Dell PowerConnect 8100 User's Configuration Guide - Page 845
Recommendations and Notes, congestion in the TCG.
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At time t2, a burst of LAN traffic is incoming at the rate of 4 Gbps, this burst is allowed to borrow the unused 0.5 Gbps bandwidth from SAN TCG and transmitted since the offered load of SAN is only 3 Gbps. At time t3, when the offered load of IPC falls to 2 Gbps and the bursty LAN traffic is at 6 Gbps, the available bandwidth for SAN and LAN is 4 Gbps each according to the TCG weights, which are set as 50% each. However, ETS allows the LAN traffic to borrow unused bandwidth from SAN traffic, and then 5 Gbps of LAN traffic is transmitted. Recommendations and Notes Lossless traffic must map user priorities one-to-one onto CoS queues. Lossless traffic must always be carried within a VLAN-tagged frame to differentiate it from untagged best-effort LAN control traffic, such as ARP and LLDP. Strict-priority CoS queues may starve other CoS queues of traffic if the offered load of the strict-priority CoS queues equals or exceeds the available capacity of the egress interfaces. It is recommended that either a CoS-queuelevel min-bandwidth setting be utilized to ensure a minimum amount of bandwidth is processed on the non-strict-priority queues if there is a possibility that the strict priority traffic is not limited in bandwidth by some other means. It is recommended that the sum of the minimum bandwidth percentages allocated to the group of CoS queues mapped to a single TCG be less than or equal to the weight percentage, so that packets are not dropped due to the congestion in the TCG. The maximum bandwidth for a TCG should always be configured to be greater than the minimum bandwidth or the weight of the TCG. In the case where all TCGs are configured as strict priority, inter-TCG scheduling is Weighted Deficit Round Robin, using the configured weights. Configuring CoS queues with a total maximum bandwidth that is less than the corresponding TCG weight will result in bandwidth being wasted in the secondary scheduler. Configuring CoS queues with a total minimum bandwidth that is greater than the corresponding TCG weight will flood the secondary scheduler and result in the minimum bandwidth parameter effectively overriding the TCG weight setting. Configuring Data Center Bridging Features 845
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-
1,189
-
1,190
-
1,191
-
1,192
-
1,193
-
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