If you have a small switched dedicated camera network this article most likely does not apply to you.
Many large networks have cameras attached directly to a heterogeneous data network. Most data being transported across a network is not sensitive to latency, jitter or dropped packets/frames. Live camera streams and voice over IP are extremely sensitive to network congestion issues.
Latency, jitter and dropped packets are a major source of choppy (lost) video.
Live camera streams need a stable reliable transmission path with low latency, low jitter and zero dropped packets. Implementing 802.1q (VLAN tagging) and assigning COS class of 5 (voice) to live camera streams on the switches in the network is the best practice. COS class of 4 (video) may not give live camera streams enough priority. These networking features will assure that in times of heavy network traffic the camera stream packets will arrive at the recording server intact and in order.
Make a special effort to avoid sending camera streams through routers. If a subnet must to be routed to another network, QoS should be enabled on the router. The VLAN should be set up for VoIP forwarding priority.