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Guide to TCP/IP, Third Edition Chapter 12: TCP/IP, NetBIOS, and WINS Objectives • Discuss the history of NetBIOS • Understand what NetBIOS is and its limitations • Understand the role of NetBIOS in Windows 2000 and higher operating systems • Understand the significance of NetBIOS over TCP/IP on your network • Understand how NetBIOS works TCP/IP, NetBIOS, and WINS 2 Objectives (continued) • Explore NetBIOS names, including structure and types • Explore the various ways of registering and resolving NetBIOS names • Understand naming conventions associated with NetBIOS over TCP/IP • Understand how NetBIOS names must change to work with DNS name resolution TCP/IP, NetBIOS, and WINS 3 Objectives (continued) • Set up a WINS server for your network • Integrate WINS services with DNS • Troubleshoot WINS and NetBIOS errors with commonly used tools TCP/IP, NetBIOS, and WINS 4 History of NetBIOS • NetBIOS – Developed by Sytek in 1983 – Adopted by IBM and Microsoft for naming network resources on small peer-to-peer networks – Original was an Application Programming Interface (API) used to call network resources • NetBIOS Extended User Interface (NetBEUI) – Extension of NetBIOS TCP/IP, NetBIOS, and WINS 5 What is NetBIOS (and Why Do I care) • NetBIOS operates by – Maintaining a list of unique names assigned to network resources – Providing the services to establish, defend, and resolve these names – Carrying the needed communications between applications that make use of these network resources TCP/IP, NetBIOS, and WINS 6 How Windows 2000, Windows XP, and Windows Server 2003 Work with NetBIOS • Windows 2000 – First Microsoft operating system to use DNS • When upgrading servers to Windows 2000 Server or Windows Server 2003 – Determine if you will still need to support NetBIOS names on your network • If uncertain if your network requires NetBIOS support – You can use the WINS performance monitor counter TCP/IP, NetBIOS, and WINS 7 NetBIOS and TCP/IP • Using DNS Only – Preferred form of networking in an all-Windows 2000 and/or Windows XP environment • Direct hosting of the (SMB) protocol • Using NBF Only – To deliberately restrict resource sharing only to the local network segment • Bind Windows File and Print Sharing to NBF, but not to TCP/IP TCP/IP, NetBIOS, and WINS 8 Combining TCP/IP and NetBIOS • NetBT or NBT – NetBIOS over TCP/IP • NetBIOS names – Can be resolved by any of several combinations of methods • Default configuration for Windows 2000 and Windows XP machines – Have both NetBT and NBF enabled TCP/IP, NetBIOS, and WINS 9 TCP/IP, NetBIOS, and WINS 10 How Does NetBIOS Work? • NetBIOS – Takes advantage of simple naming, address handling, and message formatting conventions – Supports connectionless datagrams as well as connection-oriented session frames – Supports simple name registration and challenge mechanisms TCP/IP, NetBIOS, and WINS 11 NetBIOS Traffic • Consists of NetBIOS frames of one of two types – Datagrams or session frames • NetBIOS sessions – Used in situations that require a reliable connection • When NetBIOS is run over TCP/IP as NetBT – Datagrams are carried in UDP packets and session frames are carried in TCP packets TCP/IP, NetBIOS, and WINS 12 How Does NetBIOS Work? • Registering and Challenging NetBIOS Names – Registration • Process of asserting that a name exists and belongs to a particular computer, user, process, or group • Categories of name resolution methods – Look up in a list of names on the local machine – Broadcast queries on the local subnet – Direct queries to name servers TCP/IP, NetBIOS, and WINS 13 Other NetBIOS Services • Name services – The most important NetBIOS services • NetBIOS datagram and session services – Used by applications such as Applications such as the Network Browser, LAN Manager TCP/IP, NetBIOS, and WINS 14 TCP/IP, NetBIOS, and WINS 15 NetBIOS Names • Based on – User name during logon – Information configured for the specific computer in the Network applet in Control Panel • NetBIOS names are of two general types – Unique names and group names • Unique names – Resolve to a single address TCP/IP, NetBIOS, and WINS 16 Structure of NetBIOS Names • Group names – May resolve to multiple addresses • NetBIOS names – 16 characters long, divided into two parts – First 15 characters are the name itself – Last character is a code describing the class of resource to which the name belongs TCP/IP, NetBIOS, and WINS 17 TCP/IP, NetBIOS, and WINS 18 TCP/IP, NetBIOS, and WINS 19 NetBIOS Scope Identifier • NetBIOS – Provides the NetBIOS scope identifier • Scope identifier – Adds a character string to end of the name, separated from rest of name by a period (.) • NetBIOS scope – Identifies a logical community of network hosts • DHCP scope – Identifies a range of IP addresses that a DHCP server can assign to clients TCP/IP, NetBIOS, and WINS 20 NetBIOS Name Registration and Resolution • NetBIOS names are registered and resolved using – – – – Node type NetBIOS name cache and the LMHOSTS file WINS servers configured as NetBIOS Name Servers DNS and the HOSTS file TCP/IP, NetBIOS, and WINS 21 Name Resolution Regimes by Node Type • Four basic types of NetBIOS nodes – – – – Broadcast node (b-node) Peer node (p-node) Mixed node (m-node) Hybrid node (h-node) TCP/IP, NetBIOS, and WINS 22 NetBIOS Name Cache and LMHOSTS File • NetBIOS name cache – Temporary file that resides in memory, pairing NetBIOS names and IP addresses • Names in the NetBIOS name cache – Times out after 10 minutes, by default • LMHOSTS file – Plain text file that resides in the <windows root>\system32\drivers\etc directory TCP/IP, NetBIOS, and WINS 23 WINS Name Registration and Resolution • WINS servers – NetBIOS Name Servers that set up and maintain database of NetBIOS names and their associated IP addresses – Do not participate in broadcast or b-node name registration and resolution • WINS servers – Support a special name registration regime called burst mode TCP/IP, NetBIOS, and WINS 24 DNS and The HOSTS File • Preferred configuration for Windows 2000 and Windows XP clients – Is to use DNS for name resolution • HOSTS file – Static list of IP name and address pairs, located in the <windowsroot>\system32\driver\etc directory TCP/IP, NetBIOS, and WINS 25 NetBIOS Over TCP/IP • To coexist with TCP/IP, NetBIOS had to accommodate TCP/IP’s conventions – NetBIOS scope identifier was added as a sort of analog of the TCP/IP domain – Set of steps created to make NetBIOS names and commands transportable over a TCP/IP connection TCP/IP, NetBIOS, and WINS 26 TCP/IP, NetBIOS, and WINS 27 NetBIOS and DNS Name Resolution • To convert NetBIOS name into name that is recognizable and routable by DNS – NetBIOS name had to become a usable host name – Domain portion of the name had to be added TCP/IP, NetBIOS, and WINS 28 Creating a Usable Host Name from a NetBIOS Name • NetBIOS name – Has to be restated in a way that replaces any characters not recognizable by DNS • DNS names must be printable • In the ASCII code set – None of these characters is printable TCP/IP, NetBIOS, and WINS 29 TCP/IP, NetBIOS, and WINS 30 Converting an Encoded NetBIOS Name to a Fully Qualified Domain Name • To convert the (translated) NetBIOS name into a fully qualified domain name (FQDN) – Domain portion of name has to be added as well • NetBIOS scope identifier – User-configurable string – Adds only one level of hierarchy • Internet domain names – Regulated and restricted – Conform to a deeper and rigorously enforced hierarchy TCP/IP, NetBIOS, and WINS 31 TCP/IP, NetBIOS, and WINS 32 WINS Servers • WINS – A server service – Runs under Windows NT Server, Windows 2000 Server, or Windows Server 2003 • WINS server – Registers NetBIOS names and IP addresses – Can be configured to return the IP address associated with a resource name or – The NetBIOS names associated with an IP address TCP/IP, NetBIOS, and WINS 33 Different WINS Configurations • WINS servers – Can be deployed in several different ways to meet the needs of different networks • Netsh command-line tool in Windows Server 2003 – Helpful for WINS servers over WAN links to better manage slower network connections TCP/IP, NetBIOS, and WINS 34 Different WINS Configurations (continued) • Administrator-level access to the WINS server allows you to – Check server statistics – Check the database and version numbers for consistency – Mark records for eventual deletion (called “tombstoning” the records) – Remove old records (scavenge the database) TCP/IP, NetBIOS, and WINS 35 WINS Proxy • WINS clients – Available for recent versions of DOS, OS/2, and all versions of Windows – Available for Linux and UNIX machines running Samba • You can configure any Windows 2000, Windows Server 2003, or Windows XP computer to – Be a WINS proxy by setting the Enable Proxy parameter in the Registry to 1 TCP/IP, NetBIOS, and WINS 36 TCP/IP, NetBIOS, and WINS 37 Integrating WINS and DNS • The Microsoft DNS server implementation (MS DNS) – Can be configured to use WINS to resolve NetBIOS names in the primary or root zone domain • MS DNS – Cannot resolve NetBIOS names that are not direct children of the zone root or primary DNS domain TCP/IP, NetBIOS, and WINS 38 TCP/IP, NetBIOS, and WINS 39 TCP/IP, NetBIOS, and WINS 40 Reverse DNS Lookup for NetBIOS Names • MS DNS servers in the in-addr.arpa domain – Provide reverse lookup • MS DNS servers in the reverse look-up zone root – Can be configured to use WINS-R to find NetBIOS resources associated with an IP address • WINS server – Uses a NetBIOS Adapter Status Query to find the name(s) associated with a given IP address TCP/IP, NetBIOS, and WINS 41 Windows Server 2003 WINS Improvements • Two improvements in WINS have been added to Windows Server 2003 – Filtering records – Accepting replication partners • With improved filtering and search functions – You locate records by showing only the records fitting the criteria you specify TCP/IP, NetBIOS, and WINS 42 Troubleshooting WINS and NetBIOS • Errors in Windows name resolution fall into two broad categories – Outright failure – Degradation of service • Accumulation of several instances of degradation – Seldom leads to outright failure of the service TCP/IP, NetBIOS, and WINS 43 NBTSTAT • Command-line program that returns statistics on NetBIOS • A fast way to check the status of a particular NetBIOS host, or – Get a quick snapshot of NetBIOS name resolution activity on the local network segment TCP/IP, NetBIOS, and WINS 44 WINS and DNS Consoles • WINS Console – Can search for active registrants by name or owner • DNS Console in Windows 2000 and Windows Server 2003 – More geared to monitoring and system diagnostics than the WINS server • WINS operating parameters – Are stored in a Management Information Base (MIB) TCP/IP, NetBIOS, and WINS 45 Typical Errors in NetBIOS and WINS • Misconfiguration of end nodes due to user error • Incorrect network logon due to user error • Wrong node type due to user error or misconfigured DHCP • Timeouts set too low to allow for network latency • Unwanted traffic due to misconfiguration of end nodes and/or servers, or client/server topology TCP/IP, NetBIOS, and WINS 46 Security Flaw in NetBIOS • Security Bulletin MS03-034 – Details flaw in NetBIOS that could result in disclosure of information from your computer • Operating systems are affected – – – – – Windows NT 4.0 Windows NT 4.0 Terminal Server Edition Windows 2000 Windows XP Windows Server 2003 TCP/IP, NetBIOS, and WINS 47 Summary • NetBIOS – Native Windows approach to networking • NetBIOS and NetBEUI (NBF) – Use a flat namespace and are inherently nonroutable • NetBIOS name can be resolved in three ways – Look it up in a locally held list – Ask the server (WINS, DNS, or Samba), or – Ask the whole local network segment TCP/IP, NetBIOS, and WINS 48 Summary (continued) • NetBIOS and WINS services – Typically used in a mixed-network environment • Windows networking clients or end nodes – Can be configured to use one of four basic regimes of name registration and resolution • WINS servers – Are like DNS servers designed to serve only the NetBIOS namespace TCP/IP, NetBIOS, and WINS 49