>>>>> On Thu, 30 May 2002 16:43:50 -0700,
>>>>> Bob Hinden <[EMAIL PROTECTED]> said:
> Independent of how this is resolved, I think the best place to define the
> route optimization implementation requirements for all IPv6 nodes is in the
> IPv6 Node Requirements document. I don't think it should be in the Mobile
> IPv6 specification because at a minimum implementers not planning to
> implement Mobile IPv6 might not see it. There is a design team effort
> underway to produce an IPv6 Node Requirements draft and I think they should
> have an -00 version out soon for w.g. review and comments. This discussion
> is important input into this document.
I fully agree. One of the most unfortunate things about the
correspondent node discussion is that it has been discussed only
within the mobileip wg. It was reasonable when the support of mobile
IP in correspondent nodes was optional. However, I don't think it
makes sense to decide something is mandatory for all nodes within a
single group that has a very specific goal (mobile IPv6 in this case).
In this sense I think it was an unfortunate thing to make the support
of home address option mandatory in the mobile ipv6 draft. It should
have been approved by the ipv6 (or ipngwg) wg (I don't remember if it
was though), and should have been documented in a basic specification
of IPv6 once approved.
As for SHOULD vs MUST: as other guys pointed out, it depends on how
the requirement solves a common situation and how the situation is
critical. Since the MUST affects all IPv6 nodes, the argument for the
MUST basically must convince all IPv6 implementors, including
OS/server vendors, router vendors, and even home appliance vendors.
Additionally, if the requirement is not configurable (i.e. there is no
knob to turn it off), the argument must also convince all IPv6
operators such as ISPs and (possibly) cellular phone companies.
Honestly, the argument for the MUST so far does not seem to me very
convincible - after all, mobile-ip (v4 or v6) nodes only occupy a very
small part in the current Internet. It may be true that more and more
"nomadic" nodes will come in the near future, where "nomadic" means
the node moves from a link to another link while working, but I'm not
fully convinced that all such "nomadic" nodes are speaking mobile IP.
I'm also not sure how many (correspondent-only) nodes will need to
communicate with mobile-IP nodes in the depicted by mobileip-ers.
Please note, however, that I'm not necessarily making an objection to
mobile-IP (v4 or v6) itself. I'm just saying the MUST is too strong,
considering the current situation and the uncertainty about the
future. With the fact that mobile IP is one of possible (though
perhaps likeliest) solutions to support nomadic nodes, I believe it is
better to make effects to other nodes as small as possible in order to
deploy mobile IP itself. So, I must vote for the SHOULD (or even
MAY). Even with the MUST, I can imagine that IPv6 stack implementors
who are not convinced will ignore the requirement. The result will be
a certain amount of "non-compliant" implementations and loss of
interoperability. Even with the SHOULD, the implementors will
implement the feature if communicating with mobile-IP nodes using the
route optimization becomes attractive enough, while keeping the
minimum interoperability. I don't just get why we cannot go with this
path.
Lastly, just saying "route optimization is mandatory" does not make
sense to me, because the specication of mobile ipv6 is far from
stabilized. The current specication may require, say, 1,000 new lines
to implement, which may or may not be a large cost. But what if it
requires 1,000,000 lines in draft-mobileip-ipv6-99? Can we still
allow the requirement just because it is the "route optimization"
which is a MUST? mobileip-ers may want to say that the
standardization will soon be done, but I've been seeing the same
phrase for a few years and cannot be that optimistic (e.g. please do
not forget that the notion of the "return routability" is very new.
how can we be 100% sure that it's stable and will not change?). Even
if the next revision of the draft passes a wg last call, we'll still
have a review period by the IESG, which is getting longer and longer
nowadays. So, we can only discuss if it is reasonable to make
"section xx of draft-yy-zz" mandatory for all IPv6 nodes. This, of
course, does not make sense much, which is another reason why the
SHOULD (or MAY) is better.
In summary:
- if we're going to make something mandatory for all IPv6 nodes, it
must be discussed in the ipv6 wg.
- (IMO) we cannot go with the MUST, considering the current situation
and some possible scenarios in the future. We should delay the
decision, or should go with a SHOULD or a MAY.
- it does not make sense just to say "the route optimization is
mandatory." we should be more specific.
JINMEI, Tatuya
Communication Platform Lab.
Corporate R&D Center, Toshiba Corp.
[EMAIL PROTECTED]
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