Re: [mpls] working group last call on draft-ietf-mpls-tp-p2mp-framework

"Zhenlong Cui" <c-sai@bx.jp.nec.com> Thu, 14 November 2013 11:51 UTC

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From: "Zhenlong Cui" <c-sai@bx.jp.nec.com>
To: "'Lou Berger'" <lberger@labn.net>, <mpls@ietf.org>
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Cc: draft-ietf-mpls-tp-p2mp-framework@tools.ietf.org
Subject: Re: [mpls] working group last call on draft-ietf-mpls-tp-p2mp-framework
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Lou,

I agree your opinion.

I looked through the draft, there are few comments as an attached file.
I hope you will find it informative before you post a new version of the draft.

Best reagrds,
zhenlong

> -----Original Message-----
> From: Lou Berger [mailto:lberger@labn.net]
> Sent: Saturday, November 09, 2013 6:04 AM
> To: Zhenlong Cui; mpls@ietf.org
> Cc: draft-ietf-mpls-tp-p2mp-framework@tools.ietf.org
> Subject: Re: [mpls] working group last call on draft-ietf-mpls-tp-p2mp-framework
> 
> 
> Zhenlong,
> 
> I understand you have an additional concern regarding supporting a MIP and MEP in a node that is both a branch and leaf
> node.  I think this is supported, where MIPs are associated with the P2MP branch data plane function and MEPs are associated
> with the leaf data plane function.
> This holds for both for both per-node and per-interface MIPs. I certainly agree that it is reasonable for there to be
> a more in depth discussion on this topic, and suggest that such a discussion be added to draft-hmk-mpls-tp-p2mp-oam-framework.
> 
> If you'd like, we can something like the following to our draft:
> 
>   It is worth noting that a MIP and MEP may be instantiated on a node
>   when it is both a branch and leaf node.
> 
> Please let us know if you still have concerns on our document.
> 
> Thank you,
> Lou
> 
> On 11/5/2013 11:05 AM, Lou Berger wrote:
> > Zhenlong,
> >
> > Perhaps the issue is in the slightly different language used in the
> > draft versus the section 3.7 of rfc6371.  RFC6371 says:
> >
> >    o  To send an OAM packet to a single MIP, ... The OAM packet must
> >       contain sufficient information to identify the target MIP and
> >       therefore is processed only by the target MIP and can be silently
> >       discarded by the others.
> >
> > To better align with this text, the draft should be revised to replace
> > "addressing information" with "additional information"
> >
> > Will this address your comment? If not, do you have some text/changes
> > in mind that would?
> >
> > Much thanks,
> > Lou
> >
> > On 11/4/2013 12:56 AM, Zhenlong Cui wrote:
> >> Hi Lou,
> >>
> >>  Thank you for your reply.
> >>
> >>  I was relieved to know that you already considered the case that both MEP and MIP functionality are configured on
> a transit node.
> >>
> >>  However, I think that this draft need further explanation for the OAM behavior on transit nodes.
> >>
> >>  The P2MP OAM behaviors are described in section 4.
> >>    All the traffic sent over a P2MP transport path, including OAM
> >>    packets generated by a MEP, is sent (multicast) from the root to all
> >>    the leaves, thus every OAM packet is sent to all leaves, and thus can
> >>    impact all the MEs in a P2MP MEG.  If an OAM packet is to be
> >>    processed by only a specific leaf, it requires information to
> >>    indicate to all other leaves that the packet must be discarded.  To
> >>    address a packet to an intermediate node in the tree, TTL based
> >>    addressing is used to set the radius and addressing information in
> >>    the OAM payload is used to identify the specific destination node.
> >>
> >>
> >>  My comments:
> >>
> >>  1)As defined in RFC 6426, the IF_Num is used to identify the specific destination node and interface.
> >>    The case of per-interface should also be described, if you like to mention about the per-node case in this draft.
> >>
> >>  2)May need further explanation for the OAM behavior in case that both MEP and MIP functionality are configured on
> a transit node.
> >>    e.g.)
> >>    When a transit node receive a OAM packet, the transit node has to determine whether the OAM packets should be processed
> by a MIP functionality, before it identifies the addressing information.
> >>    Because MIP functionality is usually implemented by software. This behavior will be help to block the DDOS attack.
> >>
> >>
> >> Best reagrds,
> >> zhenlong
> >>
> >>> -----Original Message-----
> >>> From: Lou Berger [mailto:lberger@labn.net]
> >>> Sent: Monday, November 04, 2013 1:17 PM
> >>> To: Zhenlong Cui; mpls@ietf.org
> >>> Cc: draft-ietf-mpls-tp-p2mp-framework@tools.ietf.org
> >>> Subject: Re: [mpls] working group last call on
> >>> draft-ietf-mpls-tp-p2mp-framework
> >>>
> >>> Zhenlong,
> >>> 	Thank you for the comments. Please see below for responses in-line.
> >>>
> >>> On 10/22/2013 2:18 AM, Zhenlong Cui wrote:
> >>>> Dear authors,
> >>>>
> >>>> I have a comment/question on this draft.
> >>>>
> >>>> As described in section 1.3, in the ring topology, we have to consider the drop-and-continue node case.
> >>>> In this case, the drop-and-continue node will become an intermediate point.
> >>>
> >>> Agreed.  This node will be both a transit node and an egress/leaf.  This case is covered in RFC4875.
> >>>
> >>>> So, can we configure a MEP on an intermediate node(= drop-and-continue node)?
> >>>
> >>> I think this is a matter of semantics.  By definition a MEP is only on egress (leaf) nodes and a MIP only on transit
> nodes.
> >>> Assuming you are asking about the case stated in the previous point,
> >>> that a node is both egress and transit, then I think it could have both MEP and MIP functionality separately instantiated.
> Section 3.7 already covers P2MP MIPs and MEPs.
> >>>
> >>>> As described in section 3.3 of RFC 6371, a MEP terminates all the
> >>>> OAM packets it receives from the MEG, may discards silently if
> >>>> addressing information in the OAM payload is different with
> >>> termination node.
> >>>> It means that the intermediate node must NOT be configured as a MEP
> >>>> when per-node OAM configuration is used, because downstream nodes can't receive the OAM packets from root node.
> >>>
> >>> Why do you say this?  If a node is both transit and egress, it will
> >>> replicate OAM packets (just like the data) when performing its transit role before then terminating the data/OAM packets
> as part of its egress role.
> >>>
> >>>>
> >>>> On the other hand, if the intermediate node can't be configured as
> >>>> a MEP, the path protection may not be able to work at this point. I think this is a serious problem.
> >>>>
> >>>
> >>> Perhaps I'm missing something, but I simply don't see an issue here
> >>> that isn't already addressed in RFC6371 (and 4875.) I guess 6371
> >>> could have shown this case as an example, or provided a related detailed walk through, but either way I don't see
> any "serious problem" here.
> >>>
> >>> Perhaps the best way to proceed on this is to propose text to the
> >>> already referenced "additional detail" draft draft-hmk-mpls-tp-p2mp-oam-framework.  Does this work for you?
> >>>
> >>> Thanks,
> >>> Lou
> >>>
> >>>> Best regards,
> >>>> zhenlong
> >>>>
> >>>>> -----Original Message-----
> >>>>> From: mpls-bounces@ietf.org [mailto:mpls-bounces@ietf.org] On
> >>>>> Behalf Of Loa Andersson
> >>>>> Sent: Friday, October 18, 2013 1:29 PM
> >>>>> To: mpls@ietf.org
> >>>>> Cc: mpls-chairs@tools.ietf.org;
> >>>>> draft-ietf-mpls-tp-p2mp-framework@tools.ietf.org
> >>>>> Subject: [mpls] working group last call on
> >>>>> draft-ietf-mpls-tp-p2mp-framework
> >>>>>
> >>>>> Working Group,
> >>>>>
> >>>>> this is to start a two week working group last call on draft-ietf-mpls-tp-p2mp-framework-04.
> >>>>>
> >>>>> Please send your comment to working group mailing lists (mpls@ietf.org).
> >>>>>
> >>>>> We did an IPR poll on this document prior to starting the wglc.
> >>>>> The each authors responded to the IPR poll that they not aware of any IPR's relating to this document.
> >>>>>
> >>>>> There are no IPRs disclosed against this document.
> >>>>>
> >>>>> The working group last call will end Friday November 1, 2913.
> >>>>>
> >>>>> /Loa
> >>>>> mpls wg co-chair
> >>>>> --
> >>>>>
> >>>>>
> >>>>> Loa Andersson                        email: loa@mail01.huawei.com
> >>>>> Senior MPLS Expert                          loa@pi.nu
> >>>>> Huawei Technologies (consultant)     phone: +46 739 81 21 64
> >>>>> _______________________________________________
> >>>>> mpls mailing list
> >>>>> mpls@ietf.org
> >>>>> https://www.ietf.org/mailman/listinfo/mpls
> >>>>
> >>>>
> >>>>
> >>>>
> >>>>
> >>
> >>
> >>
> >>
> >>
> > _______________________________________________
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> >
> >
> >
> >