A name service translates between IP addresses and hostnames. Name service is optional, but you must use it if you want to specify hosts by their hostnames instead of their IP addresses. It is simpler and more meaningful to specify hostnames in remote configuration files, Setup menus, and commands. If you try to specify a hostname without using a name service, the terminal cannot find the host.

NCD terminals can use both DNS (Domain Name System) and IEN 116 name services.

Making Sure a Name Service is Running on the Local Network

To make sure DNS is available on the name server host:

• Verify that the daemon (named or in.named) is configured in the relevant startup file on the name server host. You can use a command similar to the following to find the command line starting up the name daemon:
  

  
  # grep named /etc/rc*
  /etc/rc.local: if [-f /usr/etc/in.named -1 -f /etc/named.boot]; then
  in.named; echo -n ' named')  > /dev/console
  

• Make sure that the name server host's DNS database files are set up.
  

To make sure IEN 116 name service is available on the name server host:

• Verify that the daemon (most commonly, tnamed) is configured on the name server host. You can use a command similar to the following to find the entry starting the daemon:
  

  
  # grep tnamed /etc/inetd.conf
  name dgram udp wait root /user/etc/in.tnamed in.tnamed
  

• IEN 116 uses the /etc/hosts file as its database. If the terminal is listed, no further database configuration is necessary.
  

You should always place name service parameters at the beginning of a remote configuration file, before any parameters that use hostnames. In addition, insert an apply command after the name service parameters to make sure the name service is in effect for subsequent parameters that use hostnames.

Selecting the Name Service Protocol

Set the tcpip-name-server-protocol parameter to the name service protocol you are using (Setup -> Change Setup Parameters -> TCP/IP Name Service -> Name Server Protocol).This parameter is saved in NVRAM and takes effect immediately if set interactively.

Table 5-5 tcpip-name-server-protocol Parameter

You can specify as many name server hosts as you need. If you do not specify a name server, the terminal uses the boot host for name service.

Enter the IP addresses of hosts offering name service into the tcpip-name-servers table (Setup -> Change Setup Parameters -> TCP/IP Name Service -> Name Servers). If you enter an address of 0.0.0.0, the boot host is used for name service.

If you use BOOTP/DHCP and specify name servers for this terminal in the bootptab file, those name servers are placed in the table automatically. This parameter is saved in NVRAM.

Table 5-6 tcpip-name-servers Parameter

For example:

tcpip-name-servers = {
          { 192.43.150.001 }
          { 192.43.150.005 }
          }

If you are using DNS and set this parameter, you do not have to specify a fully qualified domain name when specifying hostnames. Set the tcpip-dns-default-domain parameter to the default domain suffix to be appended to hostnames in searches (Setup -> Change Setup Parameters -> TCP/IP Name Service -> DNS Default Domain). The suffix is not appended to fully qualified names (names that contain all the components of the domain name).

The default domain suffix is the same as the domain name obtained from the Internet authority. For example, the parameter setting specifying NCD's default domain suffix is:

tcpip-dns-default-domain = ncd.com


Table 5-7  tcpip-dns-default-domain Parameter




 Possible Values

 Result


default

nil


nil

No suffix is applied to hostnames in name service searches.


domain suffix

The suffix applied to hostnames in name service searches.

Translations are automatically placed in the local name cache. If your site does not run a name service, you can place translations into the table manually.

The terminal maintains the local name cache in the tcpip-name-local-cache parameter (Setup -> Change Setup Parameters -> TCP/IP Name Service -> Local Name Cache). Table 5-8 lists the entries in each row of the table.

Table 5-8 tcpip-name-local-cache Table Entries

By default, case is considered when the terminal searches for a name in the local name cache. To ignore case, set the tcpip-name-cache-ignore-case parameter to "true." (Change Setup Parameters -> TCP/IP Name Service -> Ignore Case on Name Cache Lookups).

To customize the local name cache, you can change the following parameters; however, the defaults work well for most sites.

Setting the Name Cache Entry Lifetime

The tcpip-name-cache-max-lifetime parameter controls the maximum amount of time that an entry in the cache is used before it is deleted automatically (Setup -> Change Setup Parameters -> TCP/IP Name Service -> Name Cache Max Lifetime).

Table 5-9 tcpip-name-cache-max-lifetime Parameter

Setting the Name Cache Size

The tcpip-name-cache-max-size parameter sets the maximum number of entries allowed in the name cache (Setup -> Change Setup Parameters -> TCP/IP Name Service -> Name Cache Max Size). When the maximum size is reached, the oldest entry is discarded when a new entry is added. You may want to restrict the size of the cache to save memory for other uses.

Table 5-10 tcpip-name-cache-max-size Parameter

The tcpip-name-server-retransmission-timeout parameter determines how long the terminal waits before sending a retransmission if the name server does not respond (Setup -> Change Setup Parameters -> TCP/IP Name Service -> Name Server Retransmission Timeout).

Table 5-11 tcpip-name-server-retransmission-timeout

The tcpip-name-server-transaction-timeout parameter determines how long the terminal waits for a response from the name server before failure is declared (Setup -> Change Setup Parameters -> TCP/IP Name Service -> Name Server Transaction Timeout). The value of this parameter should be larger than the retransmission timeout.

Table 5-12 tcpip-name-server-transaction-timeout

The unit-query-for-name-at-boot parameter controls whether, at boot time, the terminal sends a reverse name request to the DNS name servers to find the terminal's host name (Setup -> Change Setup Parameters -> Unit -> Query for Unit Name at Boot).

Table 5-13 unit-query-for-name-at-boot Parameter