Subject: [dhcwg] Server Unicast Option, in DHCPv6

From: "fer g.r." <[email-masked]>
Date: Fri, 22 Oct 2004 20:13:21 +0200

Hi, I need some help to clear some doubts on the Server Unicast Option, in 
DHCPv6.

The first doubt is on the scope has the server and client address to unicast 
communication.

Initially I though that they must be global unicast addresses, but thinking 
deeply and looking at the next on RFC3315  I think it could be more 
flexible.

RFC3315, 18.1. , Page 39, second paragraph

“If the client has a source address of sufficient scope that can be
used by the server as a return address”

Attending to the “sufficient scope” of client address. Cannot we assume that 
link-local addresses are of sufficient scope to unicast communication on the 
same link?
I think that for servers and clients on the same link, they MAY use their 
link local addr. to unicast.

Is this possible or is there any error in my supposition? I wish some one 
could give me their opinion.

Finally I have a little doubt on when a server MAY or SHOULD NOT send 
Unicast Option to a client.

RFC 3315, 22.12 says:

“When the server sends a Unicast option to the client, some messages
from the client will not be relayed by Relay Agents, and will not
include Relay Agent options from the Relay Agents.

Therefore, a server should only send a Unicast option to a client when Relay 
Agents are not sending Relay Agent options.”

I wonder the real meaning of “when Relay Agents are not sending Relay Agent 
options”.

It means that for a particular client, whose message relayed from a R.A. 
includes Relay Agent options, then the server SHOULD NOT send Unicast option 
to that client? or it means that if any message from any R.A. includes Relay 
Agent options then the server SHOULD NOT send Unicast option to any client? 
(I suppose the former).

But in any case, at the moment the R.A. don’t send Relay Agent Options in 
one message can the server assumes that since that it can send Unicast 
Options to the client/s?

Any opinions and help on these would be appreciated.

Thank, bye.

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---

From: Ted Lemon <[email-masked]>
Date: Sun, 7 Nov 2004 12:56:51 -0500

On Oct 22, 2004, at 2:13 PM, fer g.r. wrote:
> Attending to the “sufficient scope” of client address. Cannot we 
> assume that link-local addresses are of sufficient scope to unicast 
> communication on the same link?
> I think that for servers and clients on the same link, they MAY use 
> their link local addr. to unicast.

That is what the language says, and in fact it's what has to happen, or 
else the client can't communicate with the DHCP server, so I would say 
that your reading of it is correct.