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7-6 FRX/FRM 3. 3 User G uide, Rev 04
N2 Retransmit Count
is X.25 value
N2
, the maximum number of times the node will attempt to send an I-
frame after a
Retransmit Period
expiration. A larger value for this parameter increases
the probability of an eventual correct transfer between DTE and DCE, but a smaller
value permits faster detection of a permanent error condition.
T1 Retransmit Period
is the length of time before re-transmission of an I-frame if the previous transmission
is not acknowledged. If the period expires, the FRX/FRM software will reset the timer
and transmit a supervisory frame demanding immediate acknowledgment. Also, the
Maximum Retransmissions
(see that entry) counter will be incremented. The default
value of
2000 ms
allows avoidance of unnecessary retransmission of frames that have
merely been delayed.
T2 Wait Ack Period
is the length of time the node will delay acknowledgment of a received I-frame if there
is no outgoing I-frame to be sent. If during this period the node receives an I-frame for
transmission, the acknowledgment will be sent with it, and the delay timer will be
reset.
T3 Link Alive Period
is the length of time after which the node will poll its counterpart if there is no data
transfer.
Logical DCE
defines the port as (if
Y )
logical DCE or (if
N
) DTE. The port must be configured as
the opposite of the device at the other end of the connection.
Logical and physical DCE/DTE are independent of each other (e.g., a port can be a
physical DCE and logical DTE).
Generate Clock
specifies whether the port will generate the clock necessary to synchronize traffic over
the link. If the port is a physical DCE (determined by the port's I/O cable interface),
configure
Generate Clock
as
Y
, since the physical DCE generates clock. If the port is
DTE, configure
Generate Clock
as
N
.
Rcv Clock (TT) from DTE
allows the clock to be looped back from the DTE using the TT (Terminal Timing)
signal, which can be helpful on high-speed lines. Generally, if the local interface is
physical DCE and the line speed is above 256 Kbps, this parameter should be set to
Y
.
(Make sure the remote DTE is configured to provide the terminal timing.)
CSU/DSU Operating Mode
determines whether the attached modem connection can be normal or 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 18000
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.