Chapter 3 System Features
PSAX System Software Features
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PacketStar
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PSAX 2300 Multiservice Media Gateway User Guide
, Issue 1
Release 9.0.0
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
The ATM Traffic Shaping feature uses an algorithm to transmit frames seg-
mented into ATM cells into the ATM network at a steady rate. This algorithm
performs per-VC queuing with a maximum queue size of 200 cells. ATM
Traffic Shaping can be applied to PVC, SVC, or SPVC connections, on all types
of traffic, but the feature must be configured prior to traffic exiting from the
ATM trunk port. On SPVC connections, the feature must be enabled on the
active and passive sides of the end-to-end connection, as well as on the sup-
porting interface configuration window, for the feature to function as
designed. The ATM Traffic Shaping algorithm is applied to cells as they exit
the PSAX backplane or midplane, as illustrated in Figure 3-16.
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
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