Dell PowerConnect 8100 User's Configuration Guide - Page 832
ETS Operation, TCG. PC81xx switches support three TCGs internally, up to two of which
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best-effort transmit characteristics. PowerConnect 81xx switches support strict priority and Weighted Deficit Round Robin (WDRR) scheduling with up to two lossless traffic classes. WDRR schedules traffic based on average bandwidth consumed vs. frame counts. ETS Operation The normal (default) operation of PowerConnect switches, when uncongested, is that packets are scheduled for output in the order in which they are received, that is, using FIFO scheduling. The class of service (CoS) mechanism enables the administrator to schedule packets for output ahead of other packets when the switch is congested, choose which type of packets to drop when the switch is congested, and assign a minimum bandwidth guarantee to ensure scheduling fairness. These mechanisms operate at the CoS queue level; that is, the minimum bandwidth guarantees are made across all configured CoS queues. NOTE: Minimum bandwidth guarantees and scheduling mechanisms apply only when the switch is congested. When the switch is not congested, packets egress the switch as soon as they are received. ETS provides a second level of scheduling for packets selected for transmission by the CoS scheduler. ETS operates at the traffic class group (TCG) level and supports sharing of bandwidth across TCGs, bandwidth assignment for each TCG, and queue discipline (drop behavior) for each TCG. PC81xx switches support three TCGs internally, up to two of which may be configured as lossless. When a packet arrives on an ingress port, it is forwarded to the appropriate CoS queue based upon the dot1p mapping. The dot1p mapping maps the user priority contained in the received VLAN Priority Tag to the traffic class or uses the default port assignment. A traffic class identifies a particular CoS queue. If the ingress port is configured to use 802.1p CoS mapping and the port is configured to trust the user priority value in the received frame, then the frame is forwarded to the appropriate CoS queue per its 802.1p user priority value. 832 Configuring Data Center Bridging Features
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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