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

[Greg Mirsky <[e-mail]>]

Thank you, Joel and Jeff.

I'll upload the working version shortly. I hope that updates will address
all comments and concerns shared on several threads by Anoop, Dinesh, Joel,
and many others. I greatly value and appreciate the time, expertise, and
consideration you've given to this work, and have shared with me.

Regards,
Greg

On Thu, Oct 31, 2019 at 9:22 AM Jeffrey Haas <[e-mail]> wrote:

> I also agree with Joel.
>
> -- Jeff
>
>
> > On Oct 31, 2019, at 11:59 AM, Joel M. Halpern <[e-mail]>
> wrote:
> >
> > Explicitly restricting the discard behavior to the management VNI takes
> care of my concern.
> >
> > Thank you,
> > Joel
> >
> > On 10/31/2019 11:48 AM, Greg Mirsky wrote:
> >> Hi Jeff,
> >> thank you for the detailed clarification of your questions. Please find
> my follow-up notes in-lined tagged GIM2>>.
> >> Regards,
> >> Greg
> >> On Wed, Oct 30, 2019 at 2:14 PM Jeffrey Haas <[e-mail] <mailto:
> [e-mail]>> wrote:
> >>    Greg,
> >>    On Wed, Oct 30, 2019 at 01:58:30PM -0700, Greg Mirsky wrote:
> >>     > On Wed, Oct 30, 2019 at 1:27 PM Jeffrey Haas <[e-mail]
> >>    <mailto:[e-mail]>> wrote:
> >>     >
> >>     > > Greg,
> >>     > >
> >>     > > From the updated text:
> >>     > >
> >>     > > "At the same time, a service layer BFD session may be used
> >>    between the
> >>     > > tenants of VTEPs IP1 and IP2 to provide end-to-end fault
> >>    management. In
> >>     > > such case, for VTEPs BFD Control packets of that session are
> >>     > > indistinguishable from data packets.  If end-to-end defect
> >>    detection is
> >>     > > realized as the set of concatenated OAM domains, e.g., VM1-1 -
> >>    IP1 --
> >>     > > IP2 - VM2-1, then the BFD session over VXLAN between VTEPs
> SHOULD
> >>     > > follow the procedures described in Section 6.8.17 [RFC5880]."
> >>     > >
> >>     > > In the case that two VMs are running BFD to each other as a user
> >>     > > application
> >>     > > rather than as part of the virtualized environment, it's
> >>    unlikely that
> >>     > > they'd be treated as concatenated domains.  To do so, the
> >>    tenant VMs would
> >>     > > have to have a sense that they are indeed virtual.
> >>     > >
> >>     > > Is your intent in this text that BFD implementations on the
> >>    server should
> >>     > > detect BFD sessions between servers and change them to a
> >>    concatenated
> >>     > > session?
> >>     > >
> >>     > GIM>> No, we do not suggest that the concatenation of BFD
> sessions be
> >>     > automagical. That may be controlled via the management plane
> though.
> >>    Then my suggestion is we may not want this text.
> >>    It's fine to say "if tenants want to run BFD to each other, and that
> is
> >>    standard BFD (RFC 5881) from the perspective of those tenants" if
> that's
> >>    your intent.  Leave automagic out of the spec. :-)
> >> GIM2>> I'd take the passage referring to the concatenated path out.
> That will leave it as:
> >>    At the same time, a service layer BFD session may be used between the
> >>    tenants of VTEPs IP1 and IP2 to provide end-to-end fault management.
> >>    In such case, for VTEPs BFD Control packets of that session are
> >>    indistinguishable from data packets.
> >>     > > Section 5 comment:
> >>     > >
> >>     > > :   The UDP destination port and the TTL of the inner IP packet
> >>    MUST be
> >>     > > :   validated to determine if the received packet can be
> >>    processed by
> >>     > > :   BFD.  BFD Control packets with unknown MAC address MUST NOT
> be
> >>     > > :   forwarded to VMs.
> >>     > >
> >>     > > I'd suggest pushing the second sentence into the prior section
> >>    since it
> >>     > > deals with MAC addresses rather than the UDP procedures.
> >>     > >
> >>     > GIM>> Could you please clarify your suggestion - move to Section
> >>    4 or to
> >>     > the preceding paragraph? I think it is the latter but wanted to
> >>    make sure.
> >>    Full section 5 from your draft-8 candidate:
> >>    : 5.  Reception of BFD Packet from VXLAN Tunnel
> >>    :
> >>    :    Once a packet is received, the VTEP MUST validate the packet.
>    If the
> >>    :    Destination MAC of the inner Ethernet frame matches one of the
> MAC
> >>    :    addresses associated with the VTEP the packet MUST be processed
> >>    :    further.  If the Destination MAC of the inner Ethernet frame
> >>    doesn't
> >>    :    match any of VTEP's MAC addresses, then the processing of the
> >>    :    received VXLAN packet MUST follow the procedures described in
> >>    :    Section 4.1 [RFC7348].
> >>    It's not clear what that procedure is, with respect to BFD.  Section
> 4.1
> >>    basically says is that when a mapping is discovered, deliver it to
> >>    that VM
> >>    with headers removed.
> >>    Section 4.1 really doesn't discuss dropping behavior.
> >>    :
> >>    :    The UDP destination port and the TTL of the inner IP packet
> MUST be
> >>    :    validated to determine if the received packet can be processed
> by
> >>    :    BFD.
> >>    This is fine.
> >>    :    BFD Control packets with unknown MAC address MUST NOT be
> >>    :    forwarded to VMs.
> >>    This appears to be clarifying the missing point in the prior
> >>    paragraph.  If
> >>    that's the case, why is this sentence not part of the prior
> paragraph?
> >> GIM>> So I thought. Moving the sentence to the first paragraph
> highlighted the contradiction others had pointed earlier:
> >> On the one hand:
> >>    If the Destination MAC of the inner Ethernet frame doesn't
> >>    match any of VTEP's MAC addresses, then the processing of the
> >>    received VXLAN packet MUST follow the procedures described in
> >>    Section 4.1 [RFC7348].
> >> To which we add:
> >>    BFD Control packets with unknown MAC address
> >>    MUST NOT be forwarded to VMs.
> >> But the unknown MACs are treated as BUM according to the last paragraph
> in Section 4.2 of RFC 7348:
> >>    Note that multicast frames and "unknown MAC destination" frames are
> >>    also sent using the multicast tree, similar to the broadcast frames.
> >> In light of that, can this draft require that BFD packets with unknown
> MAC be dropped and not flooded over the corresponding to the VNI domain? I
> think that in addition to moving the sentence up the statement must be
> updated:
> >> OLD TEXT:
> >>    BFD Control packets with unknown MAC address
> >>    MUST NOT be forwarded to VMs.
> >> NEW TEXT:
> >>    If the BFD session is using the Management VNI (Section 6),
> >>    BFD Control packets with unknown MAC address
> >>    MUST NOT be forwarded to VMs.
> >>  Comments? Suggestions?
> >>    -- Jeff
>
>