Christopher R. Hertel
crh at nts.umn.edu
Wed Oct 3 09:51:02 GMT 2001
> > > http://support.microsoft.com/support/kb/articles/Q163/4/09.ASP
> > > Just for the "completenes" of the trhead, which also points
> > to another
> > > useful article on __MSBROWSE__ et.al.
> > > perhaps a pointer to this info would be useful in the samba docs?
> > > Anders
> > And Microsoft says:
> > +The NetBIOS naming convention allows for 16 characters in a NetBIOS
> > +name. Microsoft, however, limits NetBIOS names to 15 characters and
> > +uses the 16th character as a NetBIOS suffix.
> > This is just plain wrong, because NetBIOS names have been
> > this way since
> > 1984, when the very first papers on the PC Network Program by
> > IBM were
> > released.
> I guess Chris H might have a few comments here ?
I have seen various documents that talk about NetBIOS names, including
some old IBM docs and books which predate the document the one Richard
quotes. Some IBM documents talk about using the 16th byte as a special
character. Others do not. The RFCs do not mention this at all, though
the RFC encoding scheme doesn't disallow it either. So, to say it's "just
plain wrong" is likely a bit of an overstatement. This is probably a
practice that evolved over time until it became "standard".
Regarding the 0x1B and 0x1C names... This is much more complicated than
has been discussed.
The 0x1B name is *both* a Domain Master Browser name *and* a Primary
Domain Controller name--from Microsoft's point of view. Microsoft does
not separate these services or allow a DMB to exist without a PDC. The
ability to create a DMB without a PDC is a Samba enhancement (and a good
Forutnately, Microsoft doesn't use the 0x1B name to find the PDC.
Instead, they use a kludge on top of the already kludgy 0x1C name
These are group names. Several Domain Controllers (one PDC and many
BDCs) can register the same 0x1C name.
Unfortunately, group names are not stored correctly in the WINS server
(or in Samba's nmbd, since we copy MS behavior). The RFCs state that
the NBNS (aka. WINS) should store a complete list of the IP addresses
for which a group name has been registered. Instead, WINS stores the
limited broadcast address: 255.255.255.255. This is useless and causes
lots of trouble, as Microsoft eventually discovered.
With Windows/NT (not sure if this appeared in 3.51 or 4) Microsoft
decided that 0x1C group names were "special". For these "special"
names, they implemented something closer to RFC behavior. Instead of
storing all of the IPs associated with an 0x1C name, they store the
most recent 25 IPs. If there are 25 IPs in the list, and another DC
registers (or refreshes and isn't in the list), the bottom IP address
(the oldest one) is pushed off the list to make room for the newer
entry. If the entry is already in the list then it is moved to the top.
Basic queue management.
...except... The WINS server needs to do one more bizarre thing. It
must also keep track of the matching 0x1B name (which is a unique name).
For example, for the group name "GOOBER<1C>" the WINS server must also
find the unique name "GOOBER<1B>". The IP address of "GOOBER<1B>" will
also have a "GOOBER<1C>" entry, and that entry *must* be the first
entry in the list.
...and that is how the PDC is located. The first entry in the IP list
for the 0x1C name is the IP of the PDC.
With NT, only 0x1C group names were "special". W2K also allows for
"special" group names with suffix byte values of 0x00, 0x20, and (I
This is soooo ugly.
Christopher R. Hertel -)----- University of Minnesota
crh at nts.umn.edu Networking and Telecommunications Services
Ideals are like stars; you will not succeed in touching them
with your hands...you choose them as your guides, and following
them you will reach your destiny. --Carl Schultz
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