Re: [dhcwg] I-D Action: draft-ietf-dhc-rfc3315bis-09.txt - questions about Solicit Prefix Delegation - src LL vs GUA

Alexandre Petrescu <> Wed, 18 October 2017 20:03 UTC

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To: 神明達哉 <>
Cc: "Bernie Volz (volz)" <>, "" <>
References: <> <> <> <> <> <> <> <> <> <> <>
From: Alexandre Petrescu <>
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Date: Wed, 18 Oct 2017 22:03:26 +0200
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Subject: Re: [dhcwg] I-D Action: draft-ietf-dhc-rfc3315bis-09.txt - questions about Solicit Prefix Delegation - src LL vs GUA
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Le 18/10/2017 à 19:57, 神明達哉 a écrit :
> At Wed, 18 Oct 2017 19:42:16 +0200, Alexandre Petrescu
> <> wrote:
>>> *  If the server receives the message directly from the client
>>> and the source address in the IP datagram in which the message
>>> was received is a link-local address, then the client is on the 
>>> same link to which the interface over which the message was 
>>> received is attached.
>> That is useful guidance if the question was about on which link
>> this Client was.  In my case the link involves GTP, UDPv4 and
>> IPv6.
>> But I need guidance to the following question: if the Client sends
>> a Solicit with a LL in src, MUST the Server reply to it?  (yes/no
>> is the needed guidance).
> I don't see the need for such guidance, at least as part of 
> rfc3315bis.  What's your problem if we didn't have such guidance in 
> normative text like a "MUST"?

The problem is the following: exchange between Client and Server does
not work.  CLient believes it needs to send LL in src, whereas Server
believes the Client should use GUA in src.  There are other fields on
which the problem may reside (port number, IA_ID, and others); each
needs separate treatment.

That's a problem.

With respect to GUA-vs-LL in src there is no guidance in 3315bis.

If one wants to change this, i.e. make sure Server to accept LL in src
of Solicit, then one  typically is suggested to first come with an
actual business impact.

That is not normal.

Either LL-in-src MUST be accepted at Server as a standard, or MUST NOT.
  It's not a matter of business impact.

We can turn around phrases as much as we want, but interoperability is
not there.

>> I explain why: about 4 distinct clients use LL in src.  If I want
>> these clients to use GUA then I must delete the LL from the
>> interface.
> This one itself doesn't sound like a problem.  Do you have any 
> specific problem with the clients sending a solicit from a
> link-local address?

With respect, I think you did not understand what I wrote.  Please re-read.

Myself I dont have a problem with Clients sending Solicit with src-LL.
But Server MAY have a problem.  Because the example traces of Server I
have always uses GUA-in-src.  I dont want to follow that example, but I
cant tell the Server's Programmer that is not standard.  Because there
is no guidance.

To come back to my question: do you think it is ok to delete the LL from
the interface?


> -- jinmei