Hands-On Microsoft Windows Server 2003

Networking

Chapter 7

Windows Internet Naming Service

2

Objectives

• Describe the NetBIOS name resolution process• Describe why WINS is used and the tasks it

performs• Install WINS• Configure WINS replication• Manage WINS• Understand when to use a WINS proxy

3

NetBIOS Name Resolution

• Windows Sockets (WinSock) and NetBIOS– Standard used to access network resources

• When NetBIOS is used– NetBIOS name of remote resource must be

resolved to an IP address

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NetBIOS Name Resolution (Continued)

• Methods used to resolve NetBIOS names– NetBIOS name cache

• Contains results of Windows clients NetBIOS name resolutions

– Windows Internet Naming Service (WINS)• Client computer sends NetBIOS name query

requesting resolution of a NetBIOS name• Used early in name resolution process because it

is the method most likely to be successful

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NetBIOS Name Resolution (Continued)

– Broadcast• Packet is addressed to all computers on the

network

• Computer using the NetBIOS name being resolved responds with its IP address

– LMHOSTS• Used if no other method is successful

6

Windows Internet Naming Service (WINS) Functions

• NetBIOS name– Each tied to a service such as a file sharing

• WINS server– Central repository for NetBIOS name and service

information

• When WINS is implemented on network– Client computers and servers must be configured

to use WINS server

– Server running WINS service must be configured to use itself

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WINS Configuration in Windows XP

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Advantages of WINS• Functions across routers

– Communication is done with unicast packets– Required in routed networks because unicast

packets are routable• Can be dynamically updated

– Occurs when computers are added or removed from network

• Can be automated– Maintenance of WINS database is automatic

• Offers client configuration through DHCP– Clients can be configured with IP address of WINS

server using DHCP• Offers integration with DNS

– Can be integrated with DNS to resolve hostnames

9

Name Registration

• Performed when WIN client boots up• Places NetBIOS information about client into

WINS database• Two-packet process• Name registration request packet

– Generated by client and sent directly to WINS server

– Contains NetBIOS name that client computer is attempting to register

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Name Registration (Continued)

• Name registration response packet– Sent from WINS server to the client computer– Contains NetBIOS name that has been

registered and a time to live (TTL)

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Name Registration

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Name Registration (Continued)• NetBIOS name

– If already registered by another host, WINS server sends a challenge to that host

• If original owner of name does not respond– NetBIOS name is registered to new client– Successful name registration response packet is

sent back to new client• If original owner of name responds

– New client is sent a negative name registration response

• WINS clients– Can be configured with multiple WINS servers

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Name Renewal

• Time To Live (TTL)– Assigned to each NetBIOS name registration– When one half completed, WINS client attempts

to refresh registration– Default is six days

• Name refresh request packet– Sent from WINS client to WINS server– Contains NetBIOS name being refreshed– If client unable to contact first WINS server for

one hour, then it fails and contacts second WINS server

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Name Renewal (Continued)

• Name refresh response packet– Sent from WINS server to WINS client

– Contains NetBIOS name being renewed

– Contains new TTL

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Name Renewal

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Name Release• Properly shut down computer

– Contacts WINS server and releases NetBIOS name

• Name release request– Sent from WINS client to WINS server– Request includes NetBIOS name being released

and IP address of WINS client• Name release response

– Contains NetBIOS name being released– Contains a TTL of zero– Another computer can now register released name

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Name Release

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Name Query

• Used to resolve NetBIOS name to IP address• Name query request packet

– Sent from WINS client to WINS server– Contains NetBIOS name to be resolved

• Name query response packet– Sent from WINS server to WINS client– If WINS server is able to resolve the query

• Packet contains IP address registered in the WINS database for the NetBIOS name being resolved

– If WINS server is unable to resolve the query• Packet contains message indicating name could

not be resolved

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Name Query (Continued)

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Installing WINS

• Windows Server 2003 – Has ability to act as a WINS server– Very unusual to use another operating system as

a NetBIOS name server• If organization has several WINS servers

– WINS must be installed individually on each

• WINS is never installed automatically

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Configuring WINS Replication

• Single WINS server can handle at least 5000 WINS clients

• To control network traffic– Implement multiple WINS servers in much

smaller environments • Large network with multiple physical locations

– May reduce network traffic across WAN links if multiple WINS servers are used

– If a WINS server is located at each physical location, then WINS clients do all of their registrations and queries with the local server

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Configuring WINS Replication (Continued)

• Smaller networks – When two WINS servers are implemented, clients

are still able to resolve NetBIOS names if one WINS server fails

• Replication– Must be configured when more than one WINS

server is implemented

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Replication Properties

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Push Replication

• Occurrence based on number of changes in the WINS database

• When defined number of changes occur– Replication partner is notified

– Replication partner then requests a copy of changes

– Only changes are replicated between replication partners

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Push Replication (Continued)

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Pull Replication

• Ensures that changes are replicated between two WINS servers regularly

• Occurrence based on set time schedule• Possible to set

– Start time for replication

– Interval that replication occurs

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Pull Replication (Continued)

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Push/Pull Replication

• Combination of push and pull replication normally used

• Push replication– Ensures that during periods of high change,

records are replicated in a timely way• Pull replication

– Ensures that, during periods of low change, records are replicated even if the criterion replication is not met

• Persistent connections– Results in faster replication

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Replication Partners Folder Properties• “Replication only with partners” option

– Forces server to only replicate its records to servers configured as replication partners

• “Overwrite unique static mappings at this server” option – Allows dynamic WINS registrations from other servers to

overwrite static mappings created on server• WINS server

– Can be enabled to automatically find replication partners– May hold records for registrations not taken by itself or its

direct replication partners

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Replication Partners

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Managing WINS

• General tab of WINS server allows you to configure– How often statistics are updated – Path for backing up the WINS database– Whether the WINS database should be backed up

each time server is shut down

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General Tab - WINS Server Properties

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Intervals Tab – WINS Server Properties

• Allows you to configure– How names are expired and deleted from WINS

database• Renewal interval

– TTL given to WINS clients when a name is registered with the WINS server

• Extinction interval – Length of time an unused record exists in the

WINS database before being marked as extinct

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Intervals Tab – WINS Server Properties (Continued)

• Extinction timeout – Length of time an extinct record is kept in the

database

• Verification interval – Length of time a WINS server waits before

validating a record that is replicated from another WINS server

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Intervals Tab – WINS Server Properties

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Database Verification Tab – WINS Server Properties

• Allows you to automate database verification• When database verification occurs

– Other WINS servers are contacted to confirm that they hold the same WINS information

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Database Verification Tab – WINS Server Properties

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Advanced Tab – WINS Server Properties

• “Log detailed events to Windows event log” option– Enhances logging of events – Should only be used for troubleshooting

• Burst handling – Allows a WINS server to handle large volumes of

name registration requests in a very short period of time

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Advanced Tab – WINS Server Properties (Continued)

• “Starting version ID (hexadecimal)” field – Used to force WINS replication

• “Use computer names that are compatible with

LAN Manager” option – Restricts registered names to 15 characters

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Advanced Tab – WINS Server Properties

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Viewing Database Records

• To verify that client is registered in WINS database– View contents

• When deleting records– Choose whether to delete from just local server or all databases

• Tombstoned– Occurs when record is deleted from all servers– Status is replicated to all servers

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The Display Records window

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Adding Static Records

• If non-Microsoft servers– Provide NetBIOS resources on the network, they

may not be able to use a WINS server

– Cannot use WINS, then WINS clients cannot resolve their NetBIOS names

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Creating a static mapping

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Backing Up the Database

• WINS database– Needs to be backed up – If corrupted, WINS server stops servicing clients

resulting in client computers being unable to access NetBIOS-based resources

• Corrupted WINS database– Can be fixed if a backup of the WINS database

exists

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Backing Up the Database (Continued)

• To fix corrupted WINS database– Stop WINS Service and restore the database

– WINS server receives changes that occurred since backup from replication partners

– WINS servers determine the changes to replicate based on version ID of database records

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WINS Proxy

• Used for computers that need to participate in NetBIOS name resolution but cannot be configured to use WINS

• Allows clients to resolve NetBIOS names to IP addresses using records in a WINS database

• NetBIOS clients – Capable of using broadcasts for name resolution

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WINS Proxy

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Summary• Resolution of NetBIOS names to IP addresses

– Critical for pre-Windows 2000 clients• Pre-Windows 2000 clients

– Use NetBIOS to find domain controllers and use network resources

• Methods used to resolve NetBIOS names– NetBIOS name cache– WINS– Broadcast– LMHOSTS file

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Summary (Continued)

• Broadcast name resolution– Not suitable for large networks– Does not work across routers

• LMHOSTS file – Not suitable for large networks– File needs to be copied to every server and

workstation

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Summary (Continued)

• A WINS server – Central repository for resolving NetBIOS names – Benefits include

• WINS server functions across routers• Can be dynamically updated• Can be automated• Offers client configuration through DHCP• Offers integration with DNS

• Common tasks performed by WINS server– Name registration, name renewal– Name release, and name query

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Summary (Continued)

• Name registration– Client is assigned a TTL

• Network with two or more WINS servers – Replication must be configured between them

• Two types of WINS replication– Push– Pull

• Static mapping– Can be configured for resources that are unable

to register themselves with WINS

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Summary (Continued)

• WINS database– You can view records– Should be backed up

• WINS Proxy – Lets non-WINS clients use the WINS Service – Verifies validity of NetBIOS names over the

network