3Com S200 manual PAD XON/OFF Support Using X.25 Interrupt Packets, How It Works

PAD Port Configuration

PAD XON/OFF Support Using X.25 Interrupt Packets

What is It?There is a Customer Software Key (CSK) that enables the transmission of XON/ XOFF asynchronous data characters across a Public Data Network (PDN) using X.25 Interrupt packets.

This improves the transmission of flow control information between local and remote PAD ports on PathBuilder S200 series switches. Since X.25 Interrupt packets travel at a higher priority through the PDN, flow control information between PAD ports is communicated more thoroughly by letting you control the starting and stopping of the asynchronous data characters stream.

How It Works	By enabling the CSK for this feature whenever a PathBuilder S200 series switch
	PAD port receives an XON or XOFF flow control character from a user terminal or
	networking device, the XON/OFF enhancement sends the flow control characters
	across the PDN as X.25 Interrupt packets for faster transmission to the remote PAD
	port.

For example, as shown in Figure 5, when User 1 wants to stop User 2 from sending information, User 1 sends an XOFF character to the PAD port on the local PathBuilder S200 series switch. Then the local PathBuilder S200 series switch sends an X.25 Interrupt Packet to the remote node on the other side of the network, where the XOFF character is passed on to User 2. This stops User 2 from sending anymore data.

To let User 2 send information again, User 1 sends an XON character into the PAD port on the local PathBuilder S200 series switch, which sends an X.25 Interrupt Packet to the other node, and the XON character is passed on to User 2. This allows User 2 to begin sending data again.

X.25 ports

PAD Port PAD Port

PB S200 X.25 VC PB S200

PDN

User 1 User 2

Figure 5. Example of Transmitting XON/OFF Frames Across PDN with X.25 Interrupt Packets

Note

The user devices shown in Figure 5 can be networking devices or asynchronous user terminals. Remember that the CSK for this feature must be enabled in order to transmit flow control characters as X.25 Interrupt packets. If the CSK is not enabled, the feature is not supported.

Also, for this feature to work, user devices at both ends of the network must be connected to PathBuilder S200 series switches.

Set the PAD Profile record parameters Device Flow Control and PAD Data

Restraint to 1 for both PAD ports. Enabling the PAD Enhancement CSK.

Configuring PAD/ATPAD Ports 23