SAMBA digest 1606

[Clark, Pete]

>Date: Fri, 27 Feb 1998 13:54:39 -0500
>From: John E Hein <jhein at fallschurch.esys.com>
>To: Wajihuddin Ahmed <wahmed at isb.worldwerx.com.pk>
>Subject: Re: cross subnet browsing
>Message-ID: <199802271854.NAA10232 at lorax.ERA.COM>
>
>> <snip>

>>Another issue I considered when I was having problems was the amount
>>of time it took to resolve elections and update browse lists and so
>>on.  When I was experimenting, I may have been changing smb.conf
>>and restarting nmbd too frequently.  You may want to give it
>>10 minutes to settle between changes.
>
>>Does anyone have a good idea how long things like that (elections,
>>browse list updates, etc.) might take?  How long should I have
>>to wait to decide that a certain smb.conf setup works or does not
>>work with respect to network browsing?
>
Hmmm.  Elections should only take a few hundred milliseconds to resolve.
 Updates from Master Browser to backup browsers are performed every
fifteen minutes.  

One problem to be aware of is that there is a great deal of anecdotal
evidence to indicate that Win95 and Windows3.1 clients frequently
contend for the right to act as Master Browsers, even with NT Domain
Controllers.  In the event of contention, the offending client must be
configured NOT to act as a browser server. (MaintainBrowseList=No)

You mentioned WINS in conjunction with browsing, specifically, a WINS
server's ability to track browser servers.  This is a common assumption,
but you should be aware that WINS servers do not track master or backup
browsers.  

With regard to browsing, WINS servers are useful insofar as they permit
domain controllers to resolve the IP addresses of external domain
controllers and permit domain-to-domain browse list exchanges.  They
also ensure that subnet Master Browsers can direct datagrams to the
domain PDC (the Domain Master Browser).

Some basic facts:

1. Browsing is, essentially, a broadcast-based service that should not
cross the router;
2. Every subnet has a Master Browser determined by configuration or
election;
3. Each subnet MB periodically updates the Domain Master Browser (PDC)
with a directed datagram (not broadcast);
4. The resource list accumulated by the Domain MB is used to update each
of the subnet MBs, thus allowing resource visibility across routers;

So, browsing is a broadcast-based service that does not require, or
depend upon, the netbios name services provided by a WINS server.
Browsing works this way: a client seeking a view of network resources
broadcasts a request for a list of backup browsers; the segment master
browser responds with a list of up to three backup browsers (also on the
same subnet); the client requests a list of available resources from one
of the backups (if no response, it moves to the second on the list) and
one of the backup browser provides a copy of the last resource list that
it received from the master browser.

All Windows clients broadcast "I'm alive" messages during the boot
sequence, and once every twelve minutes thereafter, to ensure that they
are registered with the master browser on their subnet.  Any system that
boots up and is configured to perform as a master browser will force an
election and, if everything works normally, win.  Since it has an empty
resource list (having just booted) it will broadcast a "registration
demand" to which every client must respond within 30 seconds
(staggered).  

With a complete segment list in hand, it will register with the Domain
Master Browser (the PDC) and exchange updates, receiving a list of
resources known within the Domain.  It is also possible to view
resources external to the Domain if either the WINS server or PDC have
other Domain addresses registered. 

Now that I've managed to completely confuse the issue, I'll end this
thread...

	- Pete

Pete Clark, EDS
>