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July 27th, 2004 13:00
PowerConnect 3324/3348 Config Question
Hello,
I am in the process of configuring several Dell PowerConnect switches (1-5224, 6-3348's & 1-3324) to replace aging hubs etc. I have downloaded and printed the User Guides for these devices and have gone through the configuration process. I will only have 1 VLAN to start and the 3348's will each connect to the 5224 using the 3348's two 1000 Mbps ports in a LAG, no switch stacking. The 3324 will connect to the 5224 through a fiber connection using SFP's.
I want to eventually be able to use COS to prioritize Radio Frequency (RF) traffic from our DC's over other traffic such as e-mail. I thought I had setup COS for weighted round robin (WRR) on the four queues. Since there will be no stacking, I configured priorities 6 & 7 to use queue 4. I used the web based configuration tool after the initial IP address assignment was done. Everything seemed to be just fine until I reviewed the config where I discovered the following line.
"priority-queue out num-of-queues 0"
This didn't seem to fit with what I was doing so I investigated further and this line seems to me to defeat the WRR setup completely. The CLI reference manual explained this line is setting queues to be "strict priority queues" but that leaves me with questions.
First question, "What screen caused this line to be generated?"
Second question, "If I am reading the manual correctly, why isn't the config line 'no priority-queue out num-of-queues' since the manual states to use the "no" form to set all queues to strict priority?"
Third (and last for now) question, "To set all queues to WRR processing, should I change this line to 'priority-queue out num-of-queues 4'?"
I searched this forum looking for similar topics but did not find any that answered my specific questions.
Any and all help is greatly appreciated. I don't want to put these switches in place and cause problems when the objective is to improve things.
Thanks,
Greg
DELL-Randy
132 Posts
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July 27th, 2004 14:00
The entry "priority-queue out num-of-queues 0" is indicative that the 3300s are performing WRR queueing.
First inquiry -- By configuring the devices for Weighted-Round-Robin, this entry was automatically created. By default, the units are configured for Strict Priority, so the device will not show this in the configuration when a "show run" command is initiated. Since you changed the value from it's default configuration (from Strict Priority to WRR), the switch will now reflect any configuration changes you have made.
Second inquiry -- In conjunction with the first inquiry's response, since you have change the queueing algorithm from the default configuration, the output will now reflect the number of strict priority queues configured. In the instance that all queues were changed to WRR, the output will indicate how many queues are configured for strict priority -- in this case 0. Since the algorithm is never disabled, just has no queues configured, the output will not reflect "no" as you may expect to see.
Third inquiry --
PowerConnect 5000
This device does not support Strict Priority queueing. The values assigned to the queues are arbitrary as the value itself does not indicate how much bandwidth the queue will receive, but instead the increments between the values decides this factor. For instance:
If you configured Queues 0 - 3 for the following weights respectively: 10, 20, 30, 40 -- the results would be the following: Queue 0 would receive 10% of the throughput, Queue 1 = 20%, Queue 2 = 30%, and Queue 3 = 40%. You would receive the same results if the values were configured for: 5, 10, 15, 20 or 20, 40, 60, 80
PowerConnect 3300
This device is capable of supporting Strict Priority queue as well as Weighted-Round-Robin. You will have a radio button option from the webGUI that will allow you to configure a particular queue for Strict Priority or WRR. The default configuration is all queues are Strict Priority, so you will not see "priority-queue out num-of-queues 4". Once you change the queues from Strict Priority to WRR, the system is no longer at the default configuration, and now will reflect the number of Strict Priority queues configured -- "priority-queue out num-of-queues 0". This is indicative that all the queues are performing WRR.
The 3300 series switches will indicate how much of the throughput will be allocated to each queue based on the value assigned to each queue in percentages. If you change the WRR value, the percentage will change. This is unlike the 5000 that have arbitrary values.
Hope this helps.
NMTC_Greg
2 Posts
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July 27th, 2004 15:00
Randy,
Thank you for the detailed explanation. Seems everthing is just the way I want it to be.
Possibly someone could look at the CLI manual and reword the explanation of this command. I interpreted the statement " queues with higher indexes" to mean that queues 1,2 3, and 4 (all higher than 0) would be strictly priority queues.
I set the WRR weights on the 3348 and 3324 to be the same as the defaults on the 5224.
Greg