NetBIOS Names (Was: Re: Directory listing in

Richard Sharpe sharpe at
Sun Dec 31 03:46:48 GMT 2000

At 03:59 PM 12/29/00 -0600, Christopher R. Hertel wrote:
>> Although specific implementations may limit it more, RFC 1001 seems to
>> indicate that, in fact, NetBIOS names are handled as binary, really,
>> and there are no invalid characters in them at all. 

Ummm, I think the defining document here has to be the original IBM
documentation on NetBIOS ... While I have misplaced my copy of the 1985 IBM
PC Network Technical Reference, I copied information from it into Special
Edition, Using Samba, and I quote:

<quote verbatim="not quite">
NetBIOS names are always converted to uppercase when sent to other systems,
and may consist of any character, except:

  - Any character less than a space (0x20)
  - the characters " . / \ [ ] : | < > + = ; ,

While MS have bent the spec a bit (cf \001\002_MSBROWSE_\002\001), the
above would seem to indicate that an '@' is a legit character in a NetBIOS
name, while ':' or '[' or ']' are not.

I do not know of any documents that relax this spec WRT NetBIOS names.

>                                                      This is then munged
>> up into ASCII later, so the first stage at which the name has invalid
>> characters is the full-length encoded version (from RFC 1001):
>>    For example, the NetBIOS name "The NetBIOS name" in the NetBIOS
>>    scope "SCOPE.ID.COM" would be represented at level one by the
>>    ASCII character string:
>> Ugh.  We can't very well make that the URI syntax.
>:)  This is why the RFC-proposed syntax never caught on.  BTW, there is 
>an error in the above translation.  To quote my own junk:
>  RFC 1001 provides an example of First Level Encoding in Section 14.1.
>  The string "The NetBIOS name" is translated to: 
>  Decoding this string, however, we get "Tge NetBIOS tame".
>  Perhaps it's a secret message. 
>  The correct translation would be: 
>> Since both the workgroup and the scope could potentially contain
>> anything at all, there is no possible way to really tell them apart.
>According to the RFCs, the scope labels should conform to the preferred
>DNS naming syntax.  That is, start with alpha, followed by alphanumeric or
>a dash, and end with alphanumeric.  Also, they *must* be no more than 63
>characters long, and are compared without regard to case.
>Unfortunately, the Windows systems I've tried allow you to enter just 
>about any garbage string you like in the Scope field.  Ick.
>> (Who thought that up?)
>They were trying to be compatible with DNS best practices.  It's a kludge,
>and it didn't work. 
>> Given the situation, I think Chris mentioned
>> the only viable solution:  Demand a specific character be escaped if
>> used in the workgroup or scope name.  Since NT is already starting
>> to sing a different tune when it sees a ".", that may be the best
>> nominee for the job.
>> Just to summarize, I think that leaves two syntaxes:
>> (broswing) smb://[workgroup[.scope]]/
>> (specific) smb://[[domain;]user[:password]@]server/[share/[path/][file]]
>The server name also needs to have a scope, as in:
>  smb://[[domain;]user[:password]@]server[.scope]/[share/[path/][file]]
>This is nasty but true.  As with any NetBIOS name, the name exists
>*within* a scope, so the scope must be specified.  In the above, the 
>first step will be to use the NetBIOS Name Service to resolve the server 
>name to an IP address so that packets may be sent.  We need to send to 
>the correct IP address, of course.
>Now the wierd thing is that in Microsoft's implementaton the scope string 
>is *not* included in the Session Service (TCP/139) SESSION SETUP REQUEST 
>packet.  If you do include it, I think it sends back a "Called name not 
>found" message.  My reading of the RFCs is that MS got this bit wrong, 
>but the section is ambiguous enought that I forgive them.
>Chris -)-----
>PS.  See:
>     That's my documentation on the workings of NBT.  More to come.
>Christopher R. Hertel -)-----                   University of Minnesota
>crh at              Networking and Telecommunications Services
>    Ideals are like stars; you will not succeed in touching them
>    with your choose them as your guides, and following
>    them you will reach your destiny.  --Carl Schultz

Richard Sharpe, sharpe at
Samba (Team member,, Ethereal (Team member,
Contributing author, SAMS Teach Yourself Samba in 24 Hours
Author, Special Edition, Using Samba

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