
IBM3206K0424
IBM Processor for Network Resources
Preliminary
Packet Header
Page 74 of 676
pnr25.chapt03.01
August 14, 2000
Field Definitions
The following is a detailed description of the fields listed above. This data structure should be initialized at
connection setup but not modified while transmission is occurring on the connection. Only those fields
marked with a # typically need to be initialized to something other than zero.
Definition of ABR Code Variables
typedef struct {
bit8
bit8
bit16 #iMCR;
bit16 #PCR;
bit8
bit8
bit16 #ICR;
} tx_lcd_struct, *tx_lcd_struct_ptr;
#CRM;
#iCDF;
#iRDF;
#iRIF;
ABR Code Variables Definitions
(Page 1 of 4)
Field Name
Field Description
next_lcd
This field is used by the hardware to chain LCDs together on queues. It contains the address of the
next LCD if one exists.
peak_interval #
This field contains the minimum spacing allowed between consecutive cells on this connection. This
spacing is expressed in cell times. A connection that can transmit every cell time would have a value
of
‘
1
’
for this field.
average_interval #
This field contains the minimum average spacing allowed between cells transmitted on this connec-
tion. It is the inverse of the Sustainable Cell Rate. The value for this field is expressed in cell times.
Nrm #
This field specifies the maximum number of cells a source may send for each forward RM cell. Num-
ber of cells = (2**Nrm)+1.
Trm #
This field provides an upper bound on the time between forward RM cells for an active source. Time
= 100
(2**-Trm) msec.
Tadtf #
The ACR Decrease Time Factor is the time permitted between sending RM cells before the rate is
decreased to ICR. Time = Tadtf
0.01 sec.
Nc #
This field is used as a counter to determine when IBM3206K0424 cells have been sent. It should be
initialized at connection setup time to
‘
0
’
.
Ncrm #
This field is used as a counter to determine when CRM RM cells have been sent. It should be initial-
ized at connection setup time to CRM.
timestamp #
This field contains a timestamp used by the hardware to determine if transmit opportunity credits
exist and if the Burst Tolerance has been exceeded. It should be initialized at connection setup time
to the value in the current timeslot counter.
Tlrm1 & 2
These fields are used by the hardware to determine when the last RM cell was sent. They should be
initialized to
‘
0
’
.
lc_on_timewheel #
This field indicates if the LCD is currently queued to the timewheel. It should be initialized to
‘
0
’
.
remove_lcd #
If this bit is set, the LCD will be removed from the time wheel at next transmission opportunity. It
should be initialized to
‘
0
’
.