Question about Traffic Shaping [ credits ]

[Wabun]

I am trying to work out how the traffic shaping works, but the manuals are only talking about credits but no where any examples.

Having a VM and put it on his own [Virtual Machine] port group, with following parameters:

Average bandwidth:  10000 Kbits

Peak bandwidth:      25000 Kbits

Burst size:               4096 Kbytes

- How to get credits [ I understand it is adding when the VM uses less then the Average bandwidth, and what is the credit in figures, is it kbits or time to burst?

- Assume the VM is having a download started for a certain amount of time, will it start at Average speed, then go straight to the Burst and for how long, when will it fall back to Peak bandwidth? Sorry so many questions.. I find it very difficult to work out other then testing how this works, could anyone shine a light on this please?

Thanks a lot for your precious time.

Traffic Shaping concepts:

• Average Bandwidth: Target traffic rate cap that the switch tries to enforce. Every time a client uses less than the defined Average Bandwidth, credit builds up.
• Peak Bandwidth: Extra bandwidth available, above the Average Bandwidth, for a short burst. The availability of the burst depends on credit accumulated so far.
• Burst Size: Amount of traffic that can be transmitted or received at Peak speed. By combining Peak Bandwidth and Burst Size, you can calculate the maximum allowed time for the burst.

[kashifkarar01]

Hi Wabun,

One of the great features of VMware vSphere is the ability to set very granular shaping rules on the virtual switch or the port group. This granularity can help you provide additional segmentation without having other systems be subject to a traffic shaping rule as would the be situation if it only applied to a virtual switch. For the vNetwork Distributed Switch, this can be set as a bidirectional traffic shaping policy (VM to network and then network to VM). For the standard virtual network switch, the traffic shaping policy is basic; but, it still can be granular to each port group. Picture below has a standard virtual switch set to have a peak and average bandwidth of approximately 8 Megabytes per second for an example situation for a web-facing virtual switch.

Now, the calculations here are bit complicated. The average bandwidth of 409 Kbits/sec specifies that the entire port group cannot exceed that rate, and each VM will be sharing the bandwidth with other virtual machines on that port group. Note also that this figure above has other port groups. They don’t have traffic shaping, and don’t apply to this limit.

Once you’ve configured the port group and the bandwidth values, the traffic shaping pattern is ready to go! It’s important to note that this isn’t the best way to segment a single VM to not exceed a certain amount of network connectivity, however (Network I/O Control may be the better feature) which is available in dvSwitch on vSphere 5.x.

[Wabun]

Not sure how you calculated this 8Mb with 409Kbits, but perhaps you have made an error here.

Still no answer how VMware knows WHEN to BURST or give PEAK speed, no examples of this is available.

[kashifkarar01]

hi,

I was going through few posts and found this interesting hopefully this it helps:

http://www.vmwarearena.com/2014/01/vsphere-distributed-switch-part-17.html    

[Wabun]

Hi Kashifkarar01,  thanks very much, the image and article explains it a bit better, but I think the Image is not correct,

I put up one as I think it should be based on these 3 parameters, would you mind to give me your thoughts about this?

However, I still have not found how long the duration of the burst is going to be, I do realise it is somehow 'earned' as a bonus by not using all the traffic to the max.

But let's say in my example the average is 10Mb/s the peak is 25Mb/s and the burst is 40Mb/s.

How do I know the duration of the burst, as I don't want it to be for hours, you see what i mean?

Kind regards, and many thanks for your time.

[kashifkarar01 · Accepted solution]

Hi Wabun,

Hopefully this will be much clear:

I was going through this Video and made key points:    http://www.youtube.com/watch?v=PR34OsH3FcM 

I have got a

[Wabun]

Thanks,

Watched the video [nice one] and it is now more clear to me.

Burst size is the amount of DATA it is allowed to burst.

Thanks ever so much.