Re: [mpls] [bier] The first nibble issue associated with MPLS encapsulation

Eric C Rosen <erosen@juniper.net> Wed, 13 April 2016 14:48 UTC

Return-Path: <erosen@juniper.net>
X-Original-To: mpls@ietfa.amsl.com
Delivered-To: mpls@ietfa.amsl.com
Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id EE09712E313; Wed, 13 Apr 2016 07:48:22 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -1.902
X-Spam-Level:
X-Spam-Status: No, score=-1.902 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001] autolearn=ham autolearn_force=no
Authentication-Results: ietfa.amsl.com (amavisd-new); dkim=pass (1024-bit key) header.d=junipernetworks.onmicrosoft.com
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 hv9K7zKg9NwC; Wed, 13 Apr 2016 07:48:18 -0700 (PDT)
Received: from na01-bn1-obe.outbound.protection.outlook.com (mail-bn1on0723.outbound.protection.outlook.com [IPv6:2a01:111:f400:fc10::723]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-SHA384 (256/256 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id 490AF12E2E6; Wed, 13 Apr 2016 07:48:17 -0700 (PDT)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=junipernetworks.onmicrosoft.com; s=selector1-juniper-net; h=From:To:Date:Subject:Message-ID:Content-Type:MIME-Version; bh=yKEMAokHJuXZ8aYFbc90gr8Ng4ySj/cz7GyrSQDyu/k=; b=XhZXIR5vYHB3hGQ7txFi8KfyZyJo1Vjitgb45k9wctd+mN7tM7yKiy9oXq3jWxslm/6J134zZgGrvBWo8uQdhAnSii5X1A+tALeMiNyz7wh0rZtmEKAZLlyeYUDLrVm+mEbphJIv2UeBfUinvBC6zDot4m1i5IsjOf0ICg/5H3M=
Authentication-Results: juniper.net; dkim=none (message not signed) header.d=none;juniper.net; dmarc=none action=none header.from=juniper.net;
Received: from [172.28.32.220] (66.129.241.12) by BY2PR05MB789.namprd05.prod.outlook.com (10.141.225.18) with Microsoft SMTP Server (TLS) id 15.1.453.26; Wed, 13 Apr 2016 14:47:59 +0000
To: "Carlos Pignataro (cpignata)" <cpignata@cisco.com>
References: <1FEE3F8F5CCDE64C9A8E8F4AD27C19EE0D53871C@NKGEML515-MBX.china.huawei.com> <B664DB14-0A8C-4437-83E3-F9DA6C0DDA61@cisco.com> <mc51yrrf9n0wxbjsrprt9amf.1460143890063@email.android.com> <CA+RyBmXpZ-Kt77TW-=_kPYmahdw_yUHB5xhy8YtYVq2OcRJxbA@mail.gmail.com> <D32DB725.3F57B%cpignata@cisco.com> <CA+RyBmW+qonpScnLOfsGorayCvsS0vrFcn+o5nPvOqCOv9Jc3g@mail.gmail.com> <AM3PR03MB0775C55E5AD3247F373007139D940@AM3PR03MB0775.eurprd03.prod.outlook.com> <570BB266.8090608@juniper.net> <CFAC7D65-1AF0-4185-B580-2D1BB6728823@cisco.com>
From: Eric C Rosen <erosen@juniper.net>
Message-ID: <570E5C1A.7010606@juniper.net>
Date: Wed, 13 Apr 2016 10:47:54 -0400
User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:38.0) Gecko/20100101 Thunderbird/38.7.2
MIME-Version: 1.0
In-Reply-To: <CFAC7D65-1AF0-4185-B580-2D1BB6728823@cisco.com>
Content-Type: text/plain; charset="utf-8"; format=flowed
Content-Transfer-Encoding: 7bit
X-Originating-IP: [66.129.241.12]
X-ClientProxiedBy: DM3PR10CA0030.namprd10.prod.outlook.com (10.164.12.40) To BY2PR05MB789.namprd05.prod.outlook.com (10.141.225.18)
X-MS-Office365-Filtering-Correlation-Id: 730b7b82-dfe2-45a4-ceff-08d363aa9c88
X-Microsoft-Exchange-Diagnostics: 1; BY2PR05MB789; 2:v7A37LfDwsIuuzB/4M4CbznKoiEr9/xyVO0+vOgGFG4XCq3HTRgUS7K5jDyF3qTeYWpw1mgHyGYueyxT/B0hlWMbsqdqfo900Ez4U1/I9wPZwexsapNUw7GNGWg3a2vF2M8ctL1CURtYyuhovuawHQ2x4KiDKWh+yBflYvIqy6yA84dVjzCMmvFmXrjjPLom; 3:E6DnzCwL4nP/0CDy4F8/ZU9M3AUwOMl1RcGnliEIOoWds1CIfHeaL06Jjy3+m7RJi1xcjxvnXBuy/fEvKYKiqPWpEkj3ayOfaeCduHlZuKybcwcYWxPE0PBMTQnSdWBO
X-Microsoft-Antispam: UriScan:;BCL:0;PCL:0;RULEID:;SRVR:BY2PR05MB789;
X-Microsoft-Exchange-Diagnostics: 1; BY2PR05MB789; 25: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
X-Microsoft-Exchange-Diagnostics: 1; BY2PR05MB789; 20: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; 4:srqtS6hNpLj9gxb7S1sCoYeuq1CRwuFt23hsDYG6s/r9WxLl+Ahhf7FTyCqHaS/fXxU0GxdU2odxrYV7nP1vVQ8YydUvWiQnetLRfcFAsZKya8cmDe3zml+kBxN4lG4mylbFM3uJoMW7ffDEpNdRVQs/T7PD0NT20lRJ1e5JVd0ov95xD/f137sPFzza6Hwsis2TRtefHjhVmWqR12SlcrAw+eyNaJXeyXYSoOm02n3euru/f/a6hVmYsMdechHPzdpKNNz1wqSzLD36yhy0UJjxrc0UyZAMNWM55XsM/foDCF635d55oekcFczxUdJMgoBdUpx8Ugqepz2klEDOXEr9tOsJ9Ae0KrJ3Gi/x8QAdo6tuIVHcVb7Zf6Xm/8insjZdgAP70WPp/eYebKECqA==
X-Microsoft-Antispam-PRVS: <BY2PR05MB78999C349D4845F277D6D7BD4960@BY2PR05MB789.namprd05.prod.outlook.com>
X-Exchange-Antispam-Report-Test: UriScan:;
X-Exchange-Antispam-Report-CFA-Test: BCL:0; PCL:0; RULEID:(601004)(2401047)(5005006)(8121501046)(3002001)(10201501046)(6055026); SRVR:BY2PR05MB789; BCL:0; PCL:0; RULEID:; SRVR:BY2PR05MB789;
X-Forefront-PRVS: 0911D5CE78
X-Forefront-Antispam-Report: SFV:NSPM; SFS:(10019020)(4630300001)(6009001)(6049001)(24454002)(377454003)(2950100001)(33656002)(80316001)(87266999)(54356999)(76176999)(50986999)(4326007)(42186005)(65816999)(77096005)(92566002)(81166005)(86362001)(2906002)(5008740100001)(50466002)(93886004)(5004730100002)(36756003)(47776003)(110136002)(83506001)(586003)(64126003)(4001350100001)(189998001)(6116002)(230700001)(66066001)(1096002)(23676002); DIR:OUT; SFP:1102; SCL:1; SRVR:BY2PR05MB789; H:[172.28.32.220]; FPR:; SPF:None; MLV:sfv; LANG:en;
X-Microsoft-Exchange-Diagnostics: =?utf-8?B?MTtCWTJQUjA1TUI3ODk7MjM6a0crOGZHNGJrWVZ4azExSjdwZlJOdFcxalBi?= =?utf-8?B?bjYvZ09scStqZk41aGMrTzB1TVhXbmVSbVBra3B5ZmJaMms5S2JMdDhRU3U5?= =?utf-8?B?VU92cEVQTFBFT2hLeUhaRHozQkwwWFh4T1RnTUNWNDM3Nm9KeHdWc3ZTRFRX?= =?utf-8?B?anI0TjhSRkF3SkwxMzR4dnFYd25lVklvWHpoaGw3STlVSXZRUndCWFd0VkpK?= =?utf-8?B?NFlxTnRaT0xRZ3ZPMmtRWjFldGY3Z2tMcXMxbDkwRVlsemRCMzY2Z0hoLy9n?= =?utf-8?B?RmR5bDhhb0F5WU5pQjZFK1hWYWU0TlY3WS9FOXJneG9xWXhUWUdXQW9lM3JK?= =?utf-8?B?ZXJYMU1NVFB6d1VHZTRINFFnMFkxV2liMWp2TEd3dzV5NjZLRDJNSVNJZFls?= =?utf-8?B?Sm1jS05DcGViRlJJSG9BSHh5bnM1UmxEWlNLd0Q3NHYzRytnVC9lLzU3RDJT?= =?utf-8?B?Z2kwMlZjSFAzSlJCZ3lPMnllVTM5ZnpWN01BVTNQNUt1Q0l5aFZ1NG1CZnZl?= =?utf-8?B?ZTlwUmRQMEVIbTQrQm9mYjZvQW5kcEVGWmsvbll4bGZKdUdKalQwckVFcnJR?= =?utf-8?B?eEFnclZUaURESUxDQVptZ1RvamRtQUlqZG5sVmw1ekI3Q3BUL2ZMNHFkKzIw?= =?utf-8?B?bHVNR2lNeFFQa09iQmxTNUovdWM1Rys4U2dsWEJRdFV3S2NiMGpSVHNvdTZq?= =?utf-8?B?SGNuNFNkbDZmbmZIUGhTVVAvaGNCY2JaZVlXL25TZ1VZSFpSb2t6SmY1eFpY?= =?utf-8?B?cnZBNXU0bDFxRzJXNHYwVmZ3U2pBVW1SblRNNEhzRW1FOHVVeUw5OTExQ3F4?= =?utf-8?B?RWFUaEpWQ2J0S1ZhZEpNUDR6UXJJS0hWZ2t4S3g4UDQ4cERVdDN4VldmSUJi?= =?utf-8?B?NVJONGswL1Zwc0VxeVVLRWo4OXZiaHN6QlBSOWNwWWJTY1REa0crckRueDFL?= =?utf-8?B?RWY2N3huTjU5NGJtOTBmQjFubzZoNEhVRytWWkxQWUhoNVFYU1JWSmtiOE1U?= =?utf-8?B?WHc5SmVKaUsrOVRMYWVtb0VMNGs3SGN0WjFqeGpsVTMzQzFWVUh5aVNNSHo2?= =?utf-8?B?S2lZU2xqVjhvclBzUEtHQi83c2VwNHgzWWV0TmxqbGpiSTNCV0hPR0R2RzRs?= =?utf-8?B?K1BPanFzMDB3Nkcrck1IR3llcTN2OVl3eVRMNnBEQ3AvaUNyVlg1aTgxVVho?= =?utf-8?B?VFFPbWZHY2gwYkExbjl6aUlJZFdEOWJaNDI4ejhXVFJmaU9DVzBvaWNNMm9v?= =?utf-8?B?aGFVRHZGMVUydm1xZU1ac1p5U0dtKytuQisxYmJPa3M0dlVLbGZUcFNCS1dV?= =?utf-8?Q?YkkEkbTSeWoWMxnQtzNYuHIwHyTZmXo=3D?=
X-Microsoft-Exchange-Diagnostics: 1; BY2PR05MB789; 5:gIzVts/gxkR5RoqedGYeGEPkoOEh+sP+OWU1Qu5eN1tkBg/EPqe52wSRVRYqA328GE2dvG5aBGuY+6vqlMbIZmtYG15fPTZoZ0ISXATxR4LW4DExfa94mgzkkEGPfoIrtVFQYQyup8L+H3zAUqQP1w==; 24:2QVxbyKMAkYLSKhAci0rKzeSU54l6OdVG5sJXIk93Ry13iQ3UZfxoe3O5wUeCB5s9XAWcFYXK8WrYiF0H4rY6p/WTZfUDWIgpCfcO9xVSXY=
X-OriginatorOrg: juniper.net
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 13 Apr 2016 14:47:59.6071 (UTC)
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-Transport-CrossTenantHeadersStamped: BY2PR05MB789
Archived-At: <http://mailarchive.ietf.org/arch/msg/mpls/H9qpnqrvemIgbhM9cEf2UeBQe9I>
Cc: "bier@ietf.org" <bier@ietf.org>, "mpls@ietf.org" <mpls@ietf.org>, "Dr. Tony Przygienda" <tonysietf@gmail.com>
Subject: Re: [mpls] [bier] The first nibble issue associated with MPLS encapsulation
X-BeenThere: mpls@ietf.org
X-Mailman-Version: 2.1.17
Precedence: list
List-Id: Multi-Protocol Label Switching WG <mpls.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/mpls>, <mailto:mpls-request@ietf.org?subject=unsubscribe>
List-Archive: <https://mailarchive.ietf.org/arch/browse/mpls/>
List-Post: <mailto:mpls@ietf.org>
List-Help: <mailto:mpls-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/mpls>, <mailto:mpls-request@ietf.org?subject=subscribe>
X-List-Received-Date: Wed, 13 Apr 2016 14:48:23 -0000

On 4/11/2016 8:19 PM, Carlos Pignataro (cpignata) wrote:
> The format of a BIER packet have enough constrained or self-defining 
> fields, that an off-line parsing tool like Wireshark can apply enough 
> heuristics to figure it out, without the 0x5. 

I haven't worked out for myself whether this is the case or not, but it 
certainly doesn't hurt to have the 0x05 there.

> I understand why a mid-point LSR might want to not alias the MPLS 
> payload with IPv4 or IPv6, to prevent mis-hashing in the LB. Why would 
> a node be interested in knowing the payload is not a PW? What would it 
> do differently? 

I'm not sure if there is any hardware that performs PW-specific 
functions in the forwarding plane, based on the first nibble, but it 
seems prudent to avoid any possibility of confusion.

> [It is interesting that the hint is, as described, to nudge a node 
> that the packet is *not* something, instead of the packet *is* BIER.] 

Well, of course, that's why the nibble is not a protocol type field ;-)  
In the MPLS encaps, the fact that the packet is BIER is determined from 
the MPLS label.  In other proposed encapsulations, the encapsulating 
protocol would have a protocol type field.

>> This strategy does incur a risk.  Suppose IPv5 gets designed, implemented, and deployed, and folks start to deploy hardware that does MPLS load balancing by inspecting the IPv5 headers of the MPLS payloads.  If a BIER packet is traversing an MPLS tunnel, inappropriate load splitting may occur if the hardware thinks the payload is IPv5 rather than BIER.
>>
>> This particular risk doesn't seem very significant to me.
>>
> I agree that risk is quite insignificant (null in practice). The real risk I believe is if some other application over MPLS uses 0x5 in the first nibble, because they do not want to be confused with IP either, and they do not like 0x0 or 0x1.

That is possible, but I don't really see what the problem is.

I guess it is true that we'll have to say that BIER is not 100% 
compliant with RFC 4928.   I don't see that as a problem either, but it 
is certainly possible that some AD will make an issue of it.