Question: lower case NetBIOS names.

Christopher R. Hertel crh at samba.org
Wed Oct 5 11:19:20 MDT 2011 

Ibrahim, Mohammed (US - Hyderabad) wrote:
> Hi Chris,
> 
> I appreciate your quick response.
> 
> But I am afraid, it didn't answer my question, may be I was unclear. Anyways, I build servers remotely and the requestor/end user wants the DNS names to be in lowercase, cause these kind of requestors wants to install SAP on their own and say some functions would fail should the DNS or NetBIOS names are in upper case, hence, they want us to build the servers Hostname, DNS names and NetBIOS names in a lowercase.

They're crazy.  :)

If SAP requires lower-case DNS names then SAP is broken.  Similarly for
NetBIOS names.  The instances of NetBIOS names being used in lower-case is
so rare that I had to build a special tool just to be able to test
lower-case names.

Even if you enter the names in lower-case, the underlying NBT system will
convert it to upper case before encoding it for use it on the wire.

> Out of these three, DNS names is the most required thing as per their requirement.

RFC 883:
      All comparisons between character strings (e.g. labels, domain
      names, etc.) are done in a case-insensitive manner.
RFC 1035:
      Note that while upper and lower case letters are allowed in
      domain names, no significance is attached to the case.  That
      is, two names with the same spelling but different case are
      to be treated as if identical.


Further info:
 I have a W2K8r2 Enterprise Server.  It has a very creative name:
"W2K8r2_Ent".  Note that the name is mixed case.  That's how it is displayed
under Server Manager.

...but when I query the local name table using 'nbtstat -n', it comes up
all-uppercase.  Similarly, from my Linux box:

$ nmblookup -A dhcp209.ubiqx.com
Looking up status of 192.168.102.209
        MSDN-W2K8R2-ENT <00> -         B <ACTIVE>
        UBIQX_COM       <00> - <GROUP> B <ACTIVE>
        MSDN-W2K8R2-ENT <20> -         B <ACTIVE>

        MAC Address = 00-0C-29-C2-6C-96

Note that the name is given as all-uppercase.  The Windows NBT layer does
this automatically.

Now, it is possible that the SAP application registers its own name.  The
output of 'nbtstat -n' would show that.  If so, they are broken.  Converting
the names to uppercase is de facto standard.

Chris -)-----

> -----Original Message-----
> From: Christopher R. Hertel [mailto:crh at samba.org] 
> Sent: Wednesday, October 05, 2011 8:44 PM
> To: Ibrahim, Mohammed (US - Hyderabad)
> Cc: samba-technical at lists.samba.org
> Subject: Re: Question: lower case NetBIOS names.
> 
> Ibrahim,
> 
> I have written a detailed description of the workings of NetBIOS over TCP
> (NBT).  You can find it here:  http://ubiqx.org/cifs/NetBIOS.html
> 
> In general, NetBIOS names are converted to upper case before use by the
> underlying system.  This is not a requirement, but it is common practice.
> 
> DNS names and, therefore, hostnames are supposed to be compared "in a
> case-insensitive manner".  Converting NetBIOS names to upper case produces
> the same effect.
> 
> In general, it's not something you have to worry about.  The only time this
> causes trouble is if an application fails to convert the NetBIOS name to
> upper case before encoding it.  Such problems are rare, and I doubt you will
> have any problems unless you are writing your own NBT implementation and
> forget this step.
> 
> Let me know if that answers your question.
> 
> Chris -)-----
> 
> PS.  Note that you did send your query to the Samba-Technical mailing list,
>      and not directly to me.  That's okay, it's appropriate for the list,
>      but your message suggested that you intended to send directly to me.
> 
> Ibrahim, Mohammed (US - Hyderabad) wrote:
>> Hi Christopher,
>>
>> I found your email id at http://lists.samba.org/archive/samba-technical/2001-January/011827.html,
>>
>> I've a concern that we require our NetBIOS, DNS and Hostnames in lower case, when I try to do this, it doesn't allow me to do. Would you like to put some light on it, so I get to know how I can be able to change it to lowercase.
>>
>> Should you need further info, please let me know.
>>
>> Thanks,
>> -Ibrahim
>>
>>
>>
> 

-- 
"Implementing CIFS - the Common Internet FileSystem" ISBN: 013047116X
Samba Team -- http://www.samba.org/     -)-----   Christopher R. Hertel
jCIFS Team -- http://jcifs.samba.org/   -)-----   ubiqx development, uninq.
ubiqx Team -- http://www.ubiqx.org/     -)-----   crh at ubiqx.mn.org
OnLineBook -- http://ubiqx.org/cifs/    -)-----   crh at ubiqx.org

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