Not sure if the LISP WG alias was correct. Apologies if you receive multiple 
copies.

Thanks
Prasad

From: Vengada Prasad Govindan (venggovi)
Sent: Tuesday, March 30, 2021 13:50
To: lisp <[email protected]>
Cc: [email protected]
Subject: Requesting comments on draft-vgovindan-pim-jp-extensions-lisp

Hello LISP/ PIM WG members,

  1.  Problem Statement : In a multi-site LISP topology 
[Slides-72-RRG-3.pdf<https://www.ietf.org/proceedings/72/slides/RRG-3.pdf>], 
the site border nodes operate in 3 different PIM domains (2 in the underlay, 
one facing the LISP site and one facing the transit site and the third domain 
in the overlay):
     *   An important point to consider here would be the practical value of 
reusing the same locator address of the border node in both site-facing and 
transit-facing directions.
     *   Given the above consideration of reusing the locator address in both 
directions, using the same underlay multicast address range in the 2 different 
underlay PIM domains may cause packet loops.
     *   This is because the hashing of the overlay parameters to obtain the 
underlay group could result in hash collisions as described in Sec 8.1.2 of RFC 
6831
     *   The LISP border nodes downstream also face similar constraints.
     *   Hence, we propose a reasonable trade-off to make extra copies of the 
packet at the site border using different multicast address ranges to avoid 
packet loops. However this need not always de-generate to ingress replication.
  2.  The base idea of the draft is an extension of the RLOC receiver TLV 
specified in RFC8059. While RFC8059 defined the TLV for Ingress Replication 
(LISP Multicast over Unicast tunnels), the new draft tries to define TLVs 
needed for LISP multicast over Native multicast.
  3.  For a background on PIM J/P attribute hierarchy, please see 
[slides-94-pim-1.pdf<https://www.ietf.org/proceedings/94/slides/slides-94-pim-1.pdf>]
  4.  This draft was 
presented<https://datatracker.ietf.org/meeting/110/materials/slides-110-pim-jp-extension-lisp-multicast-underlay-00.pdf>
 to PIM WG @ IETF-110.  Minutes are recorded 
here<https://datatracker.ietf.org/doc/minutes-110-pim/>.
  5.  It has been suggested to consider this draft for presentation at the 
upcoming LISP WG meeting. Requesting questions/ comments about the draft in the 
mailing list.

Note: 
[Slides-72-RRG-3.pdf<https://www.ietf.org/proceedings/72/slides/RRG-3.pdf>] - 
Slides 12-14 in particular provides the protocol sequences. Also explained in 
RFC 6831

Thanks
Prasad

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