Re: [bess] Éric Vyncke's Abstain on draft-ietf-bess-mvpn-fast-failover-13: (with COMMENT)

Hi Eric,

You say "because of the use outside of a node of the IPv4-mapped IPv6 addresses in section 3.1.6.1. A reply on this topic will be welcome."

I understand your point about using IPv4-mapped IPv6 address "::ffff:127.0.0.0/104", as it is assumed to never leave a node and should never be transmitted over the Internet (RFC5156).

This I believe is something borrowed into IETF since RFC4379, which is almost the SAME time as RFC4291, when the RFC5156 hadn't been produced.

Beyond this timeline reason, the use of "::ffff:127.0.0.0/104" still has some other reasons.
One reason I can see, a SINGLE loopback IPv6 address "::1" is not enough then for RFC4379 use cases ! 
Because RFC4379 originally designed for MPLS, so it requires a "randomly chosen" loopback address for ECMP! See below RFC4379 section 4.3:

4.3.  Sending an MPLS Echo Request

   An MPLS echo request is a UDP packet.  The IP header is set as
   follows: the source IP address is a routable address of the sender;
   the destination IP address is a (randomly chosen) IPv4 address from
   the range 127/8 or IPv6 address from the range
   0:0:0:0:0:FFFF:127/104.

Ever since SRv6/IPv6 native approach is produced as an alternative of MPLS in a limited-domain, the need of "randomly chosen" loopback address is relieved because the IPv6 Flow Label could do the ECMP thing.

However, many different OAM tools like Ping/trace, Twamp/Stamp, BFD need to use mechanism like RFC4379 (now updated to RFC8029), with an IPv4/IPv6 loopback address as destination address of a tunneled packet, and with different UDP destination ports to distinguish different OAM tools.

Unfortunately this will open more attack threats because of the UDP ports opened.

I think there is still strong need for OAM to have IPv6 loopback address block(s) instead of a SINGLE one currently in RFC4291, thus the many UDP ports for differentiating OAM tools may be reduced by using many IPv6 loopback addresses. 

There is also other observations and discussions from the view of internet/app (by comparison, the OAM case is from the view of limited-domain), stating that IPv6 loopback address block(s) are needed. See <draft-smith-v6ops-larger-ipv6-loopback-prefix-04>.

Thanks
Jingrong

-----Original Message-----
From: BESS [mailto:bess-bounces@ietf.org] On Behalf Of éric Vyncke via Datatracker
Sent: Wednesday, December 16, 2020 6:06 PM
To: The IESG <iesg@ietf.org>
Cc: slitkows.ietf@gmail.com; bess-chairs@ietf.org; draft-ietf-bess-mvpn-fast-failover@ietf.org; bess@ietf.org
Subject: [bess] Éric Vyncke's Abstain on draft-ietf-bess-mvpn-fast-failover-13: (with COMMENT)

Éric Vyncke has entered the following ballot position for
draft-ietf-bess-mvpn-fast-failover-13: Abstain

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The document, along with other ballot positions, can be found here:
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----------------------------------------------------------------------
COMMENT:
----------------------------------------------------------------------

Thank you for the work put into this document.

I have balloted ABSTAIN in the sense of "I oppose this document but understand that others differ and am not going to stand in the way of the others." because of the use outside of a node of the IPv4-mapped IPv6 addresses in section 3.1.6.1. A reply on this topic will be welcome.

Stéphane in his doc shepherd's write up states that no implementation is known for a document born in 2008... Does the IETF really want to have this on the proposed standards track ?

Please find below my ABSTAIN point, some non-blocking COMMENT points (but replies would be appreciated), and one nits.

I hope that this helps to improve the document,

Regards,

-éric

== ABSTAIN ==
-- Section 3.1.6.1 --
I appreciate that the BFD WG relies on "::ffff:127.0.0.0/104" but those IPv4-mapped IPv6 addresses are assumed to never leave a node and should never be transmitted over the Internet (see https://tools.ietf.org/html/rfc5156#section-2.2). This is the cause of my ABSTAIN. As the inner packet is sent over a tunnel, why not using the a link-local address or the ff02::1 link-local multicast group ?

== COMMENTS ==

-- Section 2.3 --
The use of "upstream" and "Upstream" could be confusing... The latter could have been "Upstream PE/ABSR" (often used later in the document) or "ingress node"

-- Section 3.1.6 --
Could the "BFD Discreminator" attribute be used for other purpose than this document? If so, then why not specifying it in *another* document?

Should this document clearly state that it does not define any TLV ?

== NITS ==

As I am probably not the only reader have difficulties to remember RFC contents by their number, may I suggest to prefix the RFC numbers with their titles ?
Esp in the introduction ;-)

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