VoIP QoS

Hi,

I have just installed a DELL N4032 into our environment to act as a L3 switch to route VoIP traffic from a voice VLAN to a data VLAN where the PBX is located. The VoIP and data traffic are directly connected to a CISCO 2960 series L2 switch via a 4 x 1GbE EtherChannel to 4 x 1GbE port-channel on the DELL switch:

My problem is that if a hammer the connection VoIP handsets loose their connection to the PBX. My thought is that if I configure QoS for the voice VLAN it will resolve the issue.

Can any offer some starting points for configuring QoS?

Thanks in advance,

Matt