3Com 10014299 manual PAD Remote, Access Service

68CHAPTER 4: TERMINAL SERVICE

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X.25 PAD Remote	PAD (Packet Assembly/Disassembly facility) is a definition specific to X.25 protocol.
Access Service	The traditional X.25 network requires that all its terminals are of X.25 type, and
	relevant hardware and software are needed to support X.25 protocol, which are
	the so-called packet terminals. Packet terminals must be intelligent ones, but
	many terminals uses are either non-X.25 or not intelligent (such as keyboard,
	monitor, printer, etc.) or intelligent but do not support X.25 procedures. In that
	case it is impossible for non-X.25 terminals to interconnect with each other
	through the X.25 network, or even access the X.25 network. X.25 PAD technology
	was developed to address how these devices can be enabled to communicate via
	X.25 network.
	X.25 PAD bridges the X.25 network and non-X.25 terminals — it provides a
	mechanism through which non-X.25 terminals can access the X.25 network. As
	shown in the figure below, a PAD is positioned between the X.25 network and
	terminals that do not support X.25 procedures to enable the latter to
	communicate with other terminals through the X.25 network.
	Figure 32 Access function of PAD
			P	Non-X.25 terminal
	X.25 Network	X.25	A	Non-X.25
		Procedures		Procedures

D

The main functions of the X.25 PAD are to:

■Provide support to X.25 procedures and accordingly to connect and communicate with the X.25 network.

■Provide support to non-X.25 procedures and accordingly to connect non-X.25 terminals.

■Provide non-X.25 terminals with functions of call establishment, data transmission and call clearing through the X.25 network.

■Provide non-X.25 terminals with functions of observing and changing interface parameters so as to adjust to the requirements of varied terminals.