Subject: RE: [dhcwg] [New I-D] DHCPv6 Relay Agent Link Selection(RALS) Opt ion

From: "Kostur, Andre" <[email-masked]>
Date: Tue, 3 Oct 2006 11:22:46 -0700

Additionally, if the relay has multiple interfaces with the same link-local
address, how does filling in the link address with that value help?  The
DHCP server (and the relay) would have to depend on an Interface ID option
anyway.  I'm in support of filling in the Link Address field with zeros
(when there is no site/global address). 

-----Original Message-----
From: Bernie Volz (volz) [mailto:[email-masked]] 
Sent: Tuesday, October 03, 2006 11:13 AM
To: Templin, Fred L; Amy
Cc: [email-masked]
Subject: RE: [dhcwg] [New I-D] DHCPv6 Relay Agent Link Selection(RALS)
Option

How is it better? Perhaps because you only need to test the fe80 bits
instead of checking that all 16-octets are 0? While that may be a small
consideration, I don't give it much weight.

I think there is more value in having something be 0 if it is
unset/unspecified rather than having to check for a specific value (such as
fe80...) or range of values.

And, could there be cases where there is no link-local address? If so, you'd
still have to support the 0 value.

So, my feeling is that you should use 0 unless you have something of real
value to put there.

I fully agree that this is not clearly specified in RFC 3315 and that should
definitely be cleared up in a 3315-bis document. However, I also feel that
the existing RFC 3315 text gives more weight to don't set the field (ie,
leave it 0) if you have no global/site-scoped address. In general, when an
RFC doesn't say to add something to a message or set a given field, we have
assumed it is 0.

- Bernie

-----Original Message-----
From: Templin, Fred L [mailto:[email-masked]]
Sent: Tuesday, October 03, 2006 1:51 PM
To: Bernie Volz (volz); Amy
Cc: [email-masked]
Subject: RE: [dhcwg] [New I-D] DHCPv6 Relay Agent Link Selection(RALS)
Option

Bernie,

responding to:
> In other forums there has been some discussions as to whether to place
a
> link-local address into this field, but IMHO I think that is a bad
idea
> as it conveys no information
and:
> Just to be sure - I was talking only about the link-address field.
That
> is where a link-local address is useless.

OK, but then (RFC3315, Section 20.1.1) doesn't give clear guidance on what
the realy agent should write into "link-address" when there there is no
global/site-scoped address available for the link. Should it say that the
relay agent writes "0" into link-address in that case?
(Wouldn't writing a link-local address instead be better than "0"?)

Thanks - Fred
[email-masked]
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