210 APPENDIX B: PATHBUILDER S330/S310 MODULE AND APPLICATION OVERVIEW
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.
CTX Output Queues and
Memory Partition
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.
n The first bus carries the OC3/STM-1 interface on the motherboard.
n The second bus is shared between the SAR and expansion slot 7; both are
treated as separate ports in the switch.
n The third bus is used by the four T1/E1 UNI 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 152.
To modify the CTX Buffers, follow these steps:
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 CTX buffer configuration. Modify the default.
Figure 152 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.
