Managing Buffers and Queues
4-2 Cajun P220G Switch Configuration and Operation Guid e
Figure 4-1. Buffer Memory
Each buffer is divided into two queues, one for High-priority Traffic and one for
Normal-priority Traffic. The factory default is the high-priority queue uses 20% (51K) of
the buffer. The normal-priority queue uses the remaining 80% (205K). These values can
be modified using either the Web Agent or SNMP. When you change these values, you
must reboot the switch before they can take effect.
Less buffer memory gets assigned to the high-priority queue because the high-priority
queue gets serviced more frequently than the normal-priority queue. Since a frame
spends less time on the high-priority queue, less buffer space is required for the queue.
The Service Ratio can be chosen to match traffic patterns and performance requirements
using a weighted round robin scheduling algorithm. The factory default service ratio is
99/1. If there is traffic to be serviced from both the high- and normal-priority queues, 99
packets of high-priority traffic will be processed for each normal-priority packet.
When the high-priority queue fills up, incoming frames are dropped. 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.
In
Buffer
Memory
Out
Controller
Buffer
Memory
Buffer
Memory
Buffer
Memory
Summary of Contents for P220G
Page 1: ...Cajun P220G Gigabit Switch Configuration and Operation Guide Document Number 610 0065 041...
Page 7: ...Preface viii Cajun P220G Switch Configuration and Operation Guide...
Page 37: ...Configuring the P220G Gigabit Switch 2 22 Cajun P220G Switch Configuration and Operation Guide...
Page 81: ...Analyzing Network Performance 6 10 Cajun P220G Switch Configuration and Operation G uide...
Page 93: ...Monitoring the P220G Gigabit Switch 7 12 Cajun P220G Switch Configuration and Operation Guide...