Minimal Firewall settings needed for UPLOADING and VIEWING webcasts
To broadcast/upload and watch streams you need the following stateful firewall rules, assuming you have a regular internet connection (if you are behind a corporate firewall ensure your IT department configured the firewall to these settings):
•Outgoing UDP destination port 53 to your nameserver or any IP for domain name resolution (DNS)
•Outgoing TCP destination port 80, 443 to any IP (WEB)
•Outgoing TCP destination port 1935 to any IP = RTMP (to deliver the stream)
Port Protocol Transport Description
1935 RTMP/E TCP Flash Media Server listens for RTMP/E requests on port 1935/TCP. Flash Player and AIR clients attempt to connect over ports in the following order: 1935, 80 (RTMP), 80 (RTMPT).
1935 RTMFP UDP Flash Media Server listens for RTMFP requests on port 1935/UDP.
80 RTMP, RTMPT, HTTP TCP Flash Media Server listens for HTTP requests on port 80. Flash Media Server falls back to port 80 if a client cannot connect.
8134 HTTP TCP Flash Media Server forwards HTTP requests to Apache HTTP Server on port 8134. 
1111 HTTP, RTMP TCP Flash Media Administration Server listens for HTTP and RTMP requests on port 1111.
Some firewalls reject traffic that doesn't use the HTTP protocol. This behavior can prevent communication over RTMP even if port 1935 is open. Consult the documentation for the firewall to determine how to configure it to allow RTMP traffic.  To use RTMP and RTMFP, firewalls between the server and clients must allow inbound and outbound traffic on port 1935.

  This is a screenshot of common encoding parameters like those used for this page's Flash stream...note the "Total bandwidth required to stream" info - that's the upload speed required on-site to the server, whereas the "Bit Rate" is the bandwidth the Viewer needs to download the live stream.

The flash player at the top of this page is embedded in an iframe which makes a call to a Flash server for the stream. Note that there are cross-browser differences when embedding iframes. (this page is usually optimized for Google Chrome)