Subject: Re: [Issue 1]: Preferred use of configured to v4LL address

From: Bernard Aboba <[email-masked]>
Date: Sun, 9 Feb 2003 17:36:18 -0800 (PST)

I agree with the proposed resolution to this issue in general, but wonder
about some of the implications.

For example, are we saying that a host having determined its IPv4LL
address MUST first determine whether it can obtain a routable address
(wait for DHCPv4 to complete) before claiming the address or defending it?

Are is the prohibition only to apply situations other than claim/defend?

Also, what if the host is unable to obtain a routable address? Then it
would seem like it is able to use the LLv4 address. Is the host supposed
to continue to try to obtain a routable address (e.g. try DHCP at some
interval as the original implementations did)? If it obtains a routable
address eventually, is it supposed to shut down connections that it
established previously at the LLv4 address?

My advice would be to continue to allow the host to use existing
connections, but prohibit it from establishing new ones once it has
obtained a routable address. Also if you want to go this route, then you
need to put in some language about continuing to try to obtain a routable
address.

---

From: Robert Elz <[email-masked]>
Date: Mon, 10 Feb 2003 16:24:05 +0700

Date:        Sun, 9 Feb 2003 17:36:18 -0800 (PST)
    From:        Bernard Aboba <[email-masked]>
    Message-ID:  <[email-masked]>

  | For example, are we saying that a host having determined its IPv4LL
  | address MUST first determine whether it can obtain a routable address
  | (wait for DHCPv4 to complete) before claiming the address or defending it?

That makes no sense, you can't have determined your IPv4 LL address
without claiming it (and once claimed, it must be defended if it is
to be retained).

This issue (which will become more explicit in LL23, or some other number,
once that one eventually appears on the web site - that is, LL23 (LLnn)
is al alternate proposed resolution for LL1)

  | Also, what if the host is unable to obtain a routable address? Then it
  | would seem like it is able to use the LLv4 address.

Yes.

  | Is the host supposed to continue to try to obtain a routable address

Yes, just as it would now (before LL exists) - if its DHCP (or other
mechanisms) fail, it should (from time to time) try again.

  | If it obtains a routable
  | address eventually, is it supposed to shut down connections that it
  | established previously at the LLv4 address?

No, the text I proposed in LL23 (LLnn where nn might become 23) makes
that clear I think.

  | My advice would be to continue to allow the host to use existing
  | connections, but prohibit it from establishing new ones once it has
  | obtained a routable address.

My proposed text doesn't quite go that far - rather, it prohibits it
from initiating new connections, but not from establishing a new one
initiated from some other host (which might have previously learned the
LL address and isn't yet aware that a routable address exists).

  | Also if you want to go this route, then you
  | need to put in some language about continuing to try to obtain a routable
  | address.

Yes, that would be a good idea.

kre

ps: you can find my intended LL23 (or LLnn) in a message with the
Subject: header "New Issue: TTL=255 on send, check on receive?"
(I inadvertantly sent the message with the wrong Subject line...)
It was the second of the two with the same Subject sent last Sat.

---

From: Bernard Aboba <[email-masked]>
Date: Mon, 10 Feb 2003 04:58:13 -0800 (PST)

> mechanisms) fail, it should (from time to time) try again.

But the spec doesn't require this -- or provide guidance on how frequently
this should happen, as the original did.

> No, the text I proposed in LL23 (LLnn where nn might become 23) makes

Good.

> LL address and isn't yet aware that a routable address exists).

Good.

> Yes, that would be a good idea.

I agree.