Devices(4bnu)

Devices -- list of devices for BNU communications

Description

The /etc/uucp/Devices file contains information about the devices that may be used to establish a link to a remote computer using the Basic Networking Utilities (BNU). Several types of devices can be defined in the Devices file, including automatic call units, direct links and network connections.

All entries must contain at least five fields. If a field is left blank, the field must contain a dash (-). Blank lines, and lines that begin with white space, a tab, or a hash sign (#) are ignored.

The fields in the Devices file are defined, in order, as follows:

``Type''

Specifies the device name. The device name can be a name of your choosing, but it must match the name in the third field of the Systems(4bnu) file. The two names Direct and ACU are reserved. Generally the ``Type'' field is the name of a computer directly linked to the computer on which the Devices file in question is located (to differentiate it from other directly linked computers) or the name of a network accessible to the computer on which the Devices file is located (to differentiate it from other accessible networks).

Direct: Indicates a direct link to another computer or a switch.
ACU: Indicates that the link to a remote computer is made through an Automatic Call Unit (automatic dial modem). This modem may be connected either directly to your computer or indirectly through a local area network (LAN) switch.
LAN_Switch: Specifies the name of the LAN or switch. For instance, ``TCP'' could be the name for the TCP/IP network.
Sys_name: Specifies a direct link to the computer Sys_name. This naming scheme conveys the fact that the line associated with this Devices entry is for a computer defined in the Systems(4bnu) file.
CS: Indicates a TLI LAN-type connection with authentication scheme invocation.
ISDN_SYNC: Indicates a sychronous ISDN connection.
ISDN_ASYNC: Indicates an asynchronous ISDN connection.

The keyword used in the ``Type'' field of the Devices file is matched against the third field of Systems file entries, as shown in the following sample files:

#Systems file # eagle Any ACU 1200 3251 ogin: nuucp ssword: password sys1 Any CS - sys1,uucico sys2 Any CS - sys3 Any CS - sys3,login in:--in nuucp word:xx sys4 Any DK 9600 sys4 INVOKE "cr1 -r" sys5 Any DK 9600 sys5 in:--in nuucp word:xx sys6 Any LAN - network_address

#Devices file # ACU term/01m - 2400 att4024 Direct term/00 - Any direct sysb term/03 - Any uudirect CS - - - CS LAN,eg tcp - - TLI \D

The protocol to use for a device can be designated within the ``Type'' field.

``Line''

Specifies the device name of the line (port) associated with the Devices entry. For instance, if the automatic dial modem for a particular entry is attached to the /dev/term/01m line, the name specified in the ``Line'' field is ``term/01m''. The optional modem control flag ``M'' indicates that the device should be opened without waiting for a carrier. The modem control flag is separated from the device name by a comma. For example, term/01m,M.

CS type entries must contain a dash (-) in the ``Line'' field.

``Line2''

If the keyword ACU is used in the ``Type'' field and the ACU is an 801-type dialer, ``Line2'' specifies the device name of the 801 dialer. Since 801-type ACUs do not contain a modem, separate modems are required and are connected to a different line, as defined in the ``Line'' field. This means that one line is allocated to the modem and another to the dialer. Non-801 dialers do not normally use this configuration. Although non-801 dialers therefore ignore the ``Line2'' field, the field must contain a dash (-) as a placeholder. CS entries must also contain a dash in the ``Line2'' field.

``Class''

If the ACU or Direct keywords are used in the ``Type'' field, the ``Class'' field needs to specify only the speed of the device. The ``Class'' field may, however, specify a letter and a speed, for example, ``C1200'' (Centrex), or ``D1200'' (Dimension PBX). This allows large organizations that have more than one type of telephone network to differentiate between classes of dialers. One network may be dedicated to serving only internal office communications, for example, while another handles external communications. In this case, it is necessary to distinguish which line(s) are used for internal communication and which are used for external communication.

The keyword used in the ``Class'' field of the Devices file is matched against the fourth field of Systems file entries as shown in the following Devices and Systems file lines.

#Devices file # ACU tty11 - D1200 penril

#Systems file # eagle Any ACU D1200 3251 ogin: nuucp ssword: password

Some devices can be used at any speed. In this case, the keyword Any may be specified in the ``Class'' field. If Any is specified, the line will match any speed requested in a Systems file entry. However, if the Devices file ``Class'' field specifies Any and the Systems file ``Class'' field specifies Any, the speed defaults to 1200bps.

``Dialer-Token-Pairs''

Contains pairs of dialers and tokens. The dialer portion of a dialer-token pair may specify the name of an automatic dial modem, a LAN switch, or it may specify direct or uudirect for a Direct Link device. The token portion of a dialer-token pair may be specified immediately following the dialer portion, or, if it is not present, it will be taken from a related entry in the Systems(4bnu) file. There may be any number of dialer-token pairs.

This field has the format:

dialer token [dialer token]

where the last pair may or may not be present, depending on the associated device (dialer). In most cases, the last pair contains only a dialer portion and the token portion is retrieved from the ``Phone'' field of the Systems file entry.

A valid entry for the dialer portion may be defined in the Dialers(4bnu) file or may be one of several special dialer types. These special dialer types are compiled into the software and are therefore available without having to be entered in the Dialers file.

CS: A request for a TLI network. The specific network is chosen from the networks available to the system on which the requested service is available. Generally, the returned network connection supports t_snd(3xti) and t_rcv(3xti) semantics, but may be modified using the Devconfig file.
801: Bell 801 auto dialer
TLI/TLIS: Transport Level Interface network. Generally, the network connection returned supports t_snd(3xti) and t_rcv(3xti) semantics but may be modified to support read(2) and write(2) using the Devconfig file.

The ``Dialer-Token-Pairs'' field may be structured differently, depending on the device associated with the entry.

If an automatic dial modem is connected directly to a port on your computer, the ``Dialer-Token-Pairs'' field of the associated Devices file entry should only have one pair. This pair will normally be the name of the modem. The dialer configuration files are found in /etc/uucp/default. If /etc/uucp/dialer exists, then that file is used to configure the dialer. Otherwise, the /etc/uucp/Dialers file is checked for a corresponding entry. For example, the ``28-8_Data_Fax_Modem'' has a configuration file:

#Devices file
#
ACU term/01m,M - 38400 28-8_Data_Fax_Modem

#/etc/uucp/default/28-8_Data_Fax_Modem file
#
MDM_SETUP=AT &F E0 V1 \V1 S0=0&K3\N6
MDM_SPEAKER=ATM0
MDM_DIALCMD=ATDT
MDM_HANGUP=ATH

The ``att2212c'' device is defined in the Dialers file:

#Devices file # ACU term/01m,M - 1200 att2212c

#/etc/uucp/Dialers file # att2212c =+-, "" atzod,o12=y,o4=n\r\c 06 atT\T\r\c ed

Notice that only the dialer portion (``att2212c'') is present in the ``Dialer-Token-Pairs'' field of the Devices file entry. This means that the token to be passed to the dialer (in this case the phone number) is taken from the ``Phone'' field of a Systems file entry.

If a direct link is to be established to a given computer, the ``Dialer-Token-Pairs'' field of the associated entry should contain the keyword direct or uudirect. This is true for both types of direct link entries, Direct and Sys_name (see the discussion of the ``Type'' field).

If you want to communicate with a computer that is on the same local network switch as your computer, your computer must first access the switch, and the switch can make the connection to the other computer. In this type of entry, there is only one pair. The dialer portion is used to match a Dialers file entry as shown here:

#Devices file # Datakit term/03 - 9600 datakit

#Dialers file # datakit "" "" \d TION: - - :TION \D

In the example, the token portion is left blank. This indicates that it is retrieved from the Systems file. The Systems file entry for this particular computer will contain the token in the ``Phone'' field, which is normally reserved for the telephone number of the computer (see the discussion of the ``Phone'' field in Systems(4bnu). This type of dialer-token pair contains an escape character (\D) to ensure that the contents of the ``Phone'' field will not be interpreted as a valid entry in the Dialcodes file.

If an automatic dial modem is connected to a switch, your computer must first access the switch and the switch will make the connection to the automatic dial modem. This type of entry requires two dialer-token pairs. The dialer portion of each pair (the fifth and seventh fields of the entry) will be used to match entries in the Dialers file.

#Devices file # ACU term/04 - 1200 datakit dial att2212c

#Dialers file # datakit "" "" \d TION: - - :TION \D att2212c =+-, "" atzod,o12=y,o4=n\r\c \006 atT\T\r\c ed

In the first pair, ``datakit'' is the dialer and ``dial'' is the token that is passed to the Datakit switch to tell it which device (automatic dial modem) to connect to your computer. This token will be unique for each LAN switch since each switch may be set up differently. Once the modem has been connected, the second dialer-token pair is accessed. The second dialer is ``att2212c''; the token is retrieved from the Systems file.

There are two escape characters that may appear in a ``Dialer-Token-Pairs'' field:

\T: Specifies that the ``Phone'' (token) field should be translated using the Dialcodes file. This escape character is normally placed in the Dialers file for each caller script associated with an automatic dial modem. The translation will not therefore take place until the caller script is accessed.
\D: Indicates that the ``Phone'' (token) field should not be translated using the Dialcodes file. A \D is also used in the Dialers file with entries associated with network switches (``develcon'' and ``micom'').

If the dialer is an internal dialer, \T is the default. Otherwise, \D is the default.

Files

/etc/uucp/Config
/etc/uucp/Dialcodes
/etc/uucp/Dialers
/etc/uucp/Systems
/etc/uucp/default/dialer_name

Usage

To use BNU, the system administrator must manually create the entries in the Devices file: the system-supplied Devices file contains only comment lines. The Devices file works closely with the Dialers(4bnu), Systems(4bnu), and Dialcodes(4bnu) files. Note that a change to an entry in one file may require a change to a related entry in another file.

Protocols

You can choose the protocol to use with each device. Typically, specifying a protocol is not necessary, since you can use the default. If you do specify the protocol, you must do so in the form:

type, protocol [(windows, packetsize)]

Available protocols are:

g: Generic packet protocol. This protocol provides error detection and retransmission over potentially noisy lines. By its nature, it is relatively slow.
Two parameters characterize the g protocol: windows and packetsize. windows indicates the number of packets that may be transmitted without waiting for an acknowledgement from the remote host. packetsize indicates the number of data bytes in each packet. By default, windows is set to 7 packets and packetsize is set to 64 bytes.
G: Identical to the g protocol in that it provides the same error detection and retransmission; however, the G protocol allows the number of windows and the packet size to be varied to match the characteristics of the transmission medium. When properly configured, performance can be significantly better than the g protocol.
windows may range from 1 to 7, and packetsize may range from 32 to 4096 bytes, in powers of 2.
e: Assumes error-free transmission and performs no error checking or retransmission. The e protocol is the fastest of the three protocols. Use it for reliable local area networks only.
There are no parameters to be tuned within the e protocol.
d: Makes the same assumptions as the e protocol (that is, that the underlying network provides an error-free communications channel that transfers the data in sequence without duplication), but uses Datakit-specific ioctls.
There are no parameters to be tuned within the d protocol.

By default, protocol is set to ``g(7,64)G(7,64)ed''.

The following example uses the e protocol over a TCP/IP local area network. If the e protocol is not available, g will be used instead.

   TCP,eg tcp - - TLIS \D

The next example uses the G protocol on a high-speed modem. The number of windows is set to 7, and the packet size is 512 bytes. If the G protocol is unavailable, the generic g protocol will be used.

   ACU,G(7,512)g term/11 - 9600 att2296a

Presumably, seven windows with a packet size of 512 bytes will provide optimum throughput for the specified device.

For incoming connections, the preferred protocol priority and parameters may be specified in the Config file (see Config(4bnu)) using the protocol parameter.

References

Config(4bnu), Devconfig(4bnu), Dialcodes(4bnu), Dialers(4bnu), Grades(4bnu), Limits(4bnu), Permissions(4bnu), Poll(4bnu), Sysfiles(4bnu), Systems(4bnu), atdialer(1bnu), dials(3N), ttymon(1M)