Re: [Autoconf] Using DHCPv6 without link-local? Support only EUI-64interfaces?

Teco Boot <teco@inf-net.nl> Sat, 31 July 2010 13:56 UTC

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From: Teco Boot <teco@inf-net.nl>
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Date: Sat, 31 Jul 2010 15:56:58 +0200
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To: "Templin, Fred L" <Fred.L.Templin@boeing.com>
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Subject: Re: [Autoconf] Using DHCPv6 without link-local? Support only EUI-64interfaces?
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Fred,

Do you mean DHCP relay can be used on a node, that request an address 
for itself?

I think it could work this way:
1) Node queries with link-local to All_DHCP_Relay_Agents_and_Servers.
2a) Node acts as also relay and queries with ULA (site-local) to All_DHCP_Servers.
2b) If node is provisioned with DHCP server unicast address, it could use that 
    instead of All_DHCP_Servers.
I think this is in line with your RFC 5558.

Drawback of 1: it can result in high number of relayed DHCP packets, in case 
of many neighbors.
Another drawback of 1: there is a timeout delay when there is no relay or server
at one hop.

For 2a: the network needs multicast support. Could be SMF.

For both 2a and 2b: a temporally used unicast address must be routable. So this 
DHCP mechanism can only be used as a second step, moving from the self-generated 
address to a centrally managed address.

Teco




Op 30 jul 2010, om 17:40 heeft Templin, Fred L het volgende geschreven:

> Teco,
> 
>> -----Original Message-----
>> From: autoconf-bounces@ietf.org [mailto:autoconf-bounces@ietf.org] On Behalf Of Teco Boot
>> Sent: Friday, July 30, 2010 4:58 AM
>> To: autoconf@ietf.org autoconf@ietf.org
>> Subject: [Autoconf] Using DHCPv6 without link-local? Support only EUI-64interfaces?
>> 
>> RFC3315:
>>   ...     The client
>>   MUST use a link-local address assigned to the interface for which it
>>   is requesting configuration information as the source address in the
>>   header of the IP datagram.
>> 
>> Question: can we get around a MUST in a standards track RFC?
>> I don't think so.
> 
> If the MANET router only behaves as a client on an internal
> link (e.g., a loopback) but behaves as a relay on its MANET
> interfaces, then link-locals need not be exposed for DHCPv6
> purposes. There are other reasons why link-locals might need
> to be considered for MANETs, but I'm not sure this is one
> of them.
> 
> Fred
> fred.l.templin@boeing.com
> 
>> The to be posted proposed text for to be RFC5889 would say that if link-locals are used, there are
>> potential problems when using other than modified EUI-64 IIDs, and therefore must be based on
>> modified EUI-64 IIDs.
>> 
>> Second question, on first item in charter: do we limit ourself to MANET routers that has modified
>> EUI-64 link-locals?
>> I think: better think twice.
>> 
>> Opinions?
>> 
>> Teco.
>> 
>> 
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