6    Local Area Transport Connections

The Local Area Transport (LAT) protocol supports communications between host computer systems and terminal servers with terminals, PCs, printers, modems and other devices over local area networks (LANs). The Tru64 UNIX LAT implementation is a STREAMS-based driver.

This chapter describes:

For additional introductory information on LAT, see lat_intro(7). For troubleshooting information, see Section 14.16.

6.1    LAT Environment

In the LAT environment, systems can have the following roles:

Figure 6-1 shows a sample LAN with LAT server nodes and LAT service nodes.

Figure 6-1:  Sample LAT Network Configuration

The LAT software also permits host applications to initiate connections to server ports, designated as application ports, to access remote devices. The following sections describe:

6.1.1    Types of LAT Connections

The following types of LAT connections are permitted:

6.1.2    Controlling Access in a LAT Network

Because LAT networks are local in nature, you have a high degree of control over the LAT environment and who has physical access to LAT devices. In addition to controlling physical access, the following features enable you to control LAT access:

In general, groups are set up by the network manager, system manager, and server managers to partition the LAT network into logical subdivisions and to restrict message traffic between servers and service nodes. In addition, using groups can help you manage the size of the servers' LAT databases by limiting the number of service nodes for which the server keeps information.

Note

You can use groups to restrict access, but they are not intended as a security mechanism.

To establish a connection with a LAT service node, the group enabled on a terminal server port or an outgoing port on a LAT server node must match at least one group on the service node. Similarly, for a terminal server or server node to process messages from service nodes, the group enabled on a terminal server port or an outgoing port on the server node must match at least one group on the service node. Otherwise, the messages from the service nodes are ignored.

For more information on enabling LAT service node groups and outgoing port groups, refer to latcp(8).

6.1.3    Specifying Passwords for Remote Services

The LAT protocol enables you to specify a password for access to remote services that are protected by a password. When password checking is enabled on a terminal server that offers a service that is password protected, you must specify the password when you map the application port; if you do not, all attempts to connect to the service from the terminal server are rejected. See latcp(8) for more information.

6.1.4    Load Balancing

When more than one node on a LAN offers the same service, the terminal server connects to the node with the highest rating for the service desired. The rating is based on the current load on the nodes that offer the service. This process is called load balancing.

Load balancing works in a heterogeneous environment. Therefore, service nodes with the same names may be running different operating systems.

6.2    Planning LAT

This section describes the tasks you must complet before configuring LAT.

6.2.1    Verifying That the LAT Subset Is Installed

Verify that the LAT subset is installed by entering the following command: 

# setld -i | grep LAT
 
 

If the LAT subset is not installed, install it by using the setld command. For more information on installing subsets see setld(8), the Installation Guide, or the System Administration manual.

After the LAT subset is installed, your system is configured to load the LAT module into the running kernel dynamically when the system boots.

6.2.2    Verifying DLB Support in the Kernel

After you install the LAT subset, verify that Data Link Bridge (DLB) support is in the kernel by issuing the following command: 

# sysconfig -q dlb

If the dlb: prompt is not displayed, log in as superuser and complete the following steps:

  1. Edit the configuration file and add the following entry to it: 

    options DLB

    The default configuration file is /sys/conf/HOSTNAME where HOSTNAME is the name of your host processor, in uppercase letters.

  2. Build a new kernel by issuing the doconfig command. If you are unfamiliar with rebuilding the kernel, see the System Administration manual.

  3. Reboot your system with the new kernel by issuing the following command: 

    # shutdown -r now

    This command immediately shuts down and automatically reboots the system.

6.2.3    Preparing for the Configuration

After you verify DLB support in the kernel, you configure LAT by using the latsetup utility.

Figure 6-2 shows the LAT Setup Worksheet, which you can use to record the information required to configure LAT. If you are viewing this manual online, you can use the print feature to print the worksheet. The following sections explain the information you need to record on the worksheet.

Figure 6-2:  LAT Setup Worksheet

Start LAT automatically at boot time

By default, the /sbin/init.d/lat startup and shutdown script automatically starts LAT upon reaching run level 3 and stops LAT when exiting run level 3. If you do not want LAT to be started automatically, check No; otherwise, check Yes.

Type of tty devices

The type of terminal device (tty) for each LAT connection. Tru64 UNIX supports SVR4 and BSD device types. It is best to use SVR4 devices because the SVR4 format allows you to create more devices.

SVR4 device special files have the following format:

/dev/lat/n

The value n is a number between 620 and approximately 5000. For example, /dev/lat/620, /dev/lat/777, and /dev/lat/4000 specify SVR4 devices. The SVR4 format allows you to create an unlimited number of devices.

BSD device special files have the following format:

/dev/ttyWX

The value W is a number from 0 to 9; X is an alphanumeric from 0 to 9, a lowercase a to z, or an uppercase A to Z. For example, /dev/tty02, /dev/tty0e, and /dev/tty9f specify BSD LAT terminal devices. However, all BSD terminal device names are not case sensitive. The device special files /dev/tty9f and /dev/tty9F are both converted to TTY9F.

This format enables you to specify up to 620 BSD terminal devices which are available to any serial devices (such as UUCP) running on the system. Therefore, fewer than 620 BSD devices may be available for LAT.

Number of LAT tty devices

The total of the desired number of simultaneous incoming LAT connections, the number of application ports, and the number of outgoing connections needed.

Number of LAT entries (getty) in /etc/inittab

The number of LAT getty entries to be added to the /etc/inittab file. This is the number of simultaneous incoming LAT connections desired.

6.3    Configuring LAT

Use the latsetup utility to configure and administer LAT on your system. To use the latsetup utility, LAT and DLB must be configured into the running kernel, your system must be at run level 3 or 4, and you must be logged in as superuser. See the latsetup(8) reference page for more information.

The latsetup utility allows you to do the following:

You cannot configure LAT over NetRAIN virtual interfaces or the adapters that compose NetRAIN sets. LAT is not supported over NetRAIN.

From the SysMan Menu, invoke the latsetup utility by selecting Networking-->Additional Network Services-->Configure Local Area Transport (LAT). Alternatively, enter the following command on the command line: 

# /usr/sbin/latsetup

If your terminal does not support curses, you must specify the -nocurses flag. This flag allows you to run latsetup in command-line mode.

Note

Do not run multiple latsetup processes concurrently on the same machine. The latsetup user might receive erroneous information and the /etc/inittab file might become corrupted.

6.4    Starting and Stopping LAT

To manually start LAT, enter the following command: 


# /sbin/init.d/lat start

To manually stop LAT, enter the following command: 


# /sbin/init.d/lat stop

If you stop LAT from within a LAT session, the session will hang. You will have to reboot your system to clear up the problem.

6.5    Creating a LAT Startup File

If LAT automatic startup and shutdown are enabled, when the system reaches run level 3, it loads LAT into the kernel and executes the /sbin/init.d/lat script. This script reads and executes the latcp commands in the /etc/latstartup.conf file (if this file exists), then starts LAT. See latcp(8) for more information on the latcp command.

If you do not have an /etc/latstartup.conf file, LAT is started with the default values for its parameters. Table 6-1 lists the LAT parameters and their default values.

Table 6-1:  LAT Parameters

Parameter Default Value
Node name Host name
Multicast timer 60 seconds
Network adapter All network adapters connected to broadcast media, except for NetRAIN virtual interfaces (nr) and those adapters that compose NetRAIN sets.
Service name From the LAT node name parameter. Each service has the following parameters:
  Parameter Default Value
  Service description "Compaq Tru64 UNIX Version X.X LAT  SERVICE"
  Rating Dynamic
  Group code 0
Agent status Disabled
Outgoing port groups Group 0
Maximum number of learned services 100

If you want to customize LAT on your system, you can create and modify the /etc/latstartup.conf file to include latcp commands. For example, you can define a particular node name or add service names.

Note

If your system is a member of a cluster, you must create the /etc/latstartup.conf file as a Context-Dependent Symbolic Link (CDSL). See the System Administration manual for more information.

Example 6-1 shows a sample /etc/latstartup.conf file.

Example 6-1:  Sample /etc/latstartup.conf File

/usr/sbin/latcp -n testnode     [1]
/usr/sbin/latcp -A -a lattelnet14 -i "LAT/telnet" -o  [2]
/usr/sbin/latcp -A -a testservice     [3]
/usr/sbin/latcp -g 0,21,52 -a testservice     [4]
/usr/sbin/latcp -A -a boundservice -p 620,621     [5]
/usr/sbin/latcp -c200    [6]
/usr/sbin/latcp -A -p 630 -O -V finance     [7]
/usr/sbin/latcp -u 0,1,41,97    [8]
/usr/sbin/latcp -e ln0    [9]

  1. Changes the LAT node name. [Return to example]

  2. Adds an optional service that can be used for LAT/Telnet connections. (See Section 6.11 for more information on the LAT/Telnet gateway.) [Return to example]

  3. Adds an unbound interactive testservice service. [Return to example]

  4. Adds groups 0, 21, and 52 to the testservice service. [Return to example]

  5. Adds a bound service and binds to it two LAT devices: 620 and 621, which are SVR4-style LAT devices. [Return to example]

  6. Increases the number of learned services to 200. [Return to example]

  7. Maps an outgoing port to finance service. [Return to example]

  8. Adds outgoing port groups 0, 1, 41, and 97. [Return to example]

  9. Adds the ln0 adapter. [Return to example]

A latcp command that adds a service must occur in the latstartup.conf file before a latcp command requiring the service name. Lines 3 and 4 in Example 6-1 illustrate this point.

6.6    Customizing the inittab File

You can modify the /etc/inittab file to use a program other than getty. For example, you can add the following entry to /etc/inittab to configure LAT device 620 to use the user-defined program myownprogram: 

lat620:34:respawn:/usr/sbin/myownprogram  /dev/lat/620
 

The previous example uses an absolute pathname for the device /dev/lat/620.

For more information on using user-defined programs with LAT, see Section 6.12. For more information on the /etc/inittab file and the getty utility, see inittab(4) and getty(8).

You can also modify the /etc/inittab file to add LAT devices created manually after the initial configuration by adding an entry similar to the following: 

lat621:34:respawn:/usr/sbin/getty  lat/621  console vt100
 

The second field (34) specifies the run level in which the entries will be processed. In this example, the getty process is spawned at either run level 3 or 4. In addition, this example uses a relative pathname lat/621.

6.7    Running LAT Over Specific Network Adapters

If your system is configured with multiple network adapters, by default the latcp program attempts to start the LAT protocol on all adapters that can support it (which excludes NetRAIN virtual interfaces and the adapters that compose NetRAIN sets). For adapters connected to different logical networks, this is probably desirable. However, for adapters connected to a single logical network, you should specify that the LAT protocol run over only one adapter. To specify the adapter, add the latcp -e adapter command to the /etc/latstartup.conf file. See latcp(8) for more information.

Use the netstat -i command to determine the adapters defined on your system.

6.8    Setting Up Printers

Before you set up a printer to print through LAT you should be familiar with setting up printers. See the System Administration manual, printconfig(8), lprsetup.dat(4), and lprsetup(8) for information on setting up printers. In addition, you need the following information:

This section provides information on how to set up a printer to print through LAT, using host-initiated connections.

Note

The examples in this section use the DECserver 700 server. Please refer to the documentation supplied for your terminal server.

6.8.1    Setting Up the Printer on a Terminal Server

To set up a printer, do the following:

  1. Connect the printer to a serial interface on a terminal server.

  2. Use the terminal server commands specified in the terminal server documentation to set up the server to allow access to the attached remote printer through host-initiated requests from the service node. (Service node refers to the local Tru64 UNIX LAT host.)

  3. Use the printer documentation to determine your printer's character size, flow control, parity, and speed.

  4. Compare the printer's characteristics to the terminal server's port settings. You can display the settings on the terminal server console by entering a command similar to the following: 

    
Local> SHOW PORT 7 CHARACTERISTICS

    This command displays the characteristics for port 7. Minimally, the terminal server should have settings for the port similar to the following:

    Character Size: Printer's character size
    Flow Control: XON (or -CTS/RTS, for some printers)
    Speed: Printer's speed
    Access: Remote
    Autobaud: Disabled
    Autoconnect: Disabled

    If the terminal server's port settings do not match the printer's characteristics, define the terminal server's port settings by using the DEFINE command. For example: 

    
Local> DEFINE PORT 7 SPEED 9600

  5. After you define the settings for the port, log out of that port to initialize the new settings. For example: 

    
Local> LOGOUT PORT 7

6.8.2    Testing the Port Configuration

To verify that the printer characteristics match in the printer and in the terminal server port, use the TEST PORT command on the terminal server. For example, if the configuration is correct, the following command run on a DECserver 700 prints a test pattern of characters on a printer attached to port 7: 

Local> TEST PORT 7

The printer prints 24 lines of test data unless you press the Break key at the terminal server console. If data does not print or if it is incorrect, the port or the printer is incorrectly set, or there is a hardware problem.

6.8.3    Setting Up a Service Node for the Printer

On the service node (local LAT host), use the latcp command to map an unused application port with the remote port or remote service on the terminal server. Use the terminal server name and either the name of the port or the name of the service for the printer from Section 6.8.1.

For example, the following command maps the local application port 621 for the server LOCSER to the remote printer port port07. 


# latcp -A -p 621 -H LOCSER -R port07

The following command specifies the remote printer service name instead of the remote print port: 

# latcp -A -p 621 -H LOCSER -V REMprinter07

For more information, see latcp(8).

6.8.4    Setting Up the Print Spooler on the Service Node

To set up the print spooler for the remote printer, use the lprsetup command. The following symbols must be set in the printcap file for the service node (local LAT host) to access the remote printer through host-initiated connections:

The following example shows an /etc/printcap entry for a LAT printer: 

    lp25|lp0:\
            :af=/usr/adm/lpacct:\
            :ct=LAT:\   [1]
            :lf=/usr/adm/lperr:\
            :lp=/dev/lat/621:\    [2]
            :mx#0:\
            :of=/usr/lbin/lpf:\
            :sd=/usr/spool/lpd:

  1. Specifies LAT for the ct symbol. [Return to example]

  2. Specifies the LAT application port (tty device) that was used in the latcp command to set up the service node. You must specify the full path name for the lp symbol. [Return to example]

6.8.5    Testing the Printer

After you set up the printer, print a file to ensure everything works properly. For example, if the printer name is lp25 and test is a text file, you can test the printer by issuing the following command: 

# lpr -Plp25 test

If the printer does not work, verify that all the settings are correct. If the printcap file entry has an lf symbol defined, you can check the corresponding log file for error information.

6.9    Setting Up Host-Initiated Connections

A host-initiated connection is one in which any bit-serial, asynchronous device connected to a terminal server can communicate with user-developed applications on an appropriately configured system. Examples of such devices are terminals, modems, communications ports on other host computer systems, and printers. Printer connections are discussed in Section 6.8.

This section describes how you set up a system for host-initiated connections and provides guidelines for developing applications to take advantage of these connections.

6.9.1    Setting Up the System for Host-Initiated Connections

To set up your system for LAT host-initiated connections, do the following:

  1. Use the latcp -A -p command to map an application port (tty device) on the system with a remote port or service on a terminal server. In the following example, 623 is the application port, T1301A is the terminal server name, and PORT_6 is the terminal port name. 

    # /usr/sbin/latcp -A -p 623 -HT1301A -R PORT_6

    Alternatively, you can specify a service name instead of a port name in the preceding example.

  2. Make sure the protection bits, the owner, and the group of the tty device are set appropriately for the intended use of the connection. If ordinary users will open and read the tty device, you should make the device world readable.

  3. Set up the server port characteristics to match the characteristics of the device connected to the port and to allow host-initiated connections. See your device and terminal server documentation for this information.

6.9.2    Program Interface

Applications that employ host-initiated connections are much like applications for any tty device, with the following exceptions:

The dial.c application program in the /usr/examples/lat directory is an example of a program that can be used with host-initiated connections. To access this example, you must install the OSFEXAMPLES500 optional subset.

The Tru64 UNIX LAT implementation is a STREAMS-based tty design. When a LAT tty device is opened, the POSIX line discipline module ldterm is pushed onto the stream above the LAT driver. If your application does not need the additional processing provided by ldterm, it must remove the module from the stream.

The lined.c application program in the /usr/examples/lat directory demonstrates how terminal (tty) line disciplines are changed in a Clist-based tty and a STREAMS tty environment. To access this example, you must install the OSFEXAMPLES500 optional subset. Additionally, you can use the strchg command to change the STREAMS configuration of the user's standard input.

For more information, see autopush(8) and strchg(1).

6.10    Setting Up Outgoing Connections

An outgoing connection is one in which a local user can connect to a service on a remote host by using the llogin command. To accomplish this, a named service on the remote host is associated with a terminal device special file on the local host. See llogin(1) and the Command and Shell User's Guide for information on the llogin command.

6.10.1    Setting Up the System for Outgoing Connections

To set up your system for LAT outgoing connections, do the following:

  1. Map an outgoing port (tty device) on the system with a port or service on a remote system by using the latcp -A -p command. In the following example, 621 is the outgoing port and REMOTE_SERVICE is the service name on the remote node. 

    
# /usr/sbin/latcp -A -p 621 -O -V REMOTE_SERVICE

    Alternatively, you can specify a remote node name and a port name in the preceding example.

  2. Verify that the remote service is a learned service available to your system, by using the following command: 

    
# /usr/sbin/latcp -d -l

    If the service is not displayed, the maximum number of learned services has been reached; the service might still be available. When an outgoing connection is attempted, the local host determines whether the remote service is available. If it is available, the outgoing LAT connection is made.

    To increase the maximum number of learned services, use the latcp -c command. See latcp8 and lat_intro(7) for more information on learned services.

6.10.2    Program Interface

Applications developed to employ outgoing connections adhere to the same guidelines as applications developed for host-initiated connections. See Section 6.9.2 for more information.

The getdate.c application program in the /usr/examples/lat directory is as an example of a program that can be used with outgoing connections. To access this example, you must install the OSFEXAMPLES500 optional subset.

6.11    Setting Up the LAT/Telnet Gateway

The LAT/Telnet gateway service enables a user on a LAT terminal server to connect to remote hosts running the Telnet protocol through an intermediate Tru64 UNIX host. The user does not have to log in to the local Tru64 UNIX system first. Optionally, if configured, you can use the rlogin command to connect directly to remote hosts.

To set up the LAT/Telnet gateway, perform the following steps:

  1. Define the LAT/Telnet service by using the latcp command. For example: 

    
# /usr/sbin/latcp -A -a lattelnet -i "LAT/telnet gateway" -o

    The -o flag specifies that this is an optional service. Optional services are used with specialized applications that are written especially for LAT. These services are bound to LAT tty devices for the exclusive use of the specialized applications.

  2. Edit the /etc/inittab file and modify the LAT device entries that you want to spawn the lattelnet service you created in step 1. The LAT terminals you select are dedicated to the gateway. The number of terminals selected determines the maximum number of simultaneous LAT/Telnet gateway sessions the system can deliver. For example, the following example shows LAT/Telnet gateway entries for three devices, which means that this system can deliver 3 simultaneous sessions: 

    lat624:34:respawn:/usr/sbin/lattelnet  lat/624  lattelnet
lat625:34:respawn:/usr/sbin/lattelnet  lat/625  lattelnet
lat626:34:respawn:/usr/sbin/lattelnet  lat/626  lattelnet

    If you want to use the rlogin command instead of Telnet, specify /usr/bin/rlogin as the third argument to the lattelnet program in the /etc/inittab entry. For example: 

    lat624:34:respawn:/usr/sbin/lattelnet lat/624 lattelnet /usr/bin/rlogin
 

  3. Use the init program to read the inittab file and start the gateway by using the init q command.

  4. Verify that the lattelnet process has started by using the ps command.

    The lattelnet program uses the syslog function to log messages to the /var/adm/syslog.dated/daemon.log file. Check this file to verify that no error messages were generated.

  5. Connect to the gateway from the LAT terminal server by entering the CONNECT command. For example, to connect to a remote node named REMOTE by using a local node named LOCAL as a gateway, enter: 

    Local> CONNECT LATTELNET NODE LOCAL DEST REMOTE

    You can use the preceding command line for either Telnet or rlogin.

    Alternatively, if connecting for Telnet, you can enter the service name LATTELNET and wait to be prompted for the remote node desired. The following example shows what occurs when a user on a terminal server connects to the service LATTELNET and waits for a login prompt from remote node MYTRIX: 

    Local> CONNECT LATTELNET
LAT to TELNET gateway on printf
telnet> OPEN MYTRIX
Trying...
Connected to mytrix.
Escape character is '^]'.
mytrix login:

6.12    Creating Dedicated or Optional Services

Dedicated services can be used in combination with your own specialized applications. The following specialized application programs are provided in the /usr/examples/lat directory:

Setting up a dedicated service is similar to setting up the LAT/Telnet gateway. (See Section 6.11.) To set up a dedicated service, complete the following steps:

  1. Log in as root.

  2. After you enter and compile the application code, copy the executable to the directory of your choice.

  3. Add the service by using the latcp -A -a command. For example: 

    # /usr/sbin/latcp -A -a showdate -i "LAT/date service" -o

    The -o specifies that this is a dedicated service.

  4. Edit the /etc/inittab file and add the dedicated tty device entries. For example: 

    lat630:3:respawn:/usr/sbin/latdate lat/630 showdate
 

    Note

    You need an entry in the /etc/inittab file for every simultaneous service you want to run. The previous example only allows for one user of the latdate service at any one time.

  5. Use the init program to read the inittab file and start the service by using the init q command.

To use the service at a LAT terminal, issue the CONNECT command. For example: 

Local> CONNECT SHOWDATE

A Tru64 UNIX host can also offer bound interactive and unbound interactive services. See lat_intro(7) for more information. For information on the commands used to create these services, see latcp(8).

6.13    Providing a Dedicated tty Device on a Terminal

A terminal connected to a terminal server port can offer a dedicated tty device on a given Tru64 UNIX LAT host. The terminal will always be connected to the specified tty device on the LAT host. The user at the terminal cannot switch sessions or connect to different hosts or different tty devices on that host.

6.13.1    Setting Up a Dedicated tty Device

To set up a dedicated tty device on a terminal, perform the following steps:

  1. Determine the name of the terminal server and the port name on which the terminal is connected. The following terminal server commands display the name of the server and the port name, respectively: 

    
Local> SHOW SERVER
Local> SHOW PORT number

    The number variable is the number of the port on the terminal server.

  2. On the LAT host, map an application port (tty device) to the port on the terminal server by using the latcp -A -p command. For example, the following command maps an SVR4 device (application port 630 to port 2 on the terminal server LATTERM: 

    
# latcp -A -p630 -H LATTERM -R PORT_2

    For more information, see latcp(8).

  3. On the LAT host, add a getty entry to the /etc/inittab file for the tty device that was mapped as an application port. For example: 

    lat630:34:respawn:/usr/sbin/getty        lat/630 console vt100
 

  4. On the terminal server, define the port's access to be REMOTE and log out from the port. For example: 

    
Local> DEFINE PORT 2 ACCESS REMOTE
Local> LOGOUT PORT 2

  5. Press Return on the terminal connected to the terminal server port that you just set up. When the system prompt is displayed, the terminal is connected to the dedicated tty device.

If you need to repeat the procedure, remove the getty entry from the /etc/inittab file, issue the init q command, and start the procedure from the beginning.

6.13.2    Removing a Dedicated tty Device

To remove a dedicated tty device from a terminal port and allow the terminal connected to the port to connect to any host, do the following:

  1. Log in to another terminal on the same server.

  2. Set the port's access to LOCAL and log out from the port. For example: 

    Local> DEFINE PORT 2 ACCESS LOCAL
Local> LOGOUT PORT 2

  3. Unmap the application port and remove the getty entry from the /etc/inittab file.