Chapter 17 Windows Internet Name Service WINS

WINS A NetBios name server that resolves NetBIOS name to IP addresses Is much like DNS, with clients registering names and performing name lookup, and servers handling the registration and resolution

What is a NetBIOS Name? Microsoft networks always use NetBIOS names to identify network resources Machines recognize each other through their unique NetBIOS machine name Shared resources, files, and printers are accessed using NetBIOS names A Universal Naming Convention (UNC) is used Example: \\servername\share_name\\servername\share_name Servername is NetBIOS name of the machine where the resource is located Share_name is the NetBIOS name uniquely identifying the resource

What Processes Use NetBIOS? Windows file sharing service Browser service

Benefits of WINS WINS is a dynamic database that minimizes maintenance required by administrator WINS is a centralized NetBIOS name management system Eliminates the need for static LMHOSTS files, unless they are used in addition to WINS server Decreases broadcast traffic

How are NetBIOS Names Resolved? LMHOSTS –Locally stored ASCII text file WINS –Server that does NetBIOS to IP name resolution

NetBIOS Names NetBIOS name space is flat, unlike DNS that uses a hierarchical name space The name is unique on an internetwork

NetBIOS Node Types B-Node –Name registration and name resolution are performed using broadcast only –Best option for small, single subnet networks P-Node –Name registration and name resolution are done using WINS –Eliminates local subnet broadcasts –May cause network resources on a local subnet to not be resolved

NetBIOS Node Types - Cont. M-Node –A combination of B-Node and P-Node –Name registration and resolution are done by broadcast –If broadcast is not successful, the name server (WINS) is used –This is useful when WINS server is on a remote network –Attempt is made to resolve name locally first before using WAN resources for the resolution

NetBIOS Node Types – Cont H-Node –A combination of P-Node and B-Node –Name registration and resolution are attempted first using WINS server –If this is not successful, then broadcast is used –WINS uses H-Node

NetBIOS Name Registration When a resource becomes available for use, the network resource must register its NetBIOS name The registration process ensures that the name being registered isn’t already in use Process may include broadcasts, but with WINS server, the name registration query message is sent directly to the WINS server and is registered in the database The registration query includes the soure IP address and the NetBIOS name, along with the destination computer’s IP address In order to have your computer register its NetBIOS name with the WINS server, all you have to do is configure your client to use WINS (see demonstration of this)

Name Registration – Cont. The WINS server checks the database for the NetBIOS name If the name is not found, the WINS server sends a positive name registration response which designates a time at which the client needs to renew its registration If the entry already exists in the database, the server challenges the holder of the current registration to respond. If the current holder responds successfully, a negative registration response is sent to the computer trying to register the name

Renewing Names NetBIOS names registered with a WINS server have a limited life and must be refreshed before their life expires This time is referred to as Time To Live (TTL) The default TTL is 6 days A WINS client tries to renew any NetBIOS names it holds at half the TTL Each time the computer is restarted, a new name registration message is sent to the WINS server to renew the name

Releasing of NetBIOS names Can occur two ways: –Computer can release any held NetBIOS name by sending the WINS server a Name Release message containing the NetBIOS name to release –If an end-node fails to renew the name, that name will become free to be used by another end-node

Resolving NetBios Nmaes A client that needs to resolve a NetBIOS name issues a NetBIOS Name Query Request, either by using a broadcast or by sending the request directly to a WINS server If the query is sent to a WINS server and the name can be resolved, the WINS server sends a Name Query Response to the client computer Otherwise the WINS server sends a negative Name Query Request

Database Replication Between Two or More WINS Servers NetBIOS name registrations in a WINS database are replicated to other WINS servers by configuring WINS servers as either push or pull partners Push partner – forces their updates on the pull partners The push partner informs its pull partner that the WINS database has changed The pull partner then responds with a replication request The push partner then sends the new, updated entry to its pull partner in one of two ways: –Wait until a predetermined number of WINS updates have been collected –Immediately replicate the updated entry