Subject: RE: [Tsvwg] RFC2960bis ... heads up Steve

From: [email-masked]
Date: Wed, 9 May 2001 16:16:25 +0300

Hi Randy

> The problem is not for lack of solutions :> 

The problem is finding the correct one!

> The real question is which one should we use? I lean towards A/1 but
> others leaned toward the B/2... What we thought we would do is write 
> a seperate draft defining the problem and address it to the IPv6 
> community. In particular the multi-homing IPv6 group as well as 
> the IPv6 WG itself... and see if  they had some advice/opinions..

Well, could we just ping some people on this subject (form even
a mini-design team) to work this out for the BIS draft.  As 
SCTP & IPv6 will be seeing deployment in the 2nd half of the 
year, I think we should at least get a good solution for this 
soon.

John

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From: Randall Stewart <[email-masked]>
Date: Wed, 09 May 2001 08:40:09 -0500

> year, I think we should at least get a good solution for this

John,

This was one of the reasons I added Steve to the list.. who is still
silent.. maybe I will give him a call later today and prompt him
to read the email.. I know he has a worse email backlog than I :)

R

-- 
Randall R. Stewart
Systems & Solutions Engineering
Cisco Systems Inc.
[email-masked] 815-342-5222 or 815-477-2127

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From: Kacheong Poon <[email-masked]>
Date: Wed, 9 May 2001 12:30:45 -0700 (PDT)

> year, I think we should at least get a good solution for this 

Talking about selecting the correct set of addresses in the
INIT/INIT_ACK chunk, I don't think we have a good idea about
what to do with v4 addresses, let alone v6...  I remembered
we had a brief discussion about this some time back.  But I
don't think anyone has come up with a good solution.  And
it seems to me that this kind of address selection will
necessarily involve site policy.

Just for an imaginary example, every machines in a company has
2 IPv4 addresses, each from a different ISP.  So the policy may be
that talking to another site of that company should not use
addresses from ISP x because of, say, security and cost.  I think
people can come up with all sorts of other examples which a policy
is required.

This leads me to think that whether it is appropriate to
include this kind of discussion in the 2960bis.  The concern
is that it is not really a protocol issue.  It becomes an
implementation or system administration issue.  And I don't
thinkt it is a good idea to include this kind of dicussion in
a protocol standard.

On the other hand, if we know of something that definitely
should not be done, we may consider it putting in 2960bis.  For
example, if the INIT chunk does not have a link local address,
SCTP should not include any link local addresses in the reply.
But the reverse may not be straight forward.  Should SCTP return
link local address if the INIT chunk has a link local address?
This is tricky.  It makes perfect sense in some cases but not
in other.

So I'd suggest not putting this kind of discussion in the bis,
but have another document discussing this issue.

							K. Poon.
							[email-masked]

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From: Randall Stewart <[email-masked]>
Date: Fri, 11 May 2001 13:14:35 -0500

Kacheong:

with a bit of ftp and other hookery I now can reply to this
message... messages that do not cc me directly at my cisco addres
in general are delayed until I can do extra work to get them :< still
have the northpoint flu....:<<

> necessarily involve site policy.

I disagree with this Kacheong. We do know what address set you
send.. and even more so we MUST have some sort of specification
in the IPv6 world or we will surely create a black-hole problem.

> people can come up with all sorts of other examples which a policy

And there are ways to only bind a single address... or use the
del-ip address in the add extension to knock off one from
consideration..

> thinkt it is a good idea to include this kind of dicussion in

Oh I most whole heartedly dis-agree. Any time you have an
issue that can make a protocol die... with a OOTB abort from
a site local that you listed that was duplicated at a local site..
it becomes a protocol issue. Otherwise you end up getting 
SCTP connections that break at random times in unexpected ways..

> This is tricky.  It makes perfect sense in some cases but not

No I strongly disagree.. I have been down this road... You have not
coded it .. I can see. If I put Link-Local addresses inside a
INIT-ACK you the receiver have NO WAY to know which sin6_scope_id
goes with the Link-Local address... and the sender has NO WAY of 
knowing what our scopeid is even if we had a way to send it.

Link local addresses will ONLY work if the IP source/destination
in the actual IP datagram (from address in some of my previous
email) has a link-local address..

> but have another document discussing this issue.
sorry, I disagree. This is a very very important inter-operability issue
that
by ignoring will cause horrible problems in the future...

R

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From: Kacheong Poon <[email-masked]>
Date: Fri, 11 May 2001 18:57:16 -0700 (PDT)

> in the IPv6 world or we will surely create a black-hole problem.

Maybe I miss the discussion on selecting v4 addresses...  So what
v4 addresses should be sent if a machine has 12 bound to the same
interface?  I remembered last time when we talked about this, the
conclusion is not to send all of them unless for some conditions.
I think there are other cases to be considered.  Is there a draft
talking about this which I miss?  This kind of selection definitely
involves site policy.  And I believe we have not talked about that
either.

> del-ip address in the add extension to knock off one from

The issue we are considering here is what policy should be
used, not how something is done...

> SCTP connections that break at random times in unexpected ways..

This is not a protocol issue.  The protocol spec never mentions
how addresses should be selected.  This is the correct choice because
it should not be concerned about that.  If the user of SCTP screws
up and its association is aborted, it is the user's problem.  This
becomes a protocol issue if by selecting a perfectly reasonable set of
addresses, the association is aborted.  Note the subtle difference
here.

> email) has a link-local address..

See my previous mail about a situation when this can work.  Note
that I am not suggesting people to try it!  And I am not saying that
your rule set is not good.  I just want to make sure that the rule
set is not put in the standard spec.  The rule set can be in a BCP
document.  That's fine with me.

> by ignoring will cause horrible problems in the future...

Then write another document describing it.  It is not wise to
put it in 2960 bis.

							K. Poon.
							[email-masked]