Using WINS

Using WINS

WINS, or Windows Internet Naming Service, is an essential part of the Microsoft networking topology as long as NetBIOS is still in use. But before we get into the discussion of WINS, we must define a few terms, including these two protocols—NetBIOS and NetBEUI. 
NetBIOS NetBIOS (pronounced “net-bye-ose”) is an acronym formed from network basic input/output system, a Session layer network protocol originally developed by IBM and Sytek to manage data exchange and network access. NetBIOS provides an application programming interface (API) with a consistent set of commands for requesting lower-level network services to transmit information from node to node, thus separating the applications from the underlying network operating system. Many vendors once provided either their own version of NetBIOS or an emulation of its communications services in their products.

NetBEUI NetBEUI (pronounced “net-boo-ee”) is an acronym formed from NetBIOS Extended User Interface, an implementation and extension of IBM’s NetBIOS transport protocol from Microsoft. NetBEUI communicates with the network through Microsoft’s Network Driver Interface Specification (NDIS). NetBEUI was once shipped with all versions of Microsoft’s operating systems and is generally considered to have a lot of overhead. It also has no structure to its addressing format, which does not allow determination of a network and therefore means it has no routing capability, making it suitable only for small networks; you cannot build internetworks with NetBEUI, and so it is often replaced with TCP/IP. Microsoft added extensions to NetBEUI in Windows NT to remove the limitation of 254 sessions per node. This extended version of Net- BEUI is called the NetBIOS Frame (NBF).


      WINS is used in conjunction with TCP/IP and maps NetBIOS names to IP addresses. For example, you have a print server on your LAN that you have come to know as PrintServer1. In the past, to print to that server you needed only to remember its name and to select that name from a list. However, TCP/IP is a completely different protocol and doesn’t understand Net- BIOS names; it therefore has no way of knowing the location of those servers. That’s where WINS comes in.
      Each time you access a network resource on a Windows network using TCP/IP, your system needs to know the host name or IP address. If there are no routers in your network, NetBIOS speaking devices can simply broadcast their presence on the network and broadcast a request for the unknown MAC address of a known NetBIOS name, all without a WINS server. Once routers are introduced, however, the broadcasts that NetBIOS uses for resolution do not make it through the routers, so connectivity is lost to devices not on the same subnet as the requesting device. If WINS is installed in a routed environment, you can continue using the NetBIOS names that you have previously used to access the resources because WINS provides the cross-reference from NetBIOS name to IP address for you. Once the IP address is known, ARP can be used to obtain the MAC address after the packet has been routed to the proper IP subnet.

Note:

A NetBIOS name doesn’t always refer to just a machine. Several services on a machine can also have their own NetBIOS names.

When you install and configure TCP/IP, as described later in this chapter, you’ll see a place to specify the WINS server addresses. These addresses are stored with the configuration, and
TCP/IP uses them to query for host names and addresses when necessary. WINS is similar toDNS in that it cross-references host names to addresses; however, as mentioned earlier, WINS
resolves NetBIOS names to IP addresses, but DNS resolves TCP/IP FQDNs to IP addresses.
      Another major difference between WINS and DNS is that WINS builds its own reference tables dynamically but you have to configure DNS manually. Dynamic DNS (DDNS) does exist,

but it is not yet implemented on the Internet. When a workstation running TCP/IP is booted and attached to the network, it uses the WINS address settings in the TCP/IP configuration to communicate
with the WINS server. The workstation gives the WINS server various pieces of information about itself, such as the NetBIOS host name, the actual username logged on to the workstation, and the workstation’s IP address. WINS stores this information for use on the network and periodically refreshes it to maintain accuracy.
       Microsoft, however, has developed a new DNS record—called DNS Server—that allows the DNS server to work in perfect harmony with a WINS server. The Microsoft DNS Server software
was shipped with Windows NT and later server systems. Here’s how it works: The host name portion of the DNS FQDN can be looked up on the WINS server for hosts in the local domain. Thus, you need not build complex DNS tables to establish and configure name resolution on your server; Microsoft DNS relies entirely on WINS to tell it the addresses it needs to resolve. And because WINS builds its tables automatically, you don’t have to edit the DNS tables when addresses change; WINS takes care of this for you. This feature also is not available on the Internet.
      You can use both WINS and DNS on your network, or you can use one without the other. Your choice is determined by whether your network is connected to the Internet and whether your host addresses are dynamically assigned. When you are connected to the Internet, you must use DNS to resolve host names and addresses because TCP/IP depends on DNS service for address resolution. Addresses of both DNS and WINS servers can be supplied to a host with its Dynamic Host Configuration Protocol (DHCP) lease.

Using DHCP
The primary reason for using DHCP is to centralize the management of IP addresses. When the DHCP service is used, DHCP scopes include pools of IP addresses that are assigned for automatic distribution to client computers on an as-needed basis, in the form of leases, which are periods of time for which the DHCP client may keep the configuration assignment. Clients attempt to renew their lease at 50 percent of the lease duration. The address pools are centralized on the DHCP server, allowing all IP addresses on your network to be administered from a single server. It should be apparent that this saves loads of time when changing the IP
addresses on your network. Instead of running around to every workstation and server and resetting the IP address to a new address, you simply reset the IP address pool on the DHCP
server. The next time the client machines are rebooted, they are assigned new addresses.

    If the client workstation cannot locate the DHCP server on the network automatically, either you will see an error message to that effect when you restart the client workstation or Automatic Private IP Addressing (APIPA) running on the machine will assign itself an IP address in the 169.254.0.0/16 address range.

    More capable than RARP, DHCP is an update to the Bootstrap Protocol (BootP) and can manage much more than the IP addresses of client computers. It can also assign DNS servers, WINS servers, default gateway addresses, subnet masks, and many other options.