Re: [mif] question about draft-montenegro-mif-multihoming-00.txt

[gabriel montenegro <[e-mail]>]

Please see inline.



----- Original Message ----
> Read the draft, very clear and useful, thanks for writing it.

Thanks, Marcelo.

> I only have one clarifying question at this point:
> 
> In section 6. DNS Query Behavior it reads:
> 
>   The DNS Client service queries the DNS servers in the following
>   order:
> 
>   1. The DNS Client service sends the name query to the first DNS
>     server on the preferred interface's list of DNS servers and waits
>     one second for a response.
> 
> I understand then that Windows vista still uses the preferred interface concept, 
> not for routing but yes for the DNS queries, right?

Right, as stated in the terminology section.

> And the preferred interface is the first one bound to the TCP ip stack while 
> booting, right?

That's the initial setting, but this can be modified programmatically or via UI.

> So, how this works with dual faced DNS?
> I understand that if the dual faced DNS only provides answer for a given query 
> over one of the faces, then this works more or less fine cause windows retries 
> (i say more or less cause it may result in latency, i guess)

You guess right, but see below.

> But if the dual faced does provide replies in both faces, but different 
> addresses, then how does this works? I mean, i guess it should work cause if the 
> answer of the dns query returns for instance a private address, then rfc3484 
> longest prefix match rule will prefer the source address with the same scope and 
> will use the interface with the private address, is that correct? Is it then 
> accurate to say that the source address selection mechanism is used to select 
> the right outgoing interface in case the routing table doesn't provide a unique 
> putgoing interface? (i mean, the interface selection for outgoing packet would 
> be first determined by routing and if the routing doesn't select a single 
> interface, then selected based on the source address?)

Up to Vista, RFC3484 does not apply to
determine which interface is used to send out a DNS query. The
"preferred" interface is used. Because of retries, eventually the
right interface will hopefully get used (not perfect, though). 

Windows 7 introduces a new feature called Direct Access: 

http://www.microsoft.com/directaccess

As part of that, the new Name Resolution Policy Table (NRPT) introduces the capability 
to define DNS servers per name space (per interface already exists, as the draft mentions).

If you want more info on this, please download the "DirectAccess Early Adopter's Guide" from
the above web site.

Gabriel