Quoted from the wiki of BitComet:
E.g. I can't not configure the outermost firewall, so the listening port used by BitComet is blocked, thus I can only be a client not a host. But how would it greatly slow down the download speed? I can still connect to all the other peers who can be a host as a client.
Is it merely because I would lose those client peer connections if I can be a host?
I am a programmer and interested in this problem. A technical explanation is ok and appreciated. Because now my ISP does not allow me to configure the outermost firewall, so if this affects the speed hugely, I would consider to choose another ISP who can give me a "real public ip"( I can configure the outermost firewall ).