Re: Adam Roach's Discuss on draft-ietf-6man-maxra-03: (with DISCUSS and COMMENT)

[神明達哉 <[e-mail]>]

At Thu, 26 Oct 2017 21:43:42 -0700,
Ole Troan <[e-mail]> wrote:

> It might be worth noting that if it is inclusive or exclusive has
> absolutely zero consequence for the protocol.

FWFIW, an implementation that I know of adopts the "inclusive" version
of "between" (it doesn't support 6man-maxra so it still only conforms
to RFC4861):

    MAYHAVE(val, "rltime", rai->rai_maxinterval * 3);
    if ((uint16_t)val && ((uint16_t)val < rai->rai_maxinterval ||
        (uint16_t)val > MAXROUTERLIFETIME)) {
        syslog(LOG_ERR,
            "<%s> router lifetime (%" PRIu32 ") on %s is invalid "
            "(must be 0 or between %d and %d)",
            __func__, val, ifi->ifi_ifname, rai->rai_maxinterval,
            MAXROUTERLIFETIME);
        goto getconfig_free_rai;
    }
(https://github.com/freebsd/freebsd/blob/master/usr.sbin/rtadvd/config.c)

But, more important, I agree with Bob and Ole in that "inclusive" vs
"exclusive" shouldn't cause an interoperability problem since hosts
are not supposed to reject an RA for a particular value of router
lifetime:

      Router Lifetime
                     16-bit unsigned integer.  The lifetime associated
                     with the default router in units of seconds.  The
                     field can contain values up to 65535 and receivers
                     should handle any value, while the sending rules in
                     Section 6 limit the lifetime to 9000 seconds.  [...]

If anything, if we now "clarify" it to mean "exclusive", at least one
implementation will now become technically non-compliant.  So, while
my primary suggestion is not to do anything about it, if we really
need to say something, I'd suggest clarifying "whether this 'between'
is inclusive or exclusive does not matter in terms interoperability
and is left to implementations".

--
JINMEI, Tatuya