Re: [bess] draft-ietf-bess-evpn-overlay-10 PMSI with Ingress Replication

["Ali Sajassi (sajassi)" <[e-mail]>]

Hi Marco,

If an implementation doesn’t add PMSI to an IMET route, then that implementation is broken. RFC 7432 says:
“In order to identify the P-tunnel used for sending broadcast, unknown
   unicast, or multicast traffic, the Inclusive Multicast Ethernet Tag
   route MUST carry a Provider Multicast Service Interface (PMSI) Tunnel
   attribute as specified in [RFC6514<https://tools.ietf.org/html/rfc6514>].”
An section 9 of evpn-overlay says:
“This route is tagged
   with the PMSI Tunnel attribute, which is used to encode the type of
   multicast tunnel to be used as well as the multicast tunnel
   identifier. The tunnel encapsulation is encoded by adding the BGP
   Encapsulation extended community as per section 5.1.1.”

There should be no ambiguity here. The BGP encapsulation EC can be optional if MPLS encap or static config is used – ie, section 5.1.3 says” if the BGP Encapsulation extended community is not present, then either MPLS encapsulation or a statically configured encapsulation is assumed”.

Cheers,
Ali


From: BESS <[e-mail]> on behalf of Marco Marzetti <[e-mail]>
Date: Thursday, December 14, 2017 at 6:20 AM
To: Thomas Morin <[e-mail]>
Cc: "[e-mail]" <[e-mail]>
Subject: Re: [bess] draft-ietf-bess-evpn-overlay-10 PMSI with Ingress Replication

Hello,

I have encountered an implementation that is not attaching any PMSI to the IMET.
The authors think they don't really need it because they only support Ingress Replication.
Such behavior breaks interoperability with other implementations that are dropping the NLRI if PMSI is not attached.

So i looked at draft-ietf-bess-evpn-overlay-10 and noticed that there's no clear indication of what the proper behavior is.
As said i assumed i had to look at RFC7432 and RFC6514 (and i did it), but i wasn't 100% sure and i preferred to ask.

Onestly you already made my day by confirming what i thought.
My suggestion was to make things more clear, but i admit that it could look redundant.

Thanks







On Thu, Dec 14, 2017 at 2:39 PM, Thomas Morin <[e-mail]<mailto:[e-mail]>> wrote:
Hi Marco,

Marco Marzetti, 2017-12-14 12:25:
> I am writing this email asking you to clarify what's the suggested
> behavior when PMSI Tunnel Type is set to "Ingress Replication" (type
> 6) as draft-ietf-bess-evpn-overlay-10 only suggests what to do with
> multicast tunnel trees.
>
> I think the originating PE should conform with RFC6514 and RFC7432
> (from which you've taken inspiration) and always (RFC2119 MUST)
> attach PMSI Tunnel attribute with the Tunnel Type set to Ingress
> Replication and Tunnel Identifier set to a routable address of the PE
> itself (more specifically NVE's IP address).
>
> Is that correct?
> In that case i suggest to add the following line at the end of
> Section 9.
> """
> For Ingress Replication the PE should follow what's stated in RFC6514
> Section 5 .
> """

The text of section 9 lists "Ingress Replication" in the list of tunnel
types that can be used. My understanding is that, in the absence of
anything being specifically said for Ingress Replication, an
implementation should follow what is said in RFC7432 and RFC6514. (What
other specs could it follow to implement this supported type ? RFC7432
and RFC6514 are more than an inspiration here, these are specs that the
document refers to explicitly)

So I'm not sure that it is useful or needed to add text.

Can you perhaps expand on why the current text would possibly be
ambiguous, misleading or incomplete...?

-Thomas



--
Marco