Subject: [v6ops] About RFC 6791

From: Alberto Leiva <[email-masked]>
Date: Mon, 12 Jan 2015 15:57:02 -0600

Hello

I'm trying to make sense out of RFCs 6791 and 5837 and I have three questions.

RFC 6791 says

>   the translator SHOULD implement the ICMP
>   extension defined by [RFC5837].  The ICMP message SHOULD include the
>   Interface IP Address Sub-Object and specify the source IPv6 addresses
>   of the original ICMPv6.

(1st question) Does this mean the extension should be replaced, or
should it be appended?
As in, if the packet already has an Interface Information Object
(IIO), what should the translator do with it?

Replacing sounds aggressive.
Appending sounds dangerous because it risks interfering with this from RFC 5837:

>   A single ICMP message MUST NOT contain two
>   Interface Information Objects that specify the same role.

(2nd question) What is the interface role the translator should write
in the C-Type of the IIO? (rfc5837, page 8)
RFC 6791 seems silent on this. I'm kind of casually assuming value 2
sounds like the least incorrect one, and at the same time it feels
like I'm completely missing the point of 2.
None of them seem overly concerned with remote interfaces (ie. the
translator is writing an IIO of an interface that belongs to someone
else).

(3rd question) "sub-IP component" doesn't seem to be defined anywhere.
What am I missing?

Thank you
Alberto