Can it be used for Relayed and Routed sessions?

Yes, in Routed sessions the media is encrypted between all clients and the media server. In Relayed sessions the media is encrypted between each pair of clients. When a client is connecting to an OpenTok media server or another client, the cipher to use will be negotiated. If the client supports AES-256 then this will be the cipher negotiated for the media traffic. If the client does not support it, then AES-128 will be used. In the case of Relayed sessions, both clients must support AES-256, otherwise they will fall back to AES-128.