Name resolution is a method of reconciling an IP address to a user friendly computer name. Originally networks used host files to resolve names to IP addresses. They came in the form of a text file that the computer accessed if name resolution was required. All the computers on the network and their IP address mappings had to be entered manually. The file was then copied to all the machines on the network. When a resource was required, by the user typing its name, the machine referred to the host file to find the IP address.
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This is the HOSTS file which is located inside the windows\system32\drivers\etc folder. A computer can still use the hosts file if needed. The LM host file was a windows specific version of the standard host file and enabled Microsoft’s NT LAN Manager to perform name resolution tasks The LMHOSTS file is located inside the windows\system32\drivers\etc
With the advent of larger networks the text based hosts and lmhosts files became large, unwieldy and required too much maintenance. With the advent of dynamically assigned IP addresses, IP to name mappings took on a transient nature with the possibility of IP addresses changing on a weekly basis. The days of the host/lmhost file’s were numbered as the primary tool of name resolution.
Microsoft developed a system for name resolution for small networks called NetBIOS where a broadcast with the required computer name was sent to all computers on the network segment. All the computers received the request but only the named machine responded. This system was easy to use because it was self-configuring and required no maintenance. However with larger, routed networks NetBIOS fell down as the broadcast would not be passed by a router. Using NetBIOS broadcasts restricted a machine to resources on it’s own network segment.
Microsoft developed the Windows Internet Naming Service (WINS) to overcome this problem of broadcasts not being passed by routers. Every machine is given the IP address of a WINS server in its network properties. When the machine boots up it sends the WINS server its IP address along with its NetBIOS name.
The WINS server stores these entries in the wins.mdb database file. Name resolution queries are sent to the WINS server which then searches the wins.mdb, resolves the query and then sends the details back to the client. This removes the need of a NetBIOS broadcast
Because the client can send the NetBIOS query directly to the WINS server and the WINS server sends the result direct to the client by IP address. The packets will also pass over a router.
NetBIOS is still used to provide name resolution for certain applications and for workgroups that do not utilize the Domain Naming Service (DNS) covered next. NetBIOS allows network browsing via my network places, computers near me or Microsoft Windows Network. Any name to IP address mappings resolved by NetBIOS are stored on the local machine in a cache file to speed up access to that resource in the future. NetBIOS is enabled by default but can be disabled. This improves network security by removing the ability to view the contents of the network by browsing. The disadvantage of this is the inability to view the contents of the network by browsing and the fact that the network loses a backup name resolution service.