Configuring X.25 8-9
CSU/DSU Opera ting Mode
determines whether the at tached mo dem connectio n can be n ormal o r limited distance
(LDM), where the distance depends on the wire gauge, number of splice points, and
line speed. For example, 26 gauge wire and a line speed of 64K bps allows a distance
of 15000 feet. Lowering the speed to 56K increases the allowable distance to 18400
feet. If 19 gauge wire is used, the distances can be multiplied by three.
RTS Control
if Constant means that RTS will always be asserted, and if External means that the
CSU/DSU will control RTS.
Lowest/Highest Incoming/Tw o-Way/Outgoing Channel
are the ranges of logical channel numbers (LCNs) that subscribers can use for calls
through this port. The valid values for each parameter are determined as follows:
Channel Valid Values
Lowest Incoming 1 throug h Highest Incoming
Highest Incoming Greater than/equal to Lowest Incoming
Lowest 2-Way Greater than H ighest Incoming
Highest 2-Way Greater than/equal to Lowest 2-Way
Lowest Outgoing Greater than H ighest 2-Way
Highest Outgoing Lowest Outgoing throug h 4095
Changing any parameter to a value that violates this order automatically changes any
other values now in violation, specifying the first value(s) within the valid range. If
any pair is not used, its constraints apply to the next higher or lower pair (whichever
is appropriate) in the above list.
Flow Control Negotiation
is an optional X.25 facility th at permits negotiation of the flo w control parameters
(packet and window sizes for either direction of data transmission) on a per call basis.
If this parameter is set to N, the defau lt packet and window sizes will be used. If set to
Y, a packet and/or window size included in a call packet will be used. (If either is not
included, the default for that parameter will be used.)
Throughput Class Negotiation
is an optional X.25 facility that permits negotiation of the throughput classes for either
direction of data transmission on a per call basis. If this parameter is set to N, the
defau lt ( Maximum Thro ughput Cl ass) will be used. If set to Y, any t hroug hput cl a ss
included in a call pac ket will be used. (If a cla ss for either direction is not in cluded, its
default value will be used.)
Local Charging Prevention
prevents calls (if Y) from being charge d to th is po r t. In c om i ng ca ll s fro m t he net w o rk
with Reverse Charging specified will be rejected; outgoing calls will have Reverse
Charging inserted if it is not already in the call packet.
Reverse Charge Acceptance
authorizes transmission of incoming calls that request the X.25 Reverse Charging
facility. If this param eter is set to N and a call requests Reverse Char ging, the call will
not be transmitted.
Fast Sel ect Ac cept an c e
authorizes transmission of incoming calls that request the X.25 Fast Select facility.