Discovery multicast sends UDP packets to 239.255.0.7 at high rate

[iche033]

Environment

• OS Version: 24.04
• Source or binary build?
  source build, gz-transport14

Description

When gz-sim launches, gz-transport multicast discovery spams 50+mbps of broadcast traffic to 239.255.0.7. Explicitly setting GZ_IP to 127.0.0.1 seems to suppress this, likely because most network configurations do not have multicast enabled on the loopback device.

• Expected behavior: No or reasonable network traffic to the discovery address, 239.255.0.7
• Actual behavior: Discovery multicast sends UDP packets to 239.255.0.7 at high rate, 50+mbps, periodically exceeding 150mbps

[caguero]

Thanks! Do you have a sense about how many topics where available in the simulation? Around 40-50?

With 100 topics, I'm able to reproduce a similar issue during startup, although after the initial burst the traffic really drops.