S/UNI®-ATLAS-3200 Telecom Standard Product Data Sheet
Preliminary
To allow full flexibility, the S/UNI-ATLAS-3200 supports 8 possible configurations, selected by
the Policing Config Select bits, which allow each GCRA to police any combination of user cells,
OAM cells, RM Cells, high priority cells or low priority cells.
The Theoretical Arrival Time fields (TAT1 and TAT2), Increment fields (I1 and I2), and Limit
fields (L1 and L2) must be initialized before policing is enabled. When the connection is setup,
the TAT fields must be set to all zeros, and they should not be modified by the management
software after the connection has been initialized. The Increment and Limit fields must be
programmed to the desired traffic rate. These fields relate to the traffic contract parameters as
follows:
1
I =
PCR
(
∆t
)
I = Increment Field
PCR = Peak Cell Rate (cells/s)
∆t = clock period (s)
In order to obtain the granularity required in ITU-T I.371, the Increment fields are encoded as
floating-point fields as follows:
m
512
e æ
ö
I = 2 1+
where 0 ≤ e ≤ 31
0 ≤ m ≤ 511
ç
è
The exponent, e, is a 5-bit field and the mantissa, m, is a 9-bit field. The Increment field is
formatted as follows:
MSB
4
LSB
0
0 8
e
m
The floating-point encoding format of the Increment field ensures the granularity of the S/UNI-
ATLAS-3200 is 0.19% in accordance with ITU-T I.371 5.4.1.2.
The Limit field is defined as:
τ
∆t
L =
where τ = Cell Delay Variation (s)
For a Sustained Cell Rate (SCR) conformance definition, the parameters relate as follows:
Proprietary and Confidential to PMC-Sierra, Inc., and for its Customers’ Internal Use
Document ID: PMC-1990553, Issue 4
93
PMC [ PMC-SIERRA, INC ]
