Enable packet filter (pfctl) temporarily halt network connectivity

when re-setting my packetFilter firewall with a new set of rules, all network communication completely stops for a short time, until it regains with the new set of rules. In fact, it also occurs on every switching firewall state (enable->disable and vice versa) Why does PacketFiler temporarily halt connection every time it changes state (using pfctl -Ef or pfctl -d) ?