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NetBEUI (NetBIOS Extended User Interface) is a new, extended version of NetBIOS, the program that lets computers communicate within a local area network.
A D V E R T I S E M E N T
NetBEUI (pronounced net-BOO-ee) formalizes the frame format (or arrangement of information in a data transmission) that was not specified as part of NetBIOS. NetBEUI was developed by IBM for its LAN Manager product and has been adopted by Microsoft for its Windows NT, LAN Manager, and Windows for Workgroups products. Hewlett-Packard and DEC use it in comparable products.
NetBIOS, NetBEUI, and SMB are Microsoft Protocols used to support
Microsoft Networking. The NetBIOS stack includes SMB, NetBIOS, and
NetBEUI which are described in the table below. The following are parts
of the Microsoft networking stack:
NetBEUI is the best performance choice for communication within a single LAN. Because, like NetBIOS, it does not support the routing of messages to other networks, its interface must be adapted to other protocols such as Internetwork Packet Exchange or TCP/IP. A recommended method is to install both NetBEUI and TCP/IP in each computer and set the server up to use NetBEUI for communication within the LAN and TCP/IP for communication beyond the LAN.
| Name |
Network Layer |
Description |
| Redirector |
Application |
Directs requests for network resources to the appropriate
server and makes network resources seem to be local resources. |
| SMB |
Presentation |
Server Message Block provides redirector client to server
communication |
| NetBIOS |
Session |
Controls the sessions between computers and maintains
connections. |
| NetBEUI |
Transport, Network |
Provides data transportation. It is not a routable transport
protocol which is why NBT exists on large networks to use
routable TCP protocol on large networks. This protocol may
sometimes be called the NetBIOS frame (NBF) protocol.
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| NDIS and NIC driver |
Data Link |
NDIS allows several adapter drivers to use any number of
transport protocols. The NIC driver is the driver software for
the network card. |
NetBIOS Extended User Interface (NetBEUI)
This is a separate protocol from NetBIOS. It supports small to medium
networks providing transport and network layer support. It is fast and
small and works well for the DOS operating system but NetBEUI is not
a routable protocol.
Name Resolution
There are three methods of mapping NetBIOS names to IP addresses on
small networks that don't perform routing:
- IP broadcasting - A data packet with the NetBIOS computer name is
broadcast when an associated address is not in the local cache. The host who
has that name returns its address.
- The lmhosts file - This is a file that maps IP addresses and NetBIOS
computer names.
- NBNS - NetBIOS Name Server. A server that maps NetBIOS names to IP
addresses. This service is provided by the nmbd daemon on Linux.
System wide methods of resolving NetBIOS names to IP addresses are:
- b-node - Broadcast node
- p-node - Point-to-point node queries an NBNS name server to resolve
addresses.
- m-node - First uses broadcasts, then falls back to querying an NBNS name
server.
- h-node - The system first attempts to query an NBNS name server, then
falls back to broadcasts if the nameserver fails. As a last resort, it will
look for the lmhosts file locally.
NetBIOS name services use port 137 and NetBIOS session services use port 139.
NetBIOS datagram service uses port 138.
To resolve addresses from names, a computer on a Microsoft network will check
its cache to see if the address of the computer it wants to connect to is listed
there. If not it sends a NetBIOS broadcast requesting the computer with the name
to respond with its hardware address. When the address is received, NetBIOS will
start a session between the computers. On larger networks that use routers, this
is a problem since routers do not forward broadcasts, nor is NetBEUI a routable
protocol. Therefore Microsoft implemented another method of resolving names with
the Windows Internet Name Service (WINS). The following steps are taken to
resolve NetBIOS names to IP addresses for H-node resolution on larger networks
using TCP/IP (NBT):
- NetBIOS name cache
- WINS Server
- NetBIOS broadcast
- lmhosts file
- hosts file
- DNS server
For a more complete explanation of NetBIOS name resolution, WINS, and Windows
networking in general, see the manuals in the Windows operating system section
such as the "Windows TCP/IP Reference." Also a Windows Networking manual will be
written for this section.
NetBIOS over TCP/IP (NBT)
Since NetBEUI is not a routable protocol, Microsoft implemented NBT for
larger networks. NetBIOS messages are normally encapsulated in NetBEUI datagrams,
but when using NBT, they are encapsulated in TCP/IP datagrams. The NBT protocol
is defined by RFC 1001 and RFC 1002.
NWLink
NWLink is Microsoft's implementation of IPX/SPX. NWLink will act as a
transport mechanism for NetBIOS similar to the use of TCP/IP described in the
NBT section above. NWLink is normally used to support medium networks and may be
used where NetWare servers are present.
Windows Internet Name Service (WINS)
WINS is the Microsoft implementation of NetBIOS name service. Samba on Linux
can be used as a WINS server.
Computers configured to use WINS, when booted, contact the WINS name server
and give the server their NetBIOS name and IP address. The WINS server adds the
information to its database and it may send the information to other WINS
servers on your network. When a computer that is configured to use WINS needs to
get an address of another computer, it will contact the WINS server for the
information. Without the use of a WINS server, NetBIOS will only be able to see
computers on the unrouted sections of the local network. Does this mean a WINS
server must exist in each routed section of the network? The answer is no. This
is because WINS uses TCP/IP which is routable. Only one WINS server needs to
exist on the network.
The Windows Networking Environment
A domain in a Microsoft networking environment refers to a collection of
computers using user level security. It is not the same as the term domain used
with regard to the domain name system (DNS). Domain related terms are:
- BDC - Backup Domain Controller is a backup for a PDC
- TLD - Top Level domain
- PDC - Primary Domain Controller is an NT server providing central
control of user access permissions and accounts on a network.
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