Subject: [dhcwg] DNA Issue 34: Use of DNA with IPv4LL and Static Addresses

From: Bernard Aboba <[email-masked]>
Date: Wed, 12 Oct 2005 08:52:22 -0700 (PDT)

Issue 34: Use of DNA with IPv4LL and Static Addresses
Submitter name: Stuart Cheshire
Submitter email address: [email-masked]
Date first submitted: October 12, 2005
Reference: 
Document: DNA-16
Comment type: T
Priority: S
Section: 2.1, 2.3
Rationale/Explanation of issue: 

In Section 2.1 Delete:

"A host MUST NOT use the reachability test to
confirm configuration of an IPv4 Link-Local
address or a statically assigned IPv4 address."

In Section 2.3, delete:

" As described in [RFC3927] Appendix A, once a Link-Local IPv4 address
is assigned, existing implementations do not query the DHCPv4 server
again for five minutes. This behavior violates [RFC2131] Section
4.1:

The retransmission delay SHOULD be doubled with
subsequent retransmissions up to a maximum of 64 seconds.

Instead of waiting for five minutes, a DHCP client should continue to
retry every 64 seconds, even after allocating a IPv4 Link-Local
address. If the DHCP client succeeds in obtaining a routable
address, then the IPv4 Link-Local address is deprecated, as noted in
[RFC3927] Section 1.9."

Add:

"DNAv4 applies only to previously-configured addresses that had some
lease lifetime associated with them, during which lifetime the
address may be legitimately regarded as being reserved for exclusive
use by the assigned host. DHCP-assigned addresses fit this
description, as do manually-assigned addresses, which can be treated
as equivalent to DHCP-assigned addresses with an infinite lifetime.

IPv4 Link-Local address [RFC3927] do not fit this description, since
IPv4 Link-Local addresses are not handed out by an authoritative
server, and do not come with any guaranteed usable lifetime. A
host's claim on an IPv4 Link-Local address is valid only as long as
that host remains connected to the link, actively defending against
probes for its chosen address. As soon as a host shuts down, sleeps,
or otherwise disconnects from a link, it immediately relinquishes any
claim it may have had on any IPv4 Link-Local address on that link. A
host wishing to reclaim a previously-used IPv4 Link-Local address
MUST perform the full probing and annoucement process required by
[RFC3927], and MUST NOT attempt to use DNAv4 as a shortcut to bypass
that process."

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