ITN N Mrs. Z. D. Bodwin1 Guide To TCP/IP Chapter 12 TCP/IP, NETBIOS, And WINS

ITN N Mrs. Z. D. Bodwin2 NETBIOS ( an Application Programming Interface) Developed by Sytek – 1985 Later adopted by IBM & Microsoft Original NetBIOS -not a protocol; it is an API (Application Programming Interface) –Used to call network resources

ITN N Mrs. Z. D. Bodwin3 NetBios - contd Original network protocol for DOS and Windows PCs Did not use network addresses Interface to NetBios and transport part were later separated Used routable protocols like TCP/IP and SPX/IPX

ITN N Mrs. Z. D. Bodwin4 NetBIOS - contd TheAPI retained the NetBios name The transport protocol was renamed NetBeui (NetBios Enhanced User Interface), Chatty – periodically broadcasts names over network so Network Neighborhood can catalog them.

ITN N Mrs. Z. D. Bodwin5 API A language and message format used by an application program to communicate with the operating system APIs are implemented by writing function calls in the program, which provide the linkage to a specific subroutine for execution. API implies that some program module or routine is either already in place or that

ITN N Mrs. Z. D. Bodwin6 API

ITN N Mrs. Z. D. Bodwin7 NetBIOS For backward compatibility –Win2K relies on DNS for name resolution. –Active Directory, uses LDAP (Light Directory Access Protocol) –To share resources with older Windows, enable NetBIOS –Install & configure NetBEUI (NetBios Extended User Interface), now called NetBIOS FRAME, (NBF) also

ITN N Mrs. Z. D. Bodwin8 How Windows 2000/ XP, And Windows Server 2003 Work With NetBIOS Windows 2000 and later use DNS as the preferred method of resolving names Enable NetBIOS name resolution for older versions of Windows WINS server NetBIOS over TCP/IP Windows Server 2003 DNS services are compatible with WINS

ITN N Mrs. Z. D. Bodwin9

10 How does NetBIOS work? NetBIOS is a: –Naming convention –a network API –Set of protocols for sharing resources –Can identify computer names, a user, a process –Applications use resources by using NetBios names.

ITN N Mrs. Z. D. Bodwin11 How does NetBIOS work? When a computer (end node) or a user logs into a NetBios network, it registers and resolves its names –Computer/user registers by sending Name Registration Request –If name has been claimed Challenge negative Name Registration reply

ITN N Mrs. Z. D. Bodwin12 How NetBios Work? 2 types of NetBIOS frames –Datagrams – connectionless traffic. Ex – announcements –Session – used when reliable connection is required. Ex: host to host interaction

ITN N Mrs. Z. D. Bodwin13 How does NetBIos work? - contd Name Resolution – depends on client configuration & services needed. –Local list – local machine’s cache, LMHost file, HOST file –Broadcast on subnet –Direct queries to name servers – WINS, DNS

ITN N Mrs. Z. D. Bodwin14 The Hows… Net Resolution by Node Type - computer name based on node type –B-Node (Broadcast) – broadcasts Name Registration packet locally –Takes ownership if no negative Name Registration Reply –Releases name when computer /process shuts down –Can’t use WINS –Default node type for Win2K clients Node type set by DHCP or in the Registry

ITN N Mrs. Z. D. Bodwin15 Name Resolution 1. By Node Type – contd –P-Node (Peer) – uses local WINS server –Unicast :Name Registration Request –Negative/Positive Name Registration reply –Name Release Request; TTL (default-6days_ –Multiple WINS all servers will be queried until a reply is obtained. –Win2K,Win98 – up to 12 WINS server

ITN N Mrs. Z. D. Bodwin16 Name Resolution Node Type –M-Node (mixed) –Attempts to use b-mode broadcasts first –Then it contacts WINS server –H-Node (Hybrid) –P-node first then broadcasts

ITN N Mrs. Z. D. Bodwin17 Node type resolution - contd Enhanced B-node –Uses the NetBios name cache, then, the LMHOST file, then the normal b-node resolution. –WFW3.11, LAN Manager and Win2K use this enhanced b-node

ITN N Mrs. Z. D. Bodwin18 Name Resolution - contd 2. By NetBios Name Cache & LMHosts –LMHosts – plain text file; static list –Found in \system 32\drivers\etc directory –Lists NetBIOS names with associated IP addresses –Create with plain text editor; syntax; keywords

ITN N Mrs. Z. D. Bodwin19 Name Resolution - contd 3. WINS Name Registration Wins Servers do not participate in b-node name resolution. Why? Unicast; direct communication between themselves & end nodes Handle name resolution for p-nodes, m- nodes an h-nodes Older WINS clients-one primary, one secondary WINS servers

ITN N Mrs. Z. D. Bodwin20 Wins - contd Win 98 & Win2K – clients can be configured to use 1 primary and 11 secondary Name Registration Request Packet: –Positive Name Registration Reply-if name does not exist in DB –TTL (default 6 days) –Name renewal – half TTL value

ITN N Mrs. Z. D. Bodwin21 WINS - contd Wait Acknowledgement (WACK) -if name exists in DB –WINS server acknowledges request w/o denying it –Contacts registered holder – is name still being used, server issues negative Name Registration Reply –If not – sends positive Name Registration Reply

ITN N Mrs. Z. D. Bodwin22 WINS - contd Additional features –Demand packets – imperative; nodes must comply; used during configuration process –Name Conflict Demand packet – node is informed of conflict and must release name –Name Release Demand packet – node must remove name from its table

ITN N Mrs. Z. D. Bodwin23 WINS Burst Mode – server responds to Name Registration with positive Name Registration Reply. Holds off on name conflict resolution Issues replies with different TTL. Why? Load balancing; Queue size – default 500 registrations

ITN N Mrs. Z. D. Bodwin24 Name Resolution - cont 4. DNS & HOSTS files DNS is the preferred method of name resolution for Windows 2000 and Windows XP Some applications or clients attempt to resolve names with the HOSTS file HOSTS file lists IP name and IP address pairs UNIX and Linux name resolution order –Local host –HOSTS file –DNS –NetBIOS

ITN N Mrs. Z. D. Bodwin25 Name Resolution – contd DNS naming convention (see your notes on ch. 7) HOSTS file – static list of IP names & addresses; same location as LMHosts Sometimes used by Telnet & FTP No special syntax & keywords

ITN N Mrs. Z. D. Bodwin26 Let us look at LMHOST & HOST files Go to your Windows Explorer WINNT Folder Systems32 Drivers Etc –Note the structure of each file…. Both are static files.

ITN N Mrs. Z. D. Bodwin27 NetBios over TCP/IP (NetBT or NBT) Allows NetBios to use TCP/IP addressing to make it transportable and translatable. Uses TCP/UDP ports 137Name Services 138Datagram Service 139Session Services TCP/UDP portsNetBios Services

ITN N Mrs. Z. D. Bodwin28 NetBIOS Names & IP Names 15-characters; 16 th character is service identifier. Expressed in Hex; 2-byte hex = one character (range 0x00 thru 0xFF) If NetBIOS name shorter than 15, it is padded with blanks (0x20)

ITN N Mrs. Z. D. Bodwin29 Names - contd NetBIOS names to be recognized by DNS: –Domain portion has to be added –Scope Identifier added to create NetBios domain name –Problem? Scope ID is a user string and adds only one level in the hierarchy Will not work with Internet domain names

ITN N Mrs. Z. D. Bodwin30 Windows Internet Naming Services (WINS ) Name resolution software from MS Runs under WinNT & Win2K Converts NetBIOS names to IP addresses WINS server keeps these names & addresses in DB; with TTL and version#. DB replication among WINS servers

ITN N Mrs. Z. D. Bodwin31 How WINS works? DNS or WINS Server

ITN N Mrs. Z. D. Bodwin32 WINS Server Does not perform broadcast name registration (b-node) DHCP IP address assignment updates WINS database; if will help if both are in the same machine At least one 1 secondary WINS in each subnet

ITN N Mrs. Z. D. Bodwin33 Other WINS Configurations WINS proxy – to integrate b-node clients with wins-enabled network; to resolve name query broadcasts. WINS replication – info sharing –PUSH partner – when server has updated info since last replication –PULL partner – when server pulls the

ITN N Mrs. Z. D. Bodwin34 WINS configuration Integrating WINS & DNS – DNS can use WINS to resolve NetBIOS names. Where? – primary or zone root level How? – configure DNS to point to one or more WINS servers –Each subdomain has its own Start of Authority (SOA) with its own zone root DNS –Create a special domain just for NetBIOS clients

ITN N Mrs. Z. D. Bodwin35 Large Network – each DMS can resolve NetBIOS names