMTPSA id t55sm2408745edd.23.2017. (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Thu, 25 May 2017 02:36:08 -0700 (PDT)
References: <>
To: Eric Rescorla <>, The IESG <>
Cc:, Eric Gray <>,,
From: Huub van Helvoort <>
Message-ID: <>
Date: Thu, 25 May 2017 11:36:07 +0200
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.12; rv:45.0) Gecko/20100101 Thunderbird/45.6.0
MIME-Version: 1.0
In-Reply-To: <>
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Transfer-Encoding: 7bit
Archived-At: <>
Subject: Re: [mpls] Eric Rescorla's Discuss on draft-ietf-mpls-tp-shared-ring-protection-05: (with DISCUSS and COMMENT)
X-Mailman-Version: 2.1.22
Precedence: list
List-Id: Multi-Protocol Label Switching WG <>
List-Unsubscribe: <>, <>
List-Archive: <>
List-Post: <>
List-Help: <>
List-Subscribe: <>, <>
X-List-Received-Date: Thu, 25 May 2017 09:36:13 -0000

Hello Eric,

Thank you for reviewing the security aspects of our draft.

Please see my response in-line [Huub]

> Eric Rescorla has entered the following ballot position for
> draft-ietf-mpls-tp-shared-ring-protection-05: Discuss
> The document, along with other ballot positions, can be found here:
> ----------------------------------------------------------------------
> ----------------------------------------------------------------------
> The security considerations of this document seem unacceptably
> incomplete, as they basically just point to other documents.
>     The RPS protocol defined in this document is carried in the G-ACh
>     [RFC5586], which is a generalization of the Associated Channel
>     defined in [RFC4385].  The security considerations specified in
> these
>     documents apply to the proposed RPS mechanism.
> The security considerations of those documents don't seem that great
> either. However, I believe that they miss a new security issue raised
> by the mechanism in this draft, which is that a member of the ring
> appears to be able to forge reports of errors at other parts of the
> ring. Specifically, S says:
>     When a node is in a pass-through state, it MUST transfer the
> received
>     RPS Request in the same direction.
>     When a node is in a pass-through state, it MUST enable the traffic
>     flow on protection ring tunnels in both directions.
> This seems not to involve any filtering, which suggests that node B
> can send a forged SF from C->D and from D->C, which at least
> potentially
> temporarily breaks the link there, causing traffic diversion.
> More generally, this system assumes that every node trusts every
> other node completely. That must at least be stated.
> Incidentally, the text above appears to contain a bug in that it
> doesn't talk about processing incoming RPS requests intended for
> the receiving node, but I may just have missed the section where
> it says that.
[Huub] your discuss is applicable to any OAM protocol where an
intermediate node can forge false OAM messages and affect traffic.

Regarding this draft, a forged SF may cause a protection switch if
the protocol does not detect a failure of protocol caused by a wrong
sequence or illegal combination of received RPS messages from the
clock-wise and the anti-clock-wise direction in the ring.
The protection switch itself will not cause a loss of traffic.

> ----------------------------------------------------------------------
> ----------------------------------------------------------------------
> S 4.1.1.
>     protect these LSPs that traverse the ring, a clockwise working ring
>     tunnel (RcW_D) via E->F->A->B->C->D, and its anticlockwise
> protection
>     ring tunnel (RaP_D) via D->C->B->A->F->E->D are established, Also,
> an
>     anti-clockwise working ring tunnel (RaW_D) via C->B->A->F->E->D, and
>     its clockwise protection ring tunnel (RcP_D) via D->E->F->A->B->C->D
> Why does the protection tunnel include D on both ends whereas the
> working
> tunnel does not?

[Huub] the working ring tunnel should not be a closed loop. the
protection ring tunnel is closed until a protection switch is activated,
at that time the protection ring tunnel is opened at the appropriate
location to transport the protected traffic.

> S 4.2.
>     packets are periodically exchanged between each pair of MEPs to
>     monitor the link health.  Three consecutive lost CC packets will be
>     interpreted as a link failure.
> Is this a normative statement (i.e., does it need a MUST).

[Huub] he MUST is a requirement for the SF detection described in RFC6371
and ITU-T G.806 .

> S
> Why do you ever not use short wrapping?

[Huub] wrapping is a mechanism that can be used in case an LSP is dropped
in several nodes (p-2-mp application).
Short wrapping can be used only in p-2-p application.

> S
>     A node MUST revert from pass-through state to the idle state when it
>     detects NR codes incoming from both directions.  Both directions
>     revert simultaneously from the pass-through state to the idle state.
> incoming within what time frame?

[Huub] this time depends on the propagation delay in the ring and the
RPS processing time in each node.
Because of the 50 ms switching objective a 100 ms timer could be used.

Best regards, Huub.

Always remember that you are unique...just like everyone else...