Subject: [pim] draft-ietf-pim-igmp-mld-extension-01.txt - change subnet to link

From: "James A. (Jim) Stevens" <[email-masked]>
Date: Sun, 26 Jul 2020 23:57:33 -0500

SUMMARY - I recommend changing "subnet" to "link" in
draft-ietf-pim-igmp-mld-extension-01.txt

DETAILS -

RFC 4903 (Multi-Link Subnet Issues) defined subnet and link in Section 2.2
as follows:

   The term "link" is generally used to refer to a topological area
   bounded by routers that decrement the IPv4 TTL or IPv6 Hop Limit when
   forwarding the packet.  A link-local address prefix is defined in
   both IPv4 [RFC3927] and IPv6 [RFC4291].

   The term "subnet" is generally used to refer to a topological area
   that uses the same address prefix, where that prefix is not further
   subdivided except into individual addresses.

Later on RFC 4903 section 4.1 recommends BUT DOES NOT MANDATE single-link
subnets over multi-link subnets:

   A multi-link subnet model should be avoided.  IETF working groups
   using, or considering using, multi-link subnets today should
   investigate moving to one of the other models.

Section 4 of draft-ietf-pim-igmp-mld-extension-01.txt has the following
sentence

   When defining new types, care must be taken to ensure that nodes that
   support the type can co-exist with nodes that don't, on the same subnet.

My understanding is that this sentence and is describing nodes that can
directly communicate with each other, i.e. the meaning of "link".

Also, there are some networks, such as some military MANET networking
waveforms that I work with, that support multi-link subnets and PIM
multicasting.

Thus, I recommend that the word "subnet" be changed to "link" in
draft-ietf-pim-igmp-mld-extension-01.txt

Jim Stevens

On Sun, Jul 12, 2020 at 2:02 PM <[email-masked]> wrote:
>
> Date: Sun, 12 Jul 2020 11:52:17 -0700
> From: [email-masked]
> To: <[email-masked]>
> Cc: [email-masked]
> Subject: [pim] I-D Action: draft-ietf-pim-igmp-mld-extension-01.txt
> Message-ID: <[email-masked]>
>
> A New Internet-Draft is available from the on-line Internet-Drafts
directories.
> This draft is a work item of the Protocols for IP Multicast WG of the
IETF.
>
>         Title           : IGMPv3/MLDv2 Message Extension
>         Authors         : Mahesh Sivakumar
>                           Stig Venaas
>                           Zheng(Sandy) Zhang
>                           Hitoshi Asaeda
>         Filename        : draft-ietf-pim-igmp-mld-extension-01.txt
>         Pages           : 11
>         Date            : 2020-07-12
>
> Abstract:
>    IGMP and MLD protocols are extensible, but no extensions have been
>    defined so far.  This document provides a well-defined way of
>    extending IGMP and MLD, using a list of TLVs (Type, Length and
>    Value).
>
> The IETF datatracker status page for this draft is:
> https://datatracker.ietf.org/doc/draft-ietf-pim-igmp-mld-extension/