A communications method, comprising: receiving (301, 701), by a session management network element in a first communications network, a message for requesting to establish or modify a session, wherein the message for requesting to establish or modify the session requests to establish a first connection of the session in the first communications network; and determining (302, 702), by the session management network element based on an access technology type corresponding to the session, whether to send a request message to an access management network element in the first communications network, wherein the request message requests the access management network element to allocate a connection identifier to a second connection that corresponds to the first connection and that is in a second communications network; wherein the determining, by the session management network element based on the access technology type corresponding to the session, whether to send the request message to the access management network element in the first communications network comprises: determining, by the session management network element, that the access technology type corresponding to the session is non-3rd generation partnership project, non-3GPP, access; and skipping, by the session management network element, sending the request message to the access management network element; wherein the first communications network is a 5G network, the second communications network is a 4G network, the first connection is a flow, the connection identifier of the first connection is a flow identifier, the second connection is a bearer, and the connection identifier of the second connection is a bearer identifier. receiving (301, 701), by a session management network element in a first communications network, a message for requesting to establish or modify a session, wherein the message for requesting to establish or modify the session requests to establish a first connection of the session in the first communications network; and determining (302, 702), by the session management network element based on an access technology type corresponding to the session, whether to send a request message to an access management network element in the first communications network, wherein the request message requests the access management network element to allocate a connection identifier to a second connection that corresponds to the first connection and that is in a second communications network; wherein the determining, by the session management network element based on the access technology type corresponding to the session, whether to send the request message to the access management network element in the first communications network comprises: determining, by the session management network element, that the access technology type corresponding to the session is non-3rd generation partnership project, non-3GPP, access; and skipping, by the session management network element, sending the request message to the access management network element; wherein the first communications network is a 5G network, the second communications network is a 4G network, the first connection is a flow, the connection identifier of the first connection is a flow identifier, the second connection is a bearer, and the connection identifier of the second connection is a bearer identifier. determining, by the session management network element, that the access technology type corresponding to the session is non-3rd generation partnership project, non-3GPP, access; and skipping, by the session management network element, sending the request message to the access management network element; wherein the first communications network is a 5G network, the second communications network is a 4G network, the first connection is a flow, the connection identifier of the first connection is a flow identifier, the second connection is a bearer, and the connection identifier of the second connection is a bearer identifier.