X.25 Timers

Restart Response [T20] (t20value)

This timer starts when the DTE issues a Restart Request. It terminates when the DTE receives a Restart Confirmation or a Restart Indication. If neither is received in the time allowed, the DTE retransmits the Restart Request. The valid range for values of this parameter, in tenths of a second, is 0 to 32000. The recommended value is 1800.

Call Req Response [T21] (t21value)

This timer starts when the DTE issues a Call Request. It terminates when the DTE receives a Call Connected, Clear Indication or Incoming Call. If none of these are received in the time allowed, the DTE issues a Call Request. The valid range for values of this parameter, in tenths of a second, is 0 to 32000. The recommended value is 2000.

Reset Response [T22] (t22value)

This timer starts when the DTE issues a Reset Request. It terminates when the DTE receives a Reset Confirmation or a Reset Indication. If neither is received in the time allowed, the DTE retransmits the Reset Request or sends a Clear Request. The valid range for values of this parameter, in tenths of a second, is 0 to 32000. The recommended value is 1800.

Clear Req Response [T23] (t23value)

This timer starts when the DTE issues a Clear Request. It terminates when the DTE receives a Clear Confirmation or Clear Indication. If neither is received in the time allowed, the DTE retransmits the Clear Request. The valid range for values of this parameter, in tenths of a second, is 0 to 32000. The recommended value is 1800.

DTE Window Status [T24] (t24value)

This timer does not exactly match the DTE Window Status Transmission Timer, T24. Instead, it specifies the maximum time for which data received from the remote side can remain unacknowledged due to a flow control condition. After expiration of this timer, any outstanding acknowledgments are carried by an X.25 Receive Not Ready packet. This timer makes sure that the remote side not receiving an acknowledgment does not cause resets within the virtual circuit. This timer should be about half the value of Window Rotation (see next section). The valid range for values of this parameter, in tenths of a second, is 0 to 32000. The default value is 600.

Window Rotation [T25] (t25value)

This timer starts when the DTE transmits a data packet, or the DTE's window is rotated, but there are still outstanding data packets. It terminates when there are no outstanding data packets in the window. If this does not happen within the allowed time, the DTE initiates an error procedure by transmitting a Reset Request with diagnostic 0x92. The valid range for values of this parameter, in tenths of a second, is 0 to 32000. The default value is 2000.

Interrupt Response [T26] (t26value)

This timer start when the DTE sends an Interrupt packet. It terminates when the DTE receives an Interrupt Confirmation. It this is not received in the time allowed, the DTE transmits a Reset Request. The valid range for values of this parameter, in tenths of a second, is 0 to 32000. The default value is 1800.

Registration Request [T28] (t28value)

The ISO Registration Request timer. The valid range for values of this parameter, in tenths of a second, is 0 to 32000.

Pending Ack Delay (ackdelay)

Specifies the maximum time during which a pending acknowledgment is withheld. Solstice X.25 tries to suppress the generation of Layer 3 Receiver Ready control packets. Acknowledgment carried by data or multiple acknowledgments is preferred to each data packet being explicitly and separately acknowledged. The valid range for values of this parameter, in tenths of a second, is 1 to 32000.

DTE/DCE Resolution (connectvalue)

The period in which the DTE/DCE resolution should be completed. This prevents two packet-level entities failing to resolve their DTE/DCE roles. When this timer expires, the link connection is disconnected and all pending connections aborted. The valid range for values of this parameter, in tenths of a second, is 0 to 32000.

Idle Disconnect (LAN or Dialup) (idlevalue)

The period, in tenths of a second, over which Solstice X.25 maintains an idle link-level connection. For a WAN dial-up, the idle disconnect period should not be set to zero. For LANs, the default is 600.