NetBIOS Naming

1
NetBIOS Naming

• A Network Basic Input/Output System (NetBIOS)
  name is a 16-byte character string assigned by a
  network administrator to a particular entity on a
  network.
• The NetBIOS name is either a unique (exclusive)
  or group (nonexclusive) name.
• To identify the type of resource a NetBIOS name
  identifies, the sixteenth character of the name
  is reserved for a resource identifier code.
• This leaves 15 characters for the NetBIOS name
  itself.
• The NetBIOS name space consists of only a single
  level there are no separate domain and host
  names, as in a Domain Name System (DNS) name.

2
NetBIOS Name Resolution Mechanisms

• NetBIOS name caching
• Lmhosts files
• Broadcast transmissions
• Windows Internet Name Service (WINS)
• DNS and Hosts files

3
NetBIOS Name Caching

• DNS name servers maintain a cache in which they
  store information about recently resolved names.
• With NetBIOS, individual computers cache name
  resolution data.
• Every computer running Windows that uses NetBIOS
  maintains a NetBIOS name cache in memory that
  contains the names it has recently resolved.
• Entries remain in the NetBIOS name cache for a
  relatively short period of time (10 minutes for
  Microsoft Windows 2003, by default).
• Because the cache is accessed from memory, it is
  the fastest NetBIOS name resolution mechanism by
  far.
• No matter what other mechanism the computer is
  configured to use, it always checks the cache
  first to see if the requested name is present.

4
Enabling Lmhosts

• 1. Click Start, point to Settings, and then
  select Network And Dial-Up Connections to open
  the Network And
• Dial-Up Connections window.
• 2. Select the Local Area Connection icon, and
  then select Properties from the File menu to open
  the Local Area Connection Properties dialog box.
• 3. In the General tab, select Internet Protocol
  (TCP/IP) in the components list, and then click
  Properties to open the Internet Protocol (TCP/IP)
  Properties dialog box.
• 4. Click Advanced to open the Advanced TCP/IP
  Settings dialog box.
• 5. Select the WINS tab to display the dialog box.
  
• 6. Select the Enable LMHOSTS Lookup check box,
  and then click OK three times to close the dialog
  boxes you opened.

5
Lmhosts Sample Entries

• 192.168.94.97 rhino PRE
• 192.168.94.97 rhino PRE DOMnetworking
• BEGIN_ALTERNATE
• INCLUDE \\Rhino\Public\Lmhosts
• INCLUDE \\Localsrv\Public\Lmhosts
• END_ALTERNATE

6
Broadcast Name Resolution
7
Broadcast Name Registration
8
NetBT Node Types

• B node (broadcast node). Calls for the exclusive
  use of the broadcast method for NetBIOS name
  registration and resolution
• P node (point-to-point node). Calls for the
  exclusive use of NetBIOS name servers (that is,
  WINS servers) for NetBIOS name registration and
  resolution
• M node (mixed mode node). Calls for the exclusive
  use of the broadcast method for name registration
  
• For NetBIOS name resolution, the m node uses
  broadcasts first.
• If the broadcast method fails to resolve a name,
  the m node uses a NetBIOS name server.

9
Microsoft Node Types

• Modified b node. This type calls for the
  exclusive use of the broadcast method for name
  registration.
• For name resolution, this type of node uses
  broadcasts first and the Lmhosts file next if
  broadcasts fail to resolve a name.
• H node (hybrid node). This type calls for the
  exclusive use of NetBIOS name servers for name
  registration.
• For name resolution, this type of node uses
  NetBIOS name servers first and then the broadcast
  method, if needed
• Microsoft-enhanced h node. Windows can supplement
  an h node system with Lmhosts name resolution,
  Windows Sockets calls to a DNS server, and a
  Hosts file.
• All of the alternatives are used if both WINS
  servers and broadcasts fail to resolve a name.

10
The NetBT Message Header Format
11
The NetBT Message's Question Section Format
12
The NetBT Message's Answer Section Format
13
Installing the WINS Service

• 1. On a computer running Windows 2003 Server, log
  on as Administrator.
• 2. Click Start, point to Settings, and then
  click Control Panel.
• 3. Double-click the Add/Remove Programs icon,
  and then click Add/Remove Windows Components to
  activate the Windows Components Wizard.
• 4. In the Components list, scroll down to select
  Networking Services.
• 5. Click Details to open the Networking Services
  dialog box.
• 6. In the Subcomponents Of Networking Services
  list, select the Windows Internet Name Service
  (WINS) check box.
• 7. Click OK, and then click Next.
• If prompted, type the full path to the Windows
  2003 distribution files, and then click Continue.
  
• 8. Click Finish to close the Windows Components
  Wizard.

14
The New Static Mapping Dialog Box
15
WINS Proxy Agents

• A WINS proxy agent extends the name resolution
  capabilities of the WINS server to non-WINS
  clients by listening for broadcast name
  registration and name resolution requests and
  then forwarding them to a WINS server.
• When a WINS proxy agent detects a NAME QUERY
  REQUEST broadcast, it sends the request to a WINS
  server.
• The WINS server responds to the WINS proxy agent
  with the Internet Protocol (IP) address for the
  requested NetBIOS name.
• The WINS proxy agent returns this information to
  the non-WINS client.

16
Compacting the WINS Database

• 1. Open a Command Prompt window on the WINS
  server.
• 2. Change to the systemroot\System32\Wins folder
  on the system drive.
• 3. Stop the WINS Server service by typing
• net stop wins at the command prompt.
• 4. Compact the database by typing jetpack
  wins.mdb tmp.mdb at the command prompt.
• 5. Restart the WINS Server service by typing
• net start wins at the command prompt.
• 6. Close the Command Prompt window.

17
Rules for Configuring WINS Server Replication

• Configure a push partner when servers are
  connected by fast links, because push replication
  occurs when a specified number of updated WINS
  database entries is reached.
• Configure a pull partner between sites,
  especially across slow links, because pull
  replication can be configured to occur at
  specific intervals.
• Configure each server to be both a push and pull
  partner to replicate database entries between
  them.
• Every WINS server must be both a push partner and
  a pull partner for the replication to be
  complete, but not necessarily partners with each
  other.

18
An Example of a WINS Push and Pull Partner
Configuration
19
A WINS Ring Replication Topology
20
A WINS Double Ring Replication Topology
21
Initiating Database Replication

• There are four conditions that initiate the
  replication of the WINS database
• At system startup
• At a configured interval, such as every five
  hours
• When a WINS server has reached a configured
  threshold for the number of registrations and
  modifications to the WINS database
• By forcing replication in the WINS console