Disclaimer
The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.
Liability Disclaimer
In no event shall Author be liable for any damages whatsoever (including, without limitation, damages for loss of use, data or profit) arising out of the use or inability to use the posting's information even if Author has been advised of the possibility of such damage.
Posting
BTW, whether drops are caused by microbursts or sustained congestion, unless the microbursts or sustained congestion is in the VoIP traffic, QoS can usually be used to protect VoIP traffic so that it's not impaired. QoS is often also advisable for VoIP even when there are no drops as it's also real-time sensitive.
As whether the amount of drops you're obtaining now might be mitigated; perhaps they might be. 3750-X buffer resources can be "tuned" when QoS is enabled. Also, there are QoS techniques applicable to how drops are managed.
As to the fact you're not seeing drops on the 6500 side, that can be because of additional buffer resources (as also mentioned by another poster) although much depends on the particular 6500 line card (and how it's configured). Additionally, it could be the traffic has some asymmetric behavior, which is often normal; or, some combination.
On a 3750-X, if you've disabled QoS, you have a single FIFO queue with fixed resources. If such, with its current bandwidth, is not suitable to your network application service requirements you might obtain more (WAN) bandwidth, manage your bandwidth (using QoS), or some combination of both.
You might also consider different hardware, as such often offers different features and/or hardware resource. For example, the MetroEthernet features are designed to deal better with typical lower bandwidth on MetroEthernet (i.e. they have slightly better QoS features and often larger buffers).
PS:
BTW, you might just try autoQoS on your 3750-X and see if that helps or worsens the situation.
PPS:
Also BTW, many think any drops are always bad, but that's not always true. For example, TCP (and a few other protocols) can use drops for flow transfer rate management.
