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Conference noted::pwv50ift

Title:Kit: Note 4229; Please use NOTED::PWDOSWIN5 for V4.x server
Notice:Kit: Note 4229; Please use NOTED::PWDOSWIN5 for V4.x server
Moderator:CPEEDY::KENNEDY
Created:Fri Dec 18 1992
Last Modified:Fri Jun 06 1997
Last Successful Update:Fri Jun 06 1997
Number of topics:4319
Total number of notes:18478

4196.0. "Firewalling NetBIOS-over-IP Problem" by GEC013::ZIGLER (Tom Zigler DTN 435-7979) Fri Mar 07 1997 09:21

             <<< NOTED::NOTES$9:[NOTES$LIBRARY]PWDOSWINV5.NOTE;2 >>>
                     -< PATHWORKS V5 for DOS and Windows >-
================================================================================
Note 7347.0            Firewalling NetBIOS-over-IP Problem               1 reply
GEC013::ZIGLER "Tom Zigler DTN 435-7979"             28 lines   4-MAR-1997 10:18
--------------------------------------------------------------------------------
    We have Windows NT/95 clients on the inside of an AltaVista Digital
    UNIX Firewall with a Windows NT V3.51 server and PATHWORKS for OpenVMS
    V5.0A server both on the outside of the firewall.  We are running the
    TCP/IP protocol exclusively.
    
    We defined a Start-of-Connection packet filter in the firewall that
    enables a Windows NT/95 client to make an outbound initiated connection
    to either server on port 139/TCP but permits only the corresponding
    inbound connection as an ACKed response.  In other words, a reverse
    inbound initiated TCP connection from either server is not allowed by
    the firewall.
    
    The Windows NT/95 client can successfully connect to a share point
    offered on the Windows NT server but NOT to the PATHWORKS OpenVMS
    server.
    
    A sniffer analysis of the Windows NT/95 to PATHWORKS NetBIOS-over-IP
    attempted connection to port 139/TCP reveals that this server performs
    a reverse inbound intiated connection back to the client - ugh!
    
    Can anyone explain why this difference exists?  Is there any way around
    this problem?
    
    Please advise.
    
    
    				\Thanks in Advance
    
T.RTitleUserPersonal
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4196.1it's a license probeCPEEDY::wells.lkg.dec.com::wellsPhil WellsThu Mar 13 1997 14:0714
The PATHWORKS server (and the license server, but that's a different 
questions) probe the client for a license after the first 
protocol message (SmbNegProt).

If the client doesn't have a license (or if the connect fails, etc.) 
then the PW License Registrar allocates a server based license.

So, if the PW server had some server based licenses available, I 
think you would have been able to connect.

Back connects are also to port 139 and to a fixed NetBIOS name.  How 
intelligent is this filter?

Phil