Property:NetBIOS

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BoxMatrix >> Lexicon >> Network-Protocols >> NetBIOS

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Protocol

Protocol:	NetBIOS	Wiki	Freetz	IPPF	whmf	AVM	Web
Short for:	Network Basic Input/Output System over TCP/IP
Location:	Lexicon >> Network-Protocols
Weblinks:	Wikipedia.int  -  Wikipedia.de   -  RFC-1001   -  RFC-1002
Description:	Name service and communication protocol

Goto:   FRITZ!OS   -   SMW-Browser

Details

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.

The Datagram Service is used for connectionless communication via UDP.

The Session Service provides error recovery and is used for connection-based communication permitting larger messages.

FRITZ!OS

SMB

FRITZ!OS uses NBT in conjunction with the SMB protocol, see the explanation there.

Filter

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.

Before fw 7.39 the setting is handled in the connection0 ui-module, which is maintained by libcmapi.so:

connection0:settings/filter_netbios=1

Since fw 7.39 the setting is handled in the connections ui-module, which is also maintained by libcmapi.so:

connections:settings/connection$N/filter_netbios=1

$N is the connection number, starting with 0.

This setting is stored in ar7.cfg which is maintained by libar7cfg.so.

References

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Property:NetBIOS

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