Re: [nvo3] BFD over VXLAN: Trapping BFD Control packet at VTEP

Joel Halpern Direct <jmh.direct@joelhalpern.com> Tue, 22 October 2019 19:58 UTC

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Subject: Re: [nvo3] BFD over VXLAN: Trapping BFD Control packet at VTEP
To: Greg Mirsky <gregimirsky@gmail.com>
Cc: Anoop Ghanwani <anoop@alumni.duke.edu>, Jeffrey Haas <jhaas@pfrc.org>, Santosh P K <santosh.pallagatti@gmail.com>, NVO3 <nvo3@ietf.org>, draft-ietf-bfd-vxlan@ietf.org, Dinesh Dutt <didutt@gmail.com>, rtg-bfd WG <rtg-bfd@ietf.org>, "T. Sridhar" <tsridhar@vmware.com>, xiao.min2@zte.com.cn
References: <CACi9rdu8PKsLW_Pq4ww5DEwLL8Bs6Hq1Je_jmAjES4LKBuE8MQ@mail.gmail.com> <201909251039413767352@zte.com.cn> <CACi9rdv-760M8WgZ1mOOOa=yoJqQFP=vdc3xJKLe7wCR18NSvA@mail.gmail.com> <20191021210752.GA8916@pfrc.org> <0e99a541-b2ca-85d4-4a8f-1165cf7ac01e@joelhalpern.com> <CA+-tSzziDc+Tk8AYfOr5-Xn6oO_uqW2C1dRA9LLOBBVmzVhWEQ@mail.gmail.com> <CA+RyBmVcBgeoGc2z5Gv0grv8OY34tyw+T-T-W2vn1O3AxCSQ9Q@mail.gmail.com> <0b45df12-a7c5-3b5c-db59-5a57c8dfd1b7@joelhalpern.com> <CA+RyBmV9Ynk6fZy6qkvkOz3Pm2AmK7ESy8KoEpqyxP1nvNka0w@mail.gmail.com> <14ec7c38-5a5b-83dd-b4f4-71a29494ebdc@joelhalpern.com> <CA+RyBmWDRrjTR3OAnYsush8+4ORnGdKUqp46bg5MXaPa3zCgZA@mail.gmail.com>
From: Joel Halpern Direct <jmh.direct@joelhalpern.com>
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Date: Tue, 22 Oct 2019 15:58:38 -0400
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That is input to the calculation at the VTEP.  It is NOT information 
sued by the network between the VTEPs.

As such, the VTEPs can emulate that by adjusting the source ports that 
it uses for the VFD packets.  The network does not need the VNI to 
actually be varied to achieve this purpose.

Yours,
Joel

On 10/22/2019 3:55 PM, Greg Mirsky wrote:
> Hi Joel,
> RFC 7348 suggests using information from the inner packet to calculate 
> the value to be used in the Source UDP port number:
>        -  Source Port:  It is recommended that the UDP source port number
>           be calculated using a hash of fields from the inner packet --
>           one example being a hash of the inner Ethernet frame's headers.
>           This is to enable a level of entropy for the ECMP/load-
>           balancing of the VM-to-VM traffic across the VXLAN overlay.
>  From that text, I assume that VNI may be used as input for hashing 
> function. If BFD over VXLAN doesn't support per VNI BFD session, then it 
> cannot monitor multiple paths in underlay used to balance VM-to-VM 
> traffic between the same pair of VTEPs. In my opinion, this is perfectly 
> fine if that is WG's agreement. I'm glad we are discussing this and will 
> have a conclusion.
> 
> Regards,
> Greg
> 
> On Tue, Oct 22, 2019 at 3:30 PM Joel M. Halpern <jmh@joelhalpern.com 
> <mailto:jmh@joelhalpern.com>> wrote:
> 
>     As I recall, the VNI is not in the same place nor the same size as the
>     TCP / UDP ports.  So it seems very unlikely that it would be used in
>     ECMP.  In fact, avoiding that is why VXLAN does interesting things with
>     the source UDP port.  Which the BFD can do.  And presumably MUST do if
>     it was path matching.
> 
>     Yours,
>     Joel
> 
>     On 10/22/2019 3:16 PM, Greg Mirsky wrote:
>      > Hi Joel,
>      > if the underlay may balance VXLAN between two VTEPs using VNI in
>      > addition to other fields, then Option 2 has a certain value in my
>     opinion.
>      >
>      > Regards,
>      > Greg
>      >
>      > On Tue, Oct 22, 2019 at 3:06 PM Joel M. Halpern
>     <jmh@joelhalpern.com <mailto:jmh@joelhalpern.com>
>      > <mailto:jmh@joelhalpern.com <mailto:jmh@joelhalpern.com>>> wrote:
>      >
>      >     I do not understand the value of option 2.
>      >     Which is why I asked in my initial review to move to option 1.
>      >
>      >     And option 2 requires stealing MAC addresses from the users,
>     which
>      >     seems
>      >     to me to be a very bad thing that option 1 avoids.
>      >
>      >     Yours,
>      >     Joel
>      >
>      >     On 10/22/2019 2:17 PM, Greg Mirsky wrote:
>      >      > Hi Anoop, et al.,
>      >      > I agree with your understanding of what is being defined
>     in the
>      >     current
>      >      > version of the BFD over VxLAN specification. But, as I
>      >     understand, the
>      >      > WG is discussing the scope before the WGLC is closed. I
>     believe
>      >     there
>      >      > are three options:
>      >      >
>      >      >  1. single BFD session between two VTEPs
>      >      >  2. single BFD session per VNI between two VTEPs
>      >      >  3. multiple BFD sessions per VNI between two VTEPs
>      >      >
>      >      > The current text reflects #2. Is WG accepts this scope? If
>     not,
>      >     which
>      >      > option WG would accept?
>      >      >
>      >      > Regards,
>      >      > Greg
>      >      >
>      >      > On Tue, Oct 22, 2019 at 2:09 PM Anoop Ghanwani
>      >     <anoop@alumni.duke.edu <mailto:anoop@alumni.duke.edu>
>     <mailto:anoop@alumni.duke.edu <mailto:anoop@alumni.duke.edu>>
>      >      > <mailto:anoop@alumni.duke.edu
>     <mailto:anoop@alumni.duke.edu> <mailto:anoop@alumni.duke.edu
>     <mailto:anoop@alumni.duke.edu>>>> wrote:
>      >      >
>      >      >     I concur with Joel's assessment with the following
>      >     clarifications.
>      >      >
>      >      >     The current document is already capable of monitoring
>      >     multiple VNIs
>      >      >     between VTEPs.
>      >      >
>      >      >     The issue under discussion was how do we use BFD to
>     monitor
>      >     multiple
>      >      >     VAPs that use the same VNI between a pair of VTEPs. 
>     The use case
>      >      >     for this is not clear to me, as from my understanding,
>     we cannot
>      >      >     have a situation with multiple VAPs using the same
>     VNI--there
>      >     is 1:1
>      >      >     mapping between VAP and VNI.
>      >      >
>      >      >     Anoop
>      >      >
>      >      >     On Tue, Oct 22, 2019 at 6:06 AM Joel M. Halpern
>      >     <jmh@joelhalpern.com <mailto:jmh@joelhalpern.com>
>     <mailto:jmh@joelhalpern.com <mailto:jmh@joelhalpern.com>>
>      >      >     <mailto:jmh@joelhalpern.com
>     <mailto:jmh@joelhalpern.com> <mailto:jmh@joelhalpern.com
>     <mailto:jmh@joelhalpern.com>>>> wrote:
>      >      >
>      >      >           From what I can tell, there are two separate
>     problems.
>      >      >         The document we have is a VTEP-VTEP monitoring
>     document.
>      >     There
>      >      >         is no
>      >      >         need for that document to handle the multiple VNI
>     case.
>      >      >         If folks want a protocol for doing BFD monitoring
>     of things
>      >      >         behind the
>      >      >         VTEPs (multiple VNIs), then do that as a separate
>      >     document.   The
>      >      >         encoding will be a tenant encoding, and thus sesparate
>      >     from what is
>      >      >         defined in this document.
>      >      >
>      >      >         Yours,
>      >      >         Joel
>      >      >
>      >      >         On 10/21/2019 5:07 PM, Jeffrey Haas wrote:
>      >      >          > Santosh and others,
>      >      >          >
>      >      >          > On Thu, Oct 03, 2019 at 07:50:20PM +0530,
>     Santosh P K
>      >     wrote:
>      >      >          >>     Thanks for your explanation. This helps a
>     lot. I
>      >     would
>      >      >         wait for more
>      >      >          >> comments from others to see if this what we
>     need in this
>      >      >         draft to be
>      >      >          >> supported based on that we can provide appropriate
>      >     sections
>      >      >         in the draft.
>      >      >          >
>      >      >          > The threads on the list have spidered to the point
>      >     where it
>      >      >         is challenging
>      >      >          > to follow what the current status of the draft
>     is, or
>      >     should
>      >      >         be.  :-)
>      >      >          >
>      >      >          > However, if I've followed things properly, the
>      >     question below
>      >      >         is really the
>      >      >          > hinge point on what our encapsulation for BFD
>     over vxlan
>      >      >         should look like.
>      >      >          > Correct?
>      >      >          >
>      >      >          > Essentially, do we or do we not require the
>     ability to
>      >     permit
>      >      >         multiple BFD
>      >      >          > sessions between distinct VAPs?
>      >      >          >
>      >      >          > If this is so, do we have a sense as to how we
>     should
>      >     proceed?
>      >      >          >
>      >      >          > -- Jeff
>      >      >          >
>      >      >          > [context preserved below...]
>      >      >          >
>      >      >          >> Santosh P K
>      >      >          >>
>      >      >          >> On Wed, Sep 25, 2019 at 8:10 AM
>     <xiao.min2@zte.com.cn <mailto:xiao.min2@zte.com.cn>
>      >     <mailto:xiao.min2@zte.com.cn <mailto:xiao.min2@zte.com.cn>>
>      >      >         <mailto:xiao.min2@zte.com.cn
>     <mailto:xiao.min2@zte.com.cn>
>      >     <mailto:xiao.min2@zte.com.cn <mailto:xiao.min2@zte.com.cn>>>>
>     wrote:
>      >      >          >>
>      >      >          >>> Hi Santosh,
>      >      >          >>>
>      >      >          >>>
>      >      >          >>> With regard to the question whether we should
>     allow
>      >      >         multiple BFD sessions
>      >      >          >>> for the same VNI or not, IMHO we should allow
>     it, more
>      >      >         explanation as
>      >      >          >>> follows.
>      >      >          >>>
>      >      >          >>> Below is a figure derived from figure 2 of
>     RFC8014 (An
>      >      >         Architecture for
>      >      >          >>> Data-Center Network Virtualization over Layer
>     3 (NVO3)).
>      >      >          >>>
>      >      >          >>>                      |         Data Center
>     Network (IP)
>      >      >              |
>      >      >          >>>                      |
>      >      >             |
>      >      >          >>>
>      >      >         +-----------------------------------------+
>      >      >          >>>                           |                 
>               |
>      >      >          >>>                           |       Tunnel
>     Overlay      |
>      >      >          >>>              +------------+---------+
>      >      >           +---------+------------+
>      >      >          >>>              | +----------+-------+ |       |
>      >      >         +-------+----------+ |
>      >      >          >>>              | |  Overlay Module  | |       |
>     |  Overlay
>      >      >         Module  | |
>      >      >          >>>              | +---------+--------+ |       |
>      >      >         +---------+--------+ |
>      >      >          >>>              |           |          |       |
>      >         |
>      >      >                  |
>      >      >          >>>       NVE1   |           |          |       |
>      >         |
>      >      >                  | NVE2
>      >      >          >>>              |  +--------+-------+  |       |
>      >      >         +--------+-------+  |
>      >      >          >>>              |  |VNI1 VNI2  VNI1 |  |       |  |
>      >     VNI1 VNI2
>      >      >         VNI1 |  |
>      >      >          >>>              |  +-+-----+----+---+  |       |
>      >      >         +-+-----+-----+--+  |
>      >      >          >>>              |VAP1| VAP2|    | VAP3 |     
>       |VAP1|
>      >     VAP2|
>      >      >           | VAP3|
>      >      >          >>>              +----+-----+----+------+
>      >      >           +----+-----+-----+-----+
>      >      >          >>>                   |     |    |               
>         |
>      >         |     |
>      >      >          >>>                   |     |    |               
>         |
>      >         |     |
>      >      >          >>>                   |     |    |               
>         |
>      >         |     |
>      >      >          >>>
>      >      >       
>       -------+-----+----+-------------------+-----+-----+-------
>      >      >          >>>                   |     |    |     Tenant   
>          |
>      >         |     |
>      >      >          >>>              TSI1 | TSI2|    | TSI3         
>     TSI1|
>      >     TSI2|
>      >      >           |TSI3
>      >      >          >>>                  +---+ +---+ +---+           
>       +---+
>      >     +---+
>      >      >           +---+
>      >      >          >>>                  |TS1| |TS2| |TS3|           
>       |TS4|
>      >     |TS5|
>      >      >           |TS6|
>      >      >          >>>                  +---+ +---+ +---+           
>       +---+
>      >     +---+
>      >      >           +---+
>      >      >          >>>
>      >      >          >>> To my understanding, the BFD sessions between
>     NVE1
>      >     and NVE2
>      >      >         are actually
>      >      >          >>> initiated and terminated at VAP of NVE.
>      >      >          >>>
>      >      >          >>> If the network operator want to set up one
>     BFD session
>      >      >         between VAP1 of
>      >      >          >>> NVE1 and VAP1of NVE2, at the same time
>     another BFD
>      >     session
>      >      >         between VAP3 of
>      >      >          >>> NVE1 and VAP3 of NVE2, although the two BFD
>     sessions are
>      >      >         for the same
>      >      >          >>> VNI1, I believe it's reasonable, so that's why I
>      >     think we
>      >      >         should allow it
>      >      >
>      >      >         _______________________________________________
>      >      >         nvo3 mailing list
>      >      > nvo3@ietf.org <mailto:nvo3@ietf.org> <mailto:nvo3@ietf.org
>     <mailto:nvo3@ietf.org>> <mailto:nvo3@ietf.org <mailto:nvo3@ietf.org>
>      >     <mailto:nvo3@ietf.org <mailto:nvo3@ietf.org>>>
>      >      > https://www.ietf.org/mailman/listinfo/nvo3
>      >      >
>      >
>