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Subject: RE: Netbios-ssn
From: Steve Riley (MCS) (sterileymicrosoft.com)
Date: Wed Oct 04 2000 - 15:49:07 CDT

NetBIOS has three protocols.

137/tcp,udp netbios-ns NetBIOS name service
138/udp netbios-dgm NetBIOS datagram service
139/tcp netbios-ssn NetBIOS session service

The session service a connection-oriented, sequenced, reliable communication
between two machines. The datagram service is a connectionless, unsequenced,
unreliable service. netbios-ssn compares to TCP as netbios-dgm compares to
UDP.

NetBIOS is one of those nebulous things that exists at various layers,
depending on whose book you're reading. Since NetBIOS requires some type of
network and transport, it isn't a layer 3 or 4 protocol. Most people
classify it at layer 5; I've seen some diagrams show it spanning layers 5
though 7.

___________________________________________________________
Steve Riley
Microsoft Telecommunications Consulting in Denver, Colorado
   sterileymicrosoft.com
   +1 303 521-4129 or 3035214129messaging.sprintpcs.com
   www.microsoft.com/isn/
Applying computer technology is simply finding the right wrench to pound in
the correct screw.

-----Original Message-----
From: Al Saenz [mailto:ASAENZFOUND-TECH.COM]
Sent: Wednesday, October 04, 2000 2:32 PM
To: 'firewallslists.gnac.net'
Subject: Netbios-ssn

I appreciate your time and input
Thanks

I am monitoring my network and I am noticing that Netbios-ssn connections
are being made.

What is Netbios-ssn. I know what NetBios is but I have never heard of -ssn.

Thanks again for your input.

What layer of the OSI model does NetBios run on?

Al
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