User`s guide

3: ADCCP NRM DLI Functions
DC 900-1317J 73
rate, round-trip propagation delay time (as in satellite data links), and data frame size
must all be considered to determine the optimal transmit window size.
The srej_threshold variable identifies the SREJ threshold; this field is meaningful only
when both ADCCP options 2 and 3 are enabled. The SREJ threshold is the maximum
number of consecutive missing I-frames for which the ICP uses SREJ procedures to
recover I-frames; if the number of consecutive missing I-frames exceeds the SREJ
threshold, the ICP uses REJ procedures for I-frame recovery.
The maximum possible value for the SREJ threshold is the value of the transmit window
size defined in byte 0 within word 1 in the data area. Specifying an SREJ threshold of
zero tells the ICP to use only REJ procedures to recover missing frames, but still allows
the ICP to recognize SREJ when received (if ADCCP option 3 is enabled). Normally, the
client application would both disable ADCCP option 3 and specify a SREJ threshold
value of zero.
The maxdata variable specifies the maximum number of octets allowed in I-frame data
fields for the indicated station. If the client specifies an I-frame data field size limit of
zero, the ICP chooses a default limit based upon the maximum data size for buffers (see
Section 3.4.31). This parameter allows the client to configure a different I-frame data
field size limit for each station; normally, the I-frame data field size limit is the same for
every station on the same physical link, but it may differ from the size limit for stations
on a different physical link.
If the ICP receives an I-frame whose information field exceeds this size limit, the ICP
issues a mode setting command or an FRMR response to cause a station reset; the ICP
reports the resulting station reset to the client in a
DLI_PROT_RECV_STATION_RESET packet
(see Section 3.4.21). If the client sends a normal or unnumbered data packet whose
usProtXParms[1] field (data size) exceeds the limit for the indicated station, the ICP
replies with a
DLI_PROT_RESP_ERROR packet (see Section 3.4.28).