[dhcwg] [Fwd: new issue: LL34 Better transition to routable from v4LL usingDHCP]

[Erik Guttman <erik.guttman@sun.com>]

Please send comments on this issue to <zeroconf@merit.edu>.
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 <erik.guttman@sun.com>
To: zeroconf@merit.edu
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  aboba@internaut.com
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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