Re: Rtgdir last call review of draft-ietf-bfd-vxlan-07

[Greg Mirsky <[e-mail]>]

Hi Joel,
thank you for your review and the pointed questions. Please find my
answers, comments in-line and tagged GIM>>.

Regards,
Greg


On Thu, May 23, 2019 at 3:06 PM Joel Halpern via Datatracker <
[e-mail]> wrote:

> Reviewer: Joel Halpern
> Review result: Has Issues
>
> Hello,
>
> I have been selected as the Routing Directorate reviewer for this draft.
> The
> Routing Directorate seeks to review all routing or routing-related drafts
> as
> they pass through IETF last call and IESG review, and sometimes on special
> request. The purpose of the review is to provide assistance to the Routing
> ADs.
> For more information about the Routing Directorate, please see
> http://trac.tools.ietf.org/area/rtg/trac/wiki/RtgDir
>
> Although these comments are primarily for the use of the Routing ADs, it
> would
> be helpful if you could consider them along with any other IETF Last Call
> comments that you receive, and strive to resolve them through discussion
> or by
> updating the draft.
>
> Document: ddraft-ietf-bfd-vxlan-07
> Reviewer: your-name
> Review Date: date
> IETF LC End Date: date-if-known
> Intended Status: copy-from-I-D
>
> Summary: This document does not appear to be ready for publication as a
> Proposed Standard RFC.
>
> Major issues:
>     The scoping of the BFD usage is unclear.  In places, this looks like
> it is
>     intended to be used by the underlay service provider,  who will
> monitor the
>     connectivity between VTEPs.

GIM>> I think that the DCI provider would not be able to instantiate a BFD
session using VXLAN encapsulation and, possibly, monitor that VXLAN part of
forwarding operates properly. Such BFD session may monitor the path between
the two VTEP but, if there exists ECMP environment in the transport,
ensuring that that BFD session follows the same path as VXLAN data may be
challenging.

> In other places it seems to be aimed at
>     monitoring individual VNIs.

GIM>> The BFD session between VTEPs is not actually used to monitor the
particular VNI but MAY be used to communicate, as concatenated path state
signaling, the change of VNI state using the method described in Section
6.8.17 RFC 5880 <https://tools.ietf.org/html/rfc5880#section-6.8.17>.

> This is made worse when the packet format is
>     laid out.  The inner packet is an Ethernet Packet with an IP packet
> (with
>     UDP, with BFD).  This means that it is a tenant packet.

GIM>> Could you please point to the text which suggests that the BFD
control packet is a tenant packet? Meant to be delivered to a tenant?

> The IP address is
>     a tenant IP.

GIM>> The explanation of the format states in regard to the inner IP header:
       IP header:

         Source IP: IP address of the originating VTEP.

         Destination IP: IP address of the terminating VTEP.

But the diagram shows this as being the IP address of the
>     VTEP.  Which is not a tenant entity.
>


>    There is further confusion as to whether the processing is driven by
> the VNI
>    the packet arrived with, or the VNI is ignored.
>
GIM>> The use of VNI is implementation specific. Section 6 states:
 6.  Use of the Specific VNI

   In most cases, a single BFD session is sufficient for the given VTEP
   to monitor the reachability of a remote VTEP, regardless of the
   number of VNIs in common.  When the single BFD session is used to
   monitor the reachability of the remote VTEP, an implementation SHOULD
   choose any of the VNIs but MAY choose VNI = 0.
>
>
> Minor Issues:
>    N/A
>
> Nits: N/A
>
>