|BoxMatrix >> Lexicon >> Network-Protocols >> NetBIOS||@|
|Short for:||Network Basic Input/Output System over TCP/IP|
|Location:||Lexicon >> Network-Protocols|
|Weblinks:||- - -|
|Description:||Name service and communication protocol|
NetBIOS itself is no protocol but an API for communication through the OSI session layer. There are several protocols which
wrap this API, the most modern one is
NetBIOS over TCP-IP (NBT), which is explained here.
NBT provides 3 services:
NetBIOS Name Service- Port-137-udp - and rarely Port-137-tcp
NetBIOS Datagram Service- Port-138-udp
NetBIOS Session Service- Port-139-tcp
In NetBIOS each host on the network has to register an up to 15 Characters long unique name.
Since the NetBIOS API also works over protocols other than TCP-IP it has its own
Name and Registration service,
which does not rely on a hostname or DNS.
Datagram Service is used for connectionless communication via UDP.
Session Service provides error recovery and is used for connection-based communication permitting larger messages.
In FRITZ!OS 5.07 AVM added a NetBIOS filter, which is activated by default.
It blocks TCP and UDP access to ports 139 and 445 from / to the Internet, which are used for SMB file and printer sharing.
It is implemented in kdsldmod.ko, which is the routing core.
$N is the connection number, starting with 0.
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