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PacketStar
®
PSAX 4500 Multiservice Media Gateway User Guide
, Issue 2
Release 8.0.0
Chapter 3 System Features
Multiservice Media Gateway Software Features
The algorithm processes traffic moving out of the input cell selection buffer
according to the SCR of the particular VPC/VCC. The MBSs of traffic shaped
output are set as follows:
The OC-3c TS and the STM-1 TS modules can perform Cell Bus Traffic Shap-
ing on multiple high-rate connections (such as three 40-Mbps connections).
Assigning a SCR to a connection above 75 Mbps, however, is not recom-
mended in sensitive, bursty traffic environments. Assigning a SCR above
120 Mbps will essentially eliminate any Traffic Shaping, and thus is strongly
discouraged.
The OC-3c TS and the STM-1 TS modules perform only limited traffic man-
agement on the output side. The output buffer is limited to 2 Mbps for VBR
traffic and 128 cells for CBR traffic, with only three priority levels supported:
CBR, VBR1, and VBR2. The maximum-capacity level for congestion control
is 32,000 cells, and the minimum-capacity level is 24,576 cells, with VBR
traffic being shut off first from the backplane.
ATM Traffic Shaping
Overview of ATM
Traffic Shaping
UPC allows the end system to police ingress connections for service level
agreement compliance. After a set of service categories is specified, UPC is
given a set of parameters for each, describing the traffic presented to the net-
work and the quality of service the network requires. A number of traffic
control mechanisms are defined, which the network may use to meet the
QoS objectives.
Note:
The feature that was formerly known as “Rate Shaping” is now
called “ATM Traffic Shaping” to distinguish it from the”Cell bus
traffic shaping” feature, which was formerly called “Traffic Shap-
ing”.
Configuring ATM
Traffic Shaping for
HDLC, Frame Relay,
and Ethernet Virtual
Channels
For frame relay traffic, the PSAX system software automatically calculates
egress peak cell rate based on frame relay traffic parameters.
For Ethernet and HDLC traffic, you must enter the egress PCR on the VBR-
to-ATM PVC or SPVC Connection window.
In either case, the PCR is used to shape the egress traffic not to exceed the
PCR.
Sustained Cell Rate
(SCR) of VPC/VCC
Maximum Burst Size (MBS) of Traffic
Shaped Output
0–20 Mbps
< 4 cells
20–30 Mbps
< 5 cells
30–40 Mbps
< 6 cells
75–120 Mbps
approximately 20–50 cells
