Hi Hemant,
On Mar 22, 2010, at 4:14 PM, Hemant Singh (shemant) wrote:
It is well-known by now that you needed to modify ND (RFC 4861) for
your network. Now that you are looking into DHCPv6 for address
acquisition and obtaining other parameters, here is some feedback on
the DHCPv6 front. I hear that you network has dispensed with DAD as
specified by RFC 4862. So if you use DHCPv6, please beware of RFC
4862 that mandates performing DAD on the DHCPv6 acquired address.
See section 5.4 of RFC 4862 and this text from the document.
[Duplicate Address Detection MUST be performed on all unicast
addresses prior to assigning them to an interface, regardless of
whether they are obtained through stateless autoconfiguration,
DHCPv6, or manual configuration,]
However, good news for you is that RFC 4862 is flexible in that if a
link-specific document mandates the DupAddrDetectTransmitsvariable
to be zero, the NS(DAD) can be dispense with if DHCPv6 is used. If
a link-type document hasn’t be authored yet for 6lowpan, please
write it or augment an existing document with this information –
maybe you already have such info in an existing 6lowpan document.
RFC 4862 also seems to say that disabling DAD can also be an
administrative function...
"To accommodate sites that believe the overhead of performing
Duplicate Address Detection outweighs its benefits, the use of
Duplicate Address Detection can be disabled through the administrative
setting of a per-interface configuration flag."
One other point is that if you plan to use stateless DHCPv6 in your
deployment, please do not plan on using prefix delegation (RFC 3633)
in your network because prefix delegation is only supported over
stateful DHCPv6. Please forward this email to your mailer.
For stateful DHCPv6, there hasn't been any discussion to use DHCPv6-PD
within a 6LoWPAN network - just the possibility of using DHCPv6 to
assign addresses and use relay agents to support topologies where the
server is not on-link. For stateless DHCPv6, only configuration
information you'd typically obtain through such a service.
--
Jonathan Hui
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