Subject: Re: new issue: LL34 Better transition to routable from v4LL using DHCP

From: Bernard Aboba <[email-masked]>
Date: Sat, 13 Sep 2003 22:36:11 -0700 (PDT)

>The Zeroconf list is a strange place to be re-designing DHCP.

I'd propose that we punt this issue to the DHC WG and use the following
text for Section 2.11:

2.11  Transition from Link-Local IPv4 to Routable Address

As discussed in Section 1.7, use of a routable address is preferred to
assignment of a Link-Local IPv4 address.  A Link-Local IPv4 address can be
configured due to transient failures, such as incomplete link-layer authentication,
spanning tree convergence issues, or because a DHCP server failed
to respond to an initial query, or is inoperative for some time.

Where a Link-Local IPv4 address is assigned due to a transient failure,
experience has shown that five minutes (see Appendix A.2) may be
too long an interval to wait prior to attempting to configure with DHCP.
This document does not specify a strategy for quickly recovering a
routable address in situations where a Link-Local IPv4 address is assigned
due to a transient failure.  In situations where many hosts are present on
a single subnet, frequent attempts to contact the DHCP server could result
in a heavy traffic load.  Further discussion of this issue is provided in
[DNAv4].

[DNAv4]
Aboba, B., "Detection of Network Attachment (DNA) in IPv4",
draft-ietf-dhc-dna-ipv4-01.txt, Internet draft (work in progress),
September 2003.

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From: Mark Stapp <[email-masked]>
Date: Fri, 19 Sep 2003 16:48:51 -0400

I haven't seen anyone respond to Bernard's proposal yet, and I think it 
deserves support. It's best to explicitly exclude this issue and to avoid 
trying to recommend tweaks to stable DHCP deployments in anticipation of 
wide v4LL use. As Bernard observes, there are many possible conditions that 
can lead to a temporary lapse in DHCP service. Adding another variable to 
the mix as a result of LL is unlikely to help in most existing networks.

I'd like the LL draft to avoid making requirements of DHCP, and I'd like to 
see Bernard's suggested text included.

-- Mark