Re: [mpls] I-D Action: draft-kompella-mpls-larp-10.txt

Erik Auerswald <auerswald@fg-networking.de> Wed, 14 July 2021 11:14 UTC

Return-Path: <auerswald@fg-networking.de>
X-Original-To: mpls@ietfa.amsl.com
Delivered-To: mpls@ietfa.amsl.com
Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id A61223A08EB; Wed, 14 Jul 2021 04:14:00 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -0.411
X-Spam-Level:
X-Spam-Status: No, score=-0.411 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, FAKE_REPLY_C=1.486, RCVD_IN_DNSWL_BLOCKED=0.001, SPF_HELO_NONE=0.001, SPF_NONE=0.001] autolearn=ham autolearn_force=no
Received: from mail.ietf.org ([4.31.198.44]) by localhost (ietfa.amsl.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id vkvnOW3riWDr; Wed, 14 Jul 2021 04:13:58 -0700 (PDT)
Received: from mailgw1.uni-kl.de (mailgw1.uni-kl.de [IPv6:2001:638:208:120::220]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id 1C6623A08E2; Wed, 14 Jul 2021 04:13:54 -0700 (PDT)
Received: from mail.fg-networking.de (mail.fg-networking.de [IPv6:2001:638:208:cd01::23]) by mailgw1.uni-kl.de (8.14.4/8.14.4/Debian-8+deb8u2) with ESMTP id 16EBDoul164648 (version=TLSv1/SSLv3 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Wed, 14 Jul 2021 13:13:50 +0200
Received: from login.fg-networking.de (login.fg-networking.de [IPv6:2001:638:208:cd01::41]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by mail.fg-networking.de (Postfix) with ESMTPS id 200412006C; Wed, 14 Jul 2021 13:13:43 +0200 (CEST)
Received: by login.fg-networking.de (Postfix, from userid 11002) id D858F125; Wed, 14 Jul 2021 13:13:43 +0200 (CEST)
Date: Wed, 14 Jul 2021 13:13:43 +0200
From: Erik Auerswald <auerswald@fg-networking.de>
To: draft-kompella-mpls-larp.authors@ietf.org
Cc: mpls@ietf.org
Message-ID: <20210714111337.GA106093@fg-networking.de>
MIME-Version: 1.0
Content-Type: text/plain; charset=iso-8859-1
Content-Disposition: inline
Content-Transfer-Encoding: 8bit
In-Reply-To: <162605655979.5770.14564864647635776885@ietfa.amsl.com>
User-Agent: Mutt/1.10.1 (2018-07-13)
Archived-At: <https://mailarchive.ietf.org/arch/msg/mpls/ekPKzVVgwUoxmzPd-yximgVrrLw>
Subject: Re: [mpls] I-D Action: draft-kompella-mpls-larp-10.txt
X-BeenThere: mpls@ietf.org
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: Multi-Protocol Label Switching WG <mpls.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/mpls>, <mailto:mpls-request@ietf.org?subject=unsubscribe>
List-Archive: <https://mailarchive.ietf.org/arch/browse/mpls/>
List-Post: <mailto:mpls@ietf.org>
List-Help: <mailto:mpls-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/mpls>, <mailto:mpls-request@ietf.org?subject=subscribe>
X-List-Received-Date: Wed, 14 Jul 2021 11:14:01 -0000

Dear Authors,

thanks for sending an updated version of the L-ARP draft.

The L-ARP mechanism seems to be a nice and simple solution to extend an
MPLS fabric to hosts, e.g., for hypervisor based network virtualization
over MPLS.

I think that section 3, L-ARP Protocol Operation, could be made even
clearer with a few simple changes.  I'll first describe my suggested
changes, and then provide text for direct inclusion in the draft for
your convenience.

Section 3 illustrates L-ARP operation based on an example topology,
looking at egress, ingress, and data plane operation.  This uses four
named LSRs (T1 to T4), three named hosts (H1 to H3), two named transport
labels (L3 and TL3/L1/L), and one named VPN label (VL3).

I think it would be clearer and more consistent if a single name were used
for the second named transport label instead of three different names.

I would suggest to use "TL3," since this label is a transport label to
reach H3.  (Both "TL3" and "L1" are used thrice and thus require the same
amount of changes, but "TL3" corresponds better to "VL3".  Additionally,
one could assume "L1" to be a transport label allocated by T1 to reach
H1, just as "L3" is the transport label allocated by T3 to reach H3.)

Additionally, one sentence seems to have a typo in an LSR name, using
"T" instead of "T4".

Thus I would suggest the following text changes:


1. In the second paragraph of section 3 (on page 5) replate "T" with "T4":

  OLD:

   H1 might also want to talk to a member of the MPLS Fabric, say T.

  NEW:

   H1 might also want to talk to a member of the MPLS Fabric, say T4.


2. In enumeration point 2 in section 3.3 (on page 5) replace "L1" with "TL3":

  OLD:

   2.  if it does, T1 allocates a label TL3 to reach H3 (if it doesn't
       already have such a label) and installs an L-FIB entry to swap L1
       with the label (stack) to reach H3.

  NEW:

   2.  if it does, T1 allocates a label TL3 to reach H3 (if it doesn't
       already have such a label) and installs an L-FIB entry to swap TL3
       with the label (stack) to reach H3.


3. In enumeration point 3 in section 3.3 (on page 6) replace "L" with "TL3":

  OLD:

   3.  sends a (proxy) L-ARP reply to H1 with the Source Hardware
       Address (SHA) set to (L, M), where M is T1's metric to H3.  T1
       may also set some attribute bits in the SHA.

  NEW:

   3.  sends a (proxy) L-ARP reply to H1 with the Source Hardware
       Address (SHA) set to (TL3, M), where M is T1's metric to H3.  T1
       may also set some attribute bits in the SHA.


4. In the first paragraph of section 3.4 (on page 6) replace "L1" with "TL3":

  OLD:

   To send a packet to H3 over an MPLS tunnel, H1 pushes L1 onto the
   packet, sets the destination MAC address to M1 and sends it to T1.
   On receiving this packet, T1 swaps the top label with the label(s)
   for its MPLS tunnel to H3.  If T1's reachability to H3 is via a
   SPRING label stack, the label L1 acts as an implicit binding SID.

  NEW:

   To send a packet to H3 over an MPLS tunnel, H1 pushes TL3 onto the
   packet, sets the destination MAC address to M1 and sends it to T1.
   On receiving this packet, T1 swaps the top label with the label(s)
   for its MPLS tunnel to H3.  If T1's reachability to H3 is via a
   SPRING label stack, the label TL3 acts as an implicit binding SID.


Best regards,
Erik Auerswald
-- 
Dipl.-Inform. Erik Auerswald
Gesellschaft für Fundamental Generic Networking mbH
Geschäftsführung: Volker Bauer, Jörg Mayer
Gerichtsstand: Amtsgericht Kaiserslautern - HRB: 3630