Return-Path: 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 E1B7513245F; Mon, 14 Aug 2017 17:17:16 -0700 (PDT) X-Virus-Scanned: amavisd-new at amsl.com X-Spam-Flag: NO X-Spam-Score: -14.519 X-Spam-Level: X-Spam-Status: No, score=-14.519 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, HTML_MESSAGE=0.001, RCVD_IN_DNSWL_HI=-5, RCVD_IN_MSPIKE_H3=-0.01, RCVD_IN_MSPIKE_WL=-0.01, SPF_PASS=-0.001, URIBL_BLOCKED=0.001, USER_IN_DEF_DKIM_WL=-7.5] autolearn=ham autolearn_force=no Authentication-Results: ietfa.amsl.com (amavisd-new); dkim=pass (1024-bit key) header.d=cisco.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 Zd675gRBQomR; Mon, 14 Aug 2017 17:17:14 -0700 (PDT) Received: from alln-iport-8.cisco.com (alln-iport-8.cisco.com [173.37.142.95]) (using TLSv1.2 with cipher DHE-RSA-SEED-SHA (128/128 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id F2C6B132466; Mon, 14 Aug 2017 17:17:13 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=cisco.com; i=@cisco.com; l=18775; q=dns/txt; s=iport; t=1502756233; x=1503965833; h=from:to:cc:subject:date:message-id:references: in-reply-to:mime-version; bh=mMp4nCmUMhz0pldahjkl7AKPyLs1wSSkBUsX5//eAGM=; b=b+S/oXfG2UlHpMOBJ6DqZ/1ELeTgB4oy/auFtttwvNRzV5itFMRIsCpo MJ9J+qQFGIGRxOdMEJDYsyivHOc7AwGTClzvW+TGu31tm4SkhbYbIQRyo W6nOyChqgPO6W3a2Z2Px/OfFbF1eoRr7xXynKbU9e8Yk2dUOa9LXTEskE U=; X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: =?us-ascii?q?A0BSAQDhPJJZ/5FdJa1dGQEBAQEBAQEBA?= =?us-ascii?q?QEBBwEBAQEBgm9rZDcBXI4RkBGBbog3iCyFNQ6CBCyDPIFfAoR5PxgBAgEBAQE?= =?us-ascii?q?BAQFrKIUZBgxbEhACAQg/ByERFBECBA4FiUtMAxUQrzqHPQ2EIQEBAQEBAQEBA?= =?us-ascii?q?QEBAQEBAQEBAQEBARgFgyiCAoFMgWMrgnyBPIEbgWkBEgGDYoIxBYl5jhSHaDw?= =?us-ascii?q?Ch1GHdIR1gg+FXYppiWSCToliAR84fwt3FUkSAYRLOQwQgWd2AYdYDRcHghQBA?= =?us-ascii?q?QE?= X-IronPort-AV: E=Sophos;i="5.41,375,1498521600"; d="scan'208,217";a="471464098" Received: from rcdn-core-9.cisco.com ([173.37.93.145]) by alln-iport-8.cisco.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 15 Aug 2017 00:17:12 +0000 Received: from XCH-RTP-003.cisco.com (xch-rtp-003.cisco.com [64.101.220.143]) by rcdn-core-9.cisco.com (8.14.5/8.14.5) with ESMTP id v7F0HCOl012631 (version=TLSv1/SSLv3 cipher=AES256-SHA bits=256 verify=FAIL); Tue, 15 Aug 2017 00:17:12 GMT Received: from xch-rtp-020.cisco.com (64.101.220.160) by XCH-RTP-003.cisco.com (64.101.220.143) with Microsoft SMTP Server (TLS) id 15.0.1210.3; Mon, 14 Aug 2017 20:17:11 -0400 Received: from xch-rtp-020.cisco.com ([64.101.220.160]) by XCH-RTP-020.cisco.com ([64.101.220.160]) with mapi id 15.00.1210.000; Mon, 14 Aug 2017 20:17:11 -0400 From: "Carlos Pignataro (cpignata)" To: Greg Mirsky CC: Tom Nadeau , "mpls@ietf.org" , "Kireeti Kompella (kireeti@juniper.net)" , Alia Atlas , "Reshad Rahman (rrahman)" , "rtg-bfd@ietf. org" Thread-Topic: [Technical Errata Reported] RFC5884 (5085) Thread-Index: AQHTEsasU87guosjHUWva6qlHRtDoKJ/rxSAgACYlQCABCd3gIAAIwDq Date: Tue, 15 Aug 2017 00:17:11 +0000 Message-ID: <7501E817-C95E-410A-A91E-080B36B213BE@cisco.com> References: <20170811053550.27303B81263@rfc-editor.org> <20170811173930.GJ24942@pfrc.org> , In-Reply-To: Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted Content-Type: multipart/alternative; boundary="_000_7501E817C95E410AA91E080B36B213BEciscocom_" MIME-Version: 1.0 Archived-At: Subject: Re: [mpls] [Technical Errata Reported] RFC5884 (5085) X-BeenThere: mpls@ietf.org 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: Tue, 15 Aug 2017 00:17:17 -0000 --_000_7501E817C95E410AA91E080B36B213BEciscocom_ Content-Type: text/plain; charset="Windows-1252" Content-Transfer-Encoding: quoted-printable Greg, This is my final email on this topic, since the arguments are now just sill= y and not technically constructive. 1. It's not about understanding English. It's about understanding specs! Th= e "(if any)" that you quote means there are situations in which there's no = echo reply. As I already explained to you, that's for example the case with= Reply-mode: No-reply. However, the "(if any)" does not mean an Echo Reply = is OPTIONAL. !! Or that you choose when a reply is not sent!! 2. RFC 8029 obsoleted 4379. But to my recollection, nothing changed relevan= t to this Errata. BFD for MPLS could have updated LSP ping behavior -- it just didn't. Sent from my iPad On Aug 14, 2017, at 2:12 PM, Greg Mirsky > wrote: Hi Carlos, thank you for sharing your view on how LSP Echo request with BFD Discrimina= tor used to bootstrap a BFD session over MPLS LSP. I'm surprised that you r= efer to RFC 8029 as normative reference when commenting on RFC 5884. But ev= en if we look into RFC 8029, it still has the same texts I've quoted in the= previous note that suggest that echo reply is optional. Consider one of th= em "The Sender's Handle is filled in by the sender and returned unchanged b= y the receiver in the echo reply (if any)." Though English is my third lang= uage, I interpret "if any" in that sentence as clear indication that the ec= ho reply may not be sent ever. Regards, Greg On Fri, Aug 11, 2017 at 7:45 PM, Carlos Pignataro (cpignata) > wrote: Jeff, WG, I believe there is one additional consideration =97 please see inline. On Aug 11, 2017, at 1:39 PM, Jeffrey Haas > wrote: [Note that I have adjusted the addresses in the headers to try to catch the RFC authors' current accounts.] The 5884 interop issue keeps bubbling up. Balaji submitted an errata, whic= h provides us with a good place to start technical discussion. Please note I also spent some time off-list discussing this errata with Balaji. On Thu, Aug 10, 2017 at 10:35:50PM -0700, RFC Errata System wrote: Section: 6 Original Text ------------- The egress LSR MAY respond with an LSP Ping Echo reply message that carries the local discriminator assigned by it for the BFD session. Corrected Text -------------- The egress LSR MUST respond with an LSP Ping Echo reply message that MAY carry the local discriminator assigned by it for the BFD session. Notes ----- It is not clear from the original text which of the following is optional: - The egress MUST send a reply, but the discriminator in the reply is opt= ional - The reply itself is optional Technically, the reply cannot be optional, because the egress needs to repo= rt LSP-Ping verification status to the ingress. This is correct =97 but even more so, technically, it is not up to RFC 5884= to define when an LSP-Ping reply is optional or not. That=92s=92 up to https://tools.ietf.org/html/rfc8029#section-4.4 Lacking a Reply Mode set to "Do not reply" (https://tools.ietf.org/html/rfc= 8029#page-12) the RFC 8029 procedures dictate a response be sent, independe= nt of whether the RFC 5884 procedures use that information or not. More below. The proposed text recommends to include BFD discriminator in the reply. Thi= s was the intent of the original text. My opinion follows: In section 6 - : On receipt of the LSP Ping Echo request message, the egress LSR MUST : send a BFD Control packet to the ingress LSR, if the validation of : the FEC in the LSP Ping Echo request message succeeds. This BFD : Control packet MUST set the Your Discriminator field to the : discriminator received from the ingress LSR in the LSP Ping Echo : request message. The egress LSR MAY respond with an LSP Ping Echo : reply message that carries the local discriminator assigned by it for : the BFD session. The local discriminator assigned by the egress LSR : MUST be used as the My Discriminator field in the BFD session packets : sent by the egress LSR. In the text above, I consider it quite clear that the receipt of the BFD packet contains sufficient state to bring up the BFD session. The receipt of the same Discriminator in the LSP Ping Echo Reply is optional. This makes sense partially because the reply may be dropped and we want the BFD session to come up as fast as possible. Yes, especially because the first sentence says that the egress sending a B= FD Control packet implies FEC validation passed. However, https://tools.iet= f.org/html/rfc8029#section-4.4 does more than FEC validation. The point of contention appears to be what to do if we *never* get such replies. It's worth pointing out additional text in RFC 5884, section 3.2. : Hence, BFD is used in conjunction with LSP Ping for MPLS LSP fault : detection: : : i) LSP Ping is used for bootstrapping the BFD session as described : later in this document. : : ii) BFD is used to exchange fault detection (i.e., BFD session) : packets at the required detection interval. : : iii) LSP Ping is used to periodically verify the control plane : against the data plane by ensuring that the LSP is mapped to : the same FEC, at the egress, as the ingress. iii above reminds us that the LSP may be torn down because LSP Ping fails. Thus, it seems problematic that we do not get a reply ever. However, with the BFD session in the Up state, we have information proving that the LSP is up. Thus we have contradictory intent. --- My opinion is that the MAY in the RFC 5884 procedures is intended to have the BFD session come up by the most expedient means. I do not believe the likely intent was to say "don't send Echo Reply". Among other things, that seems contrary to the intent of the general LSP Ping procedures. Having given my personal observations, we now get to the business of the Working Group: Debating intent and related text. My individual opinion is that, as written, RFC 5884 cannot mean any other t= hing that =93 The egress LSR MUST respond with an LSP Ping Echo reply messa= ge that MAY carry the local discriminator assigned by it for the BFD session=94. In other words, I support this errata. This is because RFC 5884 did not update RFC 4379=92s procedures. And thus a= response is needed based on 8029 irregardless of whether 5884 uses it. That said, it is debatable whether that LSP Ping response is useful or not.= If it is not sent, it does not comply to 8029. But if the WG wants for it = to be not send, a new spec is needed. Thanks, -- Jeff =97 Carlos Pignataro, carlos@cisco.com =93Sometimes I use big words that I do not fully understand, to make myself= sound more photosynthesis." --_000_7501E817C95E410AA91E080B36B213BEciscocom_ Content-Type: text/html; charset="Windows-1252" Content-Transfer-Encoding: quoted-printable
Greg,

This is my final email on this topic, since = the arguments are now just silly and not technically constructive. 

1. It's not about understanding English. It'= s about understanding specs! The "(if any)" that you quote means = there are situations in which there's no echo reply. As I already explained= to you, that's for example the case with Reply-mode: No-reply. However, the "(if any)" does not mean an Echo Reply is= OPTIONAL. !! Or that you choose when a reply is not sent!!
2. RFC 8029 obsoleted 4379. But to my recoll= ection, nothing changed relevant to this Errata. 

BFD for MPLS could have updated LSP ping beh= avior -- it just didn't. 

Sent from my iPad

On Aug 14, 2017, at 2:12 PM, Greg Mirsky <gregimirsky@gmail.com> wrote:

Hi Carlos,
thank you for sharing your view on how LSP Echo request with BFD Discr= iminator used to bootstrap a BFD session over MPLS LSP. I'm surprised that = you refer to RFC 8029 as normative reference when commenting on RFC 5884. B= ut even if we look into RFC 8029, it still has the same texts I've quoted in the previous note that suggest = that echo reply is optional. Consider one of them "The Sender's Handle is filled in by the s= ender and returned unchanged by the receiver in the echo reply (if any)." Though English is my third = language, I interpret "if any" in that sentence as clear indicati= on that the echo reply may not be sent ever.

Regards,
Greg

On Fri, Aug 11, 2017 at 7:45 PM, Carlos Pignatar= o (cpignata) <cpignata@cisco.com> wrote:
Jeff, WG,

I believe there is one additional consideration =97 please see inline.=

On Aug 11, 2017, at 1:39 PM, Jeffrey Haas <jhaas@pfrc.org> wrote:

[Note that I have adjusted the addresses in the headers to try to catc= h the
RFC authors' current accounts.]


The 5884 interop issue keeps bubbling up.  Balaji submitted an errata,= which
provides us with a good place to start technical discussion.

Please note I also spent some time off-list discussing this errata with
Balaji.


On Thu, Aug 10, 2017 at 10:35:50PM -0700, RFC Errata System wrote:
Section: 6

Original Text
-------------
The egress LSR MAY respond with an LSP Ping Echo
reply message that carries the local discriminator assigned by it for
the BFD session.

Corrected Text
--------------
The egress LSR MUST respond with an LSP Ping Echo reply message that
MAY carry the local discriminator assigned by it for the BFD session.


Notes
-----
It is not clear from the original text which of the following is optional:<= br>  -  The egress MUST send a reply, but the discriminator in the re= ply is optional
 -  The reply itself is optional

Technically, the reply cannot be optional, because the egress needs to repo= rt LSP-Ping verification status to the ingress.
This is correct =97 but even more so, technically, it is not up to RFC= 5884 to define when an LSP-Ping reply is optional or not.


Lacking a Reply Mode set to "Do not reply" (https://tools.iet= f.org/html/rfc8029#page-12) the RFC 8029 procedures dictate a resp= onse be sent, independent of whether the RFC 5884 procedures use that information or not.

More below.


The proposed text recommends to include BFD discriminator in the reply. Thi= s was the intent of the original text.

My opinion follows:

In section 6 -

:    On receipt of the LSP Ping Echo request message, the eg= ress LSR MUST
:    send a BFD Control packet to the ingress LSR, if the va= lidation of
:    the FEC in the LSP Ping Echo request message succeeds.&= nbsp; This BFD
:    Control packet MUST set the Your Discriminator field to= the
:    discriminator received from the ingress LSR in the LSP = Ping Echo
:    request message.  The egress LSR MAY respond with = an LSP Ping Echo
:    reply message that carries the local discriminator assi= gned by it for
:    the BFD session.  The local discriminator assigned= by the egress LSR
:    MUST be used as the My Discriminator field in the BFD s= ession packets
:    sent by the egress LSR.

In the text above, I consider it quite clear that the receipt of the BFD packet contains sufficient state to bring up the BFD session.  The rec= eipt
of the same Discriminator in the LSP Ping Echo Reply is optional.

This makes sense partially because the reply may be dropped and we want the=
BFD session to come up as fast as possible.
Yes, especially because the first sentence says that the egress sendin= g a BFD Control packet implies FEC validation passed. However, http= s://tools.ietf.org/html/rfc8029#section-4.4 does more than FEC validation.


The point of contention appears to be what to do if we *never* get such
replies.  It's worth pointing out additional text in RFC 5884, section= 3.2.

:    Hence, BFD is used in conjunction with LSP Ping for MPL= S LSP fault
:    detection:
:
:       i) LSP Ping is used for bootstrapping= the BFD session as described
:          later in this docum= ent.
:
:      ii) BFD is used to exchange fault detection= (i.e., BFD session)
:          packets at the requ= ired detection interval.
:
:     iii) LSP Ping is used to periodically verify the = control plane
:          against the data pl= ane by ensuring that the LSP is mapped to
:          the same FEC, at th= e egress, as the ingress.

iii above reminds us that the LSP may be torn down because LSP Ping fails.<= br> Thus, it seems problematic that we do not get a reply ever.

However, with the BFD session in the Up state, we have information proving<= br> that the LSP is up.  Thus we have contradictory intent.

---

My opinion is that the MAY in the RFC 5884 procedures is intended to have the BFD session come up by the most expedient means.  I do not believe= the
likely intent was to say "don't send Echo Reply".  Among oth= er things, that
seems contrary to the intent of the general LSP Ping procedures.

Having given my personal observations, we now get to the business of the Working Group: Debating intent and related text.  
My individual opinion is that, as written, RFC 5884 cannot mean any ot= her thing that =93 The egress LSR MUST respond with an LSP Ping Echo reply = message that
MAY carry the local discriminator assigned by it for the BFD session= =94.

In other words, I support this errata.

This is because RFC 5884 did not update RFC 4379=92s procedures. And t= hus a response is needed based on 8029 irregardless of whether 5884 uses it= .

That said, it is debatable whether that LSP Ping response is useful or= not. If it is not sent, it does not comply to 8029. But if the WG wants fo= r it to be not send, a new spec is needed.

Thanks,

-- Jeff


=97
Carlos Pignataro, carlos@cisco.com

=93Sometimes I use big words that I do not fully understand, to make mys= elf sound more photosynthesis."


--_000_7501E817C95E410AA91E080B36B213BEciscocom_--