Ctx Output Queues And Memory Partition - 3Com SuperStack II PathBuilder S330 Reference Manual

236 A B: P B
PPENDIX ATH UILDER
CTX Output Queues and
Memory Partition
S330/S310 M A
ODULE AND PPLICATION
If a cell carries data, then the switch tries to place it in the proper output FIFO (First
In, First Out) order. If the queue is congested and early packet discard is enabled,
an early packet discard operation is performed to check if the cell needs to be
discarded. Counters for cells received and cells dropped are also updated,
depending on the operation.
The CTX is an output buffered switch, with a bus capacity of 400Mbits total. It can
store 64K cells. The CTX terminates three Utopia buses, each capable of
terminating an OC3/STM-1 payload.
The first bus carries the OC3/STM-1 interface on the motherboard.
The second bus is shared between the SAR and expansion slot 7; both are
treated as separate ports in the switch.
The third bus is used by the four T1/E1 UNI with IMA ports; this bus can handle
up to four separate ports in the switch.
The output buffer is statically divided on power up into 256-cell blocks. Any
number of blocks can be allocated to any queue. The software sets up a
reasonable default configuration, as listed on the CTX Buffers menu, shown in
Figure 168.
To modify the CTX Buffers:
1 Open the CTX Buffers menu.
a From the Configuration Management menu, select [1] Manage Card.
b From the List Card menu, select [2] CTX.
c From the CTX menu, select [2] Manage Buffers.
2 Modify the default CTX buffer configuration as desired.
Figure 168 CTX Buffers Menu Displaying Default Memory Allocation
If you are not using a certain port and need to reallocate the buffers or do not like
the default configuration, you can define a new configuration. See "Configuring
CTX Buffers" in Chapter 4, for details.
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