Why does my IPTV streaming sometimes have lag/latency when it is behind ATP?

Zyxel_Cooldia

Problem Description

I would like place TV box behind ATP for Internet protection. However, the video streaming has latency when the TV box is behind ATP.
As confirmed, gateway is not in high CPU usage, IGMP works, and Internet bandwidth is still available. Everything looks good without issue.
Why does my IPTV streaming sometimes have lag/latency when it is behind ATP?

Solution

Because UDP traffic disperse to CPU each core for traffic processing. The advantage is CPU loading is average on each core. However, it would cause issue on real time protocol. To avoid this issue, we can fix UDP traffic on specific single core by CLI.

Show UDP disperse status
Router> debug system no-udp-disperse show
Disable UDP disperse
Router# debug system no-udp-disperse active

After disabling UDP disperse, it supposed to be fine without latency issue.