X.28 enables Packet
Assembler Disassembler (PAD) system administrators to dial in to X.25 networks
or set PAD parameters using the X.28 standard user interface. X.28 adheres to
the X.28 ITU-T standards.
The X.28 interface
is designed for asynchronous devices that require X.25 transport to access a
remote or native asynchronous or synchronous host application. For example,
dialup applications can use the X.28 interface to access a remote X.25 host.
X.28 PAD calls are often used by banks to support applications in the back
office such as ATM machines, Point of Sale (POS) authorization devices, and
alarm systems. An ATM machine may have an asynchronous connection to an alarm
host and a Cisco device. When the connection is broken, the alarm host sends a
distress call to the authorities through the Cisco device using an X.28 PAD
The X.28 PAD
Configurable PAD Options feature provides an option to prevent the padding
character from being sent when an asynchronous device connects at any access
speed below 9600 bps. The ITU X.28 recommends different padding character
combinations depending on the speed. The option prevents the padding character
from being added to a POS terminal that accepts 0 padding at a lower speed. The
x28 command is
enhanced to support this feature.