# IP Multicast - Issues

Reliability of delivery

- Broadcast and multicast are typically built on top of UDP (unacknowledged), not TCP (acknowledged). Losing a few packets may be acceptable for audio/video but not for delivery of software or critical data.

Router awareness and forwarding of information

- Many routers do not forward multicast or broadcast

Firewall issues: affects Internet vs. Intranet operation

- Firewalls do not usually propagate multicast/broadcast

- Encapsulation can be used to tunnel through firewalls

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