Dell PowerConnect 8100 User's Configuration Guide - Page 1145
How Are Traffic Queues Defined?, Which Queue Management Methods Are Supported?
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How Are Traffic Queues Defined? For each queue, you can specify: • Minimum bandwidth guarantee-A percentage of the port's maximum negotiated bandwidth reserved for the queue. Unreserved bandwidth can be utilized by lower-priority queues. If the sum of the minimum bandwidth is 100%, then there is no unreserved bandwidth and no sharing of bandwidth is possible. • Scheduler type-strict/weighted: - Strict priority scheduling gives an absolute priority based on CoS queue number, with traffic in the highest numbered queue sent first, then the next lowest numbered queue, and so on. Weighted queues are serviced after all strict priority queues have been serviced. - Weighted scheduling selects packets for transmission with a fixed weighting equal to the CoS queue number plus one. The weighted scheduler measures bandwidth based upon bytes vs. packet counts, offering a better granularity of scheduling. For example, if CoS queues 0, 1, and 2 have an equal offered load toward a congested output port, CoS queue 2 will receive 3/6 of the bandwidth, CoS queue 1 will receive 2/6 of the bandwidth, and CoS queue 0 will receive 1/6 of the bandwidth. The minimum bandwidth setting can be used to override the strict priority and weighted settings. The highest numbered strict priority queue will receive no more bandwidth than 100 percent minus the sum of the minimum bandwidths percentages assigned to the other queues. If used, it is recommended that minimum bandwidth percentages only be high enough to ensure a minimum level of service for any queue; i.e., the sum of the minimum bandwidth percentages is a small fraction of 100%. This ensures that the system can respond to bursts in traffic. Setting the minimum bandwidth percentages such that they sum to 100% effectively sets the scheduler such that sharing of bandwidth is disabled. Which Queue Management Methods Are Supported? The switch supports the following methods, configurable per-interfacequeue, for determining which packets are dropped when the queue is full: • Taildrop-Any packet forwarded to a full queue is dropped regardless of its priority. Configuring Class-of-Service 1145
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1,194
-
1,195
-
1,196
-
1,197
-
1,198
-
1,199
-
1,200
-
1,201
-
1,202
-
1,203
-
1,204
-
1,205
-
1,206
-
1,207
-
1,208
-
1,209
-
1,210
-
1,211
-
1,212
-
1,213
-
1,214
-
1,215
-
1,216
-
1,217
-
1,218
-
1,219
-
1,220
-
1,221
-
1,222
-
1,223
-
1,224
-
1,225
-
1,226
-
1,227
-
1,228
-
1,229
-
1,230
-
1,231
-
1,232
-
1,233
-
1,234
-
1,235
-
1,236
-
1,237
-
1,238
-
1,239
-
1,240
-
1,241
-
1,242
-
1,243
-
1,244
-
1,245
-
1,246
-
1,247
-
1,248
-
1,249
-
1,250
-
1,251
-
1,252
-
1,253
-
1,254
-
1,255
-
1,256
-
1,257
-
1,258
-
1,259
-
1,260
-
1,261
-
1,262
-
1,263
-
1,264
-
1,265
-
1,266
-
1,267
-
1,268
-
1,269
-
1,270
-
1,271
-
1,272
-
1,273
-
1,274
-
1,275
-
1,276
-
1,277
-
1,278
-
1,279
-
1,280
-
1,281
-
1,282
-
1,283
-
1,284
-
1,285
-
1,286
-
1,287
-
1,288
-
1,289
-
1,290
-
1,291
-
1,292
-
1,293
-
1,294