Disclosed are an information transmission method, a packet data gateway, and a policy and charging rules function. The method includes: after receiving a Mobile IPv6 support for Dual Stack Hosts and Routers (DSMIPv6) binding update signaling, a packet data network gateway (P-GW) notifying a source User Datagram Protocol (UDP) port number of the DSMIPv6 binding update signaling to a Policy and Charging Rules Function (PCRF); and the PCRF notifying the source UDP port number of the DSMIPv6 binding update signaling to a fixed broadband access network. The above-mentioned method provides the UDP port number for the fixed broadband access network according to whether the IPSec capsulation is performed on the user plane data, which makes the fixed broadband access network be able to identify the user plane data of the user equipment correctly and perform a corresponding policy control.