Re: [v6ops] DHCPv6/SLAAC Interaction Operational Guidance-//RE: new draft: draft-liu-v6ops-dhcpv6-slaac-guidance

[Alexandru Petrescu <[e-mail]>]

Le 09/01/2014 19:44, Mikael Abrahamsson a écrit :
> On Thu, 9 Jan 2014, Nick Hilliard wrote:
>
>> Can you provide a reference for the assumption that the host will
>> define the netmask to be /128 if it receives an address assignment
>>  from DHCPv6 without a specific subnet mask assignment via RA?
>
> what else would it do?
>
> I get zero hits on the word "netmask" in RFC3315. DHCPv6 will hand
> out addresses, which in IPv6 implicitly is a /128?

Right, good assumption...  but please allow me another interpretation.

It's interesting to note that that RFC3315 does define the term 'prefix
length' although it does not employ it.  This as such may make wonder
why is that term there, and what are the implications to the ongoing
editing of that document.

'Prefix length' is IPv6 language for 'subnet mask' or 'netmask'.

Moreover, if one searches for 'prefix' in that RFC, one may find
occurences which may be hard to implement, RFC3315:
> Each IA_TA option contains at most one temporary address for each of
> the prefixes on the link to which the client is attached.

Would Server know each of the prefixes on the link on which the client 
is attached?  I suppose yes, by pre-configuration.  If it knows it, then 
why not delivering it to the client.

RFC3315:
> 18.1.2. Creation and Transmission of Confirm Messages
>
>    Whenever a client may have moved to a new link, the prefixes from the
>    addresses assigned to the interfaces on that link may no longer be
>    appropriate for the link to which the client is attached.  Examples
>    of times when a client may have moved to a new link include:
[...]
> Any responding servers will indicate whether those
>    addresses are appropriate for the link to which the client is
>    attached with the status in the Reply message it returns to the
>    client.

RFC3315:
>    If the relay agent received the message to be relayed from a client,
>    the relay agent places a global or site-scoped address with a prefix
>    assigned to the link on which the client should be assigned an
>    address in the link-address field.

RFC3315:
>    NotOnLink       4 The prefix for the address is not appropriate for
>                      the link to which the client is attached.

Each of these suggest that the Server does know the prefixes on the link 
on which the client is attached.

Alex