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List:       ms-cifs
Subject:    Re: CIFS and IPv6
From:       Luke Kenneth Casson Leighton <lkcl () CB1 ! COM>
Date:       1997-04-29 19:23:02
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On Tue, 29 Apr 1997, Bala Viswanathan wrote:

> Luke, Howard, and others:
>
> > From:    Howard Jess <howard@SYNTAX.COM>
> > Subject: Re: CIFS and IPv6
> >
> > Luke, et al --
> >
> > > From:    Luke Kenneth Casson Leighton <lkcl@CB1.COM>
> > > Subject: CIFS and IPv6
> > >
> > > NetBIOS can offer multiple services at one ip address (it is completely
> > > transport independant).  with the introduction of *SMBSERVER<00> and
> > > using DNS to resolve the ip address, that facility has been totally lost.
> >
> > I don't think this facility is lost at all; for example:
>
> The facility has not been lost as far as the specs are concerned, but has
> been lost, as far as NT 4.0 is concerned (if DNS is used to resolve NetBIOS
> names).


it's the microsoft clients that particularly concern me.  they define
everyones' servers' behaviour.


> Say, from a NT 4.0 client (set up to resolve NetBIOS names through DNS lookup)
> a user tries to connect to a file server on a remote site. The NT 4.0 client
> would end up going through the following steps:
>
>     - Resolve the IP address of remote file server through DNS
>     - Sends an Adapter Status request to the NetBIOS Name service
>       at the resolved IP address.
>     - Grab the first name from the Adapter Status response, if there
>       is a response, and use that as the called name in the NetBIOS
>       connection request.

no, they grab the first <20> NetBIOS name.  this is due to the order in
which NetBIOS services come on-line in a microsoft system.  the order of
NetBIOS names registered is maintained in the Adapter Status response.
therefore, given that the CIFS server service is the first <20> name to
come up, a microsoft client can _use_ this.

it doesn't matter if everyone else's CIFS NetBIOS services are not fired
up as the first service, or if the NetBIOS service sorts the names or
doesn't sort the names, in the Adapter Status response.

> If there are multiple services (file and other) offered at the resolved
> IP address, there is no guarantee that the first name in Adapter Status
> response list references the service that the NT 4.0 user wants to use. It
> may not even be a file service for that matter.

on a Microsoft system, there is (because they take the first <20> name).

> Instead of sending an Adapter Status request, the NT 4.0 client, IMO, should
> first try with the called name constructed from the specified remote file
> service name, as described in section 2.6.1.1 (Backward Compatability) of the
> CIFS spec.

this is sufficient.  it's yet another partial solution, though, to this
problem, which hasn't been properly addressed.  what if you name your NT 4.0
server with a different NetBIOS name from DNS name, and you can't use
microsoft's combined WINS/DNS server?

luke

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