Lucent Technologies P550 - Manual (Page 238)

Tuning Your Switch Performance (Layer 2 & Layer 3)
13 -2 Cajun P550/P220 Switch Operation Guide
When the high-priority queue fills up, incoming frames are dropped. The philosophy is if
a high-priority frame is going to be late, it is not worth sending it at all. The
normal-priority queue uses either IEEE 802.3X PAUSE (variable timed XOFF) flow
control or Half Duplex collisions to shut off incoming frames before the queue overflows.
The switch implements two flow control disciplines along the entire path that frames
travel. The default case is that when output buffers fill up, frames destined for a
particular buffer will be dropped. This should only occur in a case where the output port
is very congested. However, there is an optional mode which in which normal-priority
frames are never dropped inside the switch. In this mode, input buffers may fill up. If
they do, the affected input ports may use flow control to temporarily halt traffic from
neighboring switches.
Managing Buffers and Queues
To manage buffers and queues:
1. From the System Configuration section of the Web Agent window, click
Modules and Ports. The Module Information dialog box opens.
2. In the Buffer Management column, click the Module number for the module
whose buffers you want to manage. The Buffer Management dialog box opens.
3. Use Table 3 to view your buffer management parameters.