Re: [dhcwg] Follow up from IETF-95 - draft-ietf-dhc-dhcpv6-prefix-length-hint-issue

[神明達哉 <[e-mail]>]

At Sat, 30 Apr 2016 09:51:02 +0800,
tianxiang li <[e-mail]> wrote:

> Thank you reviewing the document and providing your comments. Unlike other
> hints such as T1 T2 lifetimes, which could be easily ignored by the server,
> completely ignoring the prefix-length hint would cause some functional
> issues for the client, how the prefix-length hint should be handled is a
> bit more complicated, and it should be given more considerations. We
> believe there is actual requirement for some ISPs to clarify how it should
> work, and understand the expectations of the client and server. E.g. If a
> server has an existing binding for a prefix length different from what the
> client is currently requesting, what should it do? This is the case when
> the client changed its home router configuration and it needs a shorter
> prefix. Also, if a client didn’t get the prefix it wanted, should it
> continue to ask for the preferred prefix (during Renew/Rebind)? Or should
> the server remember what the client originally requested, and assign it a
> new prefix if it should become available? These are some issues we are
> trying to clarify in the document, so that servers which DO want to
> understand the client’s actual prefix requirement, would know how the
> prefix-length hint should be handled, to make it work well. I'm not sure
> whether there is the same problem for addresses, it might be something
> worth discussing.

The above statement basically seems to be a statement of what's
written in the draft.  So the "problem statement" still seem to be
artificial to me.  Is there actually a service provider that is
willing to behave differently depending on the hint prefix length
specified by the requesting router, for example?  If there's such an
operational case, I see the need for the clarification.  But I've not
heard of such a practical motivation yet (it's quite possible that I
simply don't know it especially most of other wg members don't seem to
have this question.  so I'm happy to be corrected).

--
JINMEI, Tatuya