D-Link DI-1750 Reference Manual page 96

Model Name
Figuer 5-10 Standard X.25 Connection Between a Dumb Terminal and an X.25 Host
PADs can also be configured to work with a protocol translation application. Figure 87 shows an
Example of a remote PC placing an analog modem call to an IP network, connecting to a
D-LINK 4500-M router, allowing its IP packets to undergo an IP-to-X.25 protocol translation, which in
turn communicates with an internal PAD device and establishes a connection with an X.25 host.
Figuer 5-11 PC Dialing In to an X.25 Host Using Protocol Translation
5.6.3 Description
X.28 emulation is the standard user interface between data terminal equipment (DTE) and a packet
assembler/disassembler (PAD). The D-Link router provides an X.28 user emulation mode, which
enables you to interact with and control the PAD. During this exchange of control information,
messages or commands sent from the terminal to the PAD are called PAD command signals.
Messages sent from the PAD to the terminal are called PAD service signals. These signals and any
transmitted data take the form of encoded character streams as defined by International Alphabet
Number 5.
For asynchronous devices such as terminals or modems to access an X.25 network host, the device's
packets must be assembled or disassembled by a PAD device. Using standard X.28 commands from
the PAD, calls can be made into an X.25 network, X.3 PAD parameters can be set, or calls can be reset.
X.3 is the ITU-T recommendation that defines various PAD parameters used in X.25 networks. There
are 22 available X.3 PAD parameters to configure. X.3 PAD parameters are internal variables that
define the operation of a PAD. For example, parameter number 9 is the crpad parameter. It determines
the number of bytes to add after a carriage return. X.3 parameters can also be set by a remote X.25
host using X.29.
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