Subject: [dhcwg] [Fwd: new issue: LL34 Better transition to routable from v4LL using DHCP]

From: Erik Guttman <[email-masked]>
Date: Thu, 11 Sep 2003 14:39:25 +0200

Please send comments on this issue to <[email-masked]>.
We are attempting to wrap up discussion of this issue by 18 Sep 03.

The zeroconf wg is trying to conclude its work; this is the last
remaining open 'issue.'   We need to get our 'transitioning back
to use of routable address' story in order, however.

Thanks,

Erik

-------- Original Message --------
Date: Thu, 11 Sep 2003 11:14:02 +0200
From: Erik Guttman <[email-masked]>
To: [email-masked]
Subject: new issue: LL34 Better transition to routable from v4LL using DHCP

Description of Issue: Better transition to routable from v4LL using DHCP
Submitter Name  Bernard Aboba
Submitter Email Address  [email-masked]
Date first submitted  11 Sep 03
Reference
Comment Type  Technical
Priority  S (must change)
Section  2.11 (new section)
Rationale/Explanation of issue:

(a)  We need to ensure an orderly method for recovering a routable
       address given LLv4 addressing.  Much of the time an LLv4 address
       is allocated inappropriately,  and so it's important to be able
       to obtain a routable address via DHCP if one is available.  The
       current LLv4 spec doesn't address this, and the current default
       retry interval of 5 minutes is way too long.

(b) Interactions of DHCP with LLv4. The LLv4 specification seems to
      imply that an LLv4 address should be allocated when a DHCPREQUEST
      or DHCPDISCOVER does not obtain an answer.  Existing implementations
      show that this behavior is problematic since the lack of response is
      most likely a temporary phenomena or the result of a bug of some
      kind rather than the lack of a DHCP server on the link.

      5 minutes is too long. I'd suggest 1 minute or even less (I've
      seen a Linux implementation which retries every 30 seconds with
      jitter and that works a lot better).

Lengthy description of problem:

Requested change:

Create a new section:
2.11  Repeatedly Attempt to Obtain A Routable Address

    As per Section 1.7, use a routable address is preferred to use of
    a link-local address.  In many cases, a link-local address is
    configured because a DHCP server failed to respond to an initial
    query, or is inoperative for some time.  Experience has shown that
    five minutes (see Appendix A.2 for example) was too long an
    interval to wait and try to configure with DHCP.

    A host which has been configured with an IPv4 link-local address
    SHOULD periodically attempt to obtain an IPv4 address via DHCP.
    The recommended policy is to attempt to configure using DHCP after
    waiting for RECONF_INTERVAL, plus a random number of seconds,
    uniformly distributed, between zero to RECONF_JITTER seconds.

Modify:
9.  Constants

Add:

     RECONF_INTERVAL      25 seconds
     RECONF_JITTER        10 seconds

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