[trill] Alvaro Retana's Discuss on draft-ietf-trill-arp-optimization-06: (with DISCUSS)

["Alvaro Retana" <[e-mail]>]

Alvaro Retana has entered the following ballot position for
draft-ietf-trill-arp-optimization-06: Discuss

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DISCUSS:
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I know this is an optional optimization, as described by the “MAY” in the
Introduction.  However, some of the other normative language is not as
strong as it should be to clearly specify the required behavior (if the
mechanisms are being used), cause confusion, or is simply out of place.

1. In 3.1 (Get Sender's IP/MAC Mapping Information for Non-zero IP) the
text says that the “RBridge MAY use different strategies to do so”.  That
“MAY” contradicts the “SHOULD” used before it, which directs the RBridge
to verify a duplicate address.  s/MAY/may

2. Still in 3.1: “…the RBridge SHOULD verify if a duplicate IP address
has already been in use…”  What are the reasons where the RBridge would
not verify this situation?  IOW, why is this “SHOULD” not a “MUST”?

3. I’m confused as to whether the APPsub-TLV is required or not.  The
source of my confusion comes from Section 3.3 (Determine How to Handle
the ARP/ND Response) which says that “R2 SHOULD initiate a link state
update to inform all the other RBridges of the target's location…The
update message can be carried by an IA APPsub-TLV [IA-draft]…”  This text
seems to say that the APPsub-TLV SHOULD be used to carry the information
— but text in Section 2 (IP/MAC Address Mappings) sounds to me as if the
use of the APPsub-TLV is optional: “If the RBridge has extracted the
sender's IP/MAC address pair from the received data packet (either ARP or
ND), it MAY save the information and use the IA APPsub-TLV…”  Also, 3.1
and 3.2 both say that an “RBridge MAY use the IA APPsub-TLV”.  And
finally the Security Considerations section seems to recommend using it… 
Maybe it’s just me, but please clarify.  [BTW, if it is required, then I
think that both the IA-draft and DirMech references should be
Normative.]

4. In Section 2 (IP/MAC Address Mappings) the “MAY” in the following
sentence is out of place since that is already the function of the
confidence (as described in draft-ietf-trill-ia-appsubtlv and RFC6325):
“A different confidence level MAY also be used to indicate the
reliability of the mapping information.”

5. In Section 3.2 (Determine How to Reply to ARP/ND), both options (?) a
and b say that the “RBridge MAY take one…”.  If the RBridge selected that
option, then I think the action is no longer optional.  s/MAY/MUST